07- Domestic Water Heating Design Manual.pdf

Domestic Water Heating Design Published by

American Society of Plumbing Engineers

Manual Second Edition

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Domestic W ater Heating Design Manual, Second Edition Water

The Domestic Water Heating Design Manual, Second Edition, is designed to provide accurate and authoritative information for the design and specification of domestic water heating systems. The publisher makes no guarantees or warranties, expressed or implied, regarding the data and information contained in this publication. All data and information are provided with the understanding that the publisher is not engaged in rendering legal, consulting, engineering, or other professional services. If legal, consulting, or engineering advice or other expert assistance is required, the services of a competent professional should be engaged.

American Society of Plumbing Engineers 2980 S. River Rd Des Plaines, IL 600018 (847) 296-0002 E-mail: [email protected] • Internet: www.aspe.org

Copyright © 2003 by American Society of Plumbing Engineers First Edition published in 1998 by American Society of Plumbing Engineers. All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage or retrieval system, without permission in writing from the publisher. ISBN 978-1-891255-18-2 Printed in the United States of America 10

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ILLUSTRATIONS Figure 2.1 Weekday vs. Weekend Consumption . . . . . 20 Figure 2.2 Seasonal Variations, Weekend Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 2.3 Seasonal Variations, Weekend Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 2.4 Consumption curve. . . . . . . . . . . . . . . . . . 27 Figure 2.5 Comparison of DHW Peak Consumption . . 29 Figure 2.6 Parts of 3-Hour DHW Peak Consumption . . 29 Figure 2.7 Parts of Peak 60 Minutes DHW Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Figure 2.8 Peak Demand Curve . . . . . . . . . . . . . . . . . 36 Fixture 14.1 Upfeed Hot Water System with Heater at Bottom of System. . . . . . . . . . . . . . . . . 239 Figure 14.2 Downfeed Hot Water System with Heater at Top of System. . . . . . . . . . . . . . . . . . . . 240 Figure 14.3 Upfeed Hot Water System with Heater at Bottom of System. . . . . . . . . . . . . . . . . 240 Figure 14.4 Downfeed Hot Water System with Heater at Top of System. . . . . . . . . . . . . . . . . . . . 241 Figure 14.5 Combination Upfeed and Downfeed Hot Water System with Heater at Bottom of System. . . . . . . . . . . . . . . . . . . . . . . . . 241 Figure 14.6 Combination Downfeed and Upfeed Hot Water System with Heater at Top of System. . 242 Figure 14.7 Instantaneous Point-of-Use Water Heater Piping Diagram. . . . . . . . . . . . . . . . . . . . . 243 Figure 14.8 Fixed Orifices and Venturi Flow Meters. 246 Figure 14.9 Preset Self-Limiting Flow Control Cartridge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 Figure 14.10 Adjustable Orifice Flow Control Valve. . 248 Figure 14.11 Adjustable Balancing Valve with Memory Stop. . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Figure 15.1 Construction of a Typical Heating Cable for Hot Water Temperature Maintenance. . . . . . . 268 Figure 15.2 Components of a Hot Water Temperature Maintenance System. . . . . . . . . . . . . . . . . . . . . . 269 Figure 15.3 Symbols Used to Indicate Components of a Heat Traced Hot Water Supply System. . . . . . 273 Figure 15.4 Partial Simplified System Typical of Hospitals, Correctional Facilities, and Hotels. . . . 276

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Figure 15.5 Typical Layout for 2 to 4-Story Hospitals, Research Labs, Correctional Facilities, and Dormitories. . . . . . . . . . . . . . . . . . . . . . . . . . Figure 17.1 Indirect Water Heater Designs. . . . . . . . Figure 17.2 Purdue Bulletin 74 Chart, Showing the Relationship Between Lime Deposits and Water Temperature . . . . . . . . . . . . . . . . . . . . . . . Figure 18.1 A Typical Electric Water Heater. . . . . . . . Figure 18.2 Electric Water Heater Element Types. . . Figure 18.3 Electric Water Heater Element Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 18.4 Location of Controls—Residential and Light-Duty, Commercial Electric Water Heaters . . Figure 18.5 Location of Controls—Commercial Electric Water Heaters. . . . . . . . . . . . . . . . . . . . . Figure 18.6 Location of Controls—Booster Type, Commercial Electric Water Heaters. . . . . . . . . . . Figure 20.1 Location and Types of Flue. . . . . . . . . . . Figure 20.2 Sacrificial Anode Installation in a Residential Gas Water Heater Tank. . . . . . . . . . . Figure 20.3 Example of Water Heater Fittings. . . . . . Figure 20.4 The Principle of Operation of the Dip Tube. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 20.5 Types of Gas Burner. . . . . . . . . . . . . . . . Figure 20.6 Commonly Used Draft Hoods. . . . . . . . . Figure 20.7 Downdraft Conditions in a Vertical Draft Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 20.8 Vent Connection to a Chimney . . . . . . . . Figure 22.1 Recirculation System Piping and Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 23.1 A Closed Hot Water System Showing the Effects as Water and Pressure Increase from (a) P1 and T1 to (b) P2 and T2. . . . . . . . . . . . . Figure 23.2 Effects of an Expansion Tank in a Closed System as Pressure and Temperature Increase from (a) P1 and T1 to (b) P2 and T2. . . . . . Figure 23.3 Sizing the Expansion Tank. . . . . . . . . . .

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TABLES Table 1.1 Hot Water Multiplier, P . . . . . . . . . . . . . . . Table 1.1(M) Hot Water Multiplier, P . . . . . . . . . . . . . Table 1.2 Typical Delivered Hot Water Temperatures for Plumbing Fixtures and Equipment . . . . . . . . . Table 1.2(M) Typical Delivered Hot Water Temperatures for Plumbing Fixtures and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Table 1.3 Time/Water Temperature Combinations Producing Skin Damage . . . . . . . . . . . . . . . . . . . . 14 Table 2.1 Occupant Demographic Characteristics . . . . 24 Table 2.2 Low, Medium, and High Guidelines: Hot Water Demands and Use for Multifamily Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Table 4.1 School Grade Divisions . . . . . . . . . . . . . . . . 45 Table 4.2 Potential Areas of Hot Water Usage . . . . . . . 46 Table 4.3 Hot Water Demand per Fixture for Schools . 49 Table 4.4 General Purpose Hot Water Requirements of Kitchen Equipment . . . . . . . . . . . 50 Table 4.5 Rinse Water (180–195°F) Requirements of Commercial Dishmachines . . . . . 50 Table 4.5(M) Rinse Water (82–91°C) Requirements of Commercial Dishmachines . . . . . 51 Table 6.1 General Purpose Hot Water Requirements for Various Kitchen Uses . . . . . . . . . 87 Table 6.2 Usage Factors for User Groups . . . . . . . . . . 88 Table 8.1 General Purpose Hot Water Requirements for Various Kitchen Uses . . . . . . . . 151 Table 8.2 Usage Factors for User Groups . . . . . . . . . 152 Table 10.1 Tank Size Selection Chart . . . . . . . . . . . . 199 Table 10.1(M) Tank Size Selection Chart . . . . . . . . . . 200 Table 10.2 Hot Water Requirements after Initial Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 Table 10.2(M) Hot Water Requirements after Initial Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 Table 11.1 Fixture/Equipment Table . . . . . . . . . . . . 209 Table 14.1 Water Contents and Weight of Tube or Piping per Linear Foot . . . . . . . . . . . . . . . . . . . 235 Table 14.1(M) Water Contents and Weight of Tube or Piping per Meter . . . . . . . . . . . . . . . . . . . . . . . 236 Table 14.2 Approximate Fixture and Appliance Water Flow Rates . . . . . . . . . . . . . . . . . . . . . . . . 236

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Table 14.3 Approximate Time Required to Get Hot Water to a Fixture . . . . . . . . . . . . . . . . . . . . Table 14.3(M) Approximate Time Required to Get Hot Water to a Fixture . . . . . . . . . . . . . . . . . . . . Table 14.4 Minimum Pipe Insulation Thickness . . . Table 14.4(M) Minimum Pipe Insulation Thickness . Table 14.5 Approximate Insulated Piping Heat Loss and Surface Temperature . . . . . . . . . . . . . Table 14.5(M) Approximate Insulated Piping Heat Loss and Surface Temperature . . . . . . . . . . . . . Table 14.6 Heat Loss from Various Size Tanks with Various Insulation Thicknesses . . . . . . . . . Table 14.6(M) Heat Loss from Various Size Tanks with Various Insulation Thicknesses . . . . . . . . . Table 15.1 Time for Hot Water to Reach Fixture . . . Table 15.1(M) Time for Hot Water to Reach Fixture (sec) . . . . . . . . . . . . . . . . . . . . Table 15.2 Water Wasted While Waiting for Hot Water to Reach Fixture (oz) . . . . . . . . . . . . Table 15.2(M) Water Wasted While Waiting for Hot Water to Reach Fixture (mL) . . . . . . . . . . . . Table 15.3 Nominal Maintenance Temperatures, °F (°C) . . . . . . . . . . . . . . . . . . . . Table 18.1 Resistance of Element . . . . . . . . . . . . . . Table 23.1 Thermodynamic Properties of Water at a Saturated Liquid . . . . . . . . . . . . . . . . . . . . Table 23.2 Nominal Volume of Piping . . . . . . . . . . .

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ACRONYMS

ACEEE — American Council for Energy Efficient Economy ADA — Americans with Disabilities Act AGA — American Gas Association ASHRAE — American Society of Heating, Refrigerating, and Air-Conditioning Engineers ASME — American Society of Mechanical Engineers ASPE — American Society of Plumbing Engineers CCU — Critical care unit DHW — Domestic hot water EPDM — Ethylene propylene diene monomer ER — Emergency room HBV — Hepatitis B virus HIV — Human immunodeficiency virus HVAC — Heating, ventilating, and air conditioning ICU — Intensive care unit LMH — Low, medium, and high LPG — Liquid petroleum gas NEC — National Electric Code NFPA — National Fire Protection Association NR — Nitrile rubber NSF — National Sanitation Foundation OB — Obstetrics OHRD — Ontario Hydro Research Division PSIG — Pounds per square inch gauge SMACNA — Sheet Metal and Air Conditioning Contractors National Association TEMA — Tubular Exchange Manufacturers Association UL — Underwriters’ Laboratories, Inc.

Contents

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CONTENTS

FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . xix ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi SECTION I — SYSTEM SIZING . . . . . . . . . . . . . . . . . . . . 1 1.

FUNDAMENTALS OF DOMESTIC WATER HEATING Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Basic Relationships and Units . . . . . . . . . . . . . . . . . . . . 3 Thermal Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Heat Recovery—Electric Water Heaters . . . . . . . . . . . . . 5 Mixed Water Temperature . . . . . . . . . . . . . . . . . . . . . . . 6 Delivered Hot Water Temperature . . . . . . . . . . . . . . . . 12 Safety and Health Concerns . . . . . . . . . . . . . . . . . . . . 13 Scalding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Legionella Pneumophila (Legionnaires’ Disease) . . . 14 Relief Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Thermal Expansion . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Storage and Recovery . . . . . . . . . . . . . . . . . . . . . . . . . 15 Stratification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Codes and Standards . . . . . . . . . . . . . . . . . . . . . . . . . 16 System Alternative Considerations . . . . . . . . . . . . . . . 17

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MULTIFAMILY BUILDINGS Introduction Background Weekday Seasonal

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Demand Flow Patterns . . . . . . . . . . . . . . . . . Identification of Demand . . . . . . . . . . . . . . . . . . . Demand Determination . . . . . . . . . . . . . . . . . . . . Application of LMH Values . . . . . . . . . . . . . . . . . Peak Demand Vs. Average Demand . . . . . . . . . . . Potential of Generating Storage . . . . . . . . . . . Time of Day of Peak Flows . . . . . . . . . . . . . . . Peak Demand and Average Demand . . . . . . . Retrofit to Existing Systems (Customized Sizing) . Research on Generation Rate and Storage Capacity . . . . . . . . . . . . . . . . . . . . . . . . . Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example 2.1 Traditional Multifamily Building Example 2.2 Special Use Housing Facility . . . Possible Traps . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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ELEMENTARY AND SECONDARY SCHOOLS Introduction . . . . . . . . . . . . . . . . . . Types of School . . . . . . . . . . . . . . . . Information Gathering . . . . . . . . . . General Considerations . . . . . . . . . . Kitchen and Food Service . . . . . . . . Showers . . . . . . . . . . . . . . . . . . . . . School Population . . . . . . . . . . . . . . Calculating the Hot Water Demand . General Purpose Demand . . . . . Kitchen Demand . . . . . . . . . . . . Shower Load . . . . . . . . . . . . . . . Examples . . . . . . . . . . . . . . . . . . . . Example 4.1 Elementary School Example 4.2 High School . . . . . References . . . . . . . . . . . . . . . . . . .

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DORMITORIES Introduction . . . . . . . . . . . . . . . . . . . . . . Student Dormitories . . . . . . . . . . . . . . . . Example 3.1 Student Dormitory . . . . Institutional Dormitories . . . . . . . . . . . . . Example 2.2 Institutional Dormitory .

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HOTELS AND MOTELS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

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Hotel and Motel Classification . . . . . . . . . . . . . . . . . . . Convention Hotel or Motel . . . . . . . . . . . . . . . . . . . Business Travelers’ Hotel or Motel . . . . . . . . . . . . . Resort Hotel or Motel . . . . . . . . . . . . . . . . . . . . . . . General Occupancy Hotel or Motel . . . . . . . . . . . . Guest Room Demand . . . . . . . . . . . . . . . . . . . . . . . . . Questions and Assumptions . . . . . . . . . . . . . . . . . Example 5.1 Guest Room Demand . . . . . . . . . . . . Food Service Demand . . . . . . . . . . . . . . . . . . . . . . . . . Questions and Assumptions . . . . . . . . . . . . . . . . . Guide to Estimating Hourly Demand . . . . . . . . . . . Example 5.2 Food Service Demand . . . . . . . . . . . . Laundry Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . Questions and Assumptions . . . . . . . . . . . . . . . . . Example 5.3 Laundry Demand . . . . . . . . . . . . . . . General Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . System Considerations . . . . . . . . . . . . . . . . . . . . . Design Criteria Considerations . . . . . . . . . . . . . . .

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HOSPITALS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . Safety and Health Concerns . . . . . . . . . . . . . . . . . User Group Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . General Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . User Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Worksheets and Tables . . . . . . . . . . . . . . . . . . . . . . . . Worksheet 6.A—User Group . . . . . . . . . . . . . . . . . Worksheet 6.B—User Group Totals . . . . . . . . . . . . Worksheet 6.A—User Group—Example 6.1 . . . . . . Table 6.1—General Purpose Hot Water Requirements for Various Kitchen Uses . . . . . . Table 6.2—Usage Factors for User Groups . . . . . . . Questions for Owner or Client . . . . . . . . . . . . . . . . . . . Patient Areas and Nurses’ Stations . . . . . . . . . . . . Hydrotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dietary and Food Service . . . . . . . . . . . . . . . . . . . . Surgical Suite . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laundry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Central Sterile Supply . . . . . . . . . . . . . . . . . . . . . . Obstetrics/Nursery . . . . . . . . . . . . . . . . . . . . . . . . Miscellaneous Areas (e.g., Lab, Administration, Maintenance, Autopsy, the Morgue) . . . . . . . . .

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Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Example 6.2—32-Bed Hospital . . . . . . . . . . . . . . . 93 Example 6.3—300-Bed Hospital . . . . . . . . . . . . . 111

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SPAS, POOLS, HEALTH CLUBS, AND ATHLETIC CENTERS Introduction . . . . . . . . . . . . . . . . . . Information Gathering . . . . . . . . . . Hot Water Requirements . . . . . . . . . Therapies/Special Needs . . . . . . Shower Rooms . . . . . . . . . . . . . Other Demands . . . . . . . . . . . . . Calculating the Hot Water Demand .

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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Considerations . . . . . . . . . . . . . . . . . . . . . . Safety and Health Concerns . . . . . . . . . . . . . . . User Group Analysis . . . . . . . . . . . . . . . . . . . . . . . . General Outline . . . . . . . . . . . . . . . . . . . . . . . . . User Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . Worksheets and Tables . . . . . . . . . . . . . . . . . . . . . . Worksheet 8.A—User Group . . . . . . . . . . . . . . . Worksheet 8.B—User Group Totals . . . . . . . . . . Worksheet 8.A—User Group—Example . . . . . . . Table 8.1—General Purpose Hot Water Requirements for Various Kitchen Uses . . . . Table 8.2—Usage Factors for User Groups . . . . . Questions for Owner or Client . . . . . . . . . . . . . . . . . Nursing/Intermediate Care Facility . . . . . . . . . . Retirement Home . . . . . . . . . . . . . . . . . . . . . . . Example: 48-Bed Nursing/Intermediate Care and Retirement Home . . . . . . . . . . . . . . . . . . . . . . . Description of User Groups . . . . . . . . . . . . . . . . Questions for Owner or Client . . . . . . . . . . . . . . User Group Worksheets, 48-Bed Nursing/ Intermediate Care and Retirement Home . . . User Group Totals Worksheet, 48-Bed Nursing/ Intermediate Care and Retirement Home . . .

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NURSING/INTERMEDIATE CARE AND RETIREMENT HOMES

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JAIL AND PRISON HOUSING UNITS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

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General . . . . . . . . . . . . . . . . . . . . . . . . . . . Hot Water Demand . . . . . . . . . . . . . . . Jail Example . . . . . . . . . . . . . . . . . . . . . . . Questions . . . . . . . . . . . . . . . . . . . . . . Calculations for Jail Housing Units . . . Auxiliary Equipment Demand . . . . . . . Recommendation . . . . . . . . . . . . . . . . . Prison Example . . . . . . . . . . . . . . . . . . . . . Design Criteria and Assumptions . . . . Questions . . . . . . . . . . . . . . . . . . . . . . Calculations for Inmate Housing Units Storage Tank Sizing . . . . . . . . . . . . . . . Kitchen Considerations . . . . . . . . . . . . Laundry Considerations . . . . . . . . . . .

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10. INDUSTRIAL FACILITIES Introduction . . . . . . . . . . . . . . . . . . . . . . Examples of Industrials . . . . . . . . . . . . . General Design Criteria . . . . . . . . . . . . . . Areas within Industrial Facilities . . . . . . . Washrooms and Toilets . . . . . . . . . . . Wash Fixtures . . . . . . . . . . . . . . . . . . Showers . . . . . . . . . . . . . . . . . . . . . . Selection of Equipment . . . . . . . . . . . . . . Water Heater . . . . . . . . . . . . . . . . . . . Storage Tank . . . . . . . . . . . . . . . . . . . Facility-Specific Design Issues . . . . . . . . . Meat and Food Processing Facilities . Manufacturing Facilities . . . . . . . . . . Pharmaceutical Facilities . . . . . . . . . . Food Product Facilities . . . . . . . . . . . Chemical Processing Facilities . . . . . . Facilities that Process Raw Materials . Printing and Publishing Facilities . . . Central Utilities . . . . . . . . . . . . . . . . . Laboratories . . . . . . . . . . . . . . . . . . . Warehouses . . . . . . . . . . . . . . . . . . . Fluid Treatment Facilities . . . . . . . . . Miscellaneous Uses of Hot Water . . . . . . . Photo Processing . . . . . . . . . . . . . . . . Ready-Mix Concrete . . . . . . . . . . . . .

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viii


11. SPORTS ARENAS AND STADIUMS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gathering Information . . . . . . . . . . . . . . . . . . . . . System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Considerations . . . . . . . . . . . . . . . . . . . Water Heating System Temperature . . . . . . . . . Design Traps to Avoid . . . . . . . . . . . . . . . . . . . Types of System . . . . . . . . . . . . . . . . . . . . . . . Special Considerations: Commercial Laundries Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . System Sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sizing Parameters . . . . . . . . . . . . . . . . . . . . . . Example 11.1 Football Stadium . . . . . . . . . . . . Example 11.2 Baseball Stadium . . . . . . . . . . .

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203 204 205 205 206 206 207 208 208 210 210 211 214

12. LAUNDRIES Introduction . . . . . . . . . . System Design Questions Storage . . . . . . . . . . . . . . Recovery . . . . . . . . . . . . . Example 12.1 . . . . . . . . .

.... .... .... .... ....

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221 221 222 222 222

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225 225 225 226 226 226 227 227 228 228 229 229

13. MISCELLANEOUS FACILITIES Religious Facilities . . . . . . . . . . . Kitchen . . . . . . . . . . . . . . . . . Baptistries . . . . . . . . . . . . . . Toilet Rooms . . . . . . . . . . . . . Other Considerations . . . . . . Grocery and Convenience Stores . Toilet Rooms . . . . . . . . . . . . . Other Considerations . . . . . . Retail Centers . . . . . . . . . . . . . . . Fast Food Restaurants . . . . . . . . Toilet Rooms . . . . . . . . . . . . . Office Buildings . . . . . . . . . . . . .

. . . . . . . . . . . .

SECTION II — EQUIPMENT . . . . . . . . . . . . . . . . . . . . 231 14. RECIRCULATING DOMESTIC HOT WATER SYSTEMS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Length and Time Criteria . . . . . . . . . . . . . . . . . . . . . 234

Contents

ix

Results of Delays in Delivering Hot Water to Fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methods of Delivering Reasonably Prompt Hot Water Supply . . . . . . . . . . . . . . . . . . . . . . . . . . Circulation Systems for Commercial, Industrial, and Large Residential Projects . . . . . . . . . . . Self-Regulating Heat Trace . . . . . . . . . . . . . . . . Point-of-Use Heaters . . . . . . . . . . . . . . . . . . . . . Potential Problems in Circulated Hot Water Maintenance Systems . . . . . . . . . . . . . . . . . . . . Water Velocities in Hot Water Piping Systems . . Balancing Systems . . . . . . . . . . . . . . . . . . . . . . Isolating Portions of Hot Water Systems . . . . . . Maintaining the Balance of Hot Water Systems . Providing Check Valves at the Ends of Hot Water Loops . . . . . . . . . . . . . . . . . . . . . A Delay in Obtaining Hot Water at Dead-End Lines . . . . . . . . . . . . . . . . . . . . . . Flow Balancing Devices . . . . . . . . . . . . . . . . . . . . . . Fixed Orifices and Venturis . . . . . . . . . . . . . . . . Factory Preset Automatic Flow Control Valves . . Flow Regulating Valves . . . . . . . . . . . . . . . . . . . Balancing Valves with Memory Stops . . . . . . . . . Sizing Hot Water Return Piping Systems and Recirculating Pumps . . . . . . . . . . . . . . . . . . . . . Example 14.1—Calculation to Determine Required Circulation Rate . . . . . . . . . . . . . . . . . . . . . . . . Recalculation of Hot Water System Losses . . . . . Establishing the Head Capacity of the Hot Water Circulating Pump . . . . . . . . . . . . . . . . . . . . . . . Hot Water Circulating Pumps . . . . . . . . . . . . . . . . . Control for Hot Water Circulating Pumps . . . . . . . . Air Elimination . . . . . . . . . . . . . . . . . . . . . . . . . . . . Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. 238 . 238 . 239 . 242 . 242 . . . . .

243 244 244 244 245

. 245 . . . . . .

245 245 245 247 248 248

. 249 . 254 . 255 . . . . . . .

257 258 258 259 259 261 261

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265 266 267 269 270

15. SELF-REGULATING HEAT TRACE SYSTEMS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . System Description . . . . . . . . . . . . . . . . . . . . Product Description . . . . . . . . . . . . . . . . . . . System Components . . . . . . . . . . . . . . . . . . . Identifying the Piping Requiring Heat Tracing

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x


Design Considerations . . . . . . . . . . . . . . . . . . . . Multiple Temperature Systems . . . . . . . . . . . Remodels and Additions . . . . . . . . . . . . . . . . Coordinating Design Information . . . . . . . . . . . . Determining the Temperature to Maintain . . . . . . Choosing the Right Cable . . . . . . . . . . . . . . . . . . Thermal Insulation . . . . . . . . . . . . . . . . . . . . . . . Heat Tracing Hot Water Piping . . . . . . . . . . . . . . Combining Horizontal Mains with Supply Risers . Hot Water Heat Tracing Terms . . . . . . . . . . . . . .

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272 272 272 273 274 274 275 275 276 278

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Codes and Standards . . . . . . . . . . . . . . . . . . . . . . Plumbing Codes . . . . . . . . . . . . . . . . . . . . . . . Tubular Exchanger Manufacturers Association Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heating Medium . . . . . . . . . . . . . . . . . . . . . . . Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heat Exchanger . . . . . . . . . . . . . . . . . . . . . . . . Countercurrent . . . . . . . . . . . . . . . . . . . . . . . . Temperature Cross . . . . . . . . . . . . . . . . . . . . . Types of Heat Exchanger . . . . . . . . . . . . . . . . . . . . Shell and Tube . . . . . . . . . . . . . . . . . . . . . . . . Plate Type Heat Exchanger . . . . . . . . . . . . . . . Selecting Heat Exchangers . . . . . . . . . . . . . . . . . .

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279 279 279 280 280 280 280 280 281 281 281 282 284 288

16. HEAT EXCHANGERS

17. INDIRECT FIRED WATER HEATERS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . Product Description . . . . . . . . . . . . . . . . . . . . Storage Tank Type Indirect Water Heaters . Instantaneous Indirect Water Heaters . . . . Water Conditions . . . . . . . . . . . . . . . . . . . . . .

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291 291 291 293 295

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297 297 298 298 298 300 300

18. ELECTRIC WATER HEATERS—STORAGE AND BOOSTER Introduction . . . . . . . . . . . . . . . . . . . . . Principal Types of Electric Water Heater Components . . . . . . . . . . . . . . . . . . . . . The Tank . . . . . . . . . . . . . . . . . . . . . Tank Fittings . . . . . . . . . . . . . . . . . . Dip Tube . . . . . . . . . . . . . . . . . . . . . Elements . . . . . . . . . . . . . . . . . . . . .

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Contents

xi

Controls for Residential and Light-Duty, Commercial Electric Water Heaters . . . . . . . Thermostat . . . . . . . . . . . . . . . . . . . . . . . . . High Limit . . . . . . . . . . . . . . . . . . . . . . . . . . Controls for Medium-Duty, Commercial Electric Water Heaters . . . . . . . . . . . . . . . . . . . . . . . Surface-Mounted Controls . . . . . . . . . . . . . Immersion Controls . . . . . . . . . . . . . . . . . . . Controls for Heavy-Duty, Commercial Electric Water Heaters . . . . . . . . . . . . . . . . . . . . . . . Immersion Thermostat . . . . . . . . . . . . . . . . Immersion High Limit . . . . . . . . . . . . . . . . . Wiring Circuits . . . . . . . . . . . . . . . . . . . . . . Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . Controls for Booster Type, Commercial Electric Water Heaters . . . . . . . . . . . . . . . . . . . . . . . Immersion Thermostat . . . . . . . . . . . . . . . . Immersion High Limit . . . . . . . . . . . . . . . . . Wiring Circuits . . . . . . . . . . . . . . . . . . . . . . Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . Options . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . 303 . . . . 303 . . . . 303 . . . . 305 . . . . 305 . . . . 305 . . . . .

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306 306 306 306 306

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308 308 308 308 308 308

19. GAS WATER HEATERS—INSTANTANEOUS WITH SEPARATE TANK . . . . . . . . . . . . . . . . . . . . 311 20. GAS WATER HEATERS—STORAGE Types of Gas Water Heaters Flues and Heat Exchangers . Tanks . . . . . . . . . . . . . . . . . Tank Fittings . . . . . . . . . . . Dip Tubes . . . . . . . . . . . . . . Burners . . . . . . . . . . . . . . . Venting Systems . . . . . . . . . Draft Hoods. . . . . . . . . . Vent Connections . . . . .

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313 313 314 314 315 319 321 321 323

Introduction . . . . . . . . . . . . . . . . . . . . . Types of Heat Pump Water Heater . . . . . Integral Heat Pump Water Heaters . Remote Heat Pump Water Heaters . . Energy Sources . . . . . . . . . . . . . . . . . . . Benefits of the Heat Pump Water Heater

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325 326 326 327 327 328

21. HEAT PUMP WATER HEATERS

xii


Drawbacks of the Heat Pump Water Heater . Heat Recovery Systems . . . . . . . . . . . . . . . . Applications . . . . . . . . . . . . . . . . . . . . . . . . Criteria for Selecting Heat Pump Water Heaters . . . . . . . . . . . . . . . . . . . . Special Requirements for Heat Pump Water Heaters . . . . . . . . . . . . . . . . . . . . Incoming Water Quality . . . . . . . . . . . . . . . Safety Controls and Devices . . . . . . . . . . . .

. . . . . . . 328 . . . . . . . 329 . . . . . . . 330 . . . . . . . 331 . . . . . . . 331 . . . . . . . 332 . . . . . . . 332

22. STEAM WATER HEATERS Introduction . . . . . . . . . . . . . . . . . . . . . . . . Instantaneous Water Heaters . . . . . . . . Storage Water Heaters . . . . . . . . . . . . . . Feedback Units . . . . . . . . . . . . . . . . . . . . . . Feed-Forward Units . . . . . . . . . . . . . . . . . . Recirculation System Piping and Operation . Design Considerations . . . . . . . . . . . . . . . . Example 22.1 . . . . . . . . . . . . . . . . . . . .

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333 333 333 334 336 338 340 341

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343 346 348 348 349 351 353 354

23. EXPANSION TANKS Introduction . . . . . . . . Expansion of Water . . . Example 23.1 . . . . Expansion of Materials Example 23.2 . . . . Boyle’s Law . . . . . . . . . Example 23.3 . . . . Summary . . . . . . . . . .

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INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

Section

I

SYSTEM SIZING Every effort has been made to include all segments of the water heating industry—designers and manufacturers—in the writing and reviewing of this manual. The writers, coordinators and reviewers of this book made every attempt to include new technologies when known and applicable. However, this manual is designed to be a “work in progress.” As engineers and designers use and apply the material in this design manual, it will be revised and updated so that future editions will represent an ever expanding base of knowledge and experience. Two important water heating system components, safety equipment and controls, have been intentionally omitted from this manual. Because specific safety equipment and controls may vary significantly according to water heater types and manufacturers and applicable code requirements, this manual includes a general synopsis of the relevant data. This approach inherently limits the scope of the information covered. Therefore, it is recommended that information concerning safety equipment and controls be closely coordinated with water heater manufacturers and checked against local code requirements.

Fundamentals of Domestic W ater Heating Water

1

3

FUNDAMENTALS OF DOMESTIC WATER HEATING

INTRODUCTION This chapter provides the information needed to size a domestic hot water system. Some of the information presented here is referred to throughout the Manual; other information will be helpful at various stages of the design process, such as selecting a type of water heater and calculating energy usage.

BASIC RELATIONSHIPS AND UNITS The equations used throughout the Manual are based on the principle of energy conservation. The fundamental formula for this expresses a steady-state heat balance for the heat input and output of the system: (1.1)

q = rwc∆T

where q = r = w = c = ∆T1 = i

time rate of heat transfer, Btu/h (kJ/h) flow rate, gph (L/h) weight of heated water, lb/gal (kg/m3) specific heat of water, Btu/lb/°F (kJ/kg/K) change in heated water temperature (temperature of leaving water minus temperature of incomn g water, represented in this manual as Th – Tc, °F [K])

Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations. 1 Be sure that the minimum supply water temperature in the equation represents the actual time of year that peak load occurs.

4


For the purposes of this manual, the specific heat of water shall be considered a constant, c = 1 Btu/lb/°F (c = 4.19 kJ/kg/K), and the weight of water shall be constant at 8.33 lb/gal (999.6 kg/m3). (The specific heat and the weight of water will actually vary with temperature and altitude.) (1.2)

[( )(

q = gph

{

1 Btu lb/°F

[(

m3 h

q=

)]

8.33 lb (∆T) gal

)(

4.188 kJ kg/K

) ]}

999.6 kg m3

(∆ T)

Example 1.1 Calculate the heat output rate required to heat 600 gph from 50 to 140°F (2.27 m3/h from 283.15 to 333.15K). Solution From Equation 1.2, q = (600 gph)(8.33 Btu/gal/°F)(140 – 50°F) = 449,820 Btu/h [q = (2.27 m3/h)(4188.32 kJ/m3/K)(333.15 – 283.15K) = 475 374 kJ/h] Note: The designer should be aware that water heaters installed in high elevations must be derated based on the elevation. The water heaters’ manufacturers’ data should be consulted for information on required modifications.

THERMAL EFFICIENCY When inefficiencies of the water heating process are considered, the actual input energy is higher than the usable, or output, energy. Direct fired water heaters (i.e., gas, oil, etc.) lose part of their total energy capability to such things as heated flue gases, inefficiencies of combustion, and radiation at heated surfaces. Their thermal efficiency, Et, is defined as the heat actually transferred to the domestic water divided by the total heat input to the water heater. Expressed as a percentage, this is: (1.3)

Et =

q × 100% q+B

where B

= heat loss of the water heater, Btu/h (kJ/h)


5

Refer to Equations 1.1 and 1.2 to determine q. Many water heaters and boilers provide input and output energy information. Example 1.2 Calculate the heat input rate required for the water heater in Example 1.1 if this is a direct, gas fired water heater with a thermal efficiency of 80%. From Example 1.1, q = 449,820 Btu/h (475 374 kJ/h). Heat input =

Solution

(

449,820 Btu/h q = = 562,275 Btu/h Et 0.80 q 475 374 kJ/h = Et 0.80

)

= 594 217.5 kJ/h

HEAT RECOVERY—ELECTRIC WATER HEATERS Assume that 1 kilowatt-hour of electrical energy will raise 410 gal (1552.02 L) of water 1°F (½°C). This can expressed in a series of formulas, as follows: 410 gal = gal of water per kWh at ∆T ∆T 1552.02 L = L of water per kWh at ∆ T ∆T

(1.4)

(

gph × ∆ T = kWh required 410 gal

(1.5)

(

)

)

L/h • ∆ T = kWh required 1552.02 L

(1.6)

gph = kW required gal of water per kWh at ∆ T

(

)

L/h = kW required L of water per kWh at ∆ T

where ∆ T = temperature rise (temperature differential), °F (°C) gph = gallons per hour of hot water required L/h = liters per hour of hot water required Equation 1.4 can be used to establish a simple table based on the required temperature rise.

6


Temperature Rise, ∆T, °F (°C) 110 100 90 80 70 60 50 40

Gal (L) of Water per kWh

(43) (38) (32) (27) (21) (16) (10) (4)

3.73 4.10 4.55 5.13 5.86 6.83 8.20 10.25

(14.12) (15.52) (17.22) (19.42) (22.18) (25.85) (31.04) (38.8)

This table can be used with Equation 1.6 to solve for the kW electric element needed to heat the required recovery volume of water. Example 1.3 An electric water heater must be sized to provide a continuous flow of 40 gph (151.42 L/h) of hot water at a temperature of 140°F (43°C). The incoming water supply during winter is 40°F (4°C). Solution

Using Equation 1.6 and the above table, we find the following: 40 gph = 9.8 kW required 4.1 gal/kWh (100°F)

[

]

151.42 L/h = 9.8 kW required 15.52 L/kWh (38°C)

MIXED WATER TEMPERATURE Mixing water at different temperatures to make a desired mixed water temperature is the main purpose of domestic hot water systems. The design of systems that effectively do that is the purpose of this manual. (1.7)

P =

(Tm – Tc) (Th – Tc)

where Th = supply hot water temperature Tc = inlet cold water temperature Tm = desired mixed water temperature


7

P is a hot water multiplier and can be used to determine the percentage of supply hot water that will blend the hot and cold water to produce a desired mixed water temperature. Values of P for a range of hot and cold water temperatures are given in Table 1.1. Example 1.4 A group of showers requires 25 gpm (1.58 L/sec) of 105°F (41°C) mixed water temperature. Determine how much 140°F (60°C) hot water must be supplied to the showers when the cold water temperature is 50°F (10°C). Solution P = (105 – 50°F)/(140 – 50°F) = 0.61. [P = (41 – 10°C)/(60 – 10°C) = 0.61]. Therefore, 0.61 (25 gpm) = 15.25 gpm of 140°F water required. [0.61 (1.58 L/sec) = 0.96 L/sec of 60°C water required.] Table 1.1 may also be used to determine P.

Table 1.1 Hot Water Multiplier, P Th =110°F Hot Water System Temperature Tc, CW Temp. (°F)

T m, Water Temperature at Fixture Outlet (°F) 110

105

100

95

45

1.00

0.92

0.85

0.77

50

1.00

0.92

0.83

0.75

55

1.00

0.91

0.82

0.73

60

1.00

0.90

0.80

0.70

65

1.00

0.89

0.78

0.67

Th = 120°F Hot Water System Temperature Tc, CW Temp. (°F)


115

110

105

100

95

45

1.00

0.93

0.87

0.80

0.73

0.67

50

1.00

0.93

0.86

0.79

0.71

0.64

55

1.00

0.92

0.85

0.77

0.69

0.62

60

1.00

0.92

0.83

0.75

0.67

0.58

65

1.00

0.91

0.82

0.73

0.64

0.55

(Continued)

8


(Table 1.1 continued) Th = 130°F Hot Water System Temperature Tc, CW Temp. (°F)


125

120

115

110

105

100

95

45

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

50

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

55

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

60

1.00

0.93

0.86

0.79

0.71

0.64

0.57

0.50

65

1.00

0.92

0.85

0.77

0.69

0.62

0.54

0.46



135

130

125

120

115

110

105

100

95

45

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

50

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

55

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

60

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

0.50

0.44

65

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

0.47

0.40



145

140

135

130

125

120

115

110

105

100

45

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

50

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

55

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47

60

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

0.44

65

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

0.41

(Continued)


9



155

150

145

140

135

130

125

120

115

110

45

1.00

0.96

0.91

0.87

0.83

0.78

0.74

0.70

0.65

0.61

0.57

50

1.00

0.95

0.91

0.86

0.82

0.77

0.73

0.68

0.64

0.59

0.55

55

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

60

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

65

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47



175

170

165

160

155

150

145

140

135

130

45

1.00

0.96

0.93

0.89

0.85

0.81

0.78

0.74

0.70

0.67

0.63

50

1.00

0.96

0.92

0.88

0.85

0.81

0.77

0.73

0.69

0.65

0.62

55

1.00

0.96

0.92

0.88

0.84

0.80

0.76

0.72

0.68

0.64

0.60

60

1.00

0.96

0.92

0.88

0.83

0.79

0.75

0.71

0.67

0.63

0.58

65

1.00

0.96

0.91

0.87

0.83

0.78

0.74

0.70

0.65

0.61

0.57

110

1.00

0.93

0.86

0.79

0.71

0.64

0.57

0.50

0.43

0.36

0.29

120

1.00

0.92

0.83

0.75

0.67

0.58

0.50

0.42

0.33

0.25

0.17

130

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10 ——

140

1.00

0.88

0.75

0.63

0.50

0.38

0.25

0.13

——

——

——

150

1.00

0.83

0.67

0.50

0.33

0.17

——

——

——

——

——

160

1.00

0.75

0.50

0.25 —— —— —— —— —— —— ——

10


Table 1.1 (M) Hot Water Multiplier, P Th = 43°C Hot Water System Temperature Tm, Water Temperature at Fixture Outlet (°C)

Tc, CW Temp. (°C)

43

41

38

35

7

1.00

0.92

0.85

0.77

10

1.00

0.92

0.83

0.75

13

1.00

0.91

0.82

0.73

16

1.00

0.90

0.80

0.70

18

1.00

0.89

0.78

0.67

Th = 49°C Hot Water System Temperature Tm, Water Temperature at Fixture Outlet (°C)

Tc, CW Temp. (°C)

49

46

43

41

38

35

7

1.00

0.93

0.87

0.80

0.73

0.67

10

1.00

0.93

0.86

0.79

0.71

0.64

13

1.00

0.92

0.85

0.77

0.69

0.62

16

1.00

0.92

0.83

0.75

0.67

0.58

18

1.00

0.91

0.82

0.73

0.64

0.55

Th = 54°C Hot Water System Temperature Tc, CW Temp. (°C)

Tm, Water Temperature at Fixture Outlet (°C) 54

52

49

46

43

41

38

35

7

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

10

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

13

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

16

1.00

0.93

0.86

0.79

0.71

0.64

0.57

0.50

18

1.00

0.92

0.85

0.77

0.69

0.62

0.54

0.46

(Continued)


11

[Table 1.1 (M) continued] Th = 60°C Hot Water System Temperature Tc, CW Temp. (°C)


58

54

52

49

46

43

41

38

35

7

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

10

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

13

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

16

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

0.50

0.44

18

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

0.47

0.40



63

60

58

54

52

49

46

43

41

38

7

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

10

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

13

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47

16

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

0.44

18

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

0.41



68

66

63

60

58

54

52

49

46

43

7

1.00

0.96

0.91

0.87

0.83

0.78

0.74

0.70

0.65

0.61

0.57

10

1.00

0.95

0.91

0.86

0.82

0.77

0.73

0.68

0.64

0.59

0.55

13

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

16

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

18

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47

(Continued)

12


[Table 1.1 (M) continued] Th = 82°C Hot Water System Temperature Tc, CW Temp. (°C) 7 10 13 16 18 43 49 54 60 66 71


79

77

74

71

68

66

63

60

58

54

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

0.96 0.96 0.96 0.96 0.96 0.93 0.92 0.90 0.88 0.83 0.75

0.93 0.92 0.92 0.92 0.91 0.86 0.83 0.80 0.75 0.67 0.50

0.89 0.88 0.88 0.88 0.87 0.79 0.75 0.70 0.63 0.50 0.25

0.85 0.85 0.84 0.83 0.83 0.71 0.67 0.60 0.50 0.33 —

0.81 0.81 0.80 0.79 0.78 0.64 0.58 0.50 0.38 0.17 —

0.78 0.77 0.76 0.75 0.74 0.57 0.50 0.40 0.25 — —

0.74 0.73 0.72 0.71 0.70 0.50 0.42 0.30 0.13 — —

0.70 0.69 0.68 0.67 0.65 0.43 0.33 0.20 — — —

0.67 0.65 0.64 0.63 0.61 0.36 0.25 0.10 — — —

0.63 0.62 0.60 0.58 0.57 0.29 0.17 — — — —

DELIVERED HOT WATER TEMPERATURE The generally accepted delivered hot water temperatures for various plumbing fixtures and equipment are given in Table 1.2. Both temperature and pressure should be verified with the client and checked against local codes and the manuals of equipment used.

Table 1.2 Typical Delivered Hot Water Temperatures for Plumbing Fixtures and Equipment Use Lavatory Showers and tubs Commercial and institutional laundry Residential dishwashing and laundry Commercial spray type dishwashing (as required by the NSF): Single or multiple tank hood or rack type: Wash Final rinse Single tank conveyor type: Wash Final rinse Single tank rack or door type: Single temperature wash and rinse Chemical sanitizing glassware: Wash Rinse

Temp. (°F) 105 110 140–180 140 150 180–195 160 180–195 165 140 75

Note: Be aware that temperatures, as dictated by codes, owners, equipment manufacturers, or regulatory agencies, will occasionally differ from those shown.


13

Table 1.2 (M) Typical Delivered Hot Water Temperatures for Plumbing Fixtures and Equipment Use Lavatory Showers and tubs Commercial and institutional laundry Residential dishwashing and laundry Commercial spray type dishwashing (as required by the NSF): Single or multiple tank hood or rack type: Wash Final rinse Single tank conveyor type: Wash Final rinse Single tank rack or door type: Single temperature wash and rinse Chemical sanitizing glassware: Wash Rinse

Temp. (°C) 41 43 60–82 60 66 82–91 71 82–91 74 60 24


SAFETY AND HEALTH CONCERNS Scalding2 A research project by Moritz and Henriques at Harvard Medical College3 looked at the relationship between time and water temperature necessary to produce a first-degree burn. A first-degree burn, the least serious type, results in no irreversible damage. The results of the research show that it takes a 3-sec exposure to 140°F (60°C) water to produce a first-degree burn. At 130°F (54°C), it takes approximately 20 sec, and at 120°F (49°C), it takes 8 min to produce a first-degree burn. The normal threshold of pain is approximately 118°F (48°C). A person exposed to 120°F (49°C) water would immediately experience discomfort; it is unlikely then that the person would be exposed for the 8 min required to produce a first-degree burn. People in some occupancies (e. g., hospitals) as well as those over

2For more information regarding “Scalding,” refer to ASPE Research Foundation. 1989. Temperature limits in service hot water systems. Journal of Environmental Health. (June): 38–48. 3Moritz, A. R., and Henriques, F. C., Jr. 1947. The relative importance of time and surface temperature in the causation of cutaneous burns. American Journal of Pathology. 23: 695–720.

14


the age of 65 and under the age of 1 may not sense pain or move quickly enough to avoid a burn once pain is sensed. If such a possibility exists, scalding protection should be considered. It is often required by code. (For more information on skin damage caused by exposure to hot water, see Table 1.3.)

Table 1.3 Time/Water Temperature Combinations Producing Skin Damage Water Temperature °F Over 140 140 135 130 125 120

°C Over 60 60 58 54 52 49

Time (sec) Less than 1 2.6 5.5 15 50 290

Source: Tom Byrley. 1979. 130 degrees F or 140 degrees F. Contractor Magazine. (September). First published in American Journal of Pathology. Note: The above data indicate conditions producing the first evidence of skin damage in adult males.

Legionella Pneumophila (Legionnaires’ Disease) Legionnaires’ disease is a potentially fatal respiratory illness. The disease gained notoriety when a number of American Legionnaires contracted it during a convention. That outbreak was attributed to the water vapor from the building’s cooling tower(s). The bacteria that cause Legionnaires’ disease are widespread in natural sources of water, including rivers, lakes, streams, and ponds. In warm water, the bacteria can grow and multiply to high concentrations. Drinking water containing the Legionella bacteria has no known effects. However, inhalation of the bacteria into the lungs, e.g., while showering, can cause Legionnaires’ disease. Much has been published about this problem, and yet there is still controversy over the exact temperatures that foster the growth of the bacteria. Further research is required, for there is still much to be learned. It is incumbent upon designers to familiarize themselves with the latest information on the subject and to take it into account when designing their systems. Designers also must be familiar with and abide by the rules of all regulating agencies with jurisdiction.


15

RELIEF VALVES Water heating systems should be protected from excessive temperatures and pressures by relief valves. Temperature and pressure relief valves are available either separately or combined. Typically they are tested to comply with the standards of the American Society of Mechanical Engineers (ASME), the American Gas Association (AGA), or the National Board of Boiler and Pressure Vessel Inspectors (NBBPVI) and are so labeled. The designer should verify which agency’s standards are applicable to the water heating system being designed and follow those standards for the sizes, types, and locations of required relief valves.

THERMAL EXPANSION Water expands as it is heated, and some way to allow for this expansion should be provided in a domestic hot water system. Use of a thermal expansion tank in the cold water piping to the water heater will do this. It is recommended that the designer contact the manufacturer of the thermal expansion tank for information on installation and sizing. The plumbing code requires some type of thermal expansion compensation—expecially when there is either a backflow prevention device on the cold water service to the building or a check valve in the system.

CONTROLS The control components for water heaters differ depending on the type of heater and the manufacturer. Generally, water heater controls should be checked with the equipment manufacturer. Also, the various regulatory and testing agencies have requirements for controls that depend on the size and type of equipment used.

STORAGE AND RECOVERY The design of a domestic water heating system begins with estimating the facility’s load profile and identifying the peak demand times. To accomplish these steps, the designer must conduct discussions with the users of the space, determine the building type, and learn of any owner requirements. The information thus gathered will establish the required capacity of the water heating equipment and the general type of system to be used. With fuel

16


fired equipment, to avoid condensation, the equipment and the operating temperature should be selected to ensure that the heater’s operating temperature is not lower than the dewpoint temperature of the flue gas.

Stratification There is a natural tendency of warm water to rise to the top of a storage tank. The result of this rising action, known as “stratification,” occurs in all unrecirculated tanks. It has been found that the percent useable storage volume in stratified horizontal and vertical tanks has a range of 65–75% to 80–90%, respectively. Not all tanks are created equal; the percent usable storage volume can be affected by such items as the flow rates, the points of connection, tank capacity and by tank recirculation systems. Stratification during recovery periods can be reduced significantly by mechanical circulation of the water in the tank. During periods of demand, however, it is useful to have good stratification since this increases the availability of water at a usable temperature. If, for example, a tank were stratified with the top half at 140°F (60°C) and the bottom half at 40°F (4°C), this tank, in theory, could still deliver half its volume at 140°F (60°C). But, if the two layers were completely mixed, the tank temperature would drop to 90°F (32°C), which, in most cases, is an unusable temperature.

CODES AND STANDARDS The need to conform to various codes and standards determines many aspects of the design of a domestic hot water system as well as the selection of components and equipment. Some of the most often used codes and standards are: 1. Regional, state, and local plumbing codes. 2. American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)/IES 90.1. 3. ASME code for fired and unfired pressure vessels. 4. ASME and AGA codes for relief valves. 5. Underwriters’ Laboratories (UL) listing for electrical components. 6. National Sanitation Foundation (NSF) listing. 7. AGA approval for gas burning components.


17

8. National Fire Protection Association (NFPA) standards. 9. National Electrical Code (NEC). In addition, the federal government, the agencies with jurisdiction over public schools and public housing, and many other agencies have specific requirements that must be observed when designing projects and selecting equipment for them.

SYSTEM ALTERNATIVE CONSIDERATIONS The design and selection of water heating systems are part of a process that involves assumptions, decisions, and trade-offs. The general organization of this manual separates application considerations and load determinations (Section I) from the selection of equipment (Section II). While this is possible for most conventional water heating systems, it does not yield the optimum solution for many advanced, high-efficiency water heating systems. These systems include refrigerant-based systems like heat pump water heaters; refrigeration heat reclaim systems; and multifunction, full-condensing equipment. These and other systems like solar water heaters have a higher cost per unit of heating capacity than most conventional systems. Often the most cost-effective configuration for these systems tends to use higher storage volumes and lower heating rates than those recommended in the following chapters. These systems are frequently configured as hybrid systems, combining both an advanced high-efficiency system as the primary, base-loaded water heater and a conventional water heater for “peaking” or supplemental water heating. Advanced, high-efficiency systems may offer significant benefits; however, their design and selection is necessarily more detailed. The seasonal and instantaneous efficiency and output of these systems vary greatly with operating conditions. Because they are not selected to meet the peak water heating load, load calculations must address not simply the peak but the water heating load shape. Their higher cost per unit of heating capacity as compared to most conventional systems places a higher premium on accurate load determination since oversizing has a more marked effect on system cost. Other considerations such as a building’s cooling load or waste heat availability may also come into play. The capacities of these systems and any related supplemental water heating equipment should be selected to achieve high average daily run time and the lowest combination of operating and equipment cost.

Section

I

SYSTEM SIZING Every effort has been made to include all segments of the water heating industry—designers and manufacturers—in the writing and reviewing of this manual. The writers, coordinators and reviewers of this book made every attempt to include new technologies when known and applicable. However, this manual is designed to be a “work in progress.” As engineers and designers use and apply the material in this design manual, it will be revised and updated so that future editions will represent an ever expanding base of knowledge and experience. Two important water heating system components, safety equipment and controls, have been intentionally omitted from this manual. Because specific safety equipment and controls may vary significantly according to water heater types and manufacturers and applicable code requirements, this manual includes a general synopsis of the relevant data. This approach inherently limits the scope of the information covered. Therefore, it is recommended that information concerning safety equipment and controls be closely coordinated with water heater manufacturers and checked against local code requirements.


1

3

FUNDAMENTALS OF DOMESTIC WATER HEATING

INTRODUCTION This chapter provides the information needed to size a domestic hot water system. Some of the information presented here is referred to throughout the Manual; other information will be helpful at various stages of the design process, such as selecting a type of water heater and calculating energy usage.

BASIC RELATIONSHIPS AND UNITS The equations used throughout the Manual are based on the principle of energy conservation. The fundamental formula for this expresses a steady-state heat balance for the heat input and output of the system: (1.1)

q = rwc∆T

where q = r = w = c = ∆T1 = i

time rate of heat transfer, Btu/h (kJ/h) flow rate, gph (L/h) weight of heated water, lb/gal (kg/m3) specific heat of water, Btu/lb/°F (kJ/kg/K) change in heated water temperature (temperature of leaving water minus temperature of incomn g water, represented in this manual as Th – Tc, °F [K])

Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations. 1 Be sure that the minimum supply water temperature in the equation represents the actual time of year that peak load occurs.

4


For the purposes of this manual, the specific heat of water shall be considered a constant, c = 1 Btu/lb/°F (c = 4.19 kJ/kg/K), and the weight of water shall be constant at 8.33 lb/gal (999.6 kg/m3). (The specific heat and the weight of water will actually vary with temperature and altitude.) (1.2)

[( )(

q = gph

{

1 Btu lb/°F

[(

m3 h

q=

)]

8.33 lb (∆T) gal

)(

4.188 kJ kg/K

) ]}

999.6 kg m3

(∆ T)

Example 1.1 Calculate the heat output rate required to heat 600 gph from 50 to 140°F (2.27 m3/h from 283.15 to 333.15K). Solution From Equation 1.2, q = (600 gph)(8.33 Btu/gal/°F)(140 – 50°F) = 449,820 Btu/h [q = (2.27 m3/h)(4188.32 kJ/m3/K)(333.15 – 283.15K) = 475 374 kJ/h] Note: The designer should be aware that water heaters installed in high elevations must be derated based on the elevation. The water heaters’ manufacturers’ data should be consulted for information on required modifications.

THERMAL EFFICIENCY When inefficiencies of the water heating process are considered, the actual input energy is higher than the usable, or output, energy. Direct fired water heaters (i.e., gas, oil, etc.) lose part of their total energy capability to such things as heated flue gases, inefficiencies of combustion, and radiation at heated surfaces. Their thermal efficiency, Et, is defined as the heat actually transferred to the domestic water divided by the total heat input to the water heater. Expressed as a percentage, this is: (1.3)

Et =

q × 100% q+B

where B

= heat loss of the water heater, Btu/h (kJ/h)


5

Refer to Equations 1.1 and 1.2 to determine q. Many water heaters and boilers provide input and output energy information. Example 1.2 Calculate the heat input rate required for the water heater in Example 1.1 if this is a direct, gas fired water heater with a thermal efficiency of 80%. From Example 1.1, q = 449,820 Btu/h (475 374 kJ/h). Heat input =

Solution

(

449,820 Btu/h q = = 562,275 Btu/h Et 0.80 q 475 374 kJ/h = Et 0.80

)

= 594 217.5 kJ/h

HEAT RECOVERY—ELECTRIC WATER HEATERS Assume that 1 kilowatt-hour of electrical energy will raise 410 gal (1552.02 L) of water 1°F (½°C). This can expressed in a series of formulas, as follows: 410 gal = gal of water per kWh at ∆T ∆T 1552.02 L = L of water per kWh at ∆ T ∆T

(1.4)

(

gph × ∆ T = kWh required 410 gal

(1.5)

(

)

)

L/h • ∆ T = kWh required 1552.02 L

(1.6)

gph = kW required gal of water per kWh at ∆ T

(

)

L/h = kW required L of water per kWh at ∆ T

where ∆ T = temperature rise (temperature differential), °F (°C) gph = gallons per hour of hot water required L/h = liters per hour of hot water required Equation 1.4 can be used to establish a simple table based on the required temperature rise.

6


Temperature Rise, ∆T, °F (°C) 110 100 90 80 70 60 50 40

Gal (L) of Water per kWh

(43) (38) (32) (27) (21) (16) (10) (4)

3.73 4.10 4.55 5.13 5.86 6.83 8.20 10.25

(14.12) (15.52) (17.22) (19.42) (22.18) (25.85) (31.04) (38.8)

This table can be used with Equation 1.6 to solve for the kW electric element needed to heat the required recovery volume of water. Example 1.3 An electric water heater must be sized to provide a continuous flow of 40 gph (151.42 L/h) of hot water at a temperature of 140°F (43°C). The incoming water supply during winter is 40°F (4°C). Solution

Using Equation 1.6 and the above table, we find the following: 40 gph = 9.8 kW required 4.1 gal/kWh (100°F)

[

]

151.42 L/h = 9.8 kW required 15.52 L/kWh (38°C)

MIXED WATER TEMPERATURE Mixing water at different temperatures to make a desired mixed water temperature is the main purpose of domestic hot water systems. The design of systems that effectively do that is the purpose of this manual. (1.7)

P =


where Th = supply hot water temperature Tc = inlet cold water temperature Tm = desired mixed water temperature


7

P is a hot water multiplier and can be used to determine the percentage of supply hot water that will blend the hot and cold water to produce a desired mixed water temperature. Values of P for a range of hot and cold water temperatures are given in Table 1.1. Example 1.4 A group of showers requires 25 gpm (1.58 L/sec) of 105°F (41°C) mixed water temperature. Determine how much 140°F (60°C) hot water must be supplied to the showers when the cold water temperature is 50°F (10°C). Solution P = (105 – 50°F)/(140 – 50°F) = 0.61. [P = (41 – 10°C)/(60 – 10°C) = 0.61]. Therefore, 0.61 (25 gpm) = 15.25 gpm of 140°F water required. [0.61 (1.58 L/sec) = 0.96 L/sec of 60°C water required.] Table 1.1 may also be used to determine P.

Table 1.1 Hot Water Multiplier, P Th =110°F Hot Water System Temperature Tc, CW Temp. (°F)


105

100

95

45

1.00

0.92

0.85

0.77

50

1.00

0.92

0.83

0.75

55

1.00

0.91

0.82

0.73

60

1.00

0.90

0.80

0.70

65

1.00

0.89

0.78

0.67



115

110

105

100

95

45

1.00

0.93

0.87

0.80

0.73

0.67

50

1.00

0.93

0.86

0.79

0.71

0.64

55

1.00

0.92

0.85

0.77

0.69

0.62

60

1.00

0.92

0.83

0.75

0.67

0.58

65

1.00

0.91

0.82

0.73

0.64

0.55

(Continued)

8




125

120

115

110

105

100

95

45

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

50

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

55

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

60

1.00

0.93

0.86

0.79

0.71

0.64

0.57

0.50

65

1.00

0.92

0.85

0.77

0.69

0.62

0.54

0.46



135

130

125

120

115

110

105

100

95

45

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

50

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

55

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

60

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

0.50

0.44

65

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

0.47

0.40



145

140

135

130

125

120

115

110

105

100

45

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

50

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

55

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47

60

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

0.44

65

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

0.41

(Continued)


9



155

150

145

140

135

130

125

120

115

110

45

1.00

0.96

0.91

0.87

0.83

0.78

0.74

0.70

0.65

0.61

0.57

50

1.00

0.95

0.91

0.86

0.82

0.77

0.73

0.68

0.64

0.59

0.55

55

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

60

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

65

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47



175

170

165

160

155

150

145

140

135

130

45

1.00

0.96

0.93

0.89

0.85

0.81

0.78

0.74

0.70

0.67

0.63

50

1.00

0.96

0.92

0.88

0.85

0.81

0.77

0.73

0.69

0.65

0.62

55

1.00

0.96

0.92

0.88

0.84

0.80

0.76

0.72

0.68

0.64

0.60

60

1.00

0.96

0.92

0.88

0.83

0.79

0.75

0.71

0.67

0.63

0.58

65

1.00

0.96

0.91

0.87

0.83

0.78

0.74

0.70

0.65

0.61

0.57

110

1.00

0.93

0.86

0.79

0.71

0.64

0.57

0.50

0.43

0.36

0.29

120

1.00

0.92

0.83

0.75

0.67

0.58

0.50

0.42

0.33

0.25

0.17

130

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10 ——

140

1.00

0.88

0.75

0.63

0.50

0.38

0.25

0.13

——

——

——

150

1.00

0.83

0.67

0.50

0.33

0.17

——

——

——

——

——

160

1.00

0.75

0.50

0.25 —— —— —— —— —— —— ——

10


Table 1.1 (M) Hot Water Multiplier, P Th = 43°C Hot Water System Temperature Tm, Water Temperature at Fixture Outlet (°C)

Tc, CW Temp. (°C)

43

41

38

35

7

1.00

0.92

0.85

0.77

10

1.00

0.92

0.83

0.75

13

1.00

0.91

0.82

0.73

16

1.00

0.90

0.80

0.70

18

1.00

0.89

0.78

0.67

Th = 49°C Hot Water System Temperature Tm, Water Temperature at Fixture Outlet (°C)

Tc, CW Temp. (°C)

49

46

43

41

38

35

7

1.00

0.93

0.87

0.80

0.73

0.67

10

1.00

0.93

0.86

0.79

0.71

0.64

13

1.00

0.92

0.85

0.77

0.69

0.62

16

1.00

0.92

0.83

0.75

0.67

0.58

18

1.00

0.91

0.82

0.73

0.64

0.55



52

49

46

43

41

38

35

7

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

10

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

13

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

16

1.00

0.93

0.86

0.79

0.71

0.64

0.57

0.50

18

1.00

0.92

0.85

0.77

0.69

0.62

0.54

0.46

(Continued)


11

[Table 1.1 (M) continued] Th = 60°C Hot Water System Temperature Tc, CW Temp. (°C)


58

54

52

49

46

43

41

38

35

7

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

10

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

13

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

16

1.00

0.94

0.88

0.81

0.75

0.69

0.63

0.56

0.50

0.44

18

1.00

0.93

0.87

0.80

0.73

0.67

0.60

0.53

0.47

0.40



63

60

58

54

52

49

46

43

41

38

7

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

10

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

13

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47

16

1.00

0.94

0.89

0.83

0.78

0.72

0.67

0.61

0.56

0.50

0.44

18

1.00

0.94

0.88

0.82

0.76

0.71

0.65

0.59

0.53

0.47

0.41



68

66

63

60

58

54

52

49

46

43

7

1.00

0.96

0.91

0.87

0.83

0.78

0.74

0.70

0.65

0.61

0.57

10

1.00

0.95

0.91

0.86

0.82

0.77

0.73

0.68

0.64

0.59

0.55

13

1.00

0.95

0.90

0.86

0.81

0.76

0.71

0.67

0.62

0.57

0.52

16

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

18

1.00

0.95

0.89

0.84

0.79

0.74

0.68

0.63

0.58

0.53

0.47

(Continued)

12


[Table 1.1 (M) continued] Th = 82°C Hot Water System Temperature Tc, CW Temp. (°C) 7 10 13 16 18 43 49 54 60 66 71


79

77

74

71

68

66

63

60

58

54

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

0.96 0.96 0.96 0.96 0.96 0.93 0.92 0.90 0.88 0.83 0.75

0.93 0.92 0.92 0.92 0.91 0.86 0.83 0.80 0.75 0.67 0.50

0.89 0.88 0.88 0.88 0.87 0.79 0.75 0.70 0.63 0.50 0.25

0.85 0.85 0.84 0.83 0.83 0.71 0.67 0.60 0.50 0.33 —

0.81 0.81 0.80 0.79 0.78 0.64 0.58 0.50 0.38 0.17 —

0.78 0.77 0.76 0.75 0.74 0.57 0.50 0.40 0.25 — —

0.74 0.73 0.72 0.71 0.70 0.50 0.42 0.30 0.13 — —

0.70 0.69 0.68 0.67 0.65 0.43 0.33 0.20 — — —

0.67 0.65 0.64 0.63 0.61 0.36 0.25 0.10 — — —

0.63 0.62 0.60 0.58 0.57 0.29 0.17 — — — —

DELIVERED HOT WATER TEMPERATURE The generally accepted delivered hot water temperatures for various plumbing fixtures and equipment are given in Table 1.2. Both temperature and pressure should be verified with the client and checked against local codes and the manuals of equipment used.

Table 1.2 Typical Delivered Hot Water Temperatures for Plumbing Fixtures and Equipment Use Lavatory Showers and tubs Commercial and institutional laundry Residential dishwashing and laundry Commercial spray type dishwashing (as required by the NSF): Single or multiple tank hood or rack type: Wash Final rinse Single tank conveyor type: Wash Final rinse Single tank rack or door type: Single temperature wash and rinse Chemical sanitizing glassware: Wash Rinse

Temp. (°F) 105 110 140–180 140 150 180–195 160 180–195 165 140 75



13

Table 1.2 (M) Typical Delivered Hot Water Temperatures for Plumbing Fixtures and Equipment Use Lavatory Showers and tubs Commercial and institutional laundry Residential dishwashing and laundry Commercial spray type dishwashing (as required by the NSF): Single or multiple tank hood or rack type: Wash Final rinse Single tank conveyor type: Wash Final rinse Single tank rack or door type: Single temperature wash and rinse Chemical sanitizing glassware: Wash Rinse

Temp. (°C) 41 43 60–82 60 66 82–91 71 82–91 74 60 24


SAFETY AND HEALTH CONCERNS Scalding2 A research project by Moritz and Henriques at Harvard Medical College3 looked at the relationship between time and water temperature necessary to produce a first-degree burn. A first-degree burn, the least serious type, results in no irreversible damage. The results of the research show that it takes a 3-sec exposure to 140°F (60°C) water to produce a first-degree burn. At 130°F (54°C), it takes approximately 20 sec, and at 120°F (49°C), it takes 8 min to produce a first-degree burn. The normal threshold of pain is approximately 118°F (48°C). A person exposed to 120°F (49°C) water would immediately experience discomfort; it is unlikely then that the person would be exposed for the 8 min required to produce a first-degree burn. People in some occupancies (e. g., hospitals) as well as those over

2For more information regarding “Scalding,” refer to ASPE Research Foundation. 1989. Temperature limits in service hot water systems. Journal of Environmental Health. (June): 38–48. 3Moritz, A. R., and Henriques, F. C., Jr. 1947. The relative importance of time and surface temperature in the causation of cutaneous burns. American Journal of Pathology. 23: 695–720.

14


the age of 65 and under the age of 1 may not sense pain or move quickly enough to avoid a burn once pain is sensed. If such a possibility exists, scalding protection should be considered. It is often required by code. (For more information on skin damage caused by exposure to hot water, see Table 1.3.)

Table 1.3 Time/Water Temperature Combinations Producing Skin Damage Water Temperature °F Over 140 140 135 130 125 120

°C Over 60 60 58 54 52 49

Time (sec) Less than 1 2.6 5.5 15 50 290

Source: Tom Byrley. 1979. 130 degrees F or 140 degrees F. Contractor Magazine. (September). First published in American Journal of Pathology. Note: The above data indicate conditions producing the first evidence of skin damage in adult males.

Legionella Pneumophila (Legionnaires’ Disease) Legionnaires’ disease is a potentially fatal respiratory illness. The disease gained notoriety when a number of American Legionnaires contracted it during a convention. That outbreak was attributed to the water vapor from the building’s cooling tower(s). The bacteria that cause Legionnaires’ disease are widespread in natural sources of water, including rivers, lakes, streams, and ponds. In warm water, the bacteria can grow and multiply to high concentrations. Drinking water containing the Legionella bacteria has no known effects. However, inhalation of the bacteria into the lungs, e.g., while showering, can cause Legionnaires’ disease. Much has been published about this problem, and yet there is still controversy over the exact temperatures that foster the growth of the bacteria. Further research is required, for there is still much to be learned. It is incumbent upon designers to familiarize themselves with the latest information on the subject and to take it into account when designing their systems. Designers also must be familiar with and abide by the rules of all regulating agencies with jurisdiction.


15

RELIEF VALVES Water heating systems should be protected from excessive temperatures and pressures by relief valves. Temperature and pressure relief valves are available either separately or combined. Typically they are tested to comply with the standards of the American Society of Mechanical Engineers (ASME), the American Gas Association (AGA), or the National Board of Boiler and Pressure Vessel Inspectors (NBBPVI) and are so labeled. The designer should verify which agency’s standards are applicable to the water heating system being designed and follow those standards for the sizes, types, and locations of required relief valves.

THERMAL EXPANSION Water expands as it is heated, and some way to allow for this expansion should be provided in a domestic hot water system. Use of a thermal expansion tank in the cold water piping to the water heater will do this. It is recommended that the designer contact the manufacturer of the thermal expansion tank for information on installation and sizing. The plumbing code requires some type of thermal expansion compensation—expecially when there is either a backflow prevention device on the cold water service to the building or a check valve in the system.

CONTROLS The control components for water heaters differ depending on the type of heater and the manufacturer. Generally, water heater controls should be checked with the equipment manufacturer. Also, the various regulatory and testing agencies have requirements for controls that depend on the size and type of equipment used.

STORAGE AND RECOVERY The design of a domestic water heating system begins with estimating the facility’s load profile and identifying the peak demand times. To accomplish these steps, the designer must conduct discussions with the users of the space, determine the building type, and learn of any owner requirements. The information thus gathered will establish the required capacity of the water heating equipment and the general type of system to be used. With fuel

16


fired equipment, to avoid condensation, the equipment and the operating temperature should be selected to ensure that the heater’s operating temperature is not lower than the dewpoint temperature of the flue gas.

Stratification There is a natural tendency of warm water to rise to the top of a storage tank. The result of this rising action, known as “stratification,” occurs in all unrecirculated tanks. It has been found that the percent useable storage volume in stratified horizontal and vertical tanks has a range of 65–75% to 80–90%, respectively. Not all tanks are created equal; the percent usable storage volume can be affected by such items as the flow rates, the points of connection, tank capacity and by tank recirculation systems. Stratification during recovery periods can be reduced significantly by mechanical circulation of the water in the tank. During periods of demand, however, it is useful to have good stratification since this increases the availability of water at a usable temperature. If, for example, a tank were stratified with the top half at 140°F (60°C) and the bottom half at 40°F (4°C), this tank, in theory, could still deliver half its volume at 140°F (60°C). But, if the two layers were completely mixed, the tank temperature would drop to 90°F (32°C), which, in most cases, is an unusable temperature.

CODES AND STANDARDS The need to conform to various codes and standards determines many aspects of the design of a domestic hot water system as well as the selection of components and equipment. Some of the most often used codes and standards are: 1. Regional, state, and local plumbing codes. 2. American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)/IES 90.1. 3. ASME code for fired and unfired pressure vessels. 4. ASME and AGA codes for relief valves. 5. Underwriters’ Laboratories (UL) listing for electrical components. 6. National Sanitation Foundation (NSF) listing. 7. AGA approval for gas burning components.


17

8. National Fire Protection Association (NFPA) standards. 9. National Electrical Code (NEC). In addition, the federal government, the agencies with jurisdiction over public schools and public housing, and many other agencies have specific requirements that must be observed when designing projects and selecting equipment for them.

SYSTEM ALTERNATIVE CONSIDERATIONS The design and selection of water heating systems are part of a process that involves assumptions, decisions, and trade-offs. The general organization of this manual separates application considerations and load determinations (Section I) from the selection of equipment (Section II). While this is possible for most conventional water heating systems, it does not yield the optimum solution for many advanced, high-efficiency water heating systems. These systems include refrigerant-based systems like heat pump water heaters; refrigeration heat reclaim systems; and multifunction, full-condensing equipment. These and other systems like solar water heaters have a higher cost per unit of heating capacity than most conventional systems. Often the most cost-effective configuration for these systems tends to use higher storage volumes and lower heating rates than those recommended in the following chapters. These systems are frequently configured as hybrid systems, combining both an advanced high-efficiency system as the primary, base-loaded water heater and a conventional water heater for “peaking” or supplemental water heating. Advanced, high-efficiency systems may offer significant benefits; however, their design and selection is necessarily more detailed. The seasonal and instantaneous efficiency and output of these systems vary greatly with operating conditions. Because they are not selected to meet the peak water heating load, load calculations must address not simply the peak but the water heating load shape. Their higher cost per unit of heating capacity as compared to most conventional systems places a higher premium on accurate load determination since oversizing has a more marked effect on system cost. Other considerations such as a building’s cooling load or waste heat availability may also come into play. The capacities of these systems and any related supplemental water heating equipment should be selected to achieve high average daily run time and the lowest combination of operating and equipment cost.

Multifamily Buildings

2

19

MULTIFAMILY BUILDINGS

INTRODUCTION When selecting and sizing domestic water heaters for multifamily buildings, the designer must take into consideration the variables affecting hot water demand that are unique to each particular project. (Note: Certain government agencies have their own design criteria, which must be strictly followed.) Demand is a function of the anticipated hot water usage of the occupants of a particular building during the period being considered. It is affected by the population of a project as well as the behavioral patterns of those occupants and the amenities offered them. Note that the design guidelines in this chapter are based on a large amount of monitored data from occupied buildings, which was collected during recent research efforts.

BACKGROUND In order to design a domestic hot water (DHW) system for multifamily buildings properly it is useful to understand the consumption and demand patterns of this type of occupancy.

Weekday Vs. Weekend Demand Patterns The weekday vs. weekend comparison of DHW, in gallons (liters), consumed in buildings reveals that there are generally a slightly higher total consumption and a greater peak demand on weekNote: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

20


ends (Saturday and Sunday) than on weekdays (Monday through Friday). This phenomenon is true in all seasons. The average weekend day consumption is 7.5% greater than the average weekday level. (Refer to Figure 2.1.) Peak demand times are also found to vary from weekdays to weekends. This is a function of the standard nine-to-five workday. Therefore, the weekend will be used as the highest demand period.

Weekday vs. Weekend Consumption Gallons (Liters) per Capita, Composite

Figure 2.1 Source: Goldner 1994, Energy use and DHW consumption research project, pp. 4–6.

Seasonal Demand Patterns Multifamily buildings have distinct seasonal variations in DHW demand levels. Since demand must be calculated using a worstcase scenario, and weekend consumption is known to be greater for multifamily buildings than weekday consumption, the effect of the seasonal influence is best seen in terms of weekend consumption. Figure 2.2 indicates that DHW demand is greater in winter than in any other season, the obvious explanations being that people take warmer showers in the winter and cooler ones


21

Seasonal Variations, Weekend Consumption Gallons (Liters) per Capita

Figure 2.2 Source: Goldner and Price 1994, p. 2.107.

in the summer and that (particularly in colder climates) the cold water to be mixed down is considerably cooler in winter and requires greater volumes of DHW. The variance can account for as much as a 45% reduction in demand from winter to summer. Using summer as the base consumption, daily average consumption rises by 10% in the fall then goes up 13% more (compounded) during the winter period. Consumption then falls by 1% (compounded) in the spring and falls another 19% (compounded) during the summer period (e.g., 100 gal × 1.10 × 1.13 × 0.99 × 0.81 = 99.7 gal). (The spring consumption is comparably higher than fall consumption, due in large part to considerably colder inlet water temperatures in spring.)

Demand Flow Patterns There is a distinct difference between weekday and weekend DHW demand patterns. Weekdays have minimal overnight usage, then a morning peak, followed by lower afternoon demand and then

22


an evening or nighttime peak. Weekend days have just one major peak, which begins later in the morning and continues until around 1:00 to 2:00 P.M. Usage then tapers off for the rest of the day. Examination of the composite weekday and weekend graphs illustrates that the weekend day peak is greater than any of the weekday peaks. In the composite weekday curve (Figure 2.1), two morning peaks can be observed, the first between 6:00 and 8:00 A.M. and the second between 9:30 A.M. and noon. It is possible to observe, by studying individual buildings, that particular sites fall into one or the other of these two peaks. Some general knowledge of the tenant populations may serve to explain this difference. Buildings occupied by large numbers of working tenants and middle-income populations appear to have the early morning peak; buildings with large percentages of children fall into the later morning peak (especially so during the summer period). Figures 2.2 and 2.3 clearly illustrate the seasonal variation in both the

Seasonal Variations, Weekend Consumption Gallons (Liters) per Capita

Figure 2.3 Source: Goldner and Price 1994.


23

usage patterns and consumption levels for summer, fall, winter, and spring. Note that the highest-peaking level occurs during winter weekends.

IDENTIFICATION OF DEMAND The first step the designer must take in calculating demand is to determine the demographic profile of the project and building occupants. Different types of building occupants have been found to have fairly predictable patterns of hot water consumption. Users can be divided into three categories—“low,” “medium,” and “high-volume” water consumers (LMH)—as a function of the building and occupant demographics. Table 2.1 shows a variety of occupant characteristics. One or some combination of these should closely describe any particular multifamily building. For example, a luxury condominium in an area inhabited predominantly by young couples will tend to fall into the “all occupants work” category of low anticipated water consumption. By contrast, a low-income housing project will generally fall somewhere between the “low-income” and “no occupants work” categories of high-volume water consumption. Keep in mind that the presence of an abundance of hot water consuming appliances, such as washing machines or dishwashers, tends to increase hot water consumption. Therefore, if the condominium in the above example intended or allowed for the future installation of a washing machine in each unit, its demographic category should be raised from low to medium. It is up to the designer to ask the necessary questions of the developer, architect, or building manager in order to determine this category. Remember, in the face of uncertainty, be conservative. It is important to note that Table 2.1 represents a graduated scale of residents’ use of DHW. Quite often a building is occupied by people from more than one of the demographic categories given in this table. In such a case, the designer should weight the demographic breakdown to select a low, medium, or high factor. After some experience with this methodology, the designer may decide that some buildings fall between groupings and select a medium-high or low-medium category. In such instances, the designer can extrapolate from the values in Table 2.2. The characteristic “high population density” in Table 2.1 is sometimes overlooked—and it shouldn’t be. This characteristic is important in the selection of the LMH factor and, thus, in system sizing. Even though a building’s other demographic factors

24


might place it in a higher LMH factor category, the existence of a high population density means a relatively lower factor (see Table 2.1). This factor must be weighted along with the other building characteristics when choosing the site’s other LMH factor. High population density is a low factor because the number of end use appliances (e.g., showers and faucets) are unaffected by the number of occupants in an apartment. A higher population density will also result in a diversity effect.

Table 2.1 Occupant Demographic Characteristics Demographic Characteristics No occupants work (stay at home) Public assistance and low income (mix) Family and single-parent households (mix) High percentage of children Low income Families Public assistance Singles Single-parent households Couples High population density Middle income Seniors One person works, 1 stays home All occupants work

LMH Factor

High

Medium

Low

Source: Goldner 1994, Energy use and DHW consumption research project.

DEMAND DETERMINATION Once the LMH factor has been determined, values for hot water demand and consumption can be selected from Table 2.2. Thus, anticipated consumption values can be determined using the known building population for intervals of 5 min, 15 min, 30 min, 1 h, 2 h, and 3 h. These values will be used later in selecting and sizing domestic hot water equipment.


25

Table 2.2 Low, Medium, and High Guidelines: Hot Water Demands and Use for Multifamily Buildings Peak 5 Min, gal (L)/person

Peak 15 Min, gal (L)/person

Peak 30 Min, gal (L)/person

Maximum H, gal (L)/person

Low

0.4 (1.5 )

1.0 (4.0)

1.7 (6.5)

2.8 (10.5)

Medium

0.7 (2.6)

1.7 (6.4)

2.9 (11.0)

4.8 (18.0)

High

1.2 (4.5)

3.0 (11.5)

5.1(19.5)

8.5 (32.5)

Maximum 2 H, gal (L)/person

Maximum 3 H, gal (L)/person

Low

4.5 (17.0)

6.1 (23.0)

20.0 (76.0)

14.0 (54.0)

Medium

8.0 (31.0)

11.0 (41.0)

49.0 (185.0)

30.0 (113.6)

14.5 (55.0)

19.0 (72.0)

90.0 (340.0)

54.0 (205.0)

High

Maximum Day, gal (L)/person

Average Day, gal (L)/person

Source: Goldner and Price 1994. Note: These volumes are for DHW delivered to the tap at 120ºF (49ºC).

Both research and practical experience in different areas of North America indicate that there are geographical variances in DHW use. There is, however, no distinct pattern that can be identified with the available data. Note that the figures presented (in Table 2.2) are for central systems. Individual apartment water heater systems are likely to have lower levels of consumption. This is because individual apartment units generally are set up as pay-as-you-go systems (with the occupant paying directly for the energy used by the heater). While there are no hard data on DHW systems on this issue, there are numerous well-documented studies of other energy uses that demonstrate that, once an apartment occupant has to pay for what he or she uses, consumption decreases. In fact, studies of conversions from electrical master metering to submetering in multifamily buildings have shown that consumption decreases between 20 and 30% when people must pay for what they use.1 The practice of defensive oversizing applied to the guidelines given in Table 2.2 will only exaggerate the capital and energy inefficiencies experienced in the past. It is therefore important for the designer to recognize the inherent safety nets in the LMH approach. First, and most important, we are using a building’s 1Hirschfeld, H.E., et al. 1996. Facilitating submetering implementation. Report No. 96-7. Prepared for New York State Energy Research and Development Authority.

26


maximum probable occupancy, which may never actually occur. Second, we are designing a system with the capabilities to satisfy the higher volume, short duration (near instantaneous) peaks (as delineated in Table 2.2), which in reality only occur a limited number of times during the year. Even if the system were not able to satisfy those loads, the result would be occupants experiencing slightly lower-temperature hot water at their taps for some short duration of time.

APPLICATION OF LMH VALUES Once a portion of the range has been selected, the figures should be converted into per apartment or per building gallonage (liter usage) by multiplying them with maximum probable occupancy levels, based on persons per apartment size/type. For example, studios = 2 persons, 1-bedroom apartments = 3 persons, and 2bedroom apartments = 3–5 persons. These populations may be dependent on local standards or regulations. Additionally, in order to calculate building energy consumption for DHW or to prepare energy budgets, the average daily figures can be converted into per apartment or per building gallonage (liter usage) by multiplying them with existing building occupancies.

PEAK DEMAND VS. AVERAGE DEMAND Potential of Generating Storage Figure 2.4 illustrates the actual consumption curve of a sample building. The bottom line, 0.75 gal (2.84 L) represents average consumption (for a 15-min period, the period for which all data are taken). This is equivalent to leveling the building’s DHW consumption across the entire day. Under one possible scenario, the building’s DHW needs would be met by generating storage during low-consumption periods (represented by the white areas under the line), which would be used during peak times. The other two lines illustrate levels of 10 and 25% excess capacity, respectively.

Time of Day of Peak Flows While flow curves show the general usage patterns of a building, peak times and flows are used to identify demands on the boiler or hot water heater more closely. Maximum 5, 15, 60, 120, and


27

Storage Potential – Bldg 7 (Fall) Gallons (Liters) per Occupied Apt. – Weekday

Figure 2.4 Consumption curve.

180-min demand times occur essentially coincidentally during both the weekend and weekday peaks. The concurrence of these peaks justifies the use of the longer duration peak consumption levels for storage models. The most frequent minimum 60-min consumption periods occur at 4:00 A.M. on both weekdays and weekend days. This demand period data should be used when evaluating DHW system sizing and storage options.

Peak Demand and Average Demand Five, 15, 60, 120, and 180-min maximum demand and hourly average consumption figures may be used to examine peak demand needs in contrast to total volume (average) consumption. This type of analysis is useful in setting new system design and sizing parameters and evaluating a mix of instantaneous generation and storage options. Monitored studies have revealed that, in comparison to use in a maximum 60-min period, average hourly

28


consumption is only 42% of peak consumption. This suggests the possibility of generating storage capacity to meet peak demand during the hours of the day with below average demand. Comparison of the 5 and 15-min peak periods demonstrates that the highest (5-min) peak requires 40% of the DHW consumed within the peak 15 min. Review of the 15 and 60-min peak periods reveals that the highest (15-min) peak is equal to one third of the DHW consumed in the peak hour. Finally, there is slightly (27%) more DHW consumed in the average hour than in the highest 15-min period of the day; this again makes a case for some type of off-peak generation and storage strategy.2 Figure 2.5 illustrates that consumption during the peak 60-min period is 61% of consumption during the maximum 120-min period and that the volume of DHW used to satisfy the 120-min maximum demand is 75% of what is needed during the peak 180-min span. In Figures 2.6 and 2.7 we can see how all of the peak volumes contribute to the 1-h and 3-h peak demand on the DHW generation and/or storage system. These relationships can be used to model various configurations of hot water supply system. As noted earlier, all these peak consumption demands occur concurrently and must be considered in the context of overall consumption patterns to further evaluate generation and storage options.

RETROFIT TO EXISTING SYSTEMS (CUSTOMIZED SIZING) If customizing is desired for an existing building, to select the most appropriate system sizing levels it would be ideal to monitor the current consumption for a short period. Research suggests that the best time to conduct this monitoring in multifamily housing applications is during a series of anticipated winter weekend peak periods. The design engineer should focus on and identify the 2 to 3-h peak periods that generally occur between 10:00 A.M. and 2:00 P.M. A system designed to meet these demands should satisfy all other year-round requirements. If this is not possible or practical, use the guidelines in Table 2.2. The designer should consult with the owner to determine if there have been problems with the current system.

2Goldner and Price 1994.


29

Comparison of DHW Peak Consumption Gallons (Liters) per Capita, Winter

Figure 2.5 Source: Goldner 1994, DHW system sizing criteria for multifamily buildings.

Parts of 3-Hour DHW Peak Consumption Gallons (Liters) per Capita, Winter

Figure 2.6 Source: Goldner 1994, Energy use and DHW consumption research project, pp. 4–20.

30


Parts of Peak 60 Minutes DHW Consumption Gallons (Liters) per Capita, Winter

Figure 2.7 Source: Goldner and Price 1994, p. 2.110.

Research on Generation Rate and Storage Capacity Recent research3 reveals that the most cost-efficient designs for conventional water heating equipment in multifamily buildings are based on either the “30/3 guideline” (systems with generators and storage tanks) or the 5-min peak demand (instantaneous systems). (If other advanced technologies that were not included in the investigation are utilized, the 30/3 or 5-min peak demand guidelines may not be appropriate. For example, hybrid systems, combining both a conventional “peaking” water heating capability with a baseload advanced high-efficency system, would tend to use more storage and have lower heating rates.) According to the 30/3 guideline, generator size is based on the peak 30-min demand and storage tank volume is based on the maximum 3-h demand. The research indicates that selection of either an instantaneous hot water heater or a separate DHW boiler and unfired storage tank configuration will produce the optimum mix of low life cycle costs and high energy efficiencies. The optimum configurations were found to be as follows: 1. For small to midsized buildings (up to 80 apartments), either a separate DHW boiler with tank system sized to the 30/3 guideline, or an instantaneous system (based on the peak 5-min demand). 3Goldner and Price 1996.


31

2. For mid to large-sized buildings (>75 apartments) and large buildings (100+ apartments), which fall toward the upper end of the LMH classification scale (i.e., toward the “high” category), an instantaneous system. 3. For buildings with more than 125 apartments, a diversification factor that lowers the probability of coincident demand should also be employed.

EXAMPLES Example 2.1 Traditional Multifamily Building Consider a 58-unit apartment building where occupants are a mix of families, singles, and middle-income couples and most of the adults work. There is a public laundry in the basement with a few washers, and the leases prohibit both washing machines and dishwashers in the apartments (although conversations with the owner confirm that a moderate number of people have such appliances). Step 1 Compute the maximum probable occupancy based on local standards/expectations and conversations with the building owner, manager, or architect. For example, multiply the number of 3-bedroom apartments (4) by the maximum number of persons in each apartment (5) to determine the total number of persons (20). This is then added to the resultant sum from all the other apartment sizes, as follows. Apt. Size

Maximum No. Persons/Apt.

No. of Apts.

3-bedroom apts. 2-bedroom apts. 1-bedroom apts. Studios Building total (rounded)

4 14 25 15

× × × ×

5 4 3.5 2.25

= = = =

20 56 87.5 33.75 198 persons

Note: The designer needs to determine the optimum usage and occupancy of the facility. For example, in some facilities, the demographic profile may require using 3, 4, or 7 occupants per 3-bedroom apartment.

32


Step 2 Determine the low, medium, or high usage factor (demographic profile) of the project and building occupants from Table 2.1, based on knowledge of the building, conversations with the building owner, and observations. Consider the effect of either currently installed or possible future additions of appliances (e.g., washers), which might move a building to a higher usage category. Based on the information above, the medium usage factor is selected. Step 3 Estimate the DHW consumption. To estimate how much hot water is used in a building for energy consumption or savings calculations, use the LMH factor and the average day hot water value in Table 2.2 (LMH guidelines). If the building is existing, substitute the maximum probable occupancy from Step 1 with the actual current (or estimated) occupancy level. Current LMH No. of Demand System Factor People Category Load Medium

153 ×

Average day: 30.0 gal/capita = 4590 gal/day (113.55 L/capita) (17 373.15 L/day)

Step 4 Size the equipment. Follow Steps A and B, below, for either “Instantaneous Systems” or “Generation and Storage Systems,” depending on the equipment used. Instantaneous systems For either an instantaneous, DHW-only system or a tankless coil in a combination heating DHW boiler, follow the two steps below. First find the system load in gallons per hour (gph) (liters per hour [L/h]) based on the peak 5-min demand. Next, convert this to a Btu/h (kJ/h) rating. This can then be used to select equipment.


33

Step A Compute the system load using the LMH factor and the 5-min peak demand values in Table 2.2 (LMH guidelines). LMH Factor

Peak No. of People

No. Periods/ H

Demand Category

Peak 5 min: 198 × 0.7 gal/capita × 12 = (2.65 L/capita)

Medium

System Load 1663 gph or 27 gpm (6294.46 L/h or 1.75 L/sec)

Step B Convert the system load to a Btu/h (kJ/h) rating. System Conversion Load 1663 gph (6.30 m3/h)

×

8.33 × lb/gal (4188.32 kJ/m3)

Temp. Rise

1/Boiler Efficiencya

90ºF × (50K)

1 = 0.8

Heater Input 1,558,439 Btu/h (1 649 151 kJ/h)

aThe efficiency can be represented as either a decimal (as shown) or a percentage, e.g., 80%.

Instantaneous DHW-only heater If sizing an instantaneous DHW-only heater, the 1,558,439 Btu/h (1 649 151 kJ/h) should be the size of the DHW heater. (Note: A higher efficiency should be used for sizing an instantaneous heater; use 85% or the efficiency specified in the equipment documentation.) Combination heating/DHW boiler When sizing the tankless coil of a combination heating/DHW boiler, the calculated recovery rate is used to size the coil. The additional load capacity for the DHW system must be added to the space heating load to select the size of the combination space heating/domestic hot water boiler.

34


Generation and storage systems For a system with a mix of generation and storage, use the following two steps: Calculate the generator size based on twice the peak 30-min period to get a Btu/h (kJ/h) rating, then calculate the storage tank volume based on the maximum 3-h demand. Step A Compute the system load using the peak 30-min and maximum 3-h hot water values in Table 2.2. LMH Factor

No. People

Medium 198

LMH Factor Medium

×

Peak 30 min: 2.9 gal/capita × (10.98 L/capita)

No. People 198

No. Periods/ H

Demand Category

2

=

1148 gph (4348.08 L/h)

Demand Category Maximum 3 h: 11.0 gal/capita = (41.64 L/capita)

×

System Load

Storage Volume 2178 gal (8244.73 L)

Step B Convert the load into equipment ratings. System Load Conversion 1148 × 8.33 gph lb/gal (4.35 (4188.32 m3/h) kJ/m3)

Temp. Rise ×

90ºF (50K)

1/Boiler Efficiencya ×

1 = 0.80

Heater Input 1,075,820 Btu/h (1 017 362 kJ/h)

aThe efficiency can be represented as either a decimal (as shown) or a per-

centage, e.g., 80%.

The 1,075,820 Btu/h (1 017 362 kJ/h) is the size of the hot water heater. This heater should then be used to supply 2100 gal (7948.50 L) in unfired storage tanks.


35

Example 2.2 Special Use Housing Facility There is a residential building in New York City that houses the families of children who have cancer and are receiving treatment at area hospitals. There are 88 residential studios, each with a single bath. There are 18 kitchen units, which are centrally located for shared use by the families. Each unit has a sink and dishwasher. There is a washing machine on each of the occupied floors. The families who occupy this residence do so because they cannot afford to stay in more expensive accommodations. Often, a child is accompanied by a single parent and together they occupy one studio for the duration of the treatment program. Calculate the 5-min, 15-min, 30-min, 1-h, 2-h, and 3-h consumption. Plot the demand vs. time curve. Solution Since this demographic group includes occupants who presently do not work (they are away from home) and has a high percentage of children, it definitely falls into the high demand category according to Table 2.1. There are 88 units with 2 occupants per unit, so the total population is 176 people. According to Table 2.2 the 5-min peak, 15-min peak, 30-min peak, 1-h peak, 2-h peak, and 3-h peak demand factors are 1.2, 3.0, 5.1, 8.5, 14.5, and 19 gal (4.5, 11.4, 19.3, 32.2, 54.9, and 71.9 L), respectively. Therefore, the anticipated demand is as follows: Demand Category 5-min peak 15-min peak 30-min peak 1-h peak 2-h peak 3-h peak

Demand Category 5-min peak 15-min peak 30-min peak 1-h peak 2-h peak 3-h peak

No. People 176 176 176 176 176 176

Demand Factor (gal) × × × × × ×

No. People 176 176 176 176 176 176

1.2 3.0 5.1 8.5 14.5 19

Demand (gal) = = = = = =

Demand Factor (L) × × × × × ×

4.5 11.4 19.3 32.2 54.9 71.9

211 528 898 1496 2552 3344

Demand (L) = = = = = =

792 2 006.4 3 396.8 5 667.2 9 662.4 12 654.4

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The equipment selected must be capable of supplying this peak load (see Figure 2.8) by means of either combined storage (first draw) capacity and recovery or instantaneous generation.

POSSIBLE TRAPS In order to avoid falling into a trap that leads to miscalculating water demand, the designer must try to learn all of the unique facets of a multifamily building. This is generally accomplished by compiling a list of questions for the owner/manager/architect during a project brainstorming session. Does the building have a central laundry? If so, the designer should select the next higher LMH value than otherwise would have been selected. Does the building have retail spaces that might be used in the future for a restaurant or other large water consuming application? If so, will the building be obligated by lease to provide hot water for the tenant? Would such a provision be a desirable selling point for the retail space to the owner? The demand will then have to be increased accordingly. For large restaurants or laundries, the

Peak Demand Curve

Figure 2.8 Source: Goldner and Price 1996, p. 8.


37

resulting flow should be added to the building’s demand. Do tenants pay for the utilities used to generate hot water? If so, hot water consumption might decrease. Do water conserving laws that restrict water flow exist in the area (as they do in New York)? Or is there an abundance of water in the area (such as there is in Chicago) with showers allowed to flow more water? (The designer should review local codes concerning water conservation requirements that may impact the hot water demand.) Is this a building with European occupants who tend to bathe rather than shower? (Bathing is believed to consume considerably more water than showering.) This is the sort of creative thinking required to accurately gauge water demand. Remember one thing especially: People never complain about having too much hot water, but we do not want to oversize the equipment as this saddles the owner/operator with both increased initial equipment costs (resulting from larger-than-necessary equipment) and higher annual energy/operating costs (resulting from lower, seasonal efficiencies due to increased cycling of equipment operating farther from full load).

BIBLIOGRAPHY Carpenter, S. C., and J. P. Kokko. 1988. Estimating hot water use in existing commercial buildings. ASHRAE Transactions. 94(2): 3–12. Ciz, J. B. 1986. Performance of domestic hot water systems in five apartment buildings (Part I—Installation and commissioning). OHRD Rpt. 86–77–K. Decioco, J., and G. Dutt. 1986. Domestic hot water service in Lumley Homes: A comparison of energy audit diagnosis with instrumented analysis. Proceedings of the 1986 ACEEE Summer Study on Energy Efficiency in Buildings. Goldner, F. S. 1994. DHW system sizing criteria for multifamily buildings. ASHRAE Transactions. 100(1): 147–165. Goldner, F. S. 1994. Energy use and DHW consumption research project: Final report–Phase 1. Report no. 94–19. Prepared for New York State Energy Research and Development Authority. Goldner, F. S., and D. C. Price. 1994. Domestic hot water loads, system sizing and selection for multifamily buildings. Proceedings of the 1994 ACEEE Summer Study on Energy Efficiency in Buildings. Goldner, F. S., and D. C. Price. 1996. DHW modeling: System sizing and selection criteria, Phase 2—Interim project report no. 1. Prepared for New York State Energy Research and Development Authority. Milligan, N. H. 1987. Performance of domestic hot water systems in five

38


apartment buildings, Part II—Analysis and results. OHRD report 87–53–K. Pearlman, M., and N. H. Milligan. 1988. Hot water and energy use in apartment buildings. ASHRAE Transactions. Vol. 94, Pt. 1. Taylor, H., and F. Force. 1986. Patterns of domestic hot water consumption for a multifamily building. Proceedings of the 1986 ACEEE Summer Study on Energy Efficiency in Buildings. Thrasher, W. H., and D. W. DeWerth. 1993. Comparison of collected and compiled existing data on service hot water use patterns in residential and commercial establishments—Phase II final report. American Gas Association Laboratories, ASHRAE research project 600–RP. Vine, E., R. Diamond, and R. Szydlowski. 1987. Domestic hot water consumption in four low income apartment buildings. Energy. Vol. 12, No. 6. Werden, R. G., and L. G. Spielvogel. 1969. Sizing of service water heating equipment in commercial and institutional buildings. Report No. 2, Project RP61. New York: Edison Electric Institute.

Dor mitories Dormitories

3

39

DORMITORIES

INTRODUCTION This chapter covers two types of buildings classified as dormitories. The first type is a student dormitory or similar housing that has a nonstructured use of hot water. The second type is an institutional type dormitory, similar to that at a military school, that has a structured hot water use.

STUDENT DORMITORIES The peak demand for hot water for this type of building is more spread out. Students tend to create schedules based upon when their classes are held. Additional hot water demand that could be anticipated is laundromat type clothes washers and possibly a residential type kitchen. This type of building tends to have multistory units.

Example 3.1 Student Dormitory The dormitory consists of two buildings four stories high joined by a high-ceiling commons, which encloses a basketball court and a tennis court. The major sleeping areas are arranged around 156 three-bedroom suites with 60 double rooms and 12 single bedrooms for resident advisers. Each room and suite has a bathroom and each suite has a kitchen alcove. There are kitchen alcoves and coin-operated laundry facilities located on each floor. On the ground floor there are food kiosks and a computer lab. The buildings have a mirror configuration with half of the suites Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

40


and rooms in each building. The laundry facility on each floor consists of two washers and two dryers for a total of eight washers in each building. Assumptions 1. The food kiosks provide their own water heating when the spaces are leased out. These food venders are similar to those found in airports and mall food courts. 2. There is a central mechanical space that serves both buildings where the water heaters and storage tanks are located. 3. A separate circulated hot water system is required for each building. 4. A minimum of two water heaters are required, with each having 65% of both buildings’ required capacity. This allows the building to operate with minimum disruptions if one heater is down for repairs. 5. As the coin-operated laundry facilities are an integral part of the building, the hot water required is calculated as part of the central system. 6. The water distribution temperature used is 120ºF (49ºC). Pressure balance or thermostatic shower valves are used at each bathroom group. 7. The suites have shower/bathtub combinations and the double and single rooms have only showers. We will use the demand for showers in our calculation. 8. Each building houses 300 students and advisors. 9. The flow from fixtures is as follows: Showers = 2.5 gpm (0.158 L/s) Kitchen sinks = 2.5 gpm (0.158 L/s) Lavatories = 1.5 gpm (0.095 L/s) 10. An outside laundry service is available to students, and some students will bring their laundry home. This will reduce the demand on the coin-operated clothes washers. Laundry detergents today are designed to get clothes clean using only cold water and many items are recommended to be washed in cold water. This reduces the demand for hot water for clothes washing. For this application we calculate that each wash cycle will use no more than 10 gal (37.9 L) for washing and 10 gal (37.9 L) for rinsing for a total of 20 gal (75.7 L). Each machine is calculated to go through two cycles during the peak design hour.


41

11. Students tend to wash dirty dishes on an infrequent basis. Therefore, the dishwasher load is lumped in with the kitchen sink by increasing the demand from 10 gph (37.9 L/h) to 15 gph (56.8 L/h). Fixtures each building Showers Suites = 78 Double rooms = 30 Single rooms = 6 Public restrooms Floor kitchen areas = 4

78 30 6 — — —— 114

Lavatories 78 30 6 4 — —— 118

Kitchen Sinks

Dishwashers

78 — — — 4 —— 82

78 — — — 4 —— 82

Coin-operated clothes washers = 8 Mop sinks = 4

Calculations1 Showers Lavatories Kitchen sinks Mop sinks

114 × 30 gph = 3420 gph 118 × 2 gph = 236 gph 82 × 15 gph = 1230 gph 4 × 20 gph = 80 gph Gross demand 4966 gph Demand factor × 0.30 1490 gph

Clothes washer: 8 × 20 gal × 2 cycles/h = 320 gph Heater sizing: 320 gph + 1490 gph = 1810 gph demand Tank storage: Using a percent useable storage capacity of 80%, the demand is, thus, 1810 gph ÷ 0.80 = 2263 gal. (Showers Lavatories Kitchen sinks Mop sinks

114 × 114 L/h = 12 996 L/h 118 × 7.6 L/h = 896.8 L/h 82 × 56.8 L/h = 4657.6 L/h 4 × 75.7 L/h = 302.8 L/h Gross demand 18 853.2 L/h Demand factor × 0.30 5656 L/h

1 Calculations for showers, lavatories, and mop sinks are based on ASPE Data Book, looseleaf Chap. 4, “Service Hot Water Systems,” Table 7.

42


Clothes washer: 8 × 75.7 L × 2 cycles/h = 1211.2 L/h Heater sizing: 1211.2 L/h + 5656 L/h = 6867.2 L/h demand Tank storage: Using a percent useable storage capacity of 80%, the demand is, thus, 6867.2 L/h ÷ 0.80 = 8584 L.) Student dormitory conclusions 1. Remember the calculated demand of 2130 gph is for only half the building. The total building recovery demand is 4260 gph and 5330 gal storage. 2. The amount of the storage required indicates a separate water heater and storage tank arrangement. 3. The water heaters should each have a 4260 gph × 0.65 = 2970 gph (16 126 L/h × 0.65 = 10 482 L/h) recovery. 4. The circulation system shall be arranged in a way that eliminates stratification in the storage tanks. 5. Piping arrangement and valving should be set up to isolate water heaters for maintenance purposes. 6. The path of access to water heaters should be reviewed to ensure that it allows replacement in the future.

INSTITUTIONAL DORMITORIES The hot water requirements for this type of building are based upon the shower and lavatory use occurring during a very short period of time because of schedules. Any additional hot water demand will be from kitchens, dining facilities, and possibly a laundry. These specialized areas should have a separate water heating system. (Refer to the chapter “Laundries” in this manual.) Note that there will be a short time in the morning (2 h) and that evening will be longer but less intense (4 to 5 h).

Example 2.2 Institutional Dormitory The building selected is a two-story coeducational unit with housing for 272 students and advisors. The arrangement is for 68 four-person bedroom groups, each of which will have 1 shower and 2 lavatories requiring hot water. There will be 30 one-person advisor bedrooms, each with a shower and lavatory. A parlor area is provided with a connected residential kitchen area with separate public toilets. A central kitchen, dining area, and laun-


43

dry are provided in a separate building with a separate domestic water heating system. Assumptions 1. Shower use will tend to be quick, in and out, with large numbers of people using hot water at the same time. 2. The peak hour usage will be early in the morning and after 5:00 P.M. This allows a long recovery time. The time selected for this example is 4 h (see note above). 3. The kitchen sink/dishwasher and mop sinks will not be used during the peak hour. 4. Recovery capacity and 80% of storage will have to meet total demand. 5. Recommend two water heaters with a capacity of 65% of the demand calculation. Calculations Student showers: Advisor showers: Lavatories:

68 heads × 7 min × 4 persons × 2.5 gpm =

4760 gph

30 heads × 7 min × 2.5 gpm =

525 gph

170 fixtures × 2 gph × 0.30 usage factor =

102 gph

Total peak hour demand

5285 gph

5285 gph = 1321 gph minimum recovery 4h Water heater sizing: 1321 gph × 0.65 = 858 gph each heater Storage tank sizing: 5285 gal – 1321 gph = 3964 gal storage required (Student showers: 68 heads × 7 min × 4 persons × 0.158 L/sec × 60 = 18 050 L/h Advisor showers: Lavatories:

30 heads × 7 min × 0.158 L/sec × 60 = 170 fixtures × 7.57 L/h × 0.30 usage factor = Total peak hour demand

1991 L/h 386 L/h 20 427 L/h

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20 427 L/h = 5107 L/h minimum recovery 4h Water heater sizing: 5107 L/h × 0.65 = 3320 L/h each heater Storage tank sizing: 20 427 L – 3320 L/h = 17 107 L storage required) Institutional dormitory conclusions 1. The amount of storage required indicates a separate water heater and storage tank arrangement. 2. The circulation system shall be arranged in a way that eliminates stratification in the storage tanks. 3. The piping arrangement and valving should be set up to isolate water heaters for maintenance purposes. 4. The path of access to the water heaters should be reviewed to ensure that it allows replacement in the future.

Elementar y and Secondar y Schools Elementary Secondary

4

45

ELEMENTARY AND SECONDARY SCHOOLS

INTRODUCTION This chapter provides guidelines for determining the hot water requirements for elementary and secondary schools.

TYPES OF SCHOOL The terms “elementary” and “secondary schools” cover grades K through 12. School districts have different ways of grouping students, especially in the middle years. This middle group may be known as either “junior high school” or “middle school” (see Table 4.1).

Table 4.1 School Grade Divisions Grade Level K

1

2

3

4

Elementary Elementary Elementary Elementary

5

6

7

8

9

Junior high Middle school Junior high

10

11

12

Senior high Senior high Senior high Senior high

The name is not important in itself but may be an initial guide to the types of activity that affect hot water requirements.

Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

46


For example, elementary schools generally do not have showers. Middle, junior, and senior high schools generally have showers for gym classes as well as sports teams that use the showers before and after regular school hours. High schools and middle schools may also have swimming pools. The designation of the school may also be a first indication of the areas of the facility in which to expect hot water requirements. Rooms that usually get hot water, beside the kitchen and laundry, are the health clinic, teachers’ workrooms, art room, teachers’ lounge, principal’s toilet, janitors’ closets, and special education rooms, which often have showers and washing machines. Science rooms, classrooms, and student toilets are areas that may have hot water but often do not. Always check with the user. (See Table 4.2.)

Table 4.2 Potential Areas of Hot Water Usage Type of School Area

Elementary

Jr./Middle

High

Classroom toilets

X

Kitchen

X

X

X

Laundry

X

X

X

Art room

X

X

X

Science room

X

X

X

Health clinic

X

X

X

Teachers’ lounge

X

X

X

Teachers’ workroom

X

X

X

Principal’s toilet

X

X

X

Student toilet rooms

X

X

X

Special ed. room

X

X

X

X

X

Showers Car wash

X

Shop room

X


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INFORMATION GATHERING The accuracy of the calculated hot water requirements will only be as good as the accuracy of the information used to determine the requirements. Therefore, a significant portion of the design time should be allotted to information gathering and validation. Sources of information include the following: 1. 2. 3. 4. 5. 6. 7.

The architect’s design documents. The architect. School staff. School district construction personnel. School district design criteria and manuals. School district maintenance personnel. Survey of existing and similar facilities.

Information will be needed to determine: 1. 2. 3. 4. 5. 6.

Which fixtures require hot water. Kitchen/food service requirements. Shower requirements. School population. After hours requirements. Hot water temperature requirements.

GENERAL CONSIDERATIONS The criteria for determining the hot water demand are presented as if one central system were being designed. In fact, the best choice may be to use multiple systems. This may be necessitated by criteria calling for a dedicated kitchen water heater or by isolated small loads. It is not the intent of this chapter to go into detail about the selection of water heating equipment or the hot water delivery system. An initial concept must be established for the purposes of grouping the load and planning for the location of equipment.

KITCHEN AND FOOD SERVICE Kitchen requirements, including dishwashers, generally are determined by the owner, the architect, and the kitchen design

48


consultant. A basic consideration is whether the kitchen is a full-service kitchen or merely a warming or holding kitchen. School criteria may call for the kitchen to have a separate water heater. The following should be determined for a full-service kitchen operation: 1. Dishwashing requirements. (Model number and hot water requirement for the dishwasher.) 2. Rinse and sterilization requirements. If done with 180ºF (60ºC) water, is the booster heater provided at the dishwasher or at a remote location? 3. Sinks and other kitchen hot water users, such as a can wash, steamers, and rinse sprays. 4. Hours of operation. Are breakfast and lunch both served? Does the kitchen operate during evenings or weekends? 5. Is any disposable table service used? This will affect the duration of dishwashing. The dishwasher may be used only for silverware and trays.

SHOWERS The shower load is often the most significant hot water requirement in secondary schools and should be carefully evaluated. The quantity of showers is usually determined by the school’s criteria, the architect’s design, and code requirements. Beyond the number of showers, the hot water requirement can be affected by such things as: 1. 2. 3. 4. 5. 6. 7.

Gym class size and schedule. Whether students are required to take showers. Time period available for showers. What temperature(s) are required. Maximum flow of shower heads. Special fixtures in the space (e.g., those for hydrotherapy). Types of extracurricular activity (sports, etc.).

SCHOOL POPULATION For new schools, the population—the total number of students and staff—is usually given in the design criteria for the school. Otherwise, it can be obtained from the school district or the architect or


49

by totaling the number of students allotted to each classroom. If the water heating system is also to serve the future expansion of the school, then the future population should be estimated.

CALCULATING THE HOT WATER DEMAND Hot water demand for schools can be divided into three categories: general purpose, kitchen, and shower. It is important to determine which, if any, of these loads occur at the same time and what the duration of the overlap is. As a general rule, if there is a kitchen, a system sized for the kitchen demand may also handle the general purpose demand. If there are also showers, the system must be sized for any concurrent shower and kitchen load. If there is no concurrent use, the system should be sized to handle the larger of the two, in which case it will also take care of the general purpose load.

General Purpose Demand Tabulate the quantities of each type of fixture. Using Table 4.3, multiply the number of fixtures by the gallons (liters) per hour for each and total the loads. This total will be the demand in gallons (liters) per hour.

Table 4.3 Hot Water Demand per Fixture for Schools Demanda (at 140°F [60°C] Final Temp.) Fixture

(gph/fixture)

Lavatory (private) Lavatory (public) Dishwasher (residential type) Sink (classroom, workroom, science room) Clothes washer (residential type) Service sink/mop basinb

2 4 20 8 30 20

(L/h/fixture) 7.57 15.14 75.70 30.28 113.55 75.70

Source: Reprinted with permission of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers from the 1987 ASHRAE Handbook. Modifications by the Washington, D.C., ASPE chapter. a Demands shown represent the quantity of 140°F (60°C) water required to produce the desired usable water temperature at the fixture. bHot water demand for general purpose service sinks and mop basins in schools is not included when supplied from the general purpose water heaters. This demand does not usually occur simultaneously with peak demands from toilets and kitchens.

50


Kitchen Demand Using the data in Table 4.4, calculate the kitchen demand in the same manner used for the general purpose demand. The dominant factor influencing the kitchen load will be the dishwasher rinse requirement. If this is not available, the hot water requirement for the dishwasher can be estimated from Table 4.5.

Table 4.4 General Purpose Hot Water Requirements of Kitchen Equipment Demand, 140°F (60°C) Type of Equipment Vegetable sink Single compartment Double compartment Triple-pot sink Prescrapper (open type) Prerinse (hand operated) Prerinse (closed type) Recirculating prerinse Lavatory or hand sink

(gph) 45 30 60 90 180 45 240 40 5

(L/h) 170.33 113.55 227.10 340.65 681.30 170.33 908.40 151.40 18.93

Source: Dunn et al. 1959. American Gas Association.

Table 4.5 Rinse Water (180–195°F) Requirements of Commercial Dishmachines Dishmachine Type

Dishmachine Size

Flow Rate (gpm)

Door type

16 x 16 in.

6.94

Inches rack

18 x 18 in. rack

8.67

20 x 20 in. rack Conveyor type

10.4

Undercounter type

5

Single tank

6.94

Multiple tank

Consumption (gph) 69 87 104 70 416

Dishes flat

5.78

347

Dishes inclined

4.62

277

Silverware washers

7

45

Utensil washers

8

75

Make-up water requirements— 180°F on certain conveyor types

2.31

139

Note: Based on water pressure of 20 psig at equipment. Based on operation at 100% mechanical capacity. Seventy percent is normal operating capacity except for rackless conveyor machines. Designer should contact equipment manufacturer for actual demand. Designer also should check local codes and regulations. Some agencies require that domestic water heating systems be sized to provide 100% capacity for dishwashers.


51

Table 4.5(M) Rinse Water (82–91°C) Requirements of Commercial Dishmachines Dishmachine Type Door type

Dishmachine Size 406 × 406 mm

Millimeters rack

457 × 457 mm rack

0.55

329.3

508 × 508 mm rack

0.66

393.64

Conveyor type

Flow Rate Consumption (L/sec) (L/h) 0.44 261.17

Undercounter type

0.32

264.95

Single tank

0.44

1574.56

Dishes flat

0.36

1313.4

Dishes inclined

0.29

1048.45

Multiple tank Silverware washers

0.44

170.33

Utensil washers

0.50

283.88

Make-up water requirements— 82°C on certain conveyor types

0.15

526.12

Note: Based on water pressure of 140 kPa at equipment. Based on operation at 100% mechanical capacity. Seventy percent is normal operating capacity except for rackless conveyor machines. Designer should contact equipment manufacturer for actual demand. Designer also should check local codes and regulations. Some agencies require that domestic water heating systems be sized to provide 100% capacity for dishwashers.

Shower Load The shower load is derived by multiplying the number of showerheads by the flow rate per shower by the amount of time the showerheads are used per hour. The load is expressed in gallons (liters) per hour. Generally, the water to showers is tempered by mixing the hot water with cold water; therefore, the actual requirement for hot water will be only a portion of the total shower flow. See Chapter 1, Equation 1.7, for the mixed water temperature formula.

52


EXAMPLES Example 4.1 Elementary School This school is not equipped with showers but does have a small (lunch only) cafeteria with a food preparation area. The general purpose demand is created by the following fixtures: Fixture Lavatory (private)

No. of Fixtures

Demanda (gph/fixture)

10

2

Total (gph) 20

Lavatory (public)

50

4

200

Sink (classroom)

20

8

160 380b

aFrom Table 4.3. bMop sinks not included.

Fixture Lavatory (private)

No. of Fixtures

Demanda (L/h/fixture)

10

7.57

Total (L/h) 75.7

Lavatory (public)

50

15.14

757

Sink (classroom)

20

30.28

605.6 1438.3b

aFrom Table 4.3. bMop sinks not included.

The kitchen demand is created by the following equipment: Equipment Vegetable sink

No. of Pieces

Demanda (gph)

1

45

Total (gph) 45

Triple-compartment sink

1

90

90

Prerinse

1

45

45

Hand sink

2

5

10

Dishwasher (door type)

1

69

69 259

aFrom Table 4.4.


53

No. of Pieces

Demanda (L/h)

Total (L/h)

Vegetable sink Triple-compartment sink

1 1

170.33 340.65

170.33 340.65

Prerinse Hand sink

1 2

170.33 18.93

170.33 37.86

Dishwasher (door type)

1

261.17

Equipment

261.17 980.34

aFrom Table 4.4.

The designer has decided with this type of system to use one or more water heater(s) to provide domestic hot water for the school. Since the kitchen requires 140°F (60°C) water, the heater(s) will raise the temperature of the water to this level and reduce it to 110°F (43°C) for general usage. Using the mixed water temperature formula found in Chapter 1 (Equation 1.7), we calculate the amount of 140°F (60°C) water needed to meet the general usage demand: (110 – 40) = 0.70 (140 – 40) – 4) = 0.70] [ (43 (60 – 4) 0.70 × 380 gph = 266 gph of 140°F water (0.70 • 1483.3 L/h = 1038.31 L/h of 60°C water) Although the general demand is slightly higher than the kitchen demand, the diversity of the general demand is such that the kitchen demand should be the factor governing the sizing of the water heater(s). For this example, the designer has selected a heater that has a storage capacity of approximately half of the kitchen demand with a recovery rate approximately equal to the kitchen demand.

54


Example 4.2 High School This school is a fully equipped high school with locker rooms, science rooms, lounges, shops, and a major kitchen. With all the activities that occur at this school, concurrent loads can be expected and must be taken into consideration when designing a system. The first step is to determine the domestic hot water demands that are generated in each category. General purpose demand Fixture Lavatory (private)

No. of Fixtures

Demanda (gph/fixture)

Total (gph)

12

2

24

Lavatory (public)

60

4

240

Sink

25

8

200

Dishwasher (residential)

2

20

40

Clothes washer (residential)

3

30b

90 594c –60b 534

aFrom Table 4.3. bOnly one of the clothes washers will be used during school hours; therefore, the total demand can be reduced by 60 gph. cMop sinks not included.

Fixture

No. of Fixtures

Demanda (L/h/fixture)

Total (L/h)

Lavatory (private)

12

7.57

Lavatory (public)

60

15.14

908.4

Sink

25

Dishwasher (residential) Clothes washer (residential)

90.84

30.28

757.00

2

75.7

151.4

3

113.55b

340.65 2248.29c –227.00b 2021.29

aFrom Table 4.3. bOnly one of the clothes washers will be used during school hours; therefore, the total demand can be reduced by 227.00 L/h. cMop sinks not included.


55

Kitchen demand Normal operating hours, not serving hours, are from 10:00 A.M. until 3:00 P.M. Equipment

No. of Pieces

Demanda (gph)

Total (gph)

Vegetable sink

2

45

90

Double-compartment sink

1

60

60

Triple-compartment sink

1

90

90

Prerinse

2

45

90

Hand sink

2

5

10

Bar sink

1

30

30

Dishwasher (conveyor type)

1

416

416 786

aFrom Tables 4.4 and 4.5.

Equipment

No. of Pieces

Demanda (L/h)

Total (L/h)

Vegetable sink

2

170.33

340.66

Double compartment sink

1

227.1

227.1

Triple compartment sink

1

340.65

340.65

Prerinse

2

170.33

340.66

Hand sink

2

18.93

37.86

Bar sink

1

113.55

113.55

Dishwasher (conveyor type)

1

1574.56

1574.56 2975.04

aFrom Tables 4.4 and 4.5.

Shower demand Showers are taken after gym classes and after athletic team practices. The total number of showers is 23. Each shower head has a flow rate of 2.5 gpm (0.16 L/sec). A worst-case scenario for usage is estimated to be 5 showers per hour per head for 6 min each. 23 heads × 2.5 gpm × 6 min × 5 showers/h = 1725 gph (23 heads • 0.16 L/sec • 60 sec • 6 min • 5 showers/h

56


= 6624 L/h) (This scenario would happen only after school when the athletic teams have completed their practices.) Possibly a better and more normal scenario to look at is the usage after gym classes. Since time is very limited, only a few quick showers will be taken. 23 heads × 2.5 gpm × 3 min × 2 showers/h = 345 gph (23 heads • 0.16 L/sec • 60 sec • 3 min • 2 showers/h = 1324.8 L/h) System selection factors At this point in the design, it must be determined how the domestic hot water is to be distributed. For this example, the designer has decided to provide two separate systems, one for the kitchen at 140ºF (60º) and one for the general and shower demands at 110ºF (43ºC). Since 110ºF (43ºC) water will be supplied to the showers and a normal shower is taken at an average of 102ºF (39ºC), the designer can compute the actual hot water usage for the showers using the mixed water temperature formula found in Chapter 1 (Equation 1.7). (102 – 40) = 0.89 (110 – 40) 1725 gph × 0.89 = 1535 gph 345 gph × 0.89 = 307 gph – 4) = 0.89 [ (39 (43 – 4) 6624 L/h • 0.89 = 5895.36 L/h

]

1324.8 L/h • 0.89 = 1179.07 L/h As previously noted, the water heater(s) for the kitchen demand will serve only that demand. Therefore, there are no loads concurrent with other demands. If the heater(s) served all demands, the kitchen demand and the normal shower demand would have to be combined. The following shows how the equipment would be sized in this case:


57

Kitchen demand Size the storage capacity of the water heater(s) for approximately half of the demand and the recovery rate for approximately 100% of the demand. General and shower demand There are a few factors that must be taken into account when sizing the equipment for this demand. One is the concurrence of the general demand and the normal shower demand. Another is the large shower demand after athletic teams practice plus the use of two clothes washers concurrent with this demand. (The length of time for heater recovery can be longer in this case, since there is all night to recover the tank.) For this example, the designer has decided to provide storage capacity of approximately 50% of the total of the general demand, 534 gph (2021.29 L/h), and normal shower demand, 307 gph (1179.07 L/h), and have recovery capacity of approximately 100% of this total demand.

REFERENCES American Society of Plumbing Engineers. 1989. Service hot water systems. Chapter 4 in ASPE Data Book. Thrasher, W. H., and D. W. DeWerth. 1993. Comparison of collected and compiled existing data on service hot water use patterns in residential and commercial establishments. ASHRAE Research Project No. RP-600.

Hotels and Motels

5

59

HOTELS AND MOTELS

INTRODUCTION The hot water demand for a hotel/motel depends on the facility’s type of occupancy and the guest room, food service, and laundry demands. Occasionally, there also will be a health club involved. These variables are discussed below. It is the responsibility of the designer to determine these variables through the application of engineering principles and by asking the appropriate questions of the owners/operators of the hotel or motel.

HOTEL AND MOTEL CLASSIFICATION A hotel or motel is classified according to its construction, its location, and the intent of the owners. The designer must do the required research to determine the appropriate classification. The following classifications are given for clarification and reference.

Convention Hotel or Motel This type of facility has an adequate number of guest rooms, meeting rooms, ballrooms, food service, etc., to support large groups with common schedules making high shower demands within a short period of time a real possibility. This classification also applies to any hotel or motel in close proximity to such a facility. If such is the case, the hotel or motel


60


owners should be contacted and asked if they wish to have a domestic water heating system capable of meeting convention demand.

Business Travelers’ Hotel or Motel It has been estimated that 45 to 50% of all hotel and motel business fits into this category, and the percentage increases each year. Owners catering to this group select locations favorable to business travelers, and the better ones select room furnishings to meet their needs. The presence of desk phones and phones by the bed is one indication of the hotel/motel’s intended primary use. The owners should be asked to verify their intended occupancy.

Resort Hotel or Motel This type of facility is found in or adjacent to locations that attract large numbers of people for the purposes of enjoyment. Some typical attractions are theme parks, mountains, beaches, and racetracks. Although most resort facilities have in common a reasonably long period of peak demand because their guests lack common time tables, you have to be careful. Facilities near race tracks and theme parks, for instance, are subject to short demand periods. If there is any doubt about this, the designer should ask the owners.

General Occupancy Hotel or Motel This type of facility is usually a mix of the other three classifications, the effect of which is the lengthening of the peak demand. An example of this type of facility is a hotel or motel in a reasonably large town that draws people for many reasons. It does not, however, have the number of meeting rooms necessary to support a full convention occupancy, and it has no ballrooms.

GUEST ROOM DEMAND Questions and Assumptions 1. How many guest rooms are there? 2. What type of occupancy does the facility serve?

Hotels and Motels

61

3. What is the average occupancy per room expected during peak occupancy? The owners can provide the best answer to this question. If they are unable to provide the information, the following assumptions may be used. • Convention hotel or motel: 1.5 to 2.0 persons per room. • Business travelers’ hotel or motel (urban): 1.5 to 2.0 persons per room. • Business travelers’ hotel or motel (nonurban): 1.25 to 1.75 persons per room. • Resort hotel or motel: 2.5 persons per room. • Resort suite/condo hotel: 2.5 to 4.0 persons per suite. • General occupancy hotel or motel: 1.5 to 2.0 persons per room. 4. What will the peak demand period be? Lacking other information, the following assumptions may be considered applicable: • Convention hotel or motel: 1-h peak. • Business travelers’ hotel or motel: 1-h peak. • Resort hotel or motel: 3-h peak. • General occupancy hotel or motel: 2-h peak. 5. What will be the greatest contributor to the guest room demand? The shower demand is almost always the greatest contributor to guest room demand. Some small factor can be assumed for lavatory demand. One significant additional load is the hot tub or whirlpool bath. If the facility under consideration has hot tubs or whirlpool baths, it is essential to ask the owners: • What is the fill capacity? • What temperature must be maintained? • Will the tubs have built-in heaters to maintain the desired temperature, or will the temperature have to be maintained by the occasional introduction of hot water? The designer also will have to make an assumption about the percentage of tubs that will be in use during the peak demand period. The owners should evaluate this assumption. 6. What percentage of guests will shower during any given peak demand period?

62


One number that may be considered is 70%. In situations where the peak demand period is 2 h, consider 70% for the entire period, then use 70% of that number for the peak hour. The 70% estimate is an assumption based on various premises. For example, in a convention hotel there will be scheduled events; for business travelers there are normal business hours. Apply the same logic for 3-h peak demand periods. 7. What is the maximum flow potential of the shower heads? 8. What is the average duration of a guest shower? In a hotel or motel, 5 min should be a reasonable assumption. 9. How much hot water should be stored? This is a value judgment based on the recovery chosen by the designer and the estimate of simultaneous shower use—both of which are affected by the classification and location of the facility. If it’s decided to provide recovery equal to the full peak demand, then it seems reasonable to accommodate those times when an inordinate number of people shower at the same time. Think of the stored water as “showers in the bank.” A general guide is to provide 15% of the hourly demand for facilities of 100 or more persons and 20% for smaller facilities.

Example 5.1 Guest Room Demand The following information is known or assumed about a convention facility. It has 300 guest rooms. We find that the minimum supply water temperature will be 40°F (4°C) and that 2.5 gpm (0.16 L/sec) maximum flow shower heads are to be used. We assume 1.5 persons per room at peak occupancy and an average shower time of 5 min per guest. We assume 70% of the guests will shower during the peak hour demand period. The temperature of hot water desired at the shower head is 105°F (41°C). Hot water will be stored at 140°F (60°C) and delivered to guest rooms after being tempered to 105°F (41°C). 300 rooms × 1.5 guests/room = 450 guests 450 guests × 70% = 315 guests showering in peak hour 315 guests × 5 min/guest × 2.5 gpm = 3938 gal of 105°F water required during peak hour (315 guests • 5 min/guest • 0.16 L/sec • 60 sec/min =

Hotels and Motels

63

15 120 L of 41°C water required during peak hour) The heat required to raise 3938 gph (15 120 L/h) of 40°F (4°C) water to 105°F (41°C) is 3938 gph × 8.33 lb/gal/°F × (105 – 40°F) = 2,132,230 Btu/h output required [15.12 m3/h • 4188.32 kJ/m3/K • (41 – 4°C) = 2 343 113.74 kJ/h output required] If it is decided to provide full recovery to reduce the storage requirements (and probably the system cost), note the efficiency of the water heaters that will be used. (It is never advisable to use only one heater for an establishment where hot water is essential to its operation.) For the purposes of this example, assume 80%. The total input required by heaters then is 2,132,230 Btu/h = 2,665,288 Btu/h 0.80

(

)

2 343 113.74 kJ/h 0.80

= 2 928 892.18 kJ/h

Storage The designer has decided to provide storage to accommodate the showering of 15% of the guests simultaneously. 3938 gph × 15% = 591 gal of 105°F water (15 120 L/h • 15% = 2268 L of 41°C water) Since 140°F (60°C) water is going to be stored, the equivalent quantity of 140°F (60°C) water is as follows (see Chapter 1, Equation 1.7, for the mixed temperature formula): 105 – 40°F = 0.65 × 591 gal = 384 gal 140 – 40°F

(

41 – 4°C 60 – 4°C

)

= 0.65 • 2268 L = 1474.2 L

If we use a storage tank with a tank efficiency of 80% and we desire to draw 384 gal (1453.59 L) from the tank during the peak hour, the quantity that must be stored is: 384 gal

64


0.80

(

= 480 gal minimum

1474.2 L 0.80

)

= 1842.75 L minimum

Select the next larger size standard tank. Another way to select the recovery capacity when using larger storage tanks is to divide the useable storage by the number of hours the peak demand lasts. Subtract the result from the peak hour demand to determine the minimum required recovery. To provide owners with the most cost-effective system, evaluate the cost of several combinations of storage, recovery, and efficiency.

FOOD SERVICE DEMAND Questions and Assumptions 1. What type of food service is being offered (full restaurant, fast food, etc.)? 2. What hours will food service be offered? 3. Are there multiple kitchens? Will there be a time when they operate simultaneously? Hot water demand Since hot water demand is driven by the kitchen equipment, the following questions need to be asked: 1. What will be the time period (total hours) of the kitchen’s longest cleanup mode? 2. What fixtures that utilize hot water will be in the kitchen? 3. What temperature water is required by each? 4. What are the manufacturer and model number of the dishwasher? You will need to obtain information about the hot water characteristics of this equipment. 5. Is a booster heater being used to furnish 180°F (82°C) water to the dishwasher?

Hotels and Motels

65

Guide to Estimating Hourly Demand The following can be used to estimate the hourly demand of 140°F (60°C) water to several types of fixture. (Lavatories can basically be ignored.) • 1-compartment sink: 30 gph (113.55 L/h) • 2-compartment sink: 60 gph (227.1 L/h) • 3-compartment sink: 90 gph (340.65 L/h) • 4-compartment sink: 120 gph (454.2 L/h) • Prerinse: 45 gph (170.33 L/h) • Can wash: 45 gph (170.33 L/h) These figures include initial fill and occasional refill or makeup. Sometimes, if a 4-compartment sink is furnished, sanitizing is done with chemicals and 180°F (82°C) water is not required.

Example 5.2 Food Service Demand Assume you have a convention hotel that serves all three meals each day. The kitchen has the following equipment: Equipment Conveyor type dishwasher 3-compartment sink

Assumed 140°F (gph)

Assumed 180°F (gph)a

320 90

320

2-compartment sink 1-compartment sink

60 30

Dishwasher prerinse Can wash

45 45 590

320

aWater is raised from 140 to 180°F by booster heater.

Assumed

Assumed

66


Equipment Conveyor type dishwasher 3-compartment sink 2-compartment sink 1-compartment sink Dishwasher prerinse Can wash

60°C (L/h)

82°C (L/h)a

1211.2 340.65 227.1 113.35 170.33 170.33

1211.2

2232.95

1211.2

aWater is raised from 60 to 82°C by booster heater.

Assume the kitchen will be in the cleanup mode for a maximum of 3 h after every meal. (Discussions with kitchen operators suggest that 3 h is a reasonable number that incorporates the necessary time for an extremely busy cleanup period.) Total hot water required per hour will be 590 gph (2232.95 L/h) of 140°F (60°C) water, 320 gph (1211.2 L/h) of which must be raised to 180°F (82°C) by a booster heater. To evaluate the storage required, consider the equipment to be served. You may assume that a large demand will occur when the cleanup effort is initiated. All the sinks will be filled, perhaps requiring 140°F (60°C) water. The dishwasher tanks will need to be filled initially; assume 30 gal (113.55 L), though you should check with the manufacturer. Therefore, you will need at least 210 gal (794.85 L) of 140°F (60°C) water for the initial fill of 3 sinks and a dishwasher tank. The normal draw down after initial fill should be no greater than the initial fill. The major running demand will be the dishwasher and prerinse, which operate continuously. If you wish to calculate initial fill with a water temperature lower than 140°F (60°C), then do so. Hands cannot be immersed in very hot water, but it may be the practice to fill the sinks initially with very hot water for hot soak purposes. Selection of water heating equipment To select a storage tank, first multiply the expected initial fill requirement by 1.1 to provide a 10% safety factor: 210 gal × 1.1 = 231 gal (794.85 L • 1.1 = 874.34 L)

Hotels and Motels

67

Then select the nominal tank size by dividing 231 gal (874.34 L) by the manufacturer’s published tank efficiency. (Assume 75%.) 231 gal = 308 gal nominal storage required 0.75

(

874.34 L 0.75

)

= 1165.79 L nominal storage required

Select the next larger size standard tank. If heaters with full demand recovery capacity are specified, the water drawn from storage during high demand periods will be quickly replaced and no greater storage capacity should be required. Selecting the storage tank size requires the engineer’s judgment. Required recovery For a kitchen, you may want to calculate full recovery, not taking into consideration storage since it is normally an insignificant percentage of the demand, particularly when a conveyor type dishwasher is used. Assume a minimum inlet temperature of 40°F (4°C). Also assume that an electric booster heater is furnished to raise the dishwasher hot water from 140 to 180°F (60 to 82°C). Using the heat transfer formula from Chapter 1 (Equation 1.2), we calculate the 140°F (60°C) water recovery as follows: 590 gph × 8.33 Btu/gal/°F × (140 – 40°F) = 491,470 Btu/h output required [(2.23 m3/h)(4188.32 kJ/m3/K)(333.15 – 277.59K) = 518 927.82 kJ/h output required] Divide the output by the efficiency of the heater to determine the input required.

LAUNDRY DEMAND Questions and Assumptions This demand is driven by the equipment used and the peak operation times. For large facilities, it can be a significant demand. For small facilities, small residential or light commercial equipment is often used. You must check the maximum operating water temperature and the gallons (liters) per hour required by each machine.

68


The manufacturer of the laundry equipment can tell you how much hot water is required for each machine. Generally, if you tell them the capacity of each machine in pounds per hour (kg/ h), they can tell you the gallons per hour (L/h) of hot water required per pound (kg). For large machines, the draw down rate can be high, so adequate storage is necessary. A number of laundry equipment manufacturers have suggested that the minimum requirement is to store 50–75% of the hourly demand, and provide a recovery equal to the hourly demand. This will provide stored water to meet the high draw down demand, and the recovery will provide for the continuous demand. Fifty percent is usually adequate, but check with the manufacturer if possible. You don’t want temperature degradation due to the addition of cold water during periods of high demand. If you have small machines, again it is helpful to check with the manufacturer for the maximum demand in gallons per hour (L/h). The temperature required by the user can be critical.

Example 5.3 Laundry Demand Consider a full-service convention hotel that has two 135-lb (61.24 kg) and one 75-lb (34.02 kg) washer extractor. The manufacturer has indicated that the machines require 2 gph of hot water for each pound (16.65 L/h of hot water for each kg) of capacity. The hotel owners have stated that they wash with 160°F (71°C) water and the laundry operates 16 h each day. Minimum supply water temperature will be 40°F (4°C). It is obvious that storage will be of little value in meeting hot water demand because of the long hours of operation. Adequate storage must be provided, however, to meet short-term, high draw down rates. Using the heat transfer formula from Chapter 1 (Equation 1.2), select the storage tank using 60% of peak hour demand. The total machine capacity is 345 lb (156.49 kg). 345 lb × 2 gph/lb = 690 gph of 160°F water (156.49 kg • 16.65 L/h/kg = 2 605.56 L/h of 71°C water) 690 × 8.33 × (160 – 40) = 689,724 Btu/h output required [2.61 m3/h • 4 188.32 kJ/m3 • K • (344.26 – 277.59 K) = 727 687.18 kJ/h output required]

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69

Divide by the heater efficiency to obtain the input required. 689,724 Btu/h output 0.80 (heater efficiency)

[

727 687.18 kJ/h output 0.80 (heater efficiency)

= 862,155 Btu/h input

= 909 608.98 kJ/h input

]

Use 60% of peak hour demand to select the minimum storage capacity. 690 gph × 0.6 = 414 gal minimum (2605.56 L/h • 0.6 = 1563.34 minimum) Select the next larger size standard unit or use multiple tanks.

GENERAL NOTES System Considerations The choice of a system(s) to meet the hotel/motel’s hot water demand is up to the designer. There are several factors and ideas that should be considered: 1. Should the hotel/motel be served by a single system? Should it be served by two systems, one serving the guest rooms and the other serving the laundry/kitchen? Does the hotel/motel need three separate systems? 2. What type(s) of tempering device should be installed to ensure safe delivery of the proper temperature water to the various areas? 3. If systems are combined, what size should the combined storage tank be? 4. Is it desirable to install a crossover bypass system so that, if one system is down, water from another system can be diverted to temporarily provide service to the down system? If this is done, it is important to remember that a tempering valve must be placed in a bypass for the lower temperature system so that, when this system is temporarily used for a higher temperature, water can be routed through the tempering valve bypass.

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Design Criteria Considerations When classifying the occupancy of a facility, be careful! In a resort facility there may be a convention hall. This means that any of the small hotels normally considered resort facilities could be (and often are!) used by people attending a convention. The key thing to look for is the convention facility. This is a good time for the designer to contact the owners or managers of the facility. If the hotel guest room system is occasionally overloaded by an unusually high occupancy rate, the result should not be an immediate and drastic drop in temperature if the system was sized reasonably. Some safety should be built into the minimum supply water temperature. If the temperature is above the minimum at the time of the large demand, then there is that spare capacity “in the bank.” There is some rationale to not sizing the system for the greatest possible demand, which may occur, say, once every 10 years. Sizing a system that way would cost the owners a lot of money. Be aware, however, that some facilities are very “high end” and their owners may direct you to size the system so they never run short.

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71

HOSPITALS

INTRODUCTION The objective of this chapter is to guide the designer step by step through the procedure of designing a domestic water heating distribution system for a hospital. It is important for the designer to realize that there is a vast difference between designing a domestic water heating system for a hospital and designing such a system for any other type of building. A hospital encompasses almost all types of hot water use, plus there are areas of operation that are unique to a hospital. The first section of this chapter addresses design considerations and areas of concern. The second gives user group requirements and offers an analysis to appraise. The final section presents some design examples. The designer is charged with identifying the variables, calculating the demand, and assuming the responsibility for laying out an economical and efficient system to provide hot water to a facility’s plumbing fixtures and other terminal points. The procedure presented here will help predict the minimum amount of hot water needed by the facility.

DESIGN CONSIDERATIONS Safety and Health Concerns See Chapter 1 for a discussion of Legionella pneumophila (Legionnaire’s disease) and scalding.


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USER GROUP ANALYSIS The specific areas of a facility, called “user groups,” should each be considered when determining hot water usage. The user groups identified below are typical of either a large or a small hospital facility. (Each facility must be reviewed to determine its layout.) The general outline that follows may be used for each user group.

General Outline Identify the following for each user group: 1. 2. 3. 4. 5. 6.

Fixtures requiring hot water. Whether the fixtures are public or private. Water temperature and pressure requirements for each fixture. Flow rates for each fixture. The usage pattern of each fixture. The acceptable time delay between the opening of a hot water tap and the delivery of hot water.

Review the plans to determine: 1. The location of each fixture. 2. The locations of fixtures with specific temperature requirements.

User Groups Patient areas General patient areas in a hospital are typically used by people admitted for surgical or medical procedures. Surgical patients are people who enter the facility to have a surgical procedure done and then remain in the facility to recover. A medical patient is a person who enters a facility with a health ailment not requiring surgery but who requires constant and/or specialized care. Surgical patients, early in their stay in the facility, are sponge bathed and, per doctors’ orders, may use the shower facilities. Medical patients typically have the use of the shower/bathing facilities at all times. Items that need to be determined include: 1. Are patient rooms private or semiprivate—or are wards used?

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2. Does each patient room have a shower/tub, or is there a central bathing area? 3. Check whether patient bathing is assisted and, if so, how many staff are available to provide assistance. 4. Determine the flow from each type of fixture. Areas of concern: 1. Many codes require 110°F (43°C) water to be used in the patient area to prevent scalding (refer to the discussion of scalding in Chapter 1). 2. Due to the number of showers/bathtubs in this area, a high use of hot water is possible. 3. In an intensive care area or isolation room, the hand washing sink/lavatory is used more frequently than in a typical patient area. Nurses’ station A nurses’ station is the area where the nursing staff work is centralized for the area it serves. Staff members prepare medicine and simple food or drink items for patients and do their required paperwork and general cleanup. Typically a staff toilet with a hand washing lavatory is located nearby. Nourishment and medication rooms typically have sinks in them. The clean and soiled utility rooms are in the vicinity of the station. The clean utility room typically has a single bowl sink while the soiled utility room typically has a double bowl sink, a hand washing lavatory, and a flushing rim sink (also known as a clinic sink) with a bedpan washer. The nurses’ station is not a heavy hot water use area and is typically part of another specific user group (i.e., patient areas have their own nurses’ stations). In many of the newer facilities, the nurses’ station is shared between departments to lower the number of staff required. This is done commonly in smaller facilities. Hydrotherapy The hydrotherapy area is a location where therapy that utilizes water occurs. The therapies may involve many different temperatures of water, but all include some hot water usage. The therapy tubs in the area may come in many sizes, from 50 to 500-gal (189.27 to 1892.71-L) capacity or larger. Items that should be determined include:

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1. The number and sizes of all the tubs/baths in the area. 2. For each type of tub, the planned number of therapies per hour. 3. The hours the department is in use. 4. Desired fill time for each tub. (Staff will fill tub as rapidly as possible.) Also determine whether the tubs are fully or partially filled for cleaning between therapies. 5. Water temperatures used for the therapies. 6. Is there a shower for bathing purposes in the area? Areas of concern: 1. Tub filling is desired to be as fast as possible. 2. Temperature is critical. (The staff will not accept an inadequate hot water supply.) 3. Before running tempered water to a thermostatic mixing valve, check with the valve’s manufacturer to make sure it will function properly under expected conditions. Dietary and food service A hospital dietary department typically is in operation 24 h a day, but that depends on the size of the facility. The department feeds not only the patients and their visitors but also the staff and sometimes the public. Normally three full meals a day are provided, but a late-night meal also is served in some facilities. Most dietary departments are designed by a food service consultant, who should be contacted and consulted. Items that need to be determined include: 1. The number of meals provided for each meal or day. Consult the food service consultant. 2. The number of dishwashers and, for each, its type, size, gallons (liters) per cycle, cycles per hour, and required temperature. 3. Number of sinks in the area and the type of each (prerinse, etc.). Obtain water usages from the food service consultant or use Table 6.1. 4. Are cart washers used? If so, during what hours are they used, and what temperatures are desired for them? 5. Are the elevated water temperatures, e.g., 180°F (82°C), to be boosted at the equipment or is a separate water heating system desired?

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Areas of concern: 1. Water temperature in the area. Typically, three temperatures are needed, 110°F (43°C) for hand washing, 140°F (60°C) for dietary use, and 180°F (82°C) for sanitizing purposes. 2. The department usually has early operating hours and runs simultaneously with other departments. 3. The department has a high water consumption. Surgical suite The surgical suite is where the facility’s surgical procedures are performed. Items that need to be determined include: 1. Hours of scheduled surgery and typical starting time. 2. Number of scrub sinks in the suite and the length of time required for the staff to wash. 3. Equipment used in the area and the water temperature it requires (e.g., an electric flash sterilizer may use hot water to shorten the warm-up time). 4. Number of showers in the suite’s locker rooms. Areas of concern: 1. The time of the suite’s startup. Note that the suite typically begins operation in the A.M., sometimes early A.M. (e.g., 6:00 A.M.), which is the same time other areas of the facility are beginning startup, i.e., during hot water peak demand. 2. The average number of emergency operations from the trauma unit or emergency room at night. Laundry A hospital produces a large amount of laundry, which needs to be cleaned. The size of the facility determines the size of the laundry department. Not all facilities have their own laundry departments; some opt to send the laundry to outside services. Items that should be determined include: 1. The number and size of each washing machine in the area (pound capacity and gallons [liters] of hot water per hour per pound [kilogram] or per cycle). 2. The planned number of laundry operations (loads) per hour per machine.

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3. The department’s start time and hours of operation. 4. The temperatures of the water used. Areas of concern: 1. The laundry department’s schedule of operation. The department commonly begins operating in the early A.M., which is the same time other areas of the facility are starting up (i.e., during hot water peak demand). The filling of the washers is typically the first thing done at startup. The probability that the washing machines will fill simultaneously is high during startup. 2. Some of the laundry may be considered contaminated and require special treatment. Verification of this possibility is required. Refer to “Laundries,” Chapter 12, for the sizing of hot water systems for this area. Due to the elevated water temperatures required, separate water heating systems may have to be used. Central sterile supply This is where surgical and other equipment/tools used in the facility are sent for cleaning or sterilization prior to disposal or reuse. The central sterile supply department is typically in operation during and after the surgical suite’s scheduled hours of operation. The department has many pieces of equipment that use hot water; it could be considered a specialized dishwashing area. Items that need to be determined include: 1. Hours that central sterile supply is in operation and when startup begins. 2. Number of times each piece of equipment is used per hour. 3. Equipment requirements with regard to water temperature, flow, water quality, and pressure. Areas of concern: 1. The department’s scheduled hours of operation. The department commonly begins operating in the A.M., which is the same time other areas of the facility start up (i.e., during hot water peak demand). 2. Water pressures, quality, and temperatures are critical in this area. Obstetrics/Nursery

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This department is where the birth process occurs. Due to the unpredictability of the birth process, it is in use 24 h a day. Many of the newer facilities provide showers or tub/shower combinations in the individual birthing rooms and post-birthing rooms. Items that need to be determined include: 1. Layout of the obstetrics department. Does each room have a tub/shower or are there central bathing facilities or both? Are there birthing rooms? After the birth, are the mother and infant transported to another room? 2. Determine the shower head flow and/or the tub flow/capacity. Areas of concern: 1. The birth process can be a long ordeal, and taking showers during the process relaxes and soothes the mother. Many facilities and health organizations recommend this. After the birth, baths and showers are taken not only to relax the mother but to flush the perineal area, which may be done in a sitz bath. 2. Hot water supply temperature is 110°F (43°C) (the same as in the patient area). Miscellaneous areas (e.g., lab, administration, maintenance, autopsy, the morgue) A hospital facility has many other areas with fixtures requiring hot water beside those noted above. Most of these areas have sinks, hand washing lavatories, and staff shower rooms. Items that need to be determined include: 1. In areas where showers are located, determine the flow rates of the shower heads. 2. Determine the water temperatures needed in those areas (maintenance may desire 140°F [60°C] temperatures for cleanup or washdown areas). Areas of concern: 1. The times that these areas are in use overlap the usage times of many of the other specific user groups. Though the fixtures may be few, they still are used and should be considered when doing calculations.

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WORKSHEETS AND TABLES Worksheet 6.A—User Group This worksheet may be copied by the designer for use in calculating the hot water requirements for an individual user group. A different sheet should be used for each user group. All water quantity usage figures—gallons per minute (gpm), (liters per second [L/sec]), gallons per hour (gph), (liters per hour [L/h]), and minutes of use per hour (min use/h)—are suggested. The designer must ascertain the correct quantities through actual fixture/device/equipment literature (e.g., shop drawings) and/or discussions with the owner and/or user. The “fixture” column lists the fixtures in a facility that use hot water. The designer may add to this list if necessary. The “quantity” column indicates the number of those fixtures located in the user group area. “Gpm” (L/sec) is the flow rate from the fixture used in the calculation. “Min use/h” is the estimated use of the fixture in 1 h. (Note: In the case of dietary demands, and perhaps other occasional demands, “gph [L/h]” will be substituted for “min use/h.”) The next section of the worksheet, “Temperature at Outlet,” is for the water temperature at the faucet outlet, not the system temperature. This is important since cold water will be added to the system hot water to obtain the desired outlet temperature. Because of this, the flow from the faucet is not all hot water. Table 1.1 is used to determine the actual amount of hot water needed at the faucet outlet. The “temperature at outlet” section is split into four subsections, each having a different faucet outlet water temperature. For the last subsection, labeled “other,” any temperature may be used, but the temperature must be the same for all fixtures used in that column. Each temperature subsection is split into two more subsections, “gpm (L/sec)” and “gph (L/h).” The equation for each is noted on the worksheet. When the fixtures in the user group are tabulated, each column is added and the totals are placed at the bottom of the sheet under “totals.” The user group “usage factors” for gpm (L/sec) and gph (L/h) are found in Table 6.2. Each total is multiplied by the appropriate usage factor to get the “user group totals,” which are used on “Worksheet 6.B—User Group Totals.” The user group totals are the amount of hot water predicted to be used in a particular user group during the peak hour(s). Designers should use their best judgment when working with these figures.

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Worksheet 6.A—User Group Temperature at Outleta (°F) A Fixture

B

Qty. GPM

Bathroom group

—

C 105° Min ___________ Use/H GPM GPH

(GPM = A × B GPH = A × B × C) 110° ___________ GPM GPH

—

Tub/shower & lavatory

2.5

10

Public lavatory

0.5

10

Private lavatory

2

4

Single bowl sink

2.5

1

Double bowl sink

2.5

Bathtub

7

10

Shower

2.5

10

1

Flushing rim sink

4.5

1

Floor receptor

4.5

1

Scrub sink, per faucet

2.5

10

Small hydro-tub (less than 100 gal)

15

—

Large hydro-tub (more than 100 gal)

15

—

Laundry tub

4.5

1

Residential washing machine

4.5

6

Residential dishwasher

4.5

Commercial dishwasher

7

—

Triple compartment sink, per faucet,

9

—

Commercial kitchen, single sink

9

—

Commercial kitchen, double sink

9

—

Commercial kitchen, prerinse

2.5

—

Hose station or cart/can wash

9

10

Sonic cleaner

4.5

—

Washer/disenfector

9

—

3

TOTALS: Usage Factors (UF) (Refer to Table 6.2): User Group Totals (UF x Totals); Transfer to Worksheet 6.B: aTemperatures are at faucet outlet NOT system temperature.

140° ___________ GPM GPH

Other ___________ GPM GPH

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Worksheet 6.A (M)— User Group Temperature at Outleta (°C) A Fixture

Qty.

Bathroom group

B

C

(L/Sec = A × B

41° Min ___________ L/Sec Use/H L/Sec L/H —

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

—

Tub/shower & lavatory

0.16

10

Public lavatory

0.03

10

Private lavatory

0.13

4

Single bowl sink

0.16

1

Double bowl sink

0.16

1

Bathtub

0.44

10

Shower

0.16

10

Flushing rim sink

0.28

1

Floor receptor

0.28

1


0.16

10

Small hydro-tub Less than 378.5 L

0.95

—

Large hydro-tub More than 378.5 L

0.95

—

Laundry tub

0.28

1


0.28

6


0.28

3


0.44

—

Triple compartment sink per faucet

0.57

—

Commercial kitchen single sink

0.57

—

Commercial kitchen double sink

0.57

—

Commercial kitchen prerinse

0.16

—


0.57

10

Sonic cleaner

0.28

—

Washer/disenfector

0.57

—

TOTALS: Usage Factors (UF) (Refer to Table 6.2): User Group Totals (UF x Totals); Transfer to Worksheet 6.B: aTemperatures are at faucet outlet NOT system temperature.

60° ___________ L/Sec L/H

Other ___________ L/Sec L/H

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Worksheet 6.B—User Group Totals This worksheet may be copied by the designer for use in calculating a facility’s hot water requirements. The “totals” found at the bottom of the sheet indicate the predicted amount of hot water the facility will use during the peak usage hour. Designers should use their best judgment when working with these numbers to determine the amount of hot water supplied to the facility. The items in the first, or “user group,” column are obtained from Worksheet 6.A. As seen, the user group totals from Worksheet 6.A are placed in the columns under the appropriate “temperature at outlet,” “gpm (L/sec),” and “gph (L/h)” headings. All of the user group totals for gpm (L/sec) are added together and the resulting number is placed in the “Subtotals” section near the bottom of the worksheet. This also is done for gph (L/h) figures. Designers need to determine when more than one water heater supply temperature (e.g., 105°F, 110°F, 140°F [41°C, 43°C, 60ºC]) will be required in the facility. When more than one water heater is required to supply different temperatures, separate Worksheets 6.A and 6.B should be used for each water heater system. Subtotal each “temperature at outlet” column, use Table 1.1 to look up the hot water multiplier for the system water temperature supplied to the facility, then multiply each subtotal by its appropriate multiplier. When this is done, total the actual gpm (L/sec) and gph (L/h) demands for the system water temperature supplied to the facility (the bottom row of the worksheet) and put the resulting numbers under “totals” at the bottom right of the worksheet. These totals are the gpm (L/sec) and gph (L/h) the water heater(s) must supply to the facility. Designers should use their best judgment when working with these figures.

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Worksheet 6.B—User Group Totals Temperature at Outleta (°F) User Group

105° 110° ___________ ___________ GPM Use/H GPM GPH

140° ___________ GPM GPH


Patient area Nurses’ station Obstetrics/Nursery Hydrotherapy Dietary & food service Surgical suite Central sterile supply Miscellaneous areas SUBTOTALS: Hot Water Multiplier, P (Water Heater Temp. _____ °F)b TOTALSc (Refer to Table 1.1): Subtotals × Hot Water Multiplier: Note: User group totals are taken from Worksheet 6.A. aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

GPM

GPH

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Worksheet 6.B (M)— User Group Totals Temperature at Outleta (°C) User Group

41° ___________ L/Sec L/H

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H


Patient area Nurses’ station Obstetrics/Nursery Hydrotherapy Dietary & food service Surgical suite Central sterile supply Miscellaneous areas SUBTOTALS: Hot Water Multiplier, P (Water Heater Temp. _____ °C)b TOTALSc (Refer to Table 1.1): Subtotals × Hot Water Multiplier: Note: User group totals are taken from Worksheet 6.A. aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

L/Sec

L/H

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Worksheet 6.A—User Group—Example 6.1 This is a copy of Worksheet 6.A with recommendations on temperatures at outlet and other comments. (See worksheet footnotes.) Designers should use their best judgment and take into account national, state, and local codes when considering these recommendations.

Worksheet 6.A— User Group—Example Temperature at Outleta (°F) A Fixture

B

Qty. GPM

Bathroom group tub/shower & lavatoryb,c 2.5 Public lavatoryb 0.5 2 Private lavatoryb 2.5 Single bowl sinkb 2.5 Double bowl sinkb 7 Bathtube 2.5 Showerb Flushing rim sinkf 4.5 4.5 Floor receptorf 2.5 Scrub sink, per faucetg Small hydro-tub 15 (less than 100 gal)d Large hydro-tub 15 (more than 100 gal)d Laundry tubf 4&5 Residential washing 4.5 machinef 4.5 Residential dishwasherf Commercial dishwasherj Triple compartment sink, per fauceth,i 9 Commercial kitchen, 9 single sinkh,i Commercial kitchen, 9 double sinkh,i Commercial kitchen, prerinseg 2.5 Hose station or 9 cart/ can washh 4.5 Sonic cleanerj 9 Washer/disenfectorj

C

(GPM = A × B GPH = A × B × C)

Min ___________ 105° Use/H GPM GPH 10 10 4 1 1 10 10 1 1 10

*l * * * * * *

110° ___________ GPM GPH

140° ___________ GPM GPH


* * * * * * * * *

* *

1

*

*

6 3 7

* *

* *

*

*

*

*

*

*

*

—k

*

90

—

*

30

—

*

60

—

*

45

10 — —

* *

* * *

*

*

TOTALS: Usage Factors (UF) (Refer to Table 6.2): User Group Totals (UF x Totals); Transfer to Worksheet 6.B: Note: GPM calculation is for a semi-instantaneous water heating system. GPH calculation is for a storage type water heating system.

(Continued)

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(Worksheet 6.A Example continued) aTemperatures are at faucet outlet NOT system temperature. bBased on ANSI standards of 2.5 gpm for showerheads, 2.5 gpm for sinks, 2.0 gpm for lavatories, and 0.5 gpm for public lavatories. cBased on the shower as the dominant fixture. dBased on the valve size used. Designer must base design on the type of valve

that is specified or present in an existing facility. eSame as “d” except two baths per hour. fBased on 4.5 gpm and ½ in. hot water supply running full open at 6 ft/sec

maximum velocity. gConsidered same as shower. hNine gpm based on ¾ in. hot water supply running full open at 6 ft/sec

maximum velocity. iBased on Table 6.1, “General Purpose Hot Water Requirements for Various Kitchen

Uses” ( gph). jBased on the equipment used. Designer must determine which model is used. kWhere a dash (—) appears, please refer to Table 6.1 for the recommended hourly

use figure. lAn asterisk (*) indicates the recommended outlet temperature.

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Worksheet 6.A(M)— User Group—Example Temperature at Outleta (°C) A Fixture

Qty.

Bathroom group tub/shower 1,2 & lavatoryb,c 1 Public lavatoryb Private lavatoryb 1 1 Single bowl sinkb Double bowl sinkb 1 4 Bathtube Showerb 1 5 Flushing rim sinkf Floor receptorf 5 Scrub sink, 6 per faucetg Small hydro-tub (less than 378.5 L)d 3 Large hydro-tub (more than 378.5 L)d 3 5 Laundry tubf Residential washing machinef 5 Residential 5 dishwasherf Commercial 9 dishwasherj Triple compartment sink per fauceth,i 7,8 Commercial kitchen 7,8 single sinkh,i Commercial kitchen 7,8 double sinkh,i Commercial kitchen prerinseg 6 Hose station or 7 cart/can washh 9 Sonic cleanerj Washer/disinfectorj 9

B

C

(L/Sec = A × B

Min ___________ 41° L/Sec Use/H L/Sec L/H

0.16 0.03 0.13 0.16 0.16 0.44 0.16 0.28 0.28

10 10 4 1 1 10 10 1 1

*l * * * * * *

0.16

10

*

*

*

*

*

*

0.95

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H


* * * * * * * * *

* *

0.95 0.28

1

*

*

0.28

6

*

*

0.28

3

*

*

0.44

*

*

0.57 —k

*

340.65

0.57

—

*

113.55

0.57

—

*

227.10

0.16

—

*

170.33

0.57 0.28 0.57

10 — —

* * *

* * *

*

TOTALS:

Usage Factors (UF) (Refer to Table 6.2): User Group Totals (UF x Totals); Transfer to Worksheet 6.B Note: L/sec calculation is for a semi-instantaneous water heating system. L/h calculation is for a storage type water heating system. aTemperatures are at faucet outlet NOT system temperature.

(Continued)

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(Worksheet 6.A[M] Example continued) bBased on ANSI standards of 0.16 L/sec for showerheads, 0.16 L/sec for sinks,

0.13 L/sec for lavatories, and 0.03 L/sec for public lavatories. cBased on the shower as the dominant fixture. dBased on the valve size used. Designer must base design on the type of valve

that is specified or present in an existing facility. eSame as “d” except two baths per hour. fBased on 0.28 L/sec and DN15 hot water supply running full open at 1.83 m/sec

maximum velocity. gConsidered same as shower. h0.57 L/sec based on DN20 hot water supply running full open at 1.83 m/

sec maximum velocity. iBased on Table 6.1, “General Purpose Hot Water Requirements for Various Kitchen

Uses” (L/h). jBased on the equipment used. Designer must determine which model is used. kWhere a dash (—) appears, please refer to Table 6.1 for the recommended hourly

use figure. lAn asterisk (*) indicates the recommended outlet temperature.

Table 6.1— General Purpose Hot Water Requirements for Various Kitchen Uses This table, which supplies information on the hot water requirements for various kitchen uses, should be used for the dietary and food service user group.

Table 6.1 General Purpose Hot Water Requirements for Various Kitchen Uses Equipment

GPH

L/H

Vegetable sink Single compartment sink Double compartment sink Triple compartment sink Prescrapper (open type) Prerinse (hand operated) Prerinse (closed type) Recirculating prerinse Bar sink Lavatories

45 30 60 90 180 45 240 40 30 5

170.33 113.55 227.10 340.65 681.30 170.33 908.40 151.40 113.55 18.93

Source: Values are extracted from Dunn et al. [1959] 1989. Chapter 4. ASPE Data Book. Table 9. Note: Requirements are for water at 140ºF (60ºC).

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Table 6.2— Usage Factors for User Groups This table provides the recommended usage factors for use with Worksheet 6.A. The following discussion gives the background of how these numbers were determined. (They represent a consensus of opinion of experienced designers; however, designers should use their best judgment when working with these figures): General The “gpm (L/sec)” figure is based on the possibility that every hot water using fixture will be operated in any 1 min (sec). The “gph (L/h)” figure is based on the possibility that every hot water using fixture will be operated during a 1-h period. These figures are based on a peak usage hour with a 3-h peak period.

Table 6.2 Usage Factors for User Groups User Groups Patient Nurses’ HydroArea Station therapy

GPM (L/Sec) 0.10 GPH (L/H) 0.40

0.05 0.50

0.25 0.90

Dietary & Food Surgical Service Suite

0.40 0.90

0.50 0.50

Central Sterile Obstetrics/ Misc. Supply Nursery Areas

0.20 0.90

0.10 0.40

0.05 0.10

Note: Based on a peak usage hour with a 3-h peak period.

Patient area This user group is split into two areas, surgical and medical patient areas. Many patients in these areas are not ambulatory and require assistance from the staff to use the toilet or the bathing facilities. Many surgical patients are not allowed to use the shower or bathing facilities until approximately the second day after surgery. Medical patients are often not allowed to use the facilities until after their conditions improve. Because of this, many are sponge bathed. The lavatory is a fixture that is heavily used by the staff. The 0.10 (10%) usage factor for the gpm (L/sec) is based on only the shower being in use (i.e., the lavatory is not in use during the same minute). Also, it is assumed that not all the patients are using the fixtures during the same minute. The 0.40 (40%) usage factor for the gph (L/h) is based on either the shower or the lavatory being used in an hour during

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peak usage time. Because the lavatory uses less water than the shower, the factor is less than 0.50 (50%). Nurses’ station This user group is in use 24 h a day but typically is used most heavily during shift changes. This is because of the preparation necessary before patients can be aided. The 0.05 (5%) usage factor for the gpm (L/sec) is based on the relationship between the staff and patients. During a peak 3h period of hot water use, the patient area is used more heavily than the nurses’ station. Since many patients need assistance using the bathing or shower facilities, staff members are in the patient areas aiding patients and not at the nurses’ station using the fixtures there. The 0.5 (50%) usage factor for the gph (L/h) is based on these same issues, but because of the time staff members spend at the nurses’ station organizing or distributing medicines and doing other work, the hand washing fixtures there are heavily used. Hydrotherapy When in operation, this area is a large water user. The staff can be split between the physical and hydrotherapy areas. The 0.25 (25%) usage factor for the gpm (L/sec) is based on the cyclical use of the therapy tubs and on the assumption that staff members also are doing physical therapy. The 0.90 (90%) usage factor for the gph (L/h) is based on the assumption that during peak usage times almost all the fixtures in this area are used. That assumes that the staff schedules water therapies during one time and physical therapies during another. Dietary and food service This area is a large water user. Depending on the size of the facility, the usage of water for food preparation and for cleaning may overlap. The 0.40 (40%) usage factor for the gpm (L/sec) is based on the assumption that cleaning (the washing of dishes, etc.) does not occur in the same minute as food preparation. Also, it assumes that the sinks are filled and then work is done using an intermittent, not a steady, water supply.

90


The 0.90 (90%) usage factor for the gph (L/h) is based on the assumption that most of the area fixtures are used during one of the hours of the facility’s peak usage time. Surgical suite Surgical procedures account for the majority of the time this area is in use. Though the scrub sinks are used intermittently during a procedure (e.g., staff leaving the room and returning will scrub again), the showers and scrub sinks are typically not used concurrently. The 0.50 (50%) usage factor for both the gpm (L/sec) and gph (L/h) are based on the above scenario. During any 1 min or h of the facility’s peak usage period, either the scrub sinks or the showers are in use. Central sterile supply This area, which houses washing equipment, is in use during the facility’s peak usage time. The 0.20 (20%) usage factor for the gpm (L/sec) is based on the assumption that some of the equipment is in a fill cycle during any 1 min. Due to the nature of equipment cycles, all the equipment does not use water during the same minute. The 0.90 (90%) usage factor for the gph (L/h) is based on most of the equipment being used in the facility’s peak usage hour. Obstetrics/Nursery This user group is in use 24 h a day. The birth process and resting afterward typically account for the majority of a patient’s time in this area. Showers are sometimes taken during labor to relax the mother, and the hand washing lavatory is used extensively during labor by the staff. The 0.10 (10%) gpm (L/sec) usage factor is based on usage in the patient area. Though a patient in the obstetrics (OB)/nursery area bathes after a birth, there is no set schedule for this because of the unpredictable nature of the birth process. Thus, at any 1 min, only 10% of the fixtures in this area are operated. (This is part of the reasoning for the 5% factor used for the nurses’ station. Fixtures in the OB/nursery user group typically are used by staff members, implying that those workers are not concurrently at the nurses’ station using fixtures there.)

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The 0.40 (40%) gph (L/h) usage factor also is based on the patient wing area. Also, many patients remain in the birthing rooms after delivery. (They’re not transferred to separate postpartum rooms.) Because of this, lavatories are used during labor by the staff and bathing or shower facilities are used by patients during the peak usage period. Both fixtures are not used extensively during the same hour. Miscellaneous areas (e.g., lab, administration, maintenance, autopsy, the morgue) The rest of the facility uses water but not during the facility’s peak usage time and not as much as those areas already discussed. This is because most of the staff are not in the miscellaneous areas. These areas must be taken into account, however, because water using fixtures are available and used there. The 0.05 (5%) usage factor for the gpm (L/sec) is based on the assumption that only a minor number of the fixtures are used during any 1 min of the facility’s peak usage time. The 0.10 (10%) usage factor for the gph (L/h) is based on the assumption that most of the fixtures in these areas are used outside of the facility’s peak usage hour. The designer must determine the usage pattern for each miscellaneous area.

QUESTIONS FOR OWNER OR CLIENT Patient Areas and Nurses’ Stations 1. Are patient rooms private or semiprivate? 2. Does each patient room have a shower/tub or is there a central bathing area? 3. Determine the flow from shower heads or tub flow/capacities.

Hydrotherapy 1. What are the number and size of each tub in the area? 2. What is the number of planned therapies per hour? 3. What hours is the department in use? 4. What is the required fill time for each tub? Are the tubs to be

92


fully filled for cleaning between patients? 5. What water temperatures are used for the therapies? 6. Is there a shower for bathing purposes in the area?

Dietary and Food Service 1. What is the number of meals provided each day? 2. What is the type of dishwasher used (number, size, gallons [liters] per cycle, cycles per hour, and temperature required)? 3. What are the type and number of sinks, prerinses, etc., in the area? 4. Are cart/can washers used and, if so, during what hours are they operational and what temperatures are required?

Surgical Suite 1. What are the hours of scheduled surgery and what is the typical starting time? 2. How many scrub sinks are in the suite? 3. What other equipment is used in the area and what temperatures are required (e.g., does the electric flash sterilizer require hot water to shorten warm-up time)? 4. How many showers are in the different locker rooms?

Laundry 1. What are the number and size of each washing machine in the area (pound [kilogram] capacity and gallons per hour per pound [liters per hour per kilogram])? 2. What is the number of planned laundry operations (loads) per hour? 3. What are the start time and the hours the department is in operation? 4. What are the temperatures of water to be used?

Central Sterile Supply 1. What are the operating hours of central sterile supply and when does startup begin?

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2. How many times is each piece of equipment used per hour? 3. What equipment is in the area and what are the required water temperature, flow rate, water quality, and pressure for each piece?

Obstetrics/Nursery 1. Does each room have a tub/shower in it, or are there central bathing facilities? Is there a birthing room and after the birth are the mother and infant transported to another room? 2. Verify the shower head flow and/or tub flow/capacity. 3. What is the number of scrub sinks in the area? 4. How many flushing rim sinks are in the area’s departments?

Miscellaneous Areas (e.g., Lab, Administration, Maintenance, Autopsy, the Morgue) 1. What are the flow rates of the shower heads in a given area? 2. Check the water temperatures required in these areas. 3. Determine the acceptable time delay between the hot tap opening and the delivery of hot water. (Keep the length of branch piping as short as possible. Discuss this issue with all users.)

EXAMPLES Example 6.2—32-Bed Hospital The facility in question is a 32-patient-bed hospital (having 24 patient-care, 6 obstetrics, and 2 intensive care, or ICU, beds). A facility of this size typically is located outside of a metropolitan area. The facility is a complete care, 24 h/day hospital without a laundry (a facility of this size typically does not produce enough laundry to warrant its own laundry facility). Description of user groups Patient area The facility has 24 patient-care beds (12 for medical patients and 12 for surgical patients). The facility has a wing arrangement with medical patients in one wing and surgical patients

94


in the other. The rooms are single patient rooms with a shower (2.5 gpm [0.16 L/sec] typical) and lavatory (2.0 gpm [0.13 L/ sec] typical) in each. There is a tub room with a single bathtub. Each wing has a clean utility room (single bowl sink, 2.5 gpm [0.16 L/sec] typical) and a soiled utility room (double bowl sink, hand washing lavatory, and flushing rim sink with bedpan washer). Each wing has a janitors’ closet with a receptor. Nurses’ station Because of the size of the facility, one nurses’ station provides service to the medical, surgical, and ICU patient beds. This station has a medical drug dispensing room (single sink), a staff toilet room (hand washing lavatory), and a sink at the station for general water use. A second nurses’ station, for obstetrics, has a general use sink. This station shares the use of the drug dispensing and toilet rooms with the other station. An on-call room for staff members, which has a shower and lavatory, is also provided in this area. Hydrotherapy The hydrotherapy area has a hip/leg tub (100 gal [378.50 L]), arms/hips/leg/back tub (110 gal [416.35 L]), and a hands/ elbows/arms tub (25 gal [94.63 L]) with a hand washing lavatory in the area. The 25-gal (94.63-L) arm tank is filled using the hip/leg tub valve. In this example, a mixing valve will be used at a maximum flow of 15 gpm (0.95 L/sec). There is also a shower with lavatory provided for outpatient services. Dietary and food service Because of the size of the facility, the dietary department provides three hot meals a day and a cold meal at night. It is a full-service department with the following equipment: triple compartment sink with prerinse, scrapping sink with prerinse, dishwasher, double sink for food thawing, sink for vegetable preparations, and a hand washing lavatory. The department starts operation at 6:00 A.M. The department requires 140°F (60°C) water at all fixtures except the hand washing lavatory, where 110°F (43°C) supply water is required. A 105°F (41°C) faucet outlet temperature is assumed. The dishwasher requires 180°F (82°C) water and the 140°F (60°C) water will be

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boosted at the dishwasher with an electric booster heater. Surgical suite The facility has two operating rooms with two double scrub sinks in the suite, and the department runs from 6:00 A.M. to 12:00 P.M. Monday through Friday. The department also has two general purpose sinks, a flash sterilizer (steam is provided from a central system), janitors’ receptor, two flushing rim sinks (one in recovery), and two showers with lavatories in the locker areas. Central sterile supply The central sterile supply operates between 6:00 A.M. (when surgery starts at 6:00 A.M.; otherwise 8:00 A.M.) and 4:00 P.M. The department has two gravity sterilizers, a sonic cleaner, washer disinfector, hand washing lavatory, double sink, and flushing rim sink with bedpan washer. The sonic cleaner and washer disinfector are typically used once an hour. Obstetrics/Nursery This department has six labor and delivery rooms set up so that the mother and infant may remain in one room for the duration of their stay. If an overflow occurs, the surgical patient wing is adjacent to the OB and the mother is transferred to an open room. Each room has a tub/shower with two hand washing lavatories. The OB department shares the soiled and clean utility rooms with the surgical patient wing. Miscellaneous areas Same-day surgery is a place where minor surgeries can be performed as outpatient services (patients need not stay in the facility overnight). The area has a general use sink and is adjacent to the emergency room (ER), thus sharing many of ER’s fixtures. Hours are between 6:00 A.M. and 5:00 P.M. The ER has a scrub sink, flushing rim sink with bedpan washer, two general use sinks, a double sink, and a toilet room with lavatory. This department is considered to be in use 24 h a day. Radiology is the department where X-rays are taken. The department typically has a general use sink in each procedure room. In this example, the department has two general radiology rooms and a CT scan room, each with a sink. The

96


area also has a janitors’ closet with receptor, a toilet room with lavatory, and a dark room with a sink and processor. (You need to determine if the processor requires hot water.) In this case, the processor is a cold water unit. The maintenance area has a cart wash area and service sink, both using 140°F (60°C) water. Also the area has male and female staff locker rooms, each with one shower and two lavatories. Questions for owner or client (This is a sample application of the questions from the previously defined user group analysis. Answers to questions appear in boldface type.) Patient areas and nurses’ stations 1. Are patient rooms private or semiprivate? • Private 2. Does each patient room have a shower/tub or is there a central bathing area? • Shower with one central tub per wing 3. Determine the flow from shower heads or tub flow/capacities. • 2.5 gpm (0.16 L/sec) for shower head, lavatory at 2.0 gpm (0.13 L/sec) Hydrotherapy 1. What are the number and size of each tub in the area? • 1 at 100 gal (378.50 L), 1 at 110 gal (416.35 L), and 1 at 25 gal (94.63 L) 2. What is the number of planned therapies per hour? • Two 3. What hours is the department in use? • 8:00 A.M. – 5:00 P.M. 4. What is the required fill time for each tub? Are the tubs to be fully filled for cleaning between patients? • 15 gpm (0.95 L/sec) valve is to be used. • Yes 5. What water temperatures are used for the therapies?

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• 103°F (39°C) 6. Is there a shower for bathing purposes in the area? • Yes, with a 2.5 gpm (0.16 L/sec) shower head and a 2.0 gpm (0.13 L/sec) lavatory Dietary and food service 1. What is the number of meals provided each day? • 200 2. How many dishwashers are there and what are the type, size, gallons (liters) per cycle, cycles per hour, and temperature required for each? • One • Hobart AM14 • 1.2 gal/rack at 53 racks = 64 gal/cycle (4.54 L/ rack at 53 racks = 240.62 L/cycle) • One cycle/h • 140°F (60°C) 3. What is the number of sinks, prerinse, etc. in the area and what is the type of each? • Triple compartment sink with prerinse • Scrapping sink with prerinse • Double sink for food thawing • Single sink for vegetable prep • A hand washing lavatory 4. Are cart/can washers used and, if so, during what hours are they operational and what temperatures are required? • Yes • Washed after meals are served • 140°F (60°C) Surgical suite 1. What are the hours of scheduled surgery and what is the typical starting time? • 6:00 A.M. – 12:00 P.M. typical 2. How many scrub sinks are in the suite? • Two double scrub sinks at 2.5 gpm/faucet (0.16 L/ sec/faucet) 3. What other equipment is used in the area and what tem-

98


peratures are required (e.g., does the electric flash sterilizer require hot water to shorten warm-up time)? • Two sinks • Janitors’ receptors • Two flushing rim sinks • Steam flash sterilizer 4. How many showers are in the different locker rooms? • Two showers (1 in the locker room for each sex) and 2 lavatories Laundry 1. What is the number and what are the sizes of the washing machines in the area (pound [kilogram] capacity and gallons per hour per pound [liters per hour per kilogram])? • None—facility sends laundry out. 2. What is the number of planned laundry operations (loads) per hour? 3. What are the start time and the hours the department is in operation? 4. What are the temperatures of water to be used? Central sterile supply 1. What are the operating hours of central sterile supply and when does startup begin? • 6:00 A.M. – 4:00 P.M. 2. How many times is each piece of equipment used per hour? • Sonic cleaner (5 gph [18.93 L/h]) and washer (27 gph [102.20 L/h]) 3. What equipment is in the area and what is the required water temperature, flow rate, water quality, and pressure for each piece? • 140°F (60°C) is needed at the equipment. • 35 psig (241.32 kPa) • 120°F (49°C) supplied at the sink and lavatory • 110°F (43°C) and 105°F (41°C) outlet temperatures, respectively • The equipment in the area is electric.

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Obstetrics/Nursery 1. Does each room have a tub/shower in it, or are there central bathing facilities? • Individual room tub/showers and two lavatories 2. Is there a birthing room and after the birth are the mother and infant transported to another room? • Typically, no to both questions 3. Determine the shower head flow and/or tub flow/ capacity. • 2.5 gpm (0.16 L/sec) showers and 2.0 gpm (0.13 L/ sec) lavatories 4. What is the number of scrub sinks in the area? • None (If surgical procedure is required, patient is transported to surgical suite.) 5. How many flushing rim sinks are in the area’s departments? • It shares with the surgical patient wing. Miscellaneous areas (e.g., lab, administration, maintenance, autopsy, the morgue) (Refer to the description of the facility for information.) 1. What are the flow rates of the shower heads in a given area? 2. Check the water temperatures required in the areas. 3. Determine the acceptable time delay between the hot tap opening and the delivery of hot water. (Keep the length of branch piping as short as possible. Discuss this issue with all users.)

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User group worksheets, 32-bed hospital

Worksheet 6.A —User Group: Patient Area Temperature at Outleta (°F) A

B

C

(GPM = A × B GPH = A × B × C)

Fixture

Qty. GPM

105° Min ___________ Use/H GPM GPH

Bathroom Group Tub/Shower & Lavatory Private Lavatory Single Bowl Sink Double Bowl Sink Bathtub Flushing Rim Sink Floor Receptor

24 2 1 1 1 1 1

10 4 1 1 10 1 1

2.5 2 2.5 2.5 7 4.5 4.5

TOTALS:

60 4 2.5 2.5 7

76

Usage Factors (UF) (Refer to Table 6.2): User Group Totals – UF × Totals; Transfer to Worksheet 6.B:

0.1 7.6

110° ___________ GPM GPH

140° ___________ GPM GPH


600 16 2.5 2.5 70

691 0.4 276

4.5 4.5

4.5 4.5

9

9

0.1

0.4

0.9

3.6

aTemperatures are at faucet outlet NOT system temperature.

Worksheet 6.A (M)—User Group: Patient Area Temperature at Outleta (°C) A Fixture Bathroom Group Tub/Shower & Lavatory Private Lavatory Single Bowl Sink Double Bowl Sink Bathtub Flushing Rim Sink Floor Receptor

Qty.

24 2 1 1 1 1 1

B

C

(L/Sec = A × B

41° Min ___________ L/Sec Use/H L/Sec L/H

0.16 0.13 0.16 0.16 0.44 0.28 0.28

10 4 1 1 10 1 1

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

3.84 2304.0 0.26 62.4 0.16 9.6 0.16 9.6 0.44 264 0.28 0.28

16.8 16.8

TOTALS:

4.86 2649.6

0.56

33.6

Usage Factor – UF – Refer to Table 6.2: Group Totals – UF × Totals; Transfer to Worksheet 6.B

0.1

0.1

0.4

0.06

13.44

0.4

0.49 1059.84


60° ___________ L/Sec L/H


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Worksheet 6.A— User Group: Nurses’ Station Temperature at Outleta (°F) A

B

C

(GPM = A × B GPH = A × B × C)

Fixture

Qty. GPM

105° Min ___________ Use/H GPM GPH

Bathroom Group Tub/Shower & Lavatory

1

2.5

10

Private Lavatory

1

2

4

2

8

Single Bowl Sink

2

2.5

1

5

5

2.5

TOTALS:

9.5

Usage Factors (UF) (Refer to Table 6.2):

0.05

User Group Totals (UF × Totals); Transfer to Worksheet 6.B:

0.5

110° ___________ GPM GPH

140° ___________ GPM GPH


25

38 0.5 19


Worksheet 6.A (M)— User Group: Nurses’ Station Temperature at Outleta (°C) A Fixture

Qty.

B

C

(L/Sec = A × B



1

0.16

10

0.16

96

Private Lavatory

1

0.13

4

0.13

31.2

Single Bowl Sink

2

0.16

1

0.32

19.2

TOTALS:

0.61 146.4

Usage Factor – UF – Refer to Table 6.2:

0.1

0.5

Group Totals – UF × Totals; Transfer to Worksheet 6.B

0.03

73.2

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H


60° ___________ L/Sec L/H


102


Worksheet 6.A—User Group: Hydrotherapy Temperature at Outleta (°F) A Fixture

B

Qty. GPM


C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

1

2.5

10

2.5

25

Public Lavatory

1

0.5

10

0.5

5

Small Hydro-Tub Less Than 100 Gal

2 (4 fills) 15

110° ___________ GPM GPH

140° ___________ GPM GPH

12

TOTALS:

3


0.25

User Group Totals (UF × Totals); Transfer to Worksheet 5B:

0.75

30 0.9

103° ___________ GPM GPH

30

360

30

360

0.25

27

7.5

0.9 324


Worksheet 6.A(M)—User Group: Hydrotherapy Temperature at Outleta (°C) A Fixture

Qty.

B

C

(L/Sec = A × B



1

0.16

10

0.16

96

Public Lavatory

1

0.03

10

0.50

18

Small Hydro-Tub Less Than 378.5 Liters

2 (4 fills) 0.95

12

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

39° ___________ L/Sec L/H

1.89 1368

TOTALS:

0.66 114

1.89 1368


0.25

0.25

User Group Totals (UF × Totals); Transfer to Worksheet 5B:

0.17 102.6

0.9


0.9

0.47 1231.2

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Worksheet 6.A—User Group: Dietary & Food Service Temperature at Outleta (°F) A Fixture

B

Qty. GPM

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH 0.5

110° ___________ GPM GPH

140° ___________ GPM GPH

Public Lavatory

1

0.5

10

Commercial Dishwasher

5

1

7

64 gphb

7

64

Triple Compartment Sink

2

9

90 gphb

18

180

Commercial Kitchen Single Sink

1

9

30 gphb

9

30

Commercial Kitchen Double Sink

1

9

60 gphb

9

60

Commercial Kitchen Prerinse

1

2.5

45 gphb

2.5

45

Hose Station or Cart/Can Wash

1

9

10

9

90

54.5

469

TOTALS:

0.5

5


0.4

0.9

0.4


0.2

4.5

21.8

aTemperatures are at faucet outlet NOT system temperature. bThese values are in total gph and do not reflect min use/h.

0.9 422


104


Worksheet 6.A(M)—User Group: Dietary & Food Service Temperature at Outleta (°C) A Fixture

Qty.

B

C

(L/Sec = A × B


Public Lavatory

1

0.03

10


1

0.44

64


2

0.57


1


0.03

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

18 0.44

242.24

340.65 L/hb

1.14

681.30

0.57

113.55 L/hb

0.57

113.55

1

0.57

227.1 L/hb

0.57

227.1


1

0.16

170.33 L/hb

0.16

170.33


1

0.57

37.85 L/hb

0.57

37.85

TOTALS:

0.03

18


0.4

0.9


0.01

16.2

aTemperatures are at faucet outlet NOT system temperature. bThese values are in total L/h and do not reflect min use/h.

3.45 1472.37 0.4

0.9

1.38 1325.13


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Worksheet 6.A—User Group: Surgical Suite Temperature at Outleta (°F) A Fixture

B

C

Qty. GPM

Private Lavatory Single Bowl Sink Shower Flushing Rim Sink Floor Receptor Scrub Sink, Per Faucet

2 2 2 2 1 4

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

2 2.5 2.5 4.5 4.5 2.5

4 1 10 1 1 10

TOTALS:

4 5 5

110° ___________ GPM GPH

140° ___________ GPM GPH


16 5 50

10

100

24

171

9 4.5

9 4.5

13.5

13.5

Usage Factors (UF) (Refer to Table 6.2): 0.5 0.5 0.5 0.5 User Group Totals (UF x Totals); Transfer to Worksheet 6.B: 12 85.5 6.8 6.8 aTemperatures are at faucet outlet NOT system temperature.

Worksheet 6.A(M)—User Group: Surgical Suite Temperature at Outleta (°C) A Fixture

Qty.

B

C

(L/Sec = A × B


Private Lavatory

2

0.13

4

0.26

62.4

Single Bowl Sink

2

0.16

1

0.32

19.2

Shower

2

0.16

10

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

0.32 192

Flushing Rim Sink

2

0.28

1

0.56

33.6

Floor Receptor

1

0.28

1

0.28

16.8

Scrub Sink, Per Faucet 4

0.16

10

0.64 384

TOTALS:

1.54 657.6

0.84

50.4

Usage Factor s (UF) (Refer to Table 6.2):

0.5

0.5

0.5


0.77 328.8

0.42

25.2

0.5


60° ___________ L/Sec L/H


106


Worksheet 6.A—User Group: Central Sterile Supply Temperature at Outleta (°F) A Fixture

B

Qty. GPM

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

Private Lavatory

1

2

4

2

8

Double Bowl Sink

1

2.5

1

2.5

2.5

Flushing Rim Sink

1

4.5

1 5 gphb

Sonic Cleaner

1

4.5

Washer/Disenfector

1

9

110° ___________ GPM GPH

4.5

140° ___________ GPM GPH


4.5 4.5

27 gphb

5

9

27 32

TOTALS:

4.5

10.5

4.5

4.5

13.5


0.2

0.9

0.2

0.9

0.2

0.9

User Group Totals ( UF × Totals); Transfer to Worksheet 5B:

0.9

9.5

0.9

4.1

2.7

28.8


Worksheet 6.A(M)—User Group: Central Sterile Supply Temperature at Outleta (°C) A Fixture

Qty.

B

C

(L/Sec = A × B


Private Lavatory

1

0.13

4

0.13

31.2

Double Bowl Sink

1

0.16

1

0.16

9.6

Flushing Rim Sink

1

0.28

1

Sonic Cleaner

1

Washer/Disenfector 1

0.28

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

0.28

60° ___________ L/Sec L/H

16.8

18.93 L/hb

0.28

0.57 102.2 L/hb

18.93

0.57 102.2

TOTALS:

0.29

40.8

0.28

16.8


0.2

0.9

0.2

0.9

User Group Totals ( UF × Totals); Transfer to Worksheet 5B:

0.06

36.72

0.06

15.12


0.85 121.13 0.2

0.9

0.17 109.02


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107

Worksheet 6.A—User Group: Obstetrics/Nursery Temperature at Outleta (°F) A Fixture

B

Qty. GPM


6

2.5

Private Lavatory

6

2

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

10

15

150

4

12

48

27

198

TOTALS: Usage Factor (UF) (Refer to Table 6.2):

0.1

0.4


2.7

79.2

110° ___________ GPM GPH

140° ___________ GPM GPH


aTemperatures are at faucet outlet NOT System Temperature.

Worksheet 6.A(M)—User Group: Obstetrics/Nursery Temperature at Outleta (°C) A

B

C

(L/Sec = A × B

Fixture

41° Min ___________ Qty. L/Sec Use/H L/Sec L/H


6

0.16

10

Private Lavatory

6

0.13

4

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

0.96 576 0.78 187.2

TOTALS:

1.74 763.2

Usage Factor (UF) (Refer to Table 6.2):

0.1


0.17 305.28

0.4


60° ___________ L/Sec L/H


108


Worksheet 6.A—User Group: Miscellaneous Areas Temperature at Outleta (°F) A Fixture

B

Qty. GPM

Private Lavatory 6 Single Bowl Sink 7 Double Bowl Sink 1 Shower 2 Flushing Rim Sink 1 Floor Receptor 2 Scrub Sink, Per Faucet 1 Hose Station or Cart/Can Wash 1

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

2 2.5 2.5 2.5 4.5 4.5 2.5

4 1 1 10 1 1 10

9

10

TOTALS:

12 17.5 2.5 5

2.5

140° ___________ GPM GPH


48 17.5 2.5 50 4.5 9

39.5

Usage Factors (UF) (Refer to Table 6.2): User Group Totals ( UF × Totals); Transfer to Worksheet 6.B:

110° ___________ GPM GPH

4.5 9

2.5

143

13.5

13.5

9

90

9

90

0.05

0.1

0.05

0.1

0.05

0.1

2.0

14.3

0.7

1.4

0.5

9

aNote: Temperatures are at faucet outlet NOT system temperature.

Worksheet 6.A(M)—User Group: Miscellaneous Areas Temperature at Outleta (°C) A Fixture Private Lavatory Single Bowl Sink Double Bowl Sink Shower Flushing Rim Sink Floor Receptor Scrub Sink, Per Faucet Hose Station or Cart/Can Wash

B

C

(L/Sec = A × B

41° Min ___________ Qty. L/Sec Use/H L/Sec L/H 6 7 1 2 1 2 1

0.13 0.16 0.16 0.16 0.28 0.28 0.16

4 1 1 10 1 1 10

1

0.57

10

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

0.78 187.2 1.12 67.2 0.16 9.6 0.32 192 0.28 0.56 0.16

16.8 33.6

9.6 0.57 342

TOTALS:

2.54 552

0.84

50.4

0.57 342

Usage Factors (UF) (Refer to Table 6.2): User Group Totals (UF × Totals); Transfer to Worksheet 6.B:

0.05

0.1

0.5

0.1

0.05

0.1

0.13

55.2

0.42

5.04

0.03

34.2

aNote: Temperatures are at faucet outlet NOT system temperature.


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109

User group totals worksheet, 32-bed hospital


105° 110° ___________ ___________ GPM Use/H GPM GPH

PATIENT AREA

7.6

276

NURSES’ STATION

0.5

19

HYDROTHERAPY

0.75

27

DIETARY & FOOD SERVICE SURGICAL SUITE

0.2 12

4.5

0.9

4.1

2.7

28.8

0.7

1.4

0.5

9

9.3

15.9

9.5

2.7

79.2

MISCELLANEOUS AREAS

2

14.3 515

7.5

324

7.5

324

422

6.8

0.9

26.7

21.8 6.8

OBSTETRICS & NURSERY

Other (103°) ___________ GPM GPH

3.6

85.5

CENTRAL STERILE SUPPLY

SUBTOTALS:

0.9

140° ___________ GPM GPH

25

459

1

1

HOT WATER MULTIPLIER, P (Water Heater Temp. 140°F)b

0.61

0.61

0.67

0.67

0.59

0.59 TOTALSc

(Refer to Table 1.1): Subtotals × Hot Water Multiplier:

16.2

314

6.2

10.7

25

459

4.4

191

Note: User group totals are taken from Worksheet 6.A. aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

GPM

GPH

52

976

110


Worksheet 6.B(M)— User Group Totals Temperature at Outleta (°C) User Group

41° ___________ L/Sec L/H

PATIENT AREA

0.49 1059.84

43° ___________ L/Sec L/H 0.06

60° ___________ L/Sec L/H

Other (39°) ___________ L/Sec L/H

13.44

NURSES’ STATION

0.03

73.2

HYDROTHERAPY

0.17

102.6

DIETARY & FOOD SERVICE

0.01

16.2

SURGICAL SUITE

0.77

328.8

0.42

25.2


0.06

40.8

0.06

15.12 0.17

109.02

OBSTETRICS & NURSERY

0.17

325.28

MISCELLANEOUS AREAS

0.13

55.2

0.42

5.04 0.03

34.2

SUBTOTALS:

1.83 2001.91

0.96

0.61

0.67

0.47 1231.2 1.38 1325.13

58.8

1.58 1468.35 0.47 1231.2

HOT WATER MULTIPLIER, P (Water Heater Temp. 60°C)b

0.61

0.67 1

1

0.59

0.59

TOTALSc (Refer to Table 1.1): Subtotals × Hot Water Multiplier:

L/Sec 1.12 1221.17

0.64

39.4

1.58 1468.35 0.28

L/H

726.41 3.62 3455.83

Note: User group totals are taken from Worksheet 6.A. aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

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111

Example 6.3—300-Bed Hospital This is an example of a 300-patient-bed hospital. A facility of this size typically is located around a metropolitan area. This is a complete-care, 24 h/day hospital with a full-service kitchen and a laundry (this size hospital typically produces enough laundry to warrant its own laundry facility). Refer to the attached worksheets for specific fixture quantities. Description of user groups Patient area The hospital has 300 patient-care beds, including those in intensive care suites, critical care suites, postsurgery rooms, emergency suites, and patient-care rooms. The facility is divided by floor, with medical patients and surgical patients housed on different floors. Patient rooms are private or semiprivate rooms with a shower (2.5 gpm [0.16 L/sec] typical) and a lavatory (2.0 gpm [0.13 L/sec] typical) in each. In the emergency care, intensive care and critical care suites, each bed has a lavatory, and each suite has a flushing rim sink with a bedpan washer. There are tub rooms on each floor with a single bathtub for those who desire to take a bath. Each floor has a clean utility room (single bowl sink, 2.5 gpm [0.16 L/sec] typical) and a soiled utility room (double bowl sink, hand washing lavatory, and flushing rim sink with bedpan washer). Each floor has a janitors’ closet with receptor. Nurses’ station Because of the size of the facility, each suite has a nurses’ station, which provides service to the medical, surgical, intensive care unit, and critical care unit (CCU) patient beds. Each station has a medical drug dispensing room (single sink), a staff toilet room (hand washing lavatory), and a sink for general use. There are also nurses’ stations at the emergency services area and the same-day surgery suites. These nurses’ stations each have a general use sink at the station and a toilet room with lavatory. An on-call room, which has a shower and lavatory for staff members, is located in each of these areas.

112


Hydrotherapy The hydrotherapy area has a large hydrotherapy tub (500 gal [1892.5 L]), 3 hip/leg tubs (100 gal [378.5 L]), arms/hips/ leg/back tubs (110 gal [416.35 L]) and a hands/elbows/ arms tub (25 gal [94.6]), and there is a hand washing lavatory in the area. Men’s and women’s locker rooms with showers and lavatories are provided for outpatient services. Dietary and food service The dietary department provides three hot meals a day and a cold meal at night for all the patient rooms and the staff dining room. It is a full-service department with the following equipment: triple compartment sink with prerinse, scraping sink with prerinse, dishwasher, double sinks for food prep/ thawing, single sinks for vegetable preparation, and hand washing sinks. The department starts operation at 6:00 A.M. and could make up to 1200 meals a day. All fixtures require 140°F (60°C) water except the hand washing lavatory, which requires 110°F (43°C) water. The dishwasher requires 180°F (82°C) water, and the 140°F (60°C) supply water temperature will be raised at the dishwater with an electric booster heater. This facility also has a guest cafeteria, which serves three meals a day and has the following equipment: triple compartment sink with prerinse, scraping sink with prerinse, dishwasher, double sink for food thawing, single sink for vegetable preparation, and a hand washing sink. Surgical/recovery suite The facility has 24 operating rooms, each with two double scrub sinks. The surgery department runs from 6:00 A.M. to 12:00 P.M. Monday through Friday with on-call services the remainder of the time. The department also has general purpose sinks, flash sterilizers (steam is provided from a boiler in the boiler room), two janitors’ receptors, flushing rim sinks (one in recovery), and showers with lavatories in the men’s and women’s staff locker areas. The area also has four toilet rooms with lavatories and two dark rooms. Each dark room has a sink and a processor, which requires tempered water. Thermostatic mixing valves should be used to provide the tempered 110°F (43°C) water.

Hospitals

113

Laundry Refer to the “Laundries” chapter for the sizing of hot water systems for this area. Central sterile supply The central sterile supply starts at 6:00 A.M. if there is scheduled surgery at that time; if not, it starts at 8:00 A.M. The department stops at 4:00 P.M. The area has four gravity steam sterilizers (steam is supplied from the boiler room), a sonic cleaner, washer disinfector, cart washer, hand washing lavatories, double compartment sink with prerinse hose, and flushing rim sink with bedpan washer. The sonic cleaner and washer disinfector are typically used 2 cycles per hour. Obstetrics/Nursery The department has two delivery rooms and four separate labor rooms. Each delivery room has two scrub-up sinks, a steam sterilizer (steam is supplied from the boiler room), and a single wash-up sink. There is a soiled utility room with a flushing rim sink and a single wash-up sink. Each labor room has a toilet with lavatory. There are three levels of nursery in this facility: one (level I) is for the newborns requiring standard care; one (level II) is for newborns requiring extra observation; and one (the neonatal intensive care unit, or NICU) is for newborns requiring critical care. An isolation room is used for newborns who need to be isolated. Each nursery has a lavatory, a single wash-up sink, and a larger sink used to wash and bathe the newborns. There is one shared soiled utility room with a washup sink and a flushing rim sink. Miscellaneous areas Same-day (outpatient) surgery is where minor surgeries are performed as outpatient services (i.e., the patients need not stay overnight in the facility). The area has a general use sink, a flushing rim sink, and scrub sinks adjacent to the two operating rooms. Hours of operation are between 6:00 A.M. and 8:00 P.M. The emergency room is in use 24 h a day. It has a scrub sink, a flushing rim sink with bedpan washer, and a general use sink in each of the four trauma rooms (areas used for

114


severely injured or critical patients). Each of the 12 examination pods is equipped with a lavatory. The pelvic exam room has a toilet with lavatory. There are two cast rooms, each with a lavatory. Radiology is where X-rays are taken. The department has two general radiology rooms, three CT scan rooms, and two magnetic resonance imaging (MRI) machines , each with a flushing rim sink and a lavatory. Each procedure room is provided with a general use sink. The area also has a janitors’ closet with receptor, a toilet room with lavatory, and three dark rooms, each with a sink and a cold water film processor. The maintenance area has a cart wash and service sink, both using 140°F (60°C) water. Also the area has male and female staff locker rooms, each with two showers and two lavatories.

Hospitals

115

User group worksheets, 300-bed hospital

Worksheet 6.A—User Group: Patient Area/OB/Nursery Temperature at Outleta (°F) A Fixture Bathroom Group Tub/Shower & Lavatory

B

Qty. GPM

C

300

2.5

10

Public Lavatory

20

0.5

Private Lavatory

5

Single Bowl Sink

20

750

7500

10

10

100

2

4

10

40

2.5

1

50

50

1

12.5

Double Bowl Sink

5

2.5

Bathtub

3

7

Flushing Rim Sink

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

10

21

110° ___________ GPM GPH

12.5 210

10

4.5

1

45

45

Floor Receptor

5

4.5

1

22.5

22.5

Scrub Sink, Per Faucet

2

2.5

10

Residential Washing Machine

2

4.5

6

TOTALS: Usage Factors (UF) (Refer to Table 6.2): User Group Totals ( UF × Totals); Transfer to Worksheet 5 B:

5

50 9

54

76.5

121.5

0.4

0.1

0.4

85.9 3184.8

7.7

48.8

859 0.1

7962


140° ___________ GPM GPH


116


Worksheet 6.A(M)—User Group: Patient Area/OB/Nursery Temperature at Outleta (°C) A Fixture Bathroom Group Tub/Shower & Lavatory

B

C

(L/Sec = A × B


L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

300

0.16

10

20

0.03

10

0.60

360

Private Lavatory

5

0.13

4

0.65

156

Single Bowl Sink

20

0.16

1

3.20

192

Double Bowl Sink

5

0.16

1

0.80

48

Bathtub

3

0.44

10

1.32

792

10

0.28

1

2.8

168

Floor Receptor

5

0.28

1

1.4

84


2

0.16

10


2

0.28

6

0.56

201.6

4.76

453.6

Public Lavatory

Flushing Rim Sink

TOTALS:

48.00 28 800

0.32

192

54.89 30 540


0.1

User Group Totals (UF × Totals); Transfer to Worksheet 6. B:

0.4 0.1

5.49 12 216

0.48

0.4 181.44


60° ___________ L/Sec L/H


Hospitals

117


B

Qty. GPM

Public Lavatory

6

0.5

Private Lavatory

20

2

Single Bowl Sink

5

2.5

Double Bowl Sink

2

2.5

Bathtub

6

Shower

6

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH 10

3

30

4

40

160

1

12.5

12.5

1

5

5

7

10

42

420

2.5

10

15

150

110° ___________ GPM GPH

Flushing Rim Sink

2

4.5

1

9

9

Floor Receptor

2

4.5

1

9

9

140° ___________ GPM GPH



3 fills/h

15

18

45

810

Large Hydro-Tub More Than 100 Gal

2 fills/h

15

30

30

900

75

1710


2

4.5

6

9

54

Residential Dishwasher

2

4.5

3

9

27

36

99

TOTALS: Usage Factors (UF) (Refer to Table 6.2): User Group Totals (UF × Totals); Transfer to Worksheet 6. B:

117.5 0.25 29.5

777.5 0.9 700

0.25 9

0.9 89.1


0.25 18.8

0.9 153

118


Worksheet 6.A(M)—User Group: Hydrotherapy Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B


L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H


Public Lavatory

6

0.03

10

Private Lavatory

20

0.13

4

0.18 108 2.6

624

Single Bowl Sink

5

0.16

1

0.80

48

Double Bowl Sink

2

0.16

1

0.32

19.2

Bathtub

6

0.44

10

2.64 1584

Shower

6

0.16

10

0.96 576

Flushing Rim Sink

2

0.28

1

0.56

33.6

Floor Receptor

2

0.28

1

0.56

33.6


3 fills/h

0.95

18

2.85 3078

Large Hydro-Tub More Than 100 Gal

2 fills/h

0.95

30

1.90 3420

Machine

2

0.28

6

0.56 201.6


2

0.28

3

0.56 100.8

TOTALS:

7.5 2959.2

2.24 369.6

4.75 6498


0.25

0.25

0.25


1.88 2663.28

0.9

0.9

0.56 332.64


0.9

1.19 5848.2

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119

Worksheet 6.A—User Group: Dietary & Food Service Temperature at Outleta (°F) A Fixture

B

Qty. GPM

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

140° ___________ GPM GPH

Public Lavatory

4

0.5

10

Single Bowl Sink

3

2.5

1

7.5

7.5

Double Bowl Sink

3

2.5

1

7.5

7.5

Floor Receptor

2

4.5

1


3

7

64 gphb

21

192


3

9

90 gphb

27

270


3

9

30 gphb

27

90


3

9

60 gphb

27

180


3

2.5

45 gphb

7.5


1

9

10

9

90

119

957

TOTALS:

2

110° ___________ GPM GPH

20

9

17


0.4

User Group Totals ( UF× Totals); Transfer to Worksheet 6.B:

6.8

35 0.9 31

9

9

9

0.4

0.9

3.6

8.1


0.4 47

135

0.9 861


120


Worksheet 6.A(M)—User Group: Dietary & Food Service Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B


L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

Public Lavatory

4

0.03

10

0.12

72

Single Bowl Sink

3

0.16

1

0.48

28.8

Double Bowl Sink

3

0.16

1

0.48

28.8

Floor Receptor

2

0.28

1


3

0.44

242.24 L/hb

1.32

Triple Compartment Sink Per Faucet

3

0.57

340.65 L/hb

1.71 1021.95


3

0.57

113.55 L/hb

1.71

340.65


3

0.57

227.10 L/hb

1.71

681.30


3

0.16

170.33 L/hb

0.48

510.98


1

0.57

0.57

342

0.56

33.6

10

TOTALS:

1.08 129.6

0.56

33.6


0.4

0.4

0.9

User Group Totals ( UF × Totals); Transfer to Worksheet 6.B:

0.43 116.64

0.9

0.22

726.72

7.50 3623.6 0.4

0.9

30.24 3.00 3261.24



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121

Worksheet 6.A—User Group: Surgical Suite Temperature at Outleta (°F) A

B

C

(GPM = A × B GPH = A × B × C)

Fixture

Qty. GPM

105° Min ___________ Use/H GPM GPH

Public Lavatory

10

0.5

10

5

50

Single Bowl Sink

10

2.5

1

25

25

Double Bowl Sink

2

2.5

1

5

5

30

300

Shower

110° ___________ GPM GPH

12

2.5

10

Flushing Rim Sink

4

4.5

1

18

18

Floor Receptor

2

4.5

1

9

9


30

2.5

10

27

27

TOTALS: Usage Factors (UF) (Refer to Table 6.2): User Group Totals (UF × Totals); Transfer to Worksheet 6.B:

75

750

140

113

0.5 70

0.5 565

0.5 13

140° ___________ GPM GPH


0.5 13


Worksheet 6.A(M)—User Group: Surgical Suite Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B


Public Lavatory

10

0.03

10

0.30

Single Bowl Sink

10

0.16

1

1.60

96

Double Bowl Sink

2

0.16

1

0.32

19.2

1.92

Shower

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

180

12

0.16

10

Flushing Rim Sink

4

0.28

1

1152 1.12

67.2

Floor Receptor

2

0.28

1

0.56

33.6


30

0.16

10

4.80 2880

TOTALS:

8.94 4327.2

1.68 100.8


0.5

0.5

0.5


4.47 2163.6

0.84

50.4

0.5


60° ___________ L/Sec L/H


122


Worksheet 6.A — User Group: Central Sterile Supply Temperature at Outleta (°F) A Fixture Public Lavatory Double Bowl Sink Flushing Rim Sink Floor Receptor Commercial Kitchen Prerinse Hose Station or Cart/Can Wash Sonic Cleaner Washer/Disenfector

B

Qty. GPM

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

140° ___________ GPM GPH

4 4 2 1

0.5 2.5 4.5 4.5

10 1 1 1

2

2.5

45 gphb

5

90

1 1 1

9 4.5 9

10 5 gphb 27 gphb

9 4.5 9

90 5 27

TOTALS:

2 20

110° ___________ GPM GPH

20 10 9 4.5

12


0.2 2.4


30 0.9 27

14 0.2 2.7

9 4.5

14 0.9 12

28 0.2 5.5

212 0.9 191


Worksheet 6.A(M)—User Group: Central Sterile Supply Temperature at Outleta (°C) A Fixture Public Lavatory Double Bowl Sink Flushing Rim Sink Floor Receptor Commercial Kitchen Prerinse Hose Station or Cart/Can Wash Sonic Cleaner Washer/Disenfector

B

C

(L/Sec = A × B

41° Min ___________ Qty. L/Sec Use/H L/Sec L/H 10 1 1 1

0.12 0.64

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

4 4 2 1

0.03 0.16 0.28 0.28

72 38.4

2

0.16 170.33 L/hb

0.32 340.66

1 1 1

0.57 10 0.28 18.93 L/hb 0.57 102.20 L/hb

0.57 342 0.28 18.93 0.57 102.20

0.56 0.28

33.6 16.8

TOTALS:

0.76 110.4

0.84

50.4


0.2

0.9

0.2

0.9

0.15

99.36

0.17

45.36


1.74 803.79 0.2

0.9

0.35 723.41


Hospitals

123

Worksheet 6.A—User Group: Miscellaneous Areas Temperature at Outleta (°F) A

B

C

(GPM = A × B GPH = A × B × C)

Fixture

Qty. GPM

105° Min ___________ Use/H GPM GPH

Public Lavatory Private Lavatory Single Bowl Sink Double Bowl Sink Shower Flushing Rim Sink Floor Receptor Scrub Sink, Per Faucet Hose Station or Cart/Can Wash

20 30 36 8 7 18 4

0.5 2 2.5 2.5 2.5 4.5 4.5

10 4 1 1 10 1 1

10 60 90 20 17

4

2.5

10

10

1

9

10

TOTALS:

208

Usage Factor (UF) (Refer to Table 6.2): User Group Totals ( UF × Totals); Transfer to Worksheet 6.B:

0.05 10

110° ___________ GPM GPH

81 18

140° ___________ GPM GPH


100 240 90 20 175 81 18

100

725 0.1 72

99

99

9

90

9

90

0.05

0.1

0.05

0.1

5

9.9

0.5

9


Worksheet 6.A(M)—User Group: Miscellaneous Areas Temperature at Outleta (°C) A Fixture Public Lavatory Private Lavatory Single Bowl Sink Double Bowl Sink Shower Flushing Rim Sink Floor Receptor Scrub Sink, Per Faucet Hose Station or Cart/Can Wash

B

C

(L/Sec = A × B

41° Min ___________ Qty. L/Sec Use/H L/Sec L/H 20 30 36 8 7 18 4

0.03 0.13 0.16 0.16 0.16 0.28 0.28

10 4 1 1 10 1 1

0.60 3.9 5.76 1.28 1.12

4

0.16

10

0.64 384

1

0.57

10

TOTALS: Usage Factor (UF) (Refer to Table 6.2): User Group Totals ( UF × Totals); Transfer to Worksheet 6.B:

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

360 936 345.6 76.8 672 5.04 302.4 1.12 67.2

0.57 342 13.3 2774.4 0.05

0.1

0.67 277.44

6.16 369.6

0.57 342

0.05

0.1

0.05

0.1

0.31

36.96

0.02

34.2



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User group totals worksheet, 300-bed hospital

Worksheet 6.B — User Group Totals Temperature at Outleta (°F) User Group

105° 110° ___________ ___________ GPM Use/H GPM GPH

PATIENT AREA

85.9 3,184.8

7.7

48.8

29.5

9

89.1

140° ___________ GPM GPH

103° ___________ GPM GPH

NURSES STATION HYDROTHERAPY DIETARY & FOOD SERVICE SURGICAL SUITE CENTRAL STERILE SUPPLY

6.8 70 2.4

700

3.6

8.1

565

31.5

13.5

13.5

47.6

861

27

2.7

12.2

5.5

191

72.5

4.95

9.9

0.45

18.8

153

18.8

153

OBSTETRICS & NURSERY MISCELLANEOUS AREAS SUBTOTALS:

10.4

204.9 4,581

41.5

181.6

9

53.6 1061


0.61

0.61

0.67

0.67

1

1

0.59

0.59 TOTALSc 140°F


124.9 2,794.4

27.8

121

53.6 1061

11.1

90

Note: Totals are taken from Worksheet 6.A. aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

GPM

GPH

217

3,111

Hospitals

125

Worksheet 6.B(M)—User Group Totals Temperature at Outleta (°C) User Group

41° 43° 60° Other (39°) ______________ _____________ _____________ _____________ L/Sec L/H L/Sec L/H L/Sec L/H L/Sec L/H

PATIENT AREA

5.49

12 216

0.48

181.44

2 663.28

0.56

332.64

116.64

0.22

30.24

0.84

50.4

NURSES’ STATION HYDROTHERAPY

1.88


0.43

SURGICAL SUITE

4.47


0.15

99.36

0.17

45.36

0.35

723.41

0.67

277.44

0.31

36.96

0.02

34.2

13.09

17 536.32

2.58

677.04

0.61

0.61

0.67

0.67

2 163.6

1.19 5848.2 3.00 3261.24

OBSTETRICS & NURSERY MISCELLANEOUS AREAS SUBTOTALS:

3.37 4018.85 1.19 5848.2


1

1

0.59

0.59 TOTALSc


L/Sec 7.98

10 697.16

1.73

453.62

L/H

3.37 4018.85 0.70 3450.44 13.78 18 620.07

Note: Totals are taken from Worksheet 6.A aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

Spas, Pools, Health Clubs, and Athletic Centers

7

127

SPAS, POOLS, HEALTH CLUBS, AND ATHLETIC CENTERS

INTRODUCTION This chapter provides guidelines for determining the hot water requirements for spas, pools, health clubs, and athletic centers.

INFORMATION GATHERING The accuracy of the calculated hot water requirements will only be as good as the accuracy of the information used to determine the requirements. Therefore, a significant portion of the design time should be allotted to information gathering and validation. This is especially true if unique therapies or special treatments will be performed at the facility. Sources of information include the following: 1. The architect’s design documents, 2. The interior design documents, 3. The architect, 4. The interior designer, 5. The owner, 6. The spa manager or coordinator, 7. The therapist, 8. Maintenance personnel, 9. Comparisons with similar facilities, and 10. Cut sheets on each piece of equipment. Information will be used to determine: Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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1. Which fixtures require hot water, 2. The number and types of fixture required, 3. Shower room requirements, 4. Peak usage times, 5. The types of therapy specific to each room, such as: • Manicure, • Pedicure, • Vichy showers, • Hydro showers, • Body showers, • Massages. 6. Hot water requirements, such as: • Water temperature (for each type of therapy), • Demand required, • Recovery required. 7. Any special requirements that may be typical to this facility.

HOT WATER REQUIREMENTS Therapies/Special Needs The therapy load can oftentimes be a significant load. This needs to be carefully evaluated. Coordinating with the health club/spa staff, including the therapist, managers, and maintenance staff, is very important. The owner, architect, or interior designer usually determines the quantities of fixtures. The hot water requirements of therapies and special needs can be affected by such things as: 1. The schedule of each type of therapy per room per hour and the number of therapy rooms. 2. Whether cleaning/maintenance is required between therapies. 3. What temperature is required for different therapies. 4. What other activities are happening concurrently with the therapies. 5. The maximum flows for the equipment used.


129

6. The actual time of operation per therapy for each fixture. The different therapies are listed below with their typical associated water temperature(s). These temperatures can vary according to therapist and client. Manufacturers should be contacted for the flow rates of the equipment. 1. Vichy shower (requires two temperatures): • Hot water temperature 101°F (38°C), • Cold water temperature 80°F (27°C). 2. Swiss showers • Range in temperature from 80 to 101°F (27 to 38°C). 3. Mineral salt bath • Constant temperature of 101°F (38°C). 4. Water path (lower leg/ankle therapies typically consisting of two water paths) • Cold water path 55°F (13°C), • Hot water path 105°F (41°C). 5. Hydrotherapy tub • Temperature will change based on type of hydrotherapy procedure. 6. Manicures/pedicures • Constant temperature of 95°F (35°C).

Shower Rooms The locker room shower load must also be considered. Typically showers will operate concurrently with the therapies. The quantity of showers is usually determined by the owner’s requirements, the architect’s design, and/or code requirements. Facilities often include areas with showers designed for specific functions, such as family changing areas and children’s locker rooms. These areas need to be evaluated for their use during the peak hours of operation. The hot water requirements of the showers can be affected by such things as: 1. Hours of operation. 2. Occupancy at different hours. It should be noted that the occupancy will vary throughout the day. This list is only a guide; the occupancy may vary with location and owner’s re-

130


quirements. • Early morning, 5:00 to 8:00 A.M.—workforce, young professionals. • Late morning, 8:00 to 11:00 A.M.—parents with/without children, older or retired people. • Noon, 11:30 A.M. to 1:30 P.M.—workforce, young professionals. • Afternoon, 1:30 TO 4:00 P.M.—parents with children, older or retired people. • Early evening, 4:00 to 6:00 P.M.—the after work crowd, young professionals. • Late evening, 7:00 to 9:00 P.M.—families and single people. 3. Maximum flow rate of shower heads. 4. Special fixtures required. 5. Duration of showers. 6. Type of clients using the facility. Note: It is not unusual for 25 to 50% of the showers in health club facilities to be operating throughout the day. It is anticipated that during the peak hour 100% of the showers will operate simultaneously.

Other Demands There may be other demands associated with these facilities, depending on owner preferences. If any of these other services are specified, they too must be considered in the overall hot water calculation. These demands are usually not large and need to be added to the overall system capacity. 1. Laundry demand, 2. Food service demand.

CALCULATING THE HOT WATER DEMAND Hot water demand for spas can be divided into several categories: general purpose, therapies, showers, laundries, and/or food service. It is important to determine which, if any, of these loads will occur at the same time and what the duration of the overlap will be. As a general rule, if the facility is a full-service spa, including therapies, weight training, aerobics, etc., a system


131

designed for both the therapies and the shower area should be considered. If food service is also included, then this must be considered in the calculations. If there will not be concurrent usage, then the system can be designed according to the maximum demand during the peak hour. Consideration needs to be given to providing two water heaters, each sized for 60% of the total demand required.

Nursing/Inter mediate Care and Retirement Homes Nursing/Intermediate

8

133

NURSING/ INTERMEDIATE CARE AND RETIREMENT HOMES

INTRODUCTION The objective of this chapter is to guide the designer step by step through the procedure of designing a domestic water heating system for a nursing/intermediate care and retirement home. It is important for the designer to realize that there is a difference between designing a domestic water heating system for this type of facility and designing one for any other type of building. The first section of this chapter addresses design considerations and areas of concern. The second gives user group requirements and offers an analysis to appraise. A third section contains worksheets, and the final section presents a design example. The designer is charged with identifying the variables, calculating the demand, and assuming the responsibility for laying out an economical and efficient system to provide hot water to a facility’s plumbing fixtures and other terminal points. The procedure presented here will help predict the minimum amount of hot water needed by the facility. Nursing care facilities typically have residents who require nursing supervision in an inpatient setting. These residents generally have health issues or are frail from age, both of which may adversely affect their mobility and ability to care for themselves. These facilities offer 24 h per day care and typically are regulated by the state department of health. Intermediate care facilities typically have residents who either desire or need nursing supervision. These residents are healthier and more mobile than the residents of nursing care Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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facilities and may still be able to care for themselves. The nursing supervision is provided for general assistance and emergency care. Retirement homes, as discussed in this chapter, are understood to be facilities that are either adjacent or attached to nursing/intermediate care units. The facilities are so arranged to enable the spouse/friend of a person in the nursing care unit to be close by and aid in care. Residents of these facilities are fully mobile and capable of taking care of themselves. Medical assistance is available, however, if it is needed. Retirement homes are similar to apartment complexes for the elderly.

DESIGN CONSIDERATIONS Safety and Health Concerns See Chapter 1 for a discussion of Legionella pneumophila (Legionnaire’s disease) and scalding.

USER GROUP ANALYSIS The specific areas of a facility, called “user groups,” should each be considered when determining hot water usage. The user groups identified below are typical of either a large or a small nursing/ intermediate care and retirement home. (Each facility must be reviewed to determine its layout.) The general outline that follows may be used for each user group.

General Outline Identify the following for each user group: 1. Fixtures requiring hot water, 2. Whether the fixtures are public or private, 3. Water temperature and pressure requirements for each fixture, 4. Flow rates for each fixture, 5. The usage pattern of each fixture.


135

User Groups Nursing/Intermediate care facility Resident areas General resident areas in a nursing/intermediate care facility typically are sleeping quarters, which may be shared (double rooms are usual) and each of which has its own toilet room. People living in this type of facility typically require constant, specialized care. Items that need to be determined include: 1. Are resident rooms private or semiprivate? 2. Does each resident room have a shower/tub or is there a central bathing area? 3. Does each room have a lavatory? 4. The flow from each type of fixture. Areas of concern: 1. Many codes require 110°F (43°C) water in the resident area to prevent scalding (refer to the discussion of scalding in Chapter 1). 2. If the resident rooms each have a tub/shower, high hot water usage is possible. Nurses’ station A nurses’ station is the area where the nursing staff work is centralized for the area it serves. Staff members prepare medicine and simple food and drink items for residents and do their required paperwork and general cleanup. Typically a staff toilet with a hand washing lavatory is located nearby. Nourishment and medication rooms typically have sinks in them. The clean and soiled utility rooms are in the vicinity of the station. The clean utility room typically has a single bowl sink while the soiled utility room typically has a double bowl sink, hand washing lavatory, and a flushing rim sink (also known as a clinic sink) with a bedpan washer. There may also be a bedpan sanitizer, and if so, the hot water requirements of this unit will need to be addressed.

136


Hydrotherapy The hydrotherapy area is where therapy using water occurs. The therapies may involve many different temperatures of water, but all include some hot water usage. The therapy tubs in the area may come in many sizes, from 50gal to 500-gal (189.25-L to 1892.50-L) capacity or larger. Items that should be determined include: 1. The number and size of each tub in the area. 2. For each type of tub, the number of planned therapies per hour. 3. The hours the department is in use. 4. Desired fill time for each tub. (Staff will fill tub as rapidly as possible.) Also determine whether the tubs are fully or partially filled for cleaning between therapies. 5. Water temperatures used for the therapies. 6. Whether there is a shower for bathing purposes in the area. (It could be in use at the same time the tub is being cleaned or refilled.) Areas of concern: 1. Tub filling is desired to be as fast as possible. 2. Temperature is critical. (The staff will not accept an inadequate hot water supply.) Dietary and food service The dietary department provides three meals a day. Most dietary departments are designed by food service consultants, who should be contacted and consulted. Items that need to be determined include: 1. The number of meals provided for each meal or day. Consult the food service consultant. 2. The number of dishwashers and, for each, its type, size, gallons (liters) per cycle, cycles per hour, and required temperature. 3. Number of sinks in the area and the type of each (prerinse, etc.). Obtain water usages from the food service consultant or use Table 8.1.


137

4. Are cart washers used? If so, during what hours are they used and what temperatures are desired for them? 5. Are the elevated water temperatures, e.g., 180°F (82°C), to be boosted at the equipment or is a separate water heating system desired? Areas of concern: 1. Water temperatures and pressures in the area. Typically two and sometimes three temperatures are needed: 110°F (43°C) for hand washing, 140°F (60°C) for dietary use, and 180°F (82°C) for dishwashing. Some of the equipment may have higher or lower than water line pressure requirements. 2. The department usually has early operating hours and runs simultaneously with other departments. 3. The department has a high water consumption. Central bathing Central bathing is where staff members aid residents who cannot bathe themselves and where, if individual rooms do not have their own tubs/showers, all the residents shower/ bathe. The area typically has a shower, a residential style tub, and a specialized bathing tub for nonambulatory residents. Items that need to be determined include: 1. The hours of scheduled bathing and the typical starting time. 2. The type of specialized tub and the amount of water it requires. 3. The layout of the fixtures. (Does it match the room layout noted above?) Areas of concern: 1. The suite’s scheduled operating hours and the number of planned baths per hour. 2. Determine the maximum number of baths that may be performed per hour in the tub. Assume that when staff members aid residents in bathing, the maximum number possible will be done.

138


Laundry A nursing care facility produces a large amount of laundry. The size of the facility determines the size of the laundry department. Not all facilities have their own laundry department; some opt to send the laundry to an outside service. Items that should be determined include: 1. The number and size of each washing machine in the area (pound [kilogram] capacity and gallons of hot water per hour per pound or per cycle [liters of hot water per hour per kilogram or per cycle]). 2. The planned number of laundry operations (loads) per hour per machine. 3. The department’s start time and hours of operation. 4. The temperatures of the water used. Areas of concern: 1. The laundry department’s schedule of operation. The department commonly begins operating in the early A.M., which is the same time other areas of the facility begin startup (i.e., during hot water peak demand). The filling of the washers is typically the first thing done at startup. The probability that the washing machines will fill simultaneously is high during startup. Refer to the “Laundries” chapter for the sizing of hot water systems for this area. Due to the elevated water temperatures required, separate water heating systems may have to be used. Miscellaneous areas (e.g., administration and maintenance) The facility has many other areas with fixtures requiring hot water beside those noted above. Most of these areas have sinks, hand washing lavatories, and staff shower rooms. Items that need to be determined include: 1. In areas where showers are located, the flow rates of the shower heads. 2. The water temperatures needed in those areas (maintenance may desire 140°F [60°C] temperatures for cleanup or washdown areas).


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Areas of concern: 1. The times that these areas are in use overlap the usage times of many of the other specific user groups. Though the fixtures may be few, they still are used and should be considered when doing calculations. Retirement home Resident areas General resident areas in a retirement home are typically private apartments. Items that need to be determined include: 1. Number of bedrooms in each apartment and thus the number of occupants to be considered. 2. The number and types of fixture in each apartment. 3. Does each apartment have a dishwasher and/or separate laundry area? 4. The flow from each type of fixture. Areas of concern: 1. Though codes may not require 110°F (43°C) water for this type of facility (because of the generally adequate health of its occupants) that water temperature might be considered to prevent scalding (see the discussion of scalding in Chapter 1). Laundry Since a retirement home is similar to an apartment complex, the facility may have a laundry room with a number of residential type washing machines. Items that should be determined include: 1. The number of washing machines in the area and the size of each (pound [kilogram] capacity and gallons of hot water per hour per pound or per cycle [liters of hot water per hour per kilogram or per cycle]). 2. The planned number of laundry operations (loads) per hour per machine. 3. The room’s start time and the hours it is open for use.

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4. The temperatures of the water used. Areas of concern: 1. The laundry room’s scheduled hours of operation. Since residents use this area, its hours of use are not regulated—thus, it could be used at any time. There is a possibility that the washing machines will fill simultaneously. Miscellaneous areas (e.g., administration and maintenance) The facility has many other areas with fixtures requiring hot water beside those noted above. Most of these areas have sinks, hand washing lavatories, and public toilet rooms. If the facility adjoins a nursing care facility, these areas may be shared with the nursing care facility. The “items that need to be determined” and “areas of concern” are the same as those noted above for a nursing care facility.

WORKSHEETS AND TABLES Worksheet 8.A—User Group This worksheet may be copied by the designer for use in calculating the hot water requirements for an individual user group. A different sheet should be used for each user group. All water quantity usage figures—gallons per hour (gph), liters per hour (L/h), gallons per minute (gpm), liters per second (L/sec), and minutes of use per hour (min use/h)—are suggested. The designer must ascertain the correct quantities through actual fixture/device/equipment literature (e.g., shop drawings) and/ or discussions with the owner and/or user. The “fixture” column lists fixtures in a facility that use hot water. The designer may add other fixtures to this list if necessary. The “quantity” column indicates the number of those fixtures located in the user group area. “Gpm (L/sec)” is the flow rate from the fixture used in the calculation. “Min use/h” is the estimated use of the fixture in 1 h. The next section, “temperature at outlet,” is for the water temperature at the faucet outlet not the system temperature. This is important, since cold water will be added to the system hot water to obtain the desired outlet temperature. Because of this,


141

the flow from the faucet is not all hot water. Table 1.1 is used to determine the actual amount of hot water needed at the faucet outlet. The “temperature at outlet” section is split into four subsections, each having a different faucet outlet water temperature. For the last subsection, labeled “other,” any temperature may be used, but the temperature must be the same for all fixtures used in that column. Each temperature subsection is split into two more subsections, “gpm (L/sec)” and “gph (L/h).” The equation for each is noted on the worksheet. When the fixtures in the user group are tabulated, each column is added and the totals are placed at the bottom of the sheet under “totals.” The user group “usage factors” for gpm (L/sec) and gph (L/h) are found in Table 8.2. Each total is multiplied by the appropriate usage factor to get the “user group totals,” which are used on “Worksheet 8.B — User Group Totals.” The user group totals are the amount of hot water predicted to be used in a particular user group during the peak hour(s). Designers should use their best judgment when working with these figures.

142


Worksheet 8.A—User Group Temperature at Outleta (°F) A Fixture

B

Qty. GPM

C 105° Min ___________ Use/H GPM GPH

Bathroom group tub/shower & lavatory

2.5

10

Public lavatory

0.5

10

Private lavatory

2

4

Single bowl sink

2.5

1

Double Bowl Sink

2.5

Bathtub

7

10

Shower

2.5

10

4.5

1

Floor receptor

4.5

1


2.5

10

15

Large hydro-tub (more than 100 gal)

15

110° ___________ GPM GPH

1

Flushing rim sink

Small hydro-tub (less than 100 gal)

(GPM = A × B GPH = A × B × C)

Laundry tub

4.5

1


4.5

6


4.5


7

—

Triple compartment sink, per faucet

9

—

Commercial kitchen, single sink

9

—

Commercial kitchen, double sink

9

—

Commercial kitchen, prerinse

2.5

—


9

10

3

TOTALS: Usage Factors (UF) (Refer to Table 8.2): User Group Totals (UF × Totals); Transfer to Worksheet 8. B: aTemperatures are at faucet outlet NOT system temperature.

140° ___________ GPM GPH



143

Worksheet 8.A(M)—User Group Temperature at Outleta (°C) A Fixture

Qty.

B

C

(L/Sec = A × B



0.16

10

Public Lavatory

0.03

10

Private Lavatory

0.13

4

Single Bowl Sink

0.16

1

Double Bowl Sink

0.16

1

Bathtub

0.44

10

Shower

0.16

10

Flushing Rim Sink

0.28

1

Floor Receptor

0.28

1


0.16

10

Small Hydro-Tub Less Than 378.5 L

0.95

Large Hydro-Tub More Than 378.5 L

0.95

Laundry Tub

0.28

1


0.28

6


0.28

3


0.44

—


0.57

—


0.57

—


0.57

—

Commercial Kitchen Pre-rinse

0.16

—


0.57

10

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

TOTALS: Usage Factors ( UF) (Refer to Table 8.2): User Group Totals ( UF × Totals); Transfer to Worksheet 8.B: aTemperatures are at faucet outlet NOT system temperature.

60° ___________ L/Sec L/H


144


Worksheet 8.B—User Group Totals This worksheet may be copied by the designer for use in calculating a facility’s hot water requirements. The “totals” found at the bottom of the sheet indicate the predicted amount of hot water the facility will use during the peak usage hour. Designers should use their best judgment when working with these numbers to determine the amount of hot water supplied to the facility. The items in the first, or “user group,” column are obtained from Worksheet 8.A. As seen, the user group totals from Worksheet 8.A are placed in the columns under the appropriate “temperature at outlet,” “gpm (L/sec),” and “gph (L/h)” headings. All of the user group totals for gpm (L/sec) are added together and the resulting number is placed in the “Subtotals” section near the bottom of the worksheet. This also is done for the gph (L/h) figures. Designers need to determine when more than one hot water heater supply temperature (e.g., 105°F, 110°F, 140°F [41°C, 43°C, 60°C]) will be required in the facility. When more than one water heater is required to supply different temperatures, separate Worksheets 8.A and 8.B should be used for each water heater system. Subtotal each “temperature at outlet” column, use Table 1.1 to look up the hot water multiplier for the system water temperature supplied to the facility, then multiply each subtotal by its appropriate multiplier. When this is done, total the actual gpm (L/sec) and gph (L/h) demands for the system water temperature supplied to the facility (the bottom row of the worksheet), and put the resulting numbers under “totals” at the bottom right of the worksheet. These totals are the gpm (L/sec) and gph (L/h) the water heater(s) are required to supply to the facility. Designers should use their best judgment when working with these figures.


145

Worksheet 8.B — User Group Totals Temperature at Outleta (°F) User Group

105° 110° ___________ ___________ GPM Use/H GPM GPH

140° ___________ GPM GPH


Nursing care facility Resident area Nurses’ station Hydrotherapy Dietary & food service Central bathing Miscellaneous areas Retirement home Resident rooms Miscellaneous areas SUBTOTALS: Hot Water Multiplier, P (Water Heater Temp. _____ °F)b TOTALSc (Refer to Table 1.1): Subtotals × Hot Water Multiplier: Note: User group totals are taken from Worksheet 8.A. aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

GPM

GPH

146



41° ___________ L/Sec L/H

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H


Nursing care facility Resident area Nurses’ station Hydrotherapy Dietary & food service Central bathing Miscellaneous areas Retirement home Resident rooms Miscellaneous areas SUBTOTALS: Hot Water Multiplier, P (Water Heater Temp. _____ °C)b TOTALSc (Refer to Table 1.1): Subtotals × Hot Water Multiplier: Note: User group totals are taken from Worksheet 8.A. aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

L/Sec

L/H


147

Worksheet 8.A—User Group—Example This is a copy of Worksheet 8.A with recommendations on temperature at outlet and other comments. (See worksheet footnotes.) Designers should use their best judgment and take into account national, state, and local codes when considering these recommendations.

Worksheet 8.A—User Group — Example Temperature at Outleta (°F) A Fixture

B

Qty. GPM

Bathroom Group Tub/Shower & Lavatoryb,c Public Lavatoryb Private Lavatoryb Single Bowl Sinkb Double Bowl Sinkb Bathtube Showerb Flushing Rim Sinkf Floor Receptorf Small Hydro-Tub Less Than 100 Gald Large Hydro-Tub More Than 100 Gald Laundry Tubf Residential Washing Machinef Residential Dishwasherf Commercial Dishwasherj Triple Compartment Sink Per Fauceth,i Commercial Kitchen Single Sinkh,i Commercial Kitchen Double Sinkh,i Commercial Kitchen Prerinseg Hose Station or Cart/Can Washh

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

2.5 0.5 2 2.5 2.5 7 2.5 4.5 4.5

10 10 4 1 1 10 10 1 1 Based on 15 tub size Based on 15 tub size 4.5 1

*l * * * * * *

110° ___________ GPM GPH

140° ___________ GPM GPH


* * * * * * *

4.5 6 4.5 3 7 Equip. used

* *

* * *

*

9

—k

*

90

9

—

*

30

9

—

*

60

2.5

—

*

45

9

10

*

*


(Continued)

148


(Worksheet 8.A Example continued) Note: GPM calculation is for a semi-instantaneous water heating system. GPH calculation is for a storage type water heating system. aTemperatures are at faucet outlet NOT system temperature. bBased on ANSI standard of 2.5 gpm for showerheads, 2.5 gpm for sinks, 2.0 gpm for lavatories, and 0.5 gpm for public lavatories. cBased on the shower as the dominant fixture. dBased on the valve size used. Designer must base design on the type of valve that is specified or present in an existing facility. eSame as “d” except 2 baths per hour. fBased on 4.5 gpm and ½ in. hot water supply running full open at 6 ft/sec maximum velocity. gConsidered same as shower. hNine gpm based on ¾ in. hot water supply running full open at 6 ft/sec maximum velocity. iBased on Table 8.1, “General Purpose Hot Water Requirements for Various Kitches Uses” (gph). jBased on the equipment used. Designer must determine which model is used. kWhere a dash (—) appears, please refer to Table 8.1 for the recommended hourly use figure. lAn asterisk (*) indicates the recommended outlet temperature.


149

Worksheet 8.A(M)—User Group—Example Temperature at Outleta (°C) A Fixture

Qty.

Bathroom group tub/shower & 1,2 lavatoryb,c Public lavatoryb 1 b Private lavatory 1 Single bowl sinkb 1 Double bowl sinkb 1 Bathtube 4 Showerb 1 Flushing rim sinkf 5 Floor receptorf 5 Small hydro-tubd (less than 378.5 L) 3 Large hydro-tubd (more than 378.5 L) 3 Laundry tubf 5 Residential washing machinef 5 Residential dishwasherf 5 Commercial dishwasherj 9 Triple compartment sink per fauceth,i 7,8 Commercial kitchen single sinkh,i 7,8 Commercial kitchen double sinkh,i 7,8 Commercial kitchen prerinseg 6 Hose station or cart/can washh 7

B

C

(L/Sec = A × B


0.16 0.03 0.13 0.16 0.16 0.44 0.16 0.28 0.28

10 10 4 1 1 10 10 1 1 Based on 0.95 Tub Size Based on 0.95 Tub Size 0.28 1 0.28

*l * * * * * *

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H


* * * * * * *

6

0.28

3 Equip. 0.44 used

*

*

*

* *

*

0.57 —k

*

340.65

0.57

—

*

113.55

0.57

—

*

227.10

0.16

—

*

170.33

0.57

10

*

*

TOTALS: Usage Factors (UF) (Refer to Table 8.2): User Group Totals (UF × Totals); Transfer to Worksheet 8.B

(Continued)

150


(Worksheet 8.A[M] Example continued) Note: L/sec calculation is for a semi-instantaneous water heating system. L/h calculation is for a storage type water heating system. aTemperatures are at faucet outlet NOT system temperature. bBased on ANSI Standard of 0.16 L/sec for showerheads, 0.16 L/sec for sinks, 0.13 L/sec for lavatories, and 0.03 L/sec for public lavatories. cBased on the shower as the dominant fixture. dBased on the valve size used. Designer must base design on the type of valve that is specified or present in an existing facility. eSame as “d” except 2 baths per hour. fBased on 0.28 L/sec and DN15 hot water supply running full open at 1.83 m/sec maximum velocity. gConsidered same as shower. h0.57 L/sec based on DN20 hot water supply running full open at 1.83 m/sec maximum velocity. iBased on Table 8.1, “General Purpose Hot Water Requirements for Various Kitchen Uses” (L/h). jBased on the equipment used. Designer must determine which model is used. kWhere a dash (—) appears, please refer to Table 8.1 for the recommended hourly use figure. lAn asterisk (*) indicates the recommended outlet temperature.


151

Table 8.1—General Purpose Hot Water Requirements for Various Kitchen Uses This table, which supplies information on water usage for various kitchen uses, should be used for the dietary and food service user group.

Table 8.1 General Purpose Hot Water Requirements for Various Kitchen Uses Equipment

GPH

L/H

Vegetable sink

45

170.33

Single compartment sink

30

113.55

Double compartment sink

60

227.10

Triple compartment sink

90

340.65

Prescrapper (open type)

180

681.30

Prerinse (hand operated)

45

170.33

Prerinse (closed type)

240

908.40

Recirculating prerinse

40

151.40

Bar sink

30

113.55

5

18.93

Lavatories (each)

Source: Values are extracted from Dunn et al. [1959] 1989. Chapter 4. ASPE Data Book. Table 9. Note: Requirements are for water at 140°F (60°C).

152


Table 8.2—Usage Factors for User Groups This table provides the recommended usage factors for use with Worksheet 8.A. The following discussion gives the background of how these numbers were determined. (They represent a consensus of opinion of a group of experienced designers; however, designers should use their best judgment when working with these figures).

Table 8.2 Usage Factors for User Groups Nursing/Intermediate Care Facility User Groups Resident Area

GPM (L/Sec) GPH (L/H)

0.10 0.30

Nurses’ Station

0.05 0.50

Hydrotherapy

Dietary & Food Service

Central Bathing

Misc. Areas

0.25 0.90

0.40 0.90

0.25 0.90

0.05 0.10

Retirement Home User Groups GPM (L/Sec) GPH (L/H)

Resident Rooms

Laundry

Misc. Areas

0.10 0.40

0.50 0.75

0.05 0.10

Note: Based on a peak usage hour with a 3-h peak period.

General The “gpm (L/sec)” figure is based on the possibility that every hot water using fixture will be operated in any 1 min (sec). The “gph (L/h)” figure is based on the possibility that every hot water using fixture will be operated during a 1-h period. These figures are based on a peak usage hour with a 3-h peak period. Nursing/Intermediate care facility Resident area Many residents in nursing care areas are not ambulatory and require staff assistance to use the toilet/bathing facilities. Residents of intermediate care areas generally are ambulatory and thus can use the shower facilities without assistance. The lavatory is a fixture that is heavily used by the staff. The 0.10 (10%) usage factor for the gpm (L/sec) is based


153

on the fact that not all residents use their fixtures during the same minute. Also, fixtures in this user group flow less water per minute than fixtures elsewhere and are used for short periods of time. The 0.30 (30%) usage factor for the gph (L/h) is based on the fact that fixtures in this user group use less water than fixtures elsewhere and are used for short periods of time. Nurses’ station This user group is in use 24 h a day but typically is used most heavily during shift changes. This is because of the preparation necessary before residents can be aided. The 0.05 (5%) usage factor for the gpm (L/sec) is based on the relationship between the staff and residents. During a peak 3-h period of hot water use, the resident area is used more heavily than the nurses’ station. Since many residents need assistance using the bathing/shower facilities, staff members are in the resident area aiding residents and not at the nurses’ station using the fixtures there. The 0.5 (50%) usage factor for the gph (L/h) is also based on these same issues, but because of the time staff members spend at the nurses’ station organizing/distributing medicines and doing other work, the hand washing fixtures there are used extensively. Hydrotherapy When in operation, this area is a large water user. The therapy staff can be split between the physical therapy and the hydrotherapy areas. The 0.25 (25%) usage factor for the gpm (L/sec) is based on the cyclical use of the hydrotherapy tubs and on the assumption that staff members are also doing physical therapy. The 0.90 (90%) usage factor for the gph (L/h) is based on the assumption that during the peak usage time, almost all of the fixtures in this area are in use. This assumes that the staff schedules the water therapies during one time and the physical therapies during another. Dietary and food service This area is a large water user. Depending on the size of the facility, the usage of water for cooking and for cleaning may over-

154


lap. The 0.40 (40%) usage factor for the gpm (L/sec) is based on the assumption that cleaning (washing of dishes, etc.) does not occur in the same minute as food preparation. Also, it assumes that the sinks are filled and then work is done using an intermittent, not a steady, water supply. The 0.90 (90%) usage factor for the gph (L/h) is based on the assumption that most of the area fixtures are used during one of the hours of the facility’s peak usage time. Central bathing When in operation, this area is a large water user. Staff members set a schedule for bathing nonambulatory residents, and during that time only one bathing fixture is used. The worst case scenario is when the residents are assisted by staff. This is because the staff are on a schedule and bathe the residents based on that schedule. The 0.25 (25%) usage factor for the gpm (L/sec) is based on the use of one tub at a time in each room (assuming each room has a shower, a residential tub, and a non-ambulatory residents’ bathing tub). Also taken into consideration was the time needed for the staff to get the residents and to dry them off. The 0.90 (90%) usage factor for the gph (L/h) is based on the fact that during peak usage time almost all of the fixtures in this area are used. Miscellaneous areas The rest of the facility uses water, but not during the facility’s peak usage time and not as much as those areas already discussed. This is because most of the staff are not in the miscellaneous areas. These areas should be taken into account, though, because water using fixtures are available and used there. The 0.05 (5%) usage factor for the gpm (L/sec) is based on the fact that a very small number of the fixtures are used during 1 min of the facility’s peak usage time. The 0.10 (10%) usage factor for the gph (L/h) is based on the fact that most of the fixtures in these areas are not used during the facility’s peak usage hour.


155

Retirement home Resident rooms The residents of a retirement home are ambulatory and do not require staff assistance to use the toilet/bathing facilities. As noted earlier, this type of facility is similar to an apartment building, but its residents are of a uniform age group. The 0.10 (10%) usage factor for the gpm (L/sec) is based on the fact that when the shower is in use, the room’s lavatory and kitchen sink are not in use during the same minute, and not all residents are using the fixtures. The 0.40 (40%) usage factor for the gph (L/h) is based on the fact that the kitchen sink and either the shower or the lavatory are used during an hour of peak usage time. Laundry The laundry area of a retirement home is smaller than one for a typical apartment building. This is because the usage time for a retirement home laundry is more spread out over the course of the day since residents typically do not work. The 0.50 (50%) usage factor for the gpm (L/sec) is based on the assumption that when one washer starts its filling cycle another is being filled with clothes, and the second machine’s cycle begins when the first washer is still filling. Though the two washers fill at the same time, it is assumed that only half of the other washers are in use in the peak moment. Also, when a resident is using the washers, the fixtures in his/her apartment are not in use. The 0.75 (75%) usage factor for the gph (L/h) is based on most of the washers being used during a peak usage period. Also, there is the possibility that a resident may leave the laundry room and go back to his/her room and use the fixtures there. Miscellaneous areas Though the rest of the facility’s fixtures use water, they are not heavily used fixtures. That is because, if the facility is separate from the nursing care facility, the staff is small. If it is attached to the nursing care facility, staff members are generally in the other areas. Miscellaneous areas should be taken into account, though, because water using fixtures are available and used there.

156


The 0.05 (5%) usage factor for the gpm (L/sec) is based on the assumption that only a very small number of the fixtures are used during any 1 min of the facility’s peak usage time. The 0.10 (10%) usage factor for the gph (L/h) is based on the assumption that most of the fixtures in these areas are not used during the facility’s peak usage hour.

QUESTIONS FOR OWNER OR CLIENT Nursing/Intermediate Care Facility Resident areas/Nurses’ stations 1. Are resident rooms private or semiprivate? 2. Does each resident room have a shower/tub or is there a central bathing area? 3. Determine the flow from shower heads or tub flow/capacities. Hydrotherapy 1. What are the number and sizes of the tubs in the area? 2. What is the number of planned therapies per hour? 3. What hours is the department in use? 4. What is the desired fill time for each tub? 5. Are the tubs fully filled for cleaning between therapies? 6. What water temperatures are used for the therapies? 7. Is there a shower for bathing purposes in the area? Dietary and food service 1. What is the number of meals provided for each mealtime/ day? 2. How many dishwashers are there and what are the type, size, gallons (liters) per cycle, cycles per hour, and temperature required for each? 3. What are the type and number of sinks, prerinses, etc., in the area?


157

4. Are cart washers used? If so, during what hours are they used and what temperatures are desired? Central bathing 1. What are the hours of scheduled bathing and the typical starting time? 2. What is the number of tubs/showers? 3. What is the number of nonambulatory resident bathing tubs, and what are their types and water demands? 4. Is there a desired temperature of the water the staff uses to bathe residents? Laundry 1. What are the number and sizes of the washing machines in the area (pound [kilogram] capacity and gallons per hour per pound [liters per hour per kilogram])? 2. What is the number of planned laundry operations (loads) per hour? 3. What are the start time and the hours the department is in use? 4. What are the temperatures of water to be used? Miscellaneous areas (e.g., administration and maintenance) 1. If there are areas with showers, determine the flow rates of the shower heads. 2. What are the water temperatures needed in these areas? 3. What is the acceptable time delay between the hot tap opening and the delivery of acceptable water (due to the length of the branch piping)?

Retirement Home Resident areas/apartments 1. Are resident rooms single or double bedroom units? 2. Is the facility set up so that the spouse of a person in nursing or intermediate care has priority use?

158


3. What is the flow from shower heads or the tub flow/ capacities? 4. Do the apartments have dishwashers/ washing machines or the possibility of the addition of such in the future? Laundry 1. What are the number and sizes of the washing machines in the area (pound [kilogram] capacity and gallons per hour per pound [liters per hour per kilogram])? 2. What are the start time and the hours the room is available for use? 3. What water temperatures are used/needed? Miscellaneous areas (e.g., maintenance) 1. If there are areas with showers, determine the flow rate of the shower heads. 2. What water temperatures are used/needed in these areas?

EXAMPLE: 48-BED NURSING/INTERMEDIATE CARE AND RETIREMENT HOME The facility in question has a 48-resident-bed nursing/intermediate care unit with an attached 24-single-bedroom retirement home. It is a complete care, 24 h/day facility with a laundry. The laundry facility has its own water heater due to the elevated temperature and load entailed.

Description of User Groups Nursing/intermediate care facility Resident area The facility has 32 nursing care beds and 16 intermediate care beds. It has a three-wing layout with nursing care residents in one wing and intermediate care beds in the other two. (The second intermediate care wing is considered a swing care wing; it also could be used for nursing care.) The rooms are double resident rooms with a water closet and lavatory


159

(2.0 gpm [0.13 L/sec] typical) in each. Each wing has a clean utility room (single bowl sink, 2.5 gpm [0.16 L/sec] typical), a soiled utility room (double bowl sink, hand washing lavatory, and flushing rim sink with bedpan washer), and a janitors’ closet with receptor. (There are a total of 27 lavatories, 3 single sinks, 3 double bowl sinks, 3 flushing rim sinks, and 3 floor receptors in the resident area.) Nurses’ station A single nurses’ station provides service to the three wings. The station has a medical drug dispensing room (single sink), a staff toilet room (hand washing lavatory), and a sink for general use. Hydrotherapy The hydrotherapy area has a hip/leg tub (100 gal [378.50 L]), arms/hip/leg/back tub (110 gal [416.35 L]), a hands/elbows/ arms tub (25 gal [94.63 L]), and a hand washing lavatory. The 25-gal (94.63-L) arms tank is filled using the hip/leg tub valve. Dietary and food service The dietary department provides three hot meals a day and a cold meal at night. It is a full-service department with the following equipment: a triple compartment sink with prerinse, a scrapping sink with prerinse, a dishwasher, a double sink for food thawing, a sink for vegetable preparation, and a hand washing lavatory. The department starts operation at 6:00 A.M. Through a discussion with the food service consultant, the designer learned that the department makes 200 meals a day. A water temperature of 140°F (60°C) is required at all fixtures except the hand washing lavatory, where 110°F (43°C) water is needed. The dishwasher requires 180°F (82°C) rinse water and the 140°F (60°C) water will be boosted at the dishwasher with an electric booster heater. Central bathing One of the intermediate care wings has a tub room with one bathtub and one shower for residents’ private or assisted use. The tub rooms for the nursing care wing and the second intermediate care wing each have one bathtub and shower for

160


private or assisted use and a specialized tub for nonambulatory residents. (The second intermediate care wing is considered a swing care wing; it also could be used for nursing care.) Each tub room has a water closet and lavatory for staff and resident use. Laundry The facility sends the bulk of its laundry out to an off-site location. There are three residential type washers and dryers for the residents’ personal use. Miscellaneous areas The administration area has two public restrooms each with two lavatories (0.5 gpm [0.03 L/sec]). There also is a small kitchenette with a sink (2.5 gpm [0.16 L/sec]). The maintenance area has a cart wash and a service sink, both of which use 140°F (60°C) water. The area also has male and female staff locker rooms, each with one shower and two lavatories. Retirement home The retirement home is a 24-unit complex attached to the nursing/intermediate care facility. It is designed for the spouses of residents in the nursing care facility. Its hot water is supplied by the nursing care facility’s system. Resident rooms Each unit has a kitchen area with a double bowl sink and the capability for a dishwasher, and a bathroom with a tub/ shower and a lavatory. Laundry The complex has a laundry room with four residential type washing machines and a laundry tub. The room is scheduled to be open 24 h/day. Miscellaneous areas The complex has a lounge and social gathering area. There are two toilet rooms in the area, each with a lavatory, and


161

there is a single bowl sink in the lounge. A floor receptor is located in a small room off the corridor.

Questions for Owner or Client (This is a sample application of the questions from the previously defined user group analysis. Answers to questions appear in boldface type.) Nursing/intermediate care facility Resident areas/nurses’ stations 1. Are resident rooms private or semiprivate? • Semiprivate (double) 2. Does each resident room have a shower/tub or is there a central bathing area? • Central bathing 3. Determine the flow from the shower head or the tub flow/ capacity. • This is a new facility, thus, none exist. Hydrotherapy 1. What is the number and what are the sizes of the tubs in the area? • 1 at 100 gal (378.50 L), 1 at 110 gal (416.35 L), and 1 at 25 gal (94.63 L) 2. What is the number of planned therapies per hour? • Two total 3. What hours is the department in use? • 8:00 A.M. – 5:00 P.M. 4. What is the desired fill time for each tub? • 15 gpm (0.95 L/sec) valve is used, thus, fill time is 7 min. 5. Are the tubs fully filled for cleaning between therapies? • Yes 6. What water temperatures are used for the therapies? • 103°F (39°C)

162


7. Is there a shower for bathing purposes in the area? • No, but a 2.0 gpm (0.13 L/sec) lavatory is present. Dietary and food service 1. What is the number of meals provided each mealtime/ day? • 200 per day 2. How many dishwashers are there and what are the type, size, gallons per cycle, cycles per hour, and temperature required for each? • One, Hobart AM14, 1.2 gal per rack at 53 racks = 64 gal per cycle (56.78 L per rack at 53 racks = 3009.34 L per cycle), 1 cycle per h, 140°F (60°C). 3. What is the number of sinks, prerinses, etc. in the area and what is the type of each? • Triple compartment sink w/prerinse, scrapping sink w/prerinse, double sink for food thawing, sink for vegetable prep, and a hand washing sink. 4. Are cart washers used? If so, during what hours are they used and what temperatures are desired? • Yes, used after meals are served, 1400F (60°C). Central bathing 1. What are the hours of scheduled bathing and what is the typical starting time? • Staff-assisted baths are from 8:00 to 11:00 A.M. 3 days/week. • Ambulatory residents may use the bathing facilities during these times if they are scheduled and at other times if that is acceptable to staff. 2. What is the number of tubs/showers? • There are three bathing rooms, each with one tub and shower. • Each bathing room also has a hand washing lavatory, which could be used when the bath/shower is in use. 3. What is the number of nonambulatory resident bathing tubs, and what are the type and water demand of each? • Two total, 50 gal (189.25 L) each, to fill for bath use.


163

• When the special bath is used, the other tub and shower are not used. • The baths should be designed for 4 fills/h. 4. Is there a desired temperature for the water the staff uses for bathing residents? • 140°F (60°C) maximum for the baths Laundry Note: Since the fixtures in this area are for residents’ use and will be monitored, their use is covered under “Miscellaneous Areas.” 1. What is the number of the washing machines in the area and what is the size of each (pound [kilogram] capacity and gallons per hour per pound [liters per hour per kilogram])? • Three residential style • Only intermediate care residents may use, with limited supervision 2. What is the number of planned laundry operations (loads) per hour? • Nothing organized 3. What are the start time and the hours the room is in use? • The laundry room is open between 7:00 A.M. and 4:00 P.M. • Staff members desire some supervision and typically aid the residents in the use of the washers. 4. What are the temperatures of water used? Miscellaneous areas (e.g., administration and maintenance) 1. If there are areas with showers, determine the flow rate of the shower heads. • Two showers at 2.5 gpm (0.16 L/sec) each, 4 lavatories at 2.0 gpm (0.13 L/sec) each • Four public lavatories at 0.5 gpm (0.03 L/sec) each • Kitchen sink at 2.5 gpm (0.16 L/sec) • Service sink and cart wash in maintenance 2. What are the water temperatures needed in these areas? • 110°F (43°C) in administration and shower rooms

164


• 140°F (60°C) in maintenance Retirement home Resident areas/Apartments 1. Are resident rooms single or double bedroom units? • Single 2. Is the facility set up such that the spouse of a person in nursing or intermediate care has priority use? • Yes 3. What is the flow from the shower head or the tub flow/ capacity? • 2.5 gpm (0.16 L/sec) shower head 4. Do the apartments have dishwashers/washing machines or the capability of the addition of such in the future? • Dishwashers supplied by renters • Consider 24 in calculations Laundry 1. What are the number and sizes of the washing machines in the area (pound [kilogram] capacity and gallons per hour per pound [liters per hour per kilogram])? • 4 residential type 2. What are the start time and the hours the room is available for use? • Open 24 h/day 3. What are the water temperatures used/needed? • 140°F (60°C) Miscellaneous areas (e.g., maintenance) 1. If there are areas with showers, determine the flow rate of the shower heads. • None 2. What are the water temperatures used/needed in these areas? • No special temperatures

User Group Worksheets, 48-Bed Nursing/Intermediate


165

Care and Retirement Home Nursing/intermediate care facility

Worksheet 8.A—User Group: Patient Area Temperature at Outleta (°F) A

B

Fixture

Qty. GPM

Private Lavatory

27

2

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH 4

54

110° ___________ GPM GPH

3

2.5

1

7.5

7.5

Double Bowl Sink

3

2.5

1

7.5

7.5

Flushing Rim Sink

3

4.5

1

13.5

13.5

Floor Receptor

3

4.5

1

13.5

13.5

27

27

69


216

Single Bowl Sink

TOTALS:

140° ___________ GPM GPH

231


0.1

0.3

0.1

0.3


6.9

69.3

2.7

8.1


Worksheet 8.A(M)—User Group: Patient Area Temperature at Outleta (°C) A

B

C

(L/Sec = A × B

L/H = A × B × C × 60 Sec/Min)

Fixture


43° ___________ L/Sec L/H

Private Lavatory

27

0.13

4

3.51 842.4

Single Bowl Sink

3

0.16

1

0.48

28.8

Double Bowl Sink

3

0.16

1

0.48

28.8

Flushing Rim Sink

3

0.28

1

0.84

50.4

Floor Receptor

3

0.28

1

0.84

50.4

TOTALS:

4.47 900

1.68 100.8


0.1

0.1

0.3


0.45 270

0.17

30.24

0.3

60° ___________ L/Sec L/H



Worksheet 8.A—User Group: Nurses’ Station Temperature at Outleta (°F)

166


A Fixture

B

Qty. GPM

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

Private Lavatory

1

2

4

2

8

Single Bowl Sink

2

2.5

1

5

5

TOTALS:

7

13


0.05

0.5


0.4

6.5

110° ___________ GPM GPH

140° ___________ GPM GPH



Worksheet 8.A(M)—User Group: Nurses’ Station Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B


Private Lavatory

1

0.13

4

0.13

31.2

Single Bowl Sink

2

0.16

1

0.32

19.2

TOTALS:

0.64

50.4


0.05


0.03

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

0.50 25.2


60° ___________ L/Sec L/H



167


B

Qty. GPM

Private Lavatory Large Hydro-Tub More Than 100 Gal

1

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

2

4

2 (4 fills) 15

7

2

110° ___________ GPM GPH

140° ___________ GPM GPH


8

30

420

30

420

TOTALS:

2

8


0.25

0.9

0.25


0.5

7.2

7.5

0.9 378


Worksheet 8.A(M)—User Group: Hydrotherapy Temperature at Outleta (°C) A Fixture Private Lavatory

B

C

(L/Sec = A × B

41° Min ___________ Qty. L/Sec Use/H L/Sec L/H 1

0.13

4

Large Hydro-Tub 2 More Than 378.5 L (4 fills) 0.95

7

0.13

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

39° ___________ L/Sec L/H

30.28

TOTALS:

0.13

30.28


0.25

0.90


0.03

27.25


1.9

798

1.9

798

0.25

0.90

0.48 718.2

168


Worksheet 8.A—User Group: Dietary & Food Service Temperature at Outleta (°F) A

B

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

Fixture

Qty. GPM

Private Lavatory

1

2

4


1

7

64


2

9


1


2

110° ___________ GPM GPH

140° ___________ GPM GPH

8 7

64

90 GPHb

18

180

9

30 GPHb

9

30

1

9

60 GPHb

9

60


2

2.5

45 GPHb

5

90


1

9

10

9

90

57

514

TOTALS:

2

8


0.4

0.9

0.4


0.8

7.2

22.8


0.9 463



169

Worksheet 8.A(M)—User Group: Dietary & Food Service Temperature at Outleta (°C) A

B

C

(L/Sec = A × B

L/H = A × B × C × 60 Sec/Min)

Fixture


Private Lavatory

1

0.13

4


1

0.44

64


2

0.57

340.65 L/hb

1.14

681.30


1

0.57

113.55 L/hb

0.57

113.55


1

0.57

227.10 L/hb

0.57

227.10


2

0.16

170.33 L/hb

0.32

340.66


1

0.57

0.57

342

0.13

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

31.2 0.44 1689.6

10

TOTALS:

0.13

31.2


0.40

0.90


0.05

28.08


3.6 0.40

3394.21 0.90

1.44 3054.79


170


Worksheet 8.A—User Group: Central Bathing Temperature at Outleta (°F) A Fixture

B

Qty. GPM

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

Private Lavatory

3

2

4

6

24

Bathtub

3

7

10

21

210

Shower

3

Specialized Bathtub

2

2.5 15

10

7.5

200gphb 30

TOTALS:

64.5


0.25 16.1

110° ___________ GPM GPH

140° ___________ GPM GPH


75 400 709 0.9 638

aTemperatures are at faucet outlet NOT system temperature. bThis value is in total gph and does not reflect min use/h.

Worksheet 8.A(M)—User Group: Central Bathing Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B


Private Lavatory

3

0.13

4

0.39

Bathtub

3

0.44

10

1.32

Shower

3

0.16

10

0.48

Specialized Bathtub

2

0.95

757 L/hb 1.9

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

93.6 792 288 1514.00

TOTALS:

4.09 2687.6


0.25


1.02 2418.84

0.90

aTemperatures are at faucet outlet NOT system temperature. bThis value is in total L/h and does not reflect min use/h.

60° ___________ L/Sec L/H



171


B

Qty. GPM

Public Lavatory

4

0.5

Private Lavatory

5

Single Bowl Sink Shower

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH 10

2

20

2

4

10

40

1

2.5

1

2

2.5

10

2.5

25

5

50

110° ___________ GPM GPH

Flushing Rim Sink

1

4.5

1

4.5

4.5

Floor Receptor

1

4.5

1

4.5

4.5

Laundry Tub

1

4.5

1

4.5

4.5


3

4.5

6

13.5


1

9

81

10

TOTALS:

19.5

113

22.5

140° ___________ GPM GPH

90

9

90

9

90


0.05

0.1

0.05

0.1

0.05

0.1


1.0

11.3

1.1

9

0.5

9



172


Worksheet 8.A(M)—User Group: Miscellaneous Areas Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B

41° Min ___________ Qty. L/Sec Use/H L/Sec L/H 0.12

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

Public Lavatory

4

0.03

10

Private Lavatory

5

0.13

4

0.65 156

Single Bowl Sink

1

0.16

1

0.16

Shower

2

0.16

10

Flushing Rim Sink

1

0.28

1

0.28

16.8

Floor Receptor

1

0.28

1

0.28

16.8

Laundry Tub

1

0.28

1

0.28

16.8


3

0.28

6

0.84 302.4


1

0.57

10

60° ___________ L/Sec L/H

72

9.6

0.32 192

0.57 342

TOTALS:

1.25 429.6

1.70 352.8

0.57 342


0.05

0.10

0.05

0.10

0.05


0.06

42.96

0.09

35.28

0.03


0.10 34.2



173

Retirement home

Worksheet 8.A—User Group: Resident Rooms Temperature at Outleta (°F) A

B

C

(GPM = A × B GPH = A × B × C)

Fixture

Qty. GPM

105° Min ___________ Use/H GPM GPH


24

2.5

10

60

600

Double Bowl Sink

24

2.5

1

60

60


24

4.5

3

TOTALS:

120


0.1 12

660 0.4 264

110° ___________ GPM GPH

108

324

108

324

0.1 10.8

140° ___________ GPM GPH


0.4 130


Worksheet 8.A(M)—User Group: Resident Rooms Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B



24

0.16

10

3.84 230.4

Double Bowl Sink

24

0.16

1

3.84 230.4


24

0.28

3

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

6.72 1209.6

TOTALS:

7.68 460.8

6.72 1209.6


0.10

0.40 0.10

0.40


0.77 184.32 0.67

483.84


60° ___________ L/Sec L/H


174


Worksheet 8.A—User Group: Laundry Temperature at Outleta (°F) A Fixture

B

Qty. GPM

Laundry Tub

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

1

4.5

1

4

4.5

6

110° ___________ GPM GPH 4.5

140° ___________ GPM GPH


4.5

Residential Washing Machine TOTALS: Usage Factors (UF) (Refer to Table 8.2):

0.5


18

108

22.5

113

0.75 11.3

84.4


Worksheet 8.A(M)—User Group: Laundry Temperature at Outleta (°C) A

B

C

(L/Sec = A × B

L/H = A × B × C × 60 Sec/Min)

Fixture


Laundry Tub

1

0.28

1

0.28


4

0.28

6

1.12 403.2


43° ___________ L/Sec L/H 16.8

1.40 420 0.50

0.75 0.7

315


60° ___________ L/Sec L/H



175


B

Qty. GPM

C

(GPM = A × B GPH = A × B × C)

105° Min ___________ Use/H GPM GPH

Public Lavatory

2

0.5

10

Single Bowl Sink

1

2.5

1

Floor Receptor

1

4.5

1

1 2.5

110° ___________ GPM GPH

140° ___________ GPM GPH


10 2.5

12.5

4.5

4.5

4.5

4.5

TOTALS:

3.5

Usage Factors (UF) (Refer to Table 8.2):0.05

0.1

0.05

0.1


0.2

1.3

0.2

0.5


Worksheet 8.A(M)—User Group: Miscellaneous Areas Temperature at Outleta (°C) A Fixture

B

C

(L/Sec = A × B


Public Lavatory

2

0.03

10

0.06

Single Bowl Sink

1

0.16

1

0.16

Floor Receptor

1

0.28

1

L/H = A × B × C × 60 Sec/Min)

43° ___________ L/Sec L/H

36 9.6

45.6

0.28

16.8

0.28

16.8

TOTALS:

0.22

Usage Factors (UF) (Refer to Table 8.2):0.05

0.10

0.05

0.10


0.01

4.56

0.01

1.68


60° ___________ L/Sec L/H


176


User Group Totals Worksheet, 48-Bed Nursing/ Intermediate Care and Retirement Home


105° ___________ GPM GPH

110° ___________ GPM GPH

140° ___________ GPM GPH


Nursing care facility PATIENT AREAS

6.9

69.3

NURSES’ STATION

0.4

6.5

HYDROTHERAPY

0.5

7.2


0.8

CENTRAL BATHING

16.1

MISCELLANEOUS AREAS

1.0

2.7

8.1

7.2

22.8

341

0.5

9

23.3

350

7.5

378

7.5

378

638 11.3

1.1

9.0

Retirement home RESIDENT ROOMS

12

264

LAUNDRY MISCELLANEOUS AREAS SUBTOTALS:

0.2

1.3

37.9 1005

10.8

130

11.3

84.4

0.2

0.5

26.1

232


0.61

0.61

0.67

0.67

1

1

0.59

0.59 TOTALSc

(Refer to Table 1.1): Subtotals × Hot Water Multiplier

GPM 23.1

613

17.5

155.4

23.3

350

4.4

223

aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

GPH

68.3 1341


177


41° ___________ L/Sec L/H

43° ___________ L/Sec L/H

60° ___________ L/Sec L/H

Other (39°) ___________ L/Sec L/H

Nursing care facility PATIENT AREAS

0.45

NURSES’ STATION

0.03

270 25.2

HYDROTHERAPY

0.03

27.25


0.05

28.08

CENTRAL BATHING

1.02 2418.84

MISCELLANEOUS AREAS

0.06

42.96

0.77

184.32

0.17

30.24 0.48 718.2 1.44 3054.79

0.09

35.28 0.03

34.2

Retirement home RESIDENT ROOMS LAUNDRY

0.67 483.84 0.7

315

MISCELLANEOUS AREAS

0.01

SUBTOTALS:

2.42 3001.21

1.64 866.04 1.47 3088.99

0.48 718.2

0.61

0.67

0.59

4.56

0.01

1.68


0.61

0.67 1

1

0.59 TOTALSc

(Refer to Table 1.1): Subtotals × Hot Water Multiplier

L/Sec 1.48 1830.74

1.10 580.25 1.47 3088.99

L/H

0.28 423.74 4.33 5923.72

aTemperatures are at faucet outlet NOT system temperature. bTemperature of water leaving the water heater supplying the facility. cTotal hot water required. Temperature based on water heater temperature.

Jail and Prison Housing Units

9

179

JAIL AND PRISON HOUSING UNITS

INTRODUCTION The objective of this chapter is to help the designer understand and deal with the problems of designing water heating systems for jail and prison housing units. It is important that the designer recognize that each building is unique and work closely with the owner, architect, and government authorities to determine how a building will operate. A building’s operation will affect when and for how long the peak hot water demand will occur. The first part of this chapter discusses generally some of the design criteria and areas of special concern involved in designing for jail and prison housing units. The second part gives two practical examples of sizing methodology, one for jails and one for prisons.

GENERAL The design criteria used to design hot water systems for jail housing units differ from those used for prison housing units. This difference is due to the fact that the facilities are used for different purposes. Jails are used primarily to house people awaiting trial or serving short sentences. Prisons are used to house convicted criminals serving long prison terms. This difference affects the prisoners’ daily routines, which, in turn, determine when the facilities’ peak hot water demands occur. It is required that hot water temperature for the showers and lavatories in jails and prisons be limited to between 100 and


180


110°F (38 and 43°C). This temperature range has been established to prevent inmates from using hot water as a weapon.1 The generally used standard temperature is 105°F (41°C). Pushbutton type self-closing or timed-control valves are used to deliver hot water of this temperature to the showers and lavatories. Occasionally an owner will require that a shower control valve that allows some inmate control of shower water temperature be provided. New security type valves provide this feature. Hot water at the design temperature must be furnished at the fixture because of the lower-than-usual water temperature and the self-closing features of inmate control valves. The designer should take into consideration that the typical life of a jail or prison is 50 to 100 years and that any system installed must be accessible for replacement or repair. Large jail facilities and all prisons have central laundry facilities and central kitchens. The hot water systems for the laundry and kitchen areas should be separate from those for housing because these areas have very different hot water demands. For instance, the temperature of the hot water delivered will be higher, between 140 and 180°F (60 and 82°C). If a centralized water heating system is used for the general purpose and kitchen/laundry water, then a fail-safe water tempering system must be installed for the general purpose water.

Hot Water Demand The usual fixtures requiring hot water found in housing units are showers and lavatories. Some units also have small kitchens or serving areas, which may have additional sinks and small dishwashers. Such serving areas are project specific. In jails, very often one or two residential type washing machines are required for each housing unit pod (a group of 10 to 20 cells). The typical housing unit is composed of multiple pods, with each cell opening onto a day room. Currently it is recommended that there be one shower for every eight inmates and a lavatory in each cell. 2 The number and location of the showers are decided by the architect in coordination with the owner and according to specific code requirements. The shower operation is the factor that determines the required sizes of the water heater and storage tank. 1American Corrections Association, Adult Corrections Institutions, 3d ed. 2 Ibid.


181

Primary considerations 1. The standard recommendation of eight inmates per shower was made so that all inmates could shower during a 1-h period. This arrangement allows an average of 7 min for each inmate to shower. About half that time is taken up by drying and switching inmates, leaving only about 3.5 min of actual water usage per inmate. 2. Showers are the main factor affecting water heater size. Allowance should be made for the many lavatories in housing units when sizing the storage tank. 3. The efficiency of storage systems varies from manufacturer to manufacturer, but 65 to 80% is a good efficiency range to use until you have actual data on the tank and system specified.

JAIL EXAMPLE This is an example of a jail housing unit with six pods of 24 cells each (one inmate per cell) and three showers per pod. Assume that the hot water generated is 140°F (60°C) and the incoming water temperature is 50°F (10°C).

Questions 1. Will the inmates be required to shower at a specific time? • No 2. Will all the cell pods release their inmates for showering within the same hour? • Yes. (This means that the design must accommodate a 1-h recovery period.) 3. Will the shower duration per inmate be limited? • Yes, to 7 min per inmate, with 3.5 min of water usage 4. Does the facility anticipate double bunking inmates, either now or in the future? • No

Calculations for Jail Housing Units The ratio of 140 to 50°F (60 to 10°C) water flowing at the shower can be calculated using the mixed-water formula, Equation 1.7, from Chapter 1:

182


P =


where P = Percentage of mixture that is hot water Tm= Temperature of mixed water = 105°F (41°C) Th = Temperature of hot water = 140°F (60°C) Tc = Temperature of cold water = 50°F (10°C) P =

105 – 50 55 = = 0.61 140 – 50 90

( P = 4160 –– 1010 = 5031 = 0.61) With each shower flowing 2.5 gpm (0.13 L/sec), 2.5 gpm × 0.61 = 1.53 gpm will be 140°F hot water (0.13 L/sec • 0.61 = 0.08 L/sec will be 60°C hot water) 8 inmates × 3.5 min = 28 min of water flowing per shower during the peak hour 6 pods × 3 showers per pod = 18 showers total 18 showers × 28 min = 504 min 504 min × 1.53 gpm = 771.12 gal 140°F hot water per peak hour demand (504 min • 0.10 L/sec • 60 sec/min = 3024 L 60°C hot water per peak hour demand) At this time a judgment will have to be made by the designer as to whether or not the auxiliary equipment will be operating during the peak hour. For this example, we will assume it will not.

Auxiliary Equipment Demand Door type dishwasher with internal heater = 69 gph (261.17 L/h)


183

Single compartment sink = 30 gph (113.55 L/h) Clothes washing machines, 1 per pod × 6 pods = 6 6 × 2 loads @ 20 gal/load = 240 gph (6 • 2 loads @ 75.7 L/load = 908.40 L/h) Auxiliary equipment demand for 140°F water = 339 gph (Auxiliary equipment demand for 60°C water = 1283.12 L/h) Assuming that operation of the auxiliary equipment does not coincide with the peak hour demand, sizing the heater and storage tank to handle the additional load will not be necessary. The heater size required for inmate showering is more than twice the size needed for the auxiliary equipment demand.

Recommendation Heater sizing Two heaters should be selected, each sized to serve between 60 and 100% of the total demand. In prison housing units some redundancy in the water heating system is necessary. The level of redundancy should be discussed with the facility’s owners. Storage tank sizing If the water heater is sized to meet the recovery required to handle the peak shower demand, the storage tank may be sized to handle approximately 50% of the shower demand during the period of peak use. The storage tank should be large enough to prevent the heater from cycling on and off more than four times per hour during off-peak hours. This requirement necessitates finding a balance between excessive tank size and short cycling. Calculation 771.12 gph × 0.50 = 385.6 gal (2.93 m3/h • 0.50 = 1.47 m3/h) 385.6 = 481.6 gal storage tank size 0.80

184


(

1470 L = 1837.5 L storage tank size 0.80

)

The auxiliary equipment demand of 339 gph (1283.12 L/ h) will have the greatest influence on the amount of cycling done by the heater during off-peak hours. 339 gph = 5.56 gpm average flow of 140°F water 60 1283.12 L/h = 0.36 L/sec average flow of 60°C water 60 • 60

(

)

5.56 gpm × 15 min = 83.4 gal (0.36 L/sec • 60 sec/min • 15 min = 324 L) 83.4 0.80 = 104.25 gal storage

(

324 L = 405 L storage 0.80

)

The selected size of a 481.6-gal (1837.5-L) storage tank is more than adequate to meet this demand.

PRISON EXAMPLE This is an example of a housing facility for 384 inmates. It has four wings (96 inmates per wing) and each wing has four stories (24 inmates per wing per story). A central kitchen and laundry are located in a separate building. Shower areas are provided on every floor of every wing, and each of these areas has three shower heads.

Design Criteria and Assumptions 1. Inmate lavatories and showers will be supplied with 105°F (41°C) circulated hot water. Showers are to have 2.5 gpm (0.16 L/sec) flow restrictors and lavatories 2.0 gpm (0.13 L/ sec) flow restrictors. 2. There will be separate systems for the kitchen and laundry areas. 3. The water temperature for the laundry area will be 180°F (82°C) and for the kitchen area 140°F (60°C), plus there will be a separate loop of 105°F (41°C) water for the hand washing lavatories and toilets located in the kitchen area .


185

4. Water at 140°F (60°C) will be supplied to the dishwasher. The dishwasher will have a separate booster heater to raise water temperature to the 180°F (82°C) required for the final rinse cycle. 5. The storage tank capacity varies considerably—from 0% for instantaneous heaters to more than100%. Check to determine if the owner has a preference. Remember, most owners already operate existing jails or prisons; they may have established design parameters. The initial cost of equipment, the unit performance, and operating costs are also factors to be considered when sizing the storage tank. 6. Look for additional support facilities, such as the barber shop, pantries, or an emergency medical clinic. 7. Although operating hours for the laundry area are generally from 8:00 A.M. to 5:00 P.M., review operational times and schedules with the owner. 8. Sources of heat: The selection of steam, natural gas, or electricity will have an enormous impact on the type of heater and on energy consumption. Note: A central steam generation plant may favor an instantaneous type steam-to-hot-water converter with minimum hot water storage for surges. Remember, redundancy in heaters is always required for jails and prisons to allow for problems created by inmates. The cost of generating and distributing steam is also a factor to be considered. 9. The method to use for sizing the water heater and storage tank may be determined by the owner/operator of the facility. 10. One inmate per cell equals 384 inmates. A question that should be asked is whether the owner plans to expand in the future by putting more than one inmate in each cell.

Questions 1. Will the inmates be required to shower at a specific time? • No 2. Will the shower duration per inmate be limited or do inmates have control over when they shower? • Showers are limited to 7 min per inmate, with 3.5 min of water usage per shower. 3. Will all of the cell pods release their inmates for show-

186


ering within the same hour? • Yes. (This means that the design must accommodate a 1-h recovery period.) 4. Does the facility anticipate double bunking the inmates now or in the future? • No 5. Does the facility have a work-release program? • Yes 6. What is the time allocated for the work-release inmates to shower prior to leaving for their duties in the work–release program? • One hour, at the same approximate time as the other inmates.

Calculations for Inmate Housing Units Refer to the calculations done for the jail example (page 170) for the methodology for determining the 1.53 gpm (0.1 L/sec) flow per shower head and the operation time of 28 min per shower. 48 showers × 28 min = 1344 min 1344 min × 1.53 gpm = 2056 gal of 140°F hot water for peak hour demand (1344 min • 0.096 L/sec • 60 sec/min = 7741.44 L/h of 60°C hot water for peak hour demand)

Storage Tank Sizing In this example, inmate lavatories will have the only impact on tank sizing because the kitchen and laundry will have separate systems. If the water heater is sized to meet the recovery required to handle the peak shower demand, the storage tank may be sized to handle approximately 50% of the shower demand during the period of peak use. The storage tank should be large enough to prevent the heater from cycling on and off more than four times per hour during off-peak hours. This requirement necessitates finding a balance between excessive tank size and short cycling.


187

Calculation 2056 gph × 0.50 = 1028 gal 140°F hot water (7.74 m3/h • 0.50 = 3.87 m3 60°C hot water) 1028 gal = 1285 gal storage tank size 0.80 eff.

(

3870 L = 4837.5 L storage tank size 0.80 eff.

)

Kitchen Considerations 1. The item that has the greatest effect on hot water demand is the dishwasher. Some central kitchens do not have dining areas, in which case all meals are shipped to the housing units in bulk for distribution and the dishwashers are in the housing units. 2. The temperature of the hot water going to kitchen lavatories should not exceed 110°F (43°C) for safety reasons. 3. Check to see if the dishwasher has a booster heater and determine the type of energy used (steam or electricity). This information will help you decide whether or not to generate 180°F (82°C) water. Note: Some dishwashers on the market use chemicals for disinfecting, thus the higher water temperature is not required. 4. After dishwashers, compartment sinks are the next largest user of 140°F (60°C) hot water. The higher temperature is required to cut through grease on pots and pans. Some threecompartment sinks have booster heaters in the rinse tank to maintain the higher temperature. 5. Other kitchen items that use hot water are the prerinse for the dishwasher, the vegetable sinks, and the cart washdown hose bibs. 6. Always check the kitchen consultant’s plans for hot water requirements. 7. Refer to the “Hospitals” chapter for additional information on kitchens.

188


Laundry Considerations 1. Review the laundry consultant’s plans and determine the type of washing machine/extractor used. Prison laundries are similar to hospital laundries in that they process sheets, pillow cases, and uniforms. The size and number of machines are normally decided by the owner or the consultant. 2. Inmates each generate about 30 lb (13.61 kg) of laundry a week. This consists of 1 pillowcase, 2 sheets, 1 towel, and uniforms. 3. Additionally, prison laundries usually handle the uniforms of the correctional officers. 4. Sometimes prison laundries do laundry for outside hospitals as a prison industry. 5. Consider the feasibility of a heat recovery system that uses the wash-water discharge. The laundry consultant can probably advise you about this. 6. Laundry equipment suppliers are the only reliable source of information on the hot water demands and required temperaures of their washers. They can tell you how many gallons (liters) of water the machines require and the maximum number of cycles per hour they will operate. 7. Washers demand their hot water fast. It is not unusual for a 2-in. (DN50) hot water line to be connected to the larger washers. Therefore, larger than normal storage capacity is needed to handle the surges in hot water demand. One rule of thumb is to provide 75% of the maximum hourly demand in storage; don’t provide less than 50% of that amount. 8. In 1992 a new federal law (“Bloodborne Pathogen”) was passed to protect workers against the human immunodeficiency virus (HIV) and hepatitis B virus (HBV). All detention facilities are now under this new federal regulation. A major/critical new standard was created by the law: “When an officer’s uniform becomes contaminated with blood products, the officer cannot leave his workplace with the uniform on. The facility must clean that uniform and reissue it to the officer.” The law states further that “inmate labor cannot be used when handling blood contaminated items.” A washer and dryer for the aforementioned are required to achieve compliance with the law. They should be located in a space that is under the direct supervision of an officer so the security of the officers’ uniforms will not be jeopardized.

Industrial Facilities

10

189

INDUSTRIAL FACILITIES

INTRODUCTION “Industrial facility” is such a general term that it would be impossible to describe each specific type. For the purposes of this manual, the term will mean a location where any or all of the general activities described below take place and where domestic hot water is used for personnel washing as required by code and for other purposes considered unrelated to process or product that are described in this chapter. The use of hot water for process or product preparation is outside the scope of this work.

EXAMPLES OF INDUSTRIALS 1. Manufacturing facilities are places where products are created, repaired, or assembled from parts or materials received at or produced within the same facility. The products are then finished, tested, packaged, and stored or distributed. 2. Pharmaceutical facilities are locations where products concerning medicine or drugs are created or produced from materials or ingredients that are purified, combined, or produced in the same facility. The products are then tested, packaged, and stored. 3. Pilot plants are facilities where experimental manufacturing and production techniques for new products are tested on a small scale. These plants can be either located separately or included within larger facilities.


190


4. Food product facilities are places where edible food products are received or created from ingredients that are received, purified, prepared, or produced in the same facilities. The products are then tested, packaged, and stored. Such facilities include dairies, slaughter houses, and food preparation facilities. 5. Chemical processing plants are facilities where products are purified or created from ingredients received, manufactured, or produced within the facilities. The products are then chemically combined, mixed together, or processed at these same facilities; tested, packaged, and stored. 6. Steel mills, foundries, and mining, ore processing, and petroleum refinery facilities are places where naturally occurring or refined raw materials are received or recovered, then shaped, altered, processed, or refined, and finally packaged and stored or distributed. 7. Printing and publishing facilities are places where all types of reading material, photographs, etc., are received, created, assembled, and produced; then bound, packaged, and stored. 8. Central utility generating facilities are places where power is generated and include such facilities as fossil fuel, nuclear power, hydroelectric, steam-producing, and co-generation facilities. 9. Laboratories, including biology, chemistry, and physics research and development, experimental, and testing laboratories. Excluded are laboratories used exclusively for educational purposes and those within educational facilities. 10. Warehouses are facilities where products, equipment, or components are stored while awaiting either shipment or use by the facility. 11. Fluid treatment facilities are places where fluids are received and then treated or purified prior to distribution or disposal. Such facilities include sewage, industrial, and potable water treatment plants.

GENERAL DESIGN CRITERIA The work done in industrial facilities is separated into workday hours or shifts of varying lengths, depending on the nature of the workplace. A majority of the hot water usage by workers directly engaged in production within a given facility occurs at the beginning and end of their shifts or workdays and during lunch


191

periods and breaks. The use of hot water for other general purposes is spread throughout the workday and is occasionally needed for emergency purposes such as spill cleanup.

AREAS WITHIN INDUSTRIAL FACILITIES Washrooms and Toilets Routinely, washrooms and toilet rooms are provided in separate areas for a facility’s general production staff, its production staff supervisors, and its administrative/office staff. Hot water use in the toilet areas provided for the administrative/office staff is the same as that in the toilet areas of an office building. The two toilet areas have the same characteristics of use. The number and types of fixture required are governed by the applicable plumbing code. The washrooms and toilet areas for production personnel and supervisors require different design criteria because their use is affected by work shifts. The production personnel toilet areas usually consist of locker rooms, toilet rooms, wash-up facilities, and showers. The number of the various types of fixture usually is not covered in the applicable code, therefore, judgment and prior experience are required to make this decision. Consideration must be given to the number of people using the areas when shifts change and to whether their work is “clean” or “dirty.” (Dirty work makes the clothes and person of the average production worker dirty and occurs in such facilities as foundries and steel mills.) Another consideration is whether code or client policy requires that production personnel shower prior to leaving the facility.

Wash Fixtures The wash fixtures for production personnel are often single, large fixtures with multiple wash stations. These fixtures are manufactured in various standard configurations, such as circle, semicircle, and quarter circle, and in various sizes. Spray heads ranging from 0.5 to 0.75 gpm/station (0.03 to 0.05 L/sec/station) are available for light and heavy industrial facilities. Some individual wash stations are not capable of independent operation, which means that the entire fixture would have to be turned on if just one person were washing.

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Where no client preference exists, the following general design criteria should be used to select fixtures: 1. Twenty min should be allowed at the end of a shift for wash up and showers. 2. Wash fixtures must be provided for all shift personnel. These fixtures can be either individual lavatories or group wash fountains. A generally accepted ratio of one wash station or lavatory for every six people can be used as a starting point to decide the number of fixtures, with any fraction increasing the number of fixtures by one. Where no guidance is given, one station should be provided for every 5 to 12 people, the figure chosen depending on the number of people there are. 3. Where individual wash up is anticipated, individual lavatories are preferable to group wash fountains because when just one person is washing up at a time, wash fountain spray heads provide much more water than is necessary.

Showers If not governed by local code, shower heads should each be limited to a flow rate of 2.5 gpm (0.16 L/sec). Generally, males are provided with group showers, while females are given the privacy of individual shower stalls. All new and renovated installations should be Americans with Disabilities Act (ADA) compliant. The number of shower heads is based on the number of people expected to use the washroom at each change of shift. If no code requirements are provided, use the client’s preference. Allow for a total of about 20 min for a shift to complete showering. In laboratories, offices, and other similar facilities, when showers are provided adjacent to toilet rooms (as compared to toilets adjacent to lockers and washrooms), they usually are used by personnel finishing some form of exercise (such as jogging or training on facility-provided equipment) during lunch time prior to returning to work.

SELECTION OF EQUIPMENT Water Heater When an instantaneous system is used, the most critical factor to consider when selecting a water heater capable of meeting the expected load is the minimum flow rate. No diversity factor should


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be used for dirty facilities. The shower room is considered a “dump” load, which means that almost the entire storage and recovery volume is used during the shower period. Experience has shown that 20 min is usually enough time to allow for an entire shift to shower. Each shower is assumed to last 5 min. Example 10.1 A foundry with 100 shift workers assigned to an area will be used to select a storage tank and an instantaneous heater. First we select the storage type heater: One hundred people require the use of a wash fountain. Figuring 8 people per station, 12.5 or 13 stations are needed. If we provide 12 stations (two 6station units) and allow a 20-min time frame, that gives each person 1.6 min of wash time—not quite enough to wash hands. Because of the dirty working conditions in a foundry, use two 8station units, which will allow 3.2 min per person washing time. For the showers, assume that 20% of the workers will take showers and that 5 heads are required. To calculate the necessary heater capacity, add the two requirements: For a 20-min period of time, two 8-wash station units require 5 gpm (0.32 L/sec) each. 5 gpm × 20 min = 100 gal for each station (0.32 L/sec • 60 sec/min • 20 min = 384 L for each station) 100 gal × 2 stations = 200 gal (384 L • 2 stations = 768 L) For a 5-min period of time, 5 showers flow at 2.5 gpm (0.16 L/sec). 2.5 gpm × 5 min = 12.5 gal per shower (0.16 L/sec • 60 sec/min • 5 min = 48 L) 12.5 gal × 5 showers = 62.5 gal (48 L • 5 showers = 240 L) The storage type water heater selected should have a recovery and storage capacity of delivering 262.5 gal (994 L) in 20 min. If this is the only purpose of the heater, the safest (but not necessarily the most economical) selection would be to store the entire required amount of water (plus 30% additional gal) in, say, a 341-gal (1291-L) storage tank and recover the amount of water slowly over a 6-h period. Next, we select the instantaneous heater. Wash station use is

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10 gpm (0.63 L/sec) and shower use is 12.5 gpm (0.79 L/sec). The instantaneous heater should be sized to handle a demand of 22.5 gpm (1.42 L/sec).

Storage Tank Systems that require close temperature control and flow a large amount of hot water at a steady rate over an extended period of time do not require large storage tanks. If a large storage tank is provided, there is a good probability that the water temperature will be lowered, which may be unacceptable. It would be better to select a relatively small storage tank to act as a stabilizer against demand surges, have a water heater recovery rate approximately equal to demand, and use a blending valve. This arrangement will ensure a steady supply of hot water at a constant temperature, which will allow for good modulation.

FACILITY-SPECIFIC DESIGN ISSUES Meat and Food Processing Facilities Meat, food, and other such processing facilities are required by the FDA to have their work areas and equipment sanitized each day with 180°F (82°C) hot water. The amount of water used to do this depends on the amount of time allotted for cleanup, the number of people simultaneously cleaning up, and the number and flow rates of the wash-down stations. The extended period of time usually required for cleanup is too long to be considered a dump load. In addition, there should not be a significant drop in the temperature of the wash water during this period. This type of hot water use usually requires a high recovery rate to provide enough water at the accepted temperature. A storage tank will help to lower the instantaneous flow rate of the heater and balance the swing loads caused by the cleanup operation. If temperature is critical, the designer may want to store hotter water and supply the system through a tempering valve.

Manufacturing Facilities Manufacturing work is divided into two types, dirty work and clean work. (See explanation under “Washrooms and Toilets” above.) Workers engaged in clean activities generally do not take showers at the end of a shift, whereas many workers emerging


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from a dirty workplace do shower prior to going home.

Pharmaceutical Facilities Pharmaceutical facilities include many different areas, such as production areas, clean rooms, sterile areas, and often laboratories and animal facilities associated with the testing and quality control of products. In general, there is little use of potable hot water in the production areas. Because spills may contain biological matter or chemicals not permitted to be treated as regular waste, spills are cleaned up with mops or rags, which are then placed in receptacles for proper disposal. Where sterility is required, special antibacterial cleaners are used. These are sprayed on exposed piping, walls, floors, and ceilings and wiped up by hand. Large accidental spills of liquid product are often cleaned up with dedicated wet vacuum equipment, which is carried on carts that do not leave the areas where they are stored. In noncritical areas, hose stations often are provided for room wash down. These are usually supplied with cold water and steam, or hot and cold water. Potentially harmful bacteria are isolated in special areas of the facility where bacteria kill drainage systems are in place. The equipment and piping for clean in place and steam in place systems do not use domestic hot water. Laboratory sinks generally do not use much hot water. When only laboratory sinks are considered, the use of standard code– obtained water fixture units leads to oversized systems. Glass and small equipment washers and sterilizers often do use hot water. Where sterility is required, a final rinse of purified water, which does not use potable water as feedwater, will be used. Small wash sinks or lavatories are provided at the entrances to clean and sterile rooms for personnel to use for washing prior to putting on sterile or clean clothing. These sinks are used primarily by production personnel at the beginning and end of shifts, but visitors and inspectors also must wash up. Animal facilities often use a large amount of hot water for cage washing and room wash down. Another potential hot water use is for a slurry system, which disposes of shredded bedding. Animal facilities usually have routines with set times for the cages and rooms to be cleaned. Animal areas with integral cage washing machines should be provided with dedicated hot water generators. It is common to wash and sterilize vials, stoppers, and bottles

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prior to use or reuse. When the washing of relatively large quantities of glassware is required, it is common practice to have a prewash area to remove most of the gross contaminants prior to placement in a sterile washing machine. Another arrangement is to use potable hot water for prewashing and distilled or purified water for the final sterile wash.

Food Product Facilities Food product facilities use hot water for the washing of rooms and exposed piping and the cleaning of equipment. Cleaning is done during preplanned and scheduled downtime. The amount of hot water used depends on the number of operators engaged in the cleaning and the type of cleaning apparatus used. The hot water temperature is generally 180°F (82°C).

Chemical Processing Facilities Chemical processing facilities often require that personnel wear protective clothing to guard against contamination by the chemicals present during a normal workday. Experience suggests that many of these facilities are involved in dirty work and that most of the personnel take showers at the end of a shift prior to leaving for home. Often potable hot water is used for the rinsing of protective suits and the decontamination of small parts and equipment.

Facilities that Process Raw Materials This category includes facilities involved in such diverse processes as oil refinery, mineral separation and enrichment, coal processing, and paper milling. Experience suggests that many of these facilities are dirty workplaces and that personnel take showers at the end of a shift prior to leaving for home.

Printing and Publishing Facilities Printing facilities usually are divided into printers of newspapers, of magazines, of books, and of miscellaneous other materials. They provide showers for plant personnel. Often photo labs, which can use large quantities of hot water, are included.


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Central Utilities In fossil fuel power plants, toilet rooms typically are located adjacent to areas where workers normally are required to be present for extended periods of time. These areas can be far apart, and each location may require an individual water heater. Central locker rooms with wash-up fixtures and toilets are provided. Nuclear power plants must be separated from all other facilities primarily for safety reasons. The control room of a nuclear power plant must have the fixtures and piping secured and designed to withstand the movement and oscillation of an earthquake that is twice the magnitude of the largest earthquake recorded in the area. Decontamination to remove low levels of radiation from both personnel and equipment will be provided. This often involves personnel taking cold showers first to close the pores of the skin to prevent radioactive particles from entering the body. After readings of acceptable levels of radiation are achieved, hot showers may be taken. In equipment decontamination areas sinks and scrub brushes with detergent are used to remove low levels of radioactive deposits from equipment. Water is used in these areas—and could be used in significant volumes and at significant flow rates during planned shutdowns and emergency situations. A complete list of potential problems should be given in a facility’s safety analysis report, which describes all normal operating and potential emergency operating conditions.

Laboratories General laboratory rooms almost always have sinks. Hot water use at these sinks is usually light. Washers and sterilizers for glassware and small equipment are located in different parts of the laboratory complex and use hot water at random intervals. To ensure an ample supply of hot water, a worst case scenario (based on discussions with the owner) should be used to calculate storage and recovery capacity. Animal facilities are discussed above, under “pharmaceutical facilities.”

Warehouses Warehouses require hot water use only in toilet rooms. Separate toilet rooms usually are provided for staff and drivers (who are nonstaff). The toilet rooms for drivers often are used heavily for short periods of time.

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Fluid Treatment Facilities Most general areas of fluid treatment facilities have no special requirements for the use of potable hot water. These facilities usually include testing laboratories. Refer to the discussion of such in the “laboratories” section, above. Generally no hot water use is necessary in the production areas where water and waste are treated, although shower facilities are required in sewage treatment plants.

MISCELLANEOUS USES OF HOT WATER Photo Processing There are two types of photo processing in general use. One involves the use of self-contained automatic machines, which develop film and produce prints from negatives. These machines require a minimum amount of water and produce a minimum amount of waste. The other type is conventional manual processing. The film and print development systems of conventional processing use relatively large amounts of hot water for the final rinsing of film and prints. Since such a wide variety of equipment exists, exact requirements must be obtained from the equipment manufacturer and/or the client. Black and white photo processing involves the use of warm water ranging in temperature from 68 to 78°F (20 to 26°C) and has a tolerance of 2°. Color photo processing involves the use of water ranging in temperature from 68 to 94°F (20 to 34°C), depending on the film and the processing technique, and has a tolerance of only 0.5°. Developing and printing equipment is usually provided with sensitive and accurate integral mixing valves.

Ready-Mix Concrete Hot water is used to make concrete when the air temperature falls below 30°F (–1°C). When the ambient temperature is between 0 and 30°F (–18 and –1°C), hot water is used to bring the mixture to a temperature of about 65°F (18°C). When the ambient temperature is below 0°F (–18°C), it is used to bring the mixture to 70°F (21°C). The higher temperatures are necessary to prevent the concrete from freezing before it sets and to allow proper hydration of the mixture. The added heat also gives the concrete a greater early strength. Hot water also serves to warm aggregate in cold weather


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to prevent it from freezing into chunks. Along with air temperature, the size of the aggregate used affects the desired temperature. Be aware, though, that water that is too hot may produce flash setting of the concrete. The amount of water used to mix concrete is determined by weight. A generally accepted rule is that half the weight of the cement (not including sand or aggregate) should be water. That is approximately 11 gal (41.64 L) of water per 90 lb (40.82 kg) of cement or 30 gal (113.56 L) of water to make 1 yd3 (0.765 m3) of cement. Aggregate also has some moisture in it, and accepted practice allows 5 gal (18.93 L) for this moisture. This means that an actual figure of 25 gal (94.64 L) of water is required to make 1 yd3 (0.765 m3) of concrete. Be aware that concrete trucks are provided with water tanks with capacities of 150 gal (567.81 L) to add water to the mix when required. It is recommended practice to load trucks with about q of the proper amount of water at the batch plant and to add the rest of the water during the trip to the site. Once the water is added, a maximum delivery time of 1½ h is allowed. It is common practice to store hot water at 180°F (82°C), with individual plants using their own methods for correctly proportioning the hot and cold water for each batch to meet specific requirements. As a guide, Table 10.1 gives storage tank sizes in relation to the successive fast filling of trucks of various sizes. Table 10.2 gives suggested recovery capacities for the water heating equipment of trucks of different sizes at various filling intervals.

Table 10.1 Tank Size Selection Chart Capacity of Trucks No. of Trucks Filling in Succession

1 2 3 4 5 6

6 yd3 ________________ Vol. of Sugg. Water Tank Required Size (gal) (gal)

300 600 900 1200 1500 1800

350 (2)350 1000 1500 2000 2000

8 yd3 ________________ Vol. of Sugg. Water Tank Required Size (gal) (gal)

350 700 1050 1400 1750 2100

400 750 1000 1500 2000 2000

l0 yd3 ________________ Vol. of Sugg. Water Tank Required Size (gal) (gal)

400 800 1200 1600 2000 2400

500 1000 1500 2000 2000 2000a

l2 yd3 ________________ Vol. of Sugg. Water Tank Required Size (gal) (gal)

450 900 1350 1800 2250 2700

500 1000 1500 2000 (2)1500 (2)1500

Source: Courtesy of A. O. Smith Water Products. aWhere generating equipment is based on a 5-min truck load interval, use two 1,500-gal storage tanks installed in parallel.

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Table 10.1(M) Tank Size Selection Chart Capacity of Trucks 4.4 m3 ________________ No. of Vol. of Sugg. Trucks Water Tank Filling in Required Size Succession (L) (L)

6.3 m3 ________________ Vol. of Sugg. Water Tank Required Size (L) (L)



1

1200

1350

1350

1500

1500

2000

1 700

2000

2

2300

(2)1350

2700

3000

3000

4000

3 400

4000

3

3400

4000

4000

4000

4600

6000

5 100

6000

4

4500

6000

5300

6000

6100

8000

6 800

8000

5

5700

8000

6600

8000

8000

8000

8 500

(2)6000

9000

8000a

10 200

(2)6000

6

6800

8000

8000

8000

Source: Courtesy of A. O. Smith Water Products. aWhere generating equipment is based on a 5–min truck load interval, use two 6000–L storage tanks installed in parallel.

Table 10.2 Hot Water Requirements after Initial Loading Truck Capacities 6 yd3 ____________________

8 yd3

10 yd3

12 yd3

____________________ ____________________ ____________________

Time GPH ____________ Min. Input GPH ____________ Min. Input GPH Min. Input GPH ____________ Min. Input ____________ Between Fills Hot Gas Oil Hot Gas Oil Hot Gas Oil Hot Gas Oil (min) Watera (Btu/h) (GPH) Watera (Btu/h) (GPH) Watera (Btu/h) (GPH) Watera (Btu/h) (GPH) 10

1800 2,630,000 18.9

2100 3,060,000

22.0

2400 3,510,000

25.2

2700 3,940,000

28.4

1050 1,530,000

11.0

1200 1,750,000

12.6

1350 1,970,000

14.2

20

900 1,315,000

9.4

35

515

752,000

5.4

600

875,000

9.2

685 1,000,000

7.2

762 1,112,000

8.0

50

360

525,000

3.8

420

612,000

6.4

480

5.0

540

5.7

700,000

788,000

Source: Courtesy of A. O. Smith Water Products. Note: If uninsulated storage tanks are in cold rooms, allowance in recovery capacity should be made for standby loss. a180°F final temperature; cold water temperature assumed to be 40°F with a 140°F temperature rise.


201

Table 10.2(M) Hot Water Requirements after Initial Loading Truck Capacities 4.4 m3 ____________________ Time L/H ____________ Min. Input Between Fills Hot Gas Oil (min) Watera (W) (L/h)

6.3 m3 7.3 m3 8.8 m3 ____________________ ____________________ ____________________ L/H

Min. Input ____________ Hot Gas Oil Watera (W) (L/h)

L/H Hot Watera

Min. Input L/H ____________ Min. Input ____________ Gas Oil Hot Gas Oil (W) (L/h) Watera (W) (L/h)

10

6813

770 590 71.5

7949

896 580

83.3

9084 1 028 430

95.4 10 220 1 154 420 107.5

20

3407

385 295 35.6

3974

448 290

41.6

4542

47.7

512 750

5 110

577 210

53.8

35

1949

220 336 20.4

2271

256 375

34.8

2593

293 000

27.3

2 884

325 816

30.3

50

1363

153 825 14.4

1590

179 316

24.2

1817

205 100

18.9

2 044

230 884

21.6

Source: Courtesy of A. O. Smith Water Products. Note: If uninsulated storage tanks are in cold rooms, allowance in recovery capacity should be made for standby loss. a82°C final temperature; cold water temperature assumed to be 4°C with a 78°C temperature rise.

11

SPORTS ARENAS AND STADIUMS

INTRODUCTION This chapter is meant to guide the designer through the procedures and methodology needed to perform the design of domestic hot water systems and the decisionmaking for water heater selections for sports arenas and stadiums. There are many functions performed in sports arenas and stadiums that must be accounted for in the design and selection process. Remember that no two facilities will be alike. Areas that may be encountered in sports arenas and stadiums that require domestic hot water include the following: • Home team showers (may need multiple team/different sports facilities), • Visitor team showers (may need multiple team/different sports facilities), • Club house commercial laundries, • Home team laundry room, • Visitor team laundry room, • Concessionaire’s laundry room, • Concessions, • Grounds service area, • Janitors’ closets, • Private suites, • Kitchens,


204


• Public toilets, • Private toilets, • Administration areas, • Training rooms, • Stadium club bar, • First aid rooms, • Staff toilets for ticket booths, • Photo labs, • Emergency eyewash, and • Emergency showers.

GATHERING INFORMATION Before proceeding with any design, the designer must go on a fact finding mission to gather the information needed to perform the design. Following are some sample questions that may need to be asked. The designer needs to develop a list of questions for each particular project. 1. What are the system demands for the restrooms, concession areas, locker rooms, training areas, kitchen, dinning areas, and laundry areas? 2. What water temperatures are desired or required for this project—120, 140, 160 or 180°F (49, 60, 71, or 82°C)? 3. What are the duration of peak demands and the length of time between each peak for all fixtures requiring domestic hot water? 4. How many showers are available? How many people will use them? What are the estimated peak period of area operation, the average shower time, the next peak hour demand after the initial peak demand, the maximum gpm, and the delivered temperature at shower heads. It is important to remember the potential of “dump loads” in some areas, such as the team showers, where the players can be expected to shower as quickly as possible after the game. Consideration must also be given for multi-game play and events on the same day. This presents the designer with a challenge to provide the most cost-effective recovery-to-storage ratio. 5. In the training room areas, what kind of hot water using equipment/fixtures will be used? How often will they be used and

Spor ts Arenas and Stadiums Sports

205

what will be the peak operational time? Determine the number of fills per hour per equipment and the quantity of hot water required for each piece of equipment. 6. In the kitchen and concession areas, what kinds of equipment/fixtures will be used and what will be the total peak operational period? Is normal operational time prior to, during, and/or after game activities? 7. What are the local codes that apply on this project? 8. Are utilities, such as water and electricity, and fuels available for this project? What are their relative costs? Can they be obtained on an uninterruptible basis? 9. Will the owner have a residence in the facility? 10. Will this facility have a building management system? 11. What is the projected facility usage—year-round, summer, or months used—and what is the projected downtime between events? 12. What is the temperature of the domestic water service into the facility? 13. What are the special equipment needs, such as for ice resurfacing (e.g., Zambonis)?

SYSTEM DESIGN Design Considerations Once the designer has gathered all the information and answered all the necessary questions, and the owner has approved the floor plans, the next step is to calculate the hot water demand and evaluate the types of systems that would be appropriate for the project. Following are other design considerations the designer should consider: 1. It is very important to establish the entire pipe routing with the approved floor plans. 2. Some energy codes restrict the use of hot water in certain areas. 3. Consider using security type showerheads in the players’ home and visitors shower rooms. 4. Mount shower heads at a minimum of 6 ft 6 in. in home and visitors shower rooms. 5. Consider using metering or infrared faucets in public areas.

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6. If the local health department requires hot water in public areas, consider using tempered water. 7. Remember the shower and therapy loads are nearly always the main criteria for sizing the hot water system. 8. Usually concession areas are located on the upper levels of the facility and many times cannot be served economically from the central system. The designer should consider that the concession loads be designed as a separate system or that an individual system be designed for each concession. The characteristics of some systems are noted below.

Water Heating System Temperature •

On a central hot water distribution system, the temperature may be designed for 120 to 140°F (49 to 60°C).

•

For point-of-use applications, the temperature is set for 110 to 120°F (43 to 49°C).

•

Kitchens use 140°F (60°C) [use of a booster heater for the dishwasher for 180°F (82°C) may be required].

•

Commercial laundries normally use 140 or 160°F (60 or 71°C). Check with the owner or operator. Booster heaters may be required to accomplish higher water temperatures.

•

Food service areas normally use 140°F (60°C). Booster heaters maybe be required to accomplish higher water temperatures. Check with the owner or operator.

•

Showers normally require 120°F (49°C) to the fixture (minimum) if a pressure balancing or thermostatic mixing valve is installed to provide an operating differential.

Note: When supplying lower temperature water, be sure that the temperature is above the dew point of the flue gas for fossil fuel systems to avoid condensation. This is a growing problem because of the higher equipment efficiencies available.

Design Traps to Avoid 1. In the design of a hot water system, especially a central system where there may be long runs of piping, the designer should look for areas in the facility that will have expansion joints connecting segments of the building structure. At these points


207

consider using some type of expansion joint in the piping system to prevent the pipe from breaking due to building movement. There may also be a need for intermediate expansion joints for long runs of piping at other areas of the building. 2. Care should be taken to make sure that the hot water pipes and water heaters are in areas that are accessible for service. Too often, limited space is provided for equipment. 3. Do not run hot water piping in areas subject to freezing. If it is absolutely necessary to do so, provide heat tape or some other method of eliminating the freezing problem and slope all affected piping to drain. 4. Consider that the usable storage capacity of a vertical storage tank may be 75 to 80%. Check with the tank manufacturer. For large tanks, installing a tank-circulating pump to circulate the water continually can increase the percentage of usable storage capacity. Horizontal tank usable storage capacity may be up to 10% less than that of a vertical tank. 5. Insulate all the hot water piping supply and circulating pipes in the system in accordance to local, state, and federal codes. 6. Make sure to coordinate with the appropriate discipline on voltage and phase for electric water heaters and combustion air requirements and flue routing for fossil-fuel fired water heaters. 7. Check for seismic requirements.

Types of System To meet diverse heating requirements, one or more of the following system configurations may be considered. Central hot water system In the central hot water system, the designer can establish a primary hot water piping loop of a 120 to 140°F (49 to 60°C) throughout the facility. Through the use of mixing stations, the temperature can be reduced to accommodate specific equipment or fixtures to satisfy their hot water requirements. The central system can serve the showers, concessions, kitchen, public restrooms, training rooms, laundry rooms, and first aid rooms.

208


Distributed hot water system It may be advantageous in the design to provide several small hot water systems throughout the facility, each with its own hot water piping system and heater. This type of system may offer flexibility and redundancy if one system goes down. It may be desirable to connect these systems with valved crossover lines that can be opened in the event that one system is down and it is necessary to backfeed temporarily an inoperable system with an operable system. Point of use In isolated areas, such as private bathrooms, ticket booths, and private suites, the point-of-use electric type water heater could be used. This installation may save on piping and insulation.

Special Considerations: Commercial Laundries The laundry areas will have a significant amount of hot water demand. They should be designed so that each has a separate hot water system with its own water heater and storage tank. Having the laundry on a separate hot water system allows flexibility in the operation of the laundry and will not rob large quantities of hot water from the central system, as it would if the laundries were tied into that system. Some central systems can include the laundry areas on the system because the laundry rooms will not operate at the same time as the showers and training rooms operate. Note: With all systems, make sure there is a place to take the discharge from the relief valve(s) that conforms to the local codes.

Assumptions On most projects, the designer will not get all the questions answered and, therefore, will have to make some assumptions in the design and piping layout. It is good practice to note all these assumptions in a letter to the owner and architect for their review and comments. Look for opportunities to find a central location for the hot water heaters, keeping in mind accessibility and simple piping layouts. Design the showers for a 2.5 or 3.0 gpm (0.16 or 0.19 L/sec) demand. Be aware of regulations affecting the selection of the flow rate.


209

Table 11.1 represents most of the plumbing fixtures and equipment for these types of facility that require hot water.

Table 11.1 Fixture/Equipment Table Location

Type of Fixture

Hot Water Temp. at the Fixture °F

°C

Private suites

Lavatory Bar sink

105 120

41 49

First aid rooms

Lavatory

105

41

Sink

120

49

Staff ticket booth

Lavatory

105

41

Training room

Sink

120

49

Lavatory

105

41

Whirlpool

110

43

Hydrotherapy

110

43

140–160

60–71

Sink

120

49

Column showers/ showers

110

43

Lavatory

105

41

Fertilizers/pesticides Emergency storage rooms eyewash

80

27

Public toilets

Lavatory

105

41

Break rooms

Sink

120

49

Concessions

Sink

120

49

Kitchens

Sinks /lavatories Dishwasher

120/105 140–180

49/41 60–82

Laundry

Shower

Washing machines roomsa

Private toilets

Remarks

Check with operator

Check with local health dept. for requirements

Check with local health dept. for requirements

a Showers with pressure-balanced and/or thermostatic shower valves having both hot and cold water connections should have a hot water temperature supplying the valve that is hot enough to ensure proper operation of the valve. Pressure-balanced/thermostatic valves offer a level of safety. It is recommended that combination check stops be installed.

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SYSTEM SIZING Sizing Parameters Before proceeding with examples, we must set some parameters for domestic hot water loads (showers): 1. Determine the number of shower heads. 2. Determine the number of people showering. 3. Allow a minimum of 5 min/shower. 4. Determine the expected length of time for showers to operate, as follows: (11.1) no. of people × min/shower = total expected time no. of shower heads of shower operation if all people shower during peak period. 5. Determine total gpm (L/sec) flow rate for showers, as follows: (11.2) no. of shower heads × gpm flow rate = total gpm flow rate for showers 6. Determine the temperature of water, °F (°C), to be used at the shower head. 7. Determine the gallons (liters) of hot water demand for showers at the required temperature and time of operation, as follows: (11.3) total shower × total shower = gal (L) required at desired time gpm (L/sec) temperature, °F (°C), for showering peak demand of determined minutes 8. Estimate turnaround time. Be sure to add turnaround time when determining the total time during which hot water is used. Note: Add a little time in for turnaround. Use a diversity factor where applicable. Evaluate the system to determine if there will be a dump load, with most of the demand being utilized in a fraction of an hour. If this is the case, be sure to calculate recovery on the basis of gallons per hour (liters/hour). For example, if the system requires 200 gal (757 L) in 30 min, the recovery rate will be 400 gph (1514 L/h).


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Example 11.1 Football Stadium The facility is a professional football stadium, and the following information is given to the designer: 1. 150 lavatories. 2. 40 shower heads. (Assume 2.50 gpm [0.16 L/sec] per shower head, 5 min/shower, 100 people to shower, 110°F [43°C] water at shower head, 40°F [4.4°C] incoming water temperature, and 140°F [60°C] stored water.) 3. 6 service sinks. 4. 2 kitchen sinks. 5. 6 sinks. 6. 2 laundry tubs. 7. 4 hydrotherapy tubs. 8. 2 whirlpools. 9. 4 commercial washing machines. 10. 1 commercial dishwasher. The first step is to determine the demand for the information given, in gph. A table showing all the fixtures that require hot water with their demands, in gph, should be developed. Some of the gph for the fixtures shown in the table below are taken from Chapters 1, 4, 6, and 8, and from equipment manufacturers.

Hot Water Demand Table (Example 11.1) Quantity Fixture Type 150 40 6 1 6 2 4 2 4 1 10

Lavatories Showers heads Service sinks Kitchen sinks (double comp.) Bar sinks Laundry tubs Hydrotherapy tubs Whirlpools Commercial washing machines Commercial dishwasher Bradley wash fountains

GPH

L/H

Total GPH (L/H)

4 150b

15 681

20 60

76 227

600 (2,271) 6000 or 1250 gals for 12.5 min.c 120 (454) 60 (227)

30 20 100a 100a 80a

113.6 76 378.5 378.5 303

180 (681) 40 (151) 400 (1514) 200 (757) 320 (1211)

50a 10

189 38

50 (189) 100 (378.5)

a Information obtained from manufacturer of equipment. b 2.5 gpm (167 L/sec) × 60 min. c 40 heads × 2.5 gpm = 100 gpm; 12.5 min peak load × 100 gpm = 1250 gal at 110°F required in 12.5 min peak load (40 heads × 0.19 L/sec = 7.6 L/sec; 12.5 min × 7.6 L/sec × 60 sec/min = 5678 L at 43°C required in 12.5 min peak load)

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The system is designed to be a central system with a primary loop set for a temperature of 140°F (60°C), and the following requirements are needed. Calculations (for water heater to serve showers, hydrotherapy tubs, and whirlpools) 100 people = 2.5 people/head 40 shower heads 2.5 people/head × 5 min/person = 12.5 min minimum for shower peak demand 40 shower heads × 2.5 gpm = 100 gpm 12.5 min × 100 gpm = 1250 gal of 110°F water required to be available in 12.5 min at the shower heads. Shower demand to be hour after hour. (40 shower heads × 0.19 L/sec = 7.6 L/sec 12.5 min × 7.6 L/sec = 5678 L of 43°C water required to be available in 12.5 min at the shower heads. Shower demand to be hour after hour.) Total gph (L/h) for hydrotherapy tubs and whirlpools equals 600 gph (2271 L/h) (from hot water demand table). Notes: 1. Shower time could vary; the 12.5 min in this example is the bare minimum, based on a 5-min average shower. The designer needs to find out as much as possible about expected use. 2. Allow 1 fill/h for hydrotherapy tubs and whirlpools. For this example, the demands will be met by storage. Should 2 fills/h be required, the designer must have the total gph (L/h) recovery of hydrotherapy tubs and whirlpools × 2 to meet the second fill within 30 min. How is the shower load to be met? We will use a combination of storage and recovery, keeping in mind that we must allow for storage tank draw efficiency. For example, if we decide to meet the total demand with storage: 1250 gal (5678 L) at 110°F (43°C) at the shower head, 600 gal (2271 L) at 110°F (43°C) for hydrotherapy tubs and whirlpools, stored water temperature at 140°F (60°C). Using the mixed water temperature formula in Chapter 1 (Equation 1.7):


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110 – 40°F 70°F = = 0.7 140 – 40°F 100°F 43 – 4.4°C = 38.6°C ( 60 – 4.4°C 55.6°C

= 0.7

)

Therefore, 1850 gal × 0.7 = 1295 gal of 140°F water (7949 L × 0.7 = 5564.5 L of 60°C water) This is the amount that must be supplied to the tempering stations for the showers and hydrotherapy tubs and whirlpools. Storage tank size (for showers, hydrotherapy tubs, and whirlpools) To determine the tank size required, divide 1295 gal (5564.5 L) of 140°F (60°C) water by the percent of usable storage. If we assume 80% usable storage, then we should select a tank with a capacity of approximately 1619 gal (6954 L). Note: The percent usable storage capacities of tanks vary. Contact your local tank manufacturer for specific information. Recovery requirements (for showers, hydrotherapy tubs, and whirlpools) This is to be determined based on the frequency and duration of the shower plus additional equipment load requirements. energy output = 1295 gph × 8.33 lb/gal × (140 – 40°F) = 970,862 Btu/h [energy output = 5564.5 L/h × 1 kg/L × (60 – 4.4°C) = 309 386 kJ/h output] If a heater has a thermal efficiency of 80%, then input must be 1,213,577 Btu/h (386 733 kJ/h) if 1295 gph (5564.5 L) are used each hour. Water heater requirements (based on hour after hour for shower operation): recovery = 1295 gph (5564.5 L/h) at 40 to 140°F (4.4 to 60°C)

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storage = 1619 gal (6954 L) Notes: 1. Storage requirement capacity remains the same even though peak demand time may vary. The designer may choose to increase or decrease storage or recovery, balancing the two as necessary to arrive at a cost-effective system that will fit into the space available. 2. If showers are required hour after hour, then the minimum recovery must be the shower load demand recovered over a period of 1 h. If the second hour is not required but the third hour is, the recovery can be reduced by 50%. If neither the second nor the third hour is required, then the recovery can be 33% of shower and additional equipment load requirements.

Example 11.2 Baseball Stadium The following information is given to the designer. The facility is a baseball stadium that is to be designed to have separate domestic hot water systems for the home team and the visiting team. Loop no. 1 (home team) 1. 9 showers heads. (Assume 2.5 gpm/shower head, 5 min/ shower, 45 people to shower, 110°F [43°C] water at shower head, 40°F [4.4°C] incoming water temperature and 140°F [60°C] stored water.) 2. 7 lavatories. 3. 1 whirlpool. 4. 1 arm tub. 5. 2 washers. 6. 1 laundry sink. 7. 1 pantry sink. 8. 3 service sinks 9. 10 wash fountains.


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Hot Water Demand Table (Example 11.2) Quantity Fixture Type 9 9

Lavatories Showers heads

3 1

Service sinks Kitchen sinks (double comp.) Pantry sinks Laundry sinks Arm tubs Whirlpools Commercial washing machines Wash fountains

1 1 1 1 2 6

GPH

L/H

Total GPH (L/H)

4 150b

15 681

10 60

38 227

36 (136) 1350 or 500 gals (5110 or 1893 L) for 25 minc 30 (113.6) 60 (227)

6 8 35a 100a 120a

23 30 132.5 378.5 454

10

38

6 (23) 8 (30) 35 (132.5) 100 (378.5) 240 (908.5) 60 (227)

a Information obtained from manufacture of equipment. b 2.5 gpm (0.16 L/sec) × 60 min c 9 heads × 2.5 gpm = 22.5 gpm; 25 min peak load × 22.5 gpm = 562.5 gal at 110°F required in a 25 min peak load (9 heads × 0.16 L/sec = 1.42 L/sec; 25 min peak load × 1.42 L/sec × 60 sec/min = 2129 L at 43°C required in a 25 min peak load)

The system is designed to be a central system with a primary loop set for a temperature of 140°F (60°C), and the following requirements are needed. Calculations (for water heater to serve showers, arm tub, and whirlpool) 45 people = 5 people/head 9 shower heads 5 people/head × 5 min/person = 25 min minimum for shower peak demand 9 shower heads × 2.5 gpm = 22.5 gpm 25 min × 22.5 gpm = 562.5 gal of 110°F water required to be available in 25 min at the shower heads. Shower demand to be hour after hour. (9 shower heads × 0.16 L/sec = 1.4 L/sec 25 min × 1.4 L/sec × 60 sec/min = 2129 L of 43°C water required to be available in 25 min at the shower heads. Shower demand to be hour after hour.)

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total gph (L/h) for arm tub and whirlpool = 135 gph (511 L/h) (from the hot water demand table) Notes: 1. Shower time could vary; the 25 min in this example is the bare minimum. 2. Allow 1 fill/h for arm tubs and whirlpools for this example. The demand will be met by storage. Should 2 fills/ h be required, the designer must have the total gph (L/h) recovery of arm tubs and whirlpools × 2 to meet the second fill within 30 min. How is the shower load to be met? We will use a combination of storage and recovery, keeping in mind that we must allow for storage tank draw efficiency. If we decide to meet total demand with storage: 562.5 gal (2129 L) at 110°F (43°C) at the shower head and 135 gal (511 L) at 110°F (43°C) for arm tubs and whirlpool, stored water temperature at 140°F (60°C). Using the mixed water temperature formula in Chapter 1 (Equation 1.7): 110 – 40°F = 70°F = 0.7 140 – 40°F 100°F 43 – 4.4°C 38.6°C = ( 60 – 4.4°C 55.6°C

= 0.7

)

Therefore, 697.5 gal × 0.7 = 488.25 gal of 140°F water (2640 L × 0.7 = 1848 L of 60°C water) This is the amount that must be supplied to the tempering stations for the showers, arm tub, and whirlpool. To determine the tank size required, divide 488.25 gal (1848 L) of 140°F (60°C) water by the percent usable storage capacity. If we assume 80% usable storage capacity, then we should select a tank with a capacity of approximately 610 gal (2309 L). Note: Percent usable storage capacities vary. Contact your tank manufacturer for specific information. Recovery requirements This is to be determined based on the frequency and duration of the shower plus additional equipment load requirements. If


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showers are required hour after hour, then minimum recovery must be the shower load demand recovered over a period of 1 h. If the second hour is not required but the third hour is, the recovery can be reduced by 50%. If neither the second nor the third hour is required, then the recovery can be 33% of shower and additional equipment load requirements. energy output = 488.25 gph × 8.33 lb/gal × (140 – 40°F) = 406,712.25 Btu/h [energy output = 1848 L/h × 1 kg/L × (60 – 4.4°C) = 102 749 kJ/h output] If a heater has a thermal efficiency of 80%, then the input must be 508,390.3 Btu/h (128 436 kJ/h) if 488.25 gph (1848 L/h) are used each hour. Water heater requirements (based on hour after hour for shower operation) recovery = 488.25 gph at 40 to 140°F (1848 L/h at 4.4 to 60°C) storage = 610 gal (2309 L) Note: Storage requirement capacity remains the same even though peak demand time may vary. The designer may choose to increase or decrease storage or recovery, balancing the two as necessary to arrive at a cost-effective system that will fit into the space available. Loop no. 2 (visiting team) 1. 10 showers heads. (Assume 2.5 gpm/shower head, 5 min/ shower, 40 people to shower, 110°F [43°C] water at shower head, 40°F [4.4°C] incoming water temperature, and 140°F [60°C] stored water.) 2. 12 lavatories. 3. 1 whirlpool. 4. 1 arm tub. 5. 1 washer. 6. 1 laundry sink.

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7. 1 pantry sink. 8. 2 service sinks. 9. 6 wash fountains.

Hot Water Demand Table (Example 11.2) Quantity Fixture Type 12 10 2 1 1 1 6 1

GPH

L/H

Total GPH (L/H)

Lavatories Showers heads

5 150b

19 568

Service sinks Laundry sinks Commercial washing machines Whirlpool Wash fountains Arm tub

10 8 120a

38 30 454

60 (227) 1500 or 500 gal (5678 or 1893 L) for 20 minc 20 (76) 8 (30) 240 (454)

100a 10 35a

378.5 38 132.5

100 (378.5) 60 (227) 35 (132.5)

a Information obtained from manufacture of equipment. b 2.5 gpm (0.16 L/sec) × 60 min c 10 heads × 2.5 gpm = 25 gpm; 20 min peak load × 25 gpm = 500 gal at 110°F required in a 25 min peak load (10 heads × 0.16 L/sec = 1.6 L/sec ; 20 min peak load × 1.6 L/sec × 60 sec/min = 1893 L at 43°C required in a 25 min peak load)

The system is designed to be a central system with a primary loop set for a temperature of 140°F (60°C), and the following requirements are needed. Calculations (for water heater to serve showers, arm tub, and whirlpool) 40 people = 4 people/head 10 shower heads 4 people/head × 5 min/person = 20 min minimum for shower peak demand 10 shower heads × 2.5 gpm = 25 gpm (10 shower heads × 0.16 L/sec = 1.6 L/sec) 20 min × 25 gpm = 500 gal of 110°F water required to be available in 20 min at the shower heads (20 min × 1.6 L/sec = 1893 L of 43°C water required to be available in 20 min at the shower heads)


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total gph for arm tub and whirlpool = 135 gph (total L/h for arm tub and whirlpool = 511 L/h) Notes: 1. Shower time could vary; the 20 min in this example is the bare minimum. 2. Allow 1 fill/h for the arm tub and whirlpool in this example. Meet the demands by storage. Should 2 fills/h be required, the designer must have the total gph (L/h) recovery of the arm tub and whirlpool × 2 to meet the second fill within 30 min. How is the shower load to be met? We will use a combination of storage and recovery, keeping in mind that we must allow for the percent usable storage capacity of the tank. If we decide to meet the total demand with storage: 500 gal (1893 L) at 110°F (43°C) at the shower head and 135 gal (511 L) at 110°F (43°C) for arm tub and whirlpool stored water temperature at 140°F (60°C). Using the mixed water temperature formula in Chapter 1 (Equation 1.7): 110 – 40°F 70°F = = 0.7 140 – 40°F 100°F 43 – 4.4°C 38.6°C = (60 – 4.4°C 55.6°C

)

= 0.7

Therefore, 635 gal × 0.7 = 444.5 gal of 140°F water (2404 L × 0.7 = 1683 L of 60°C water) This is the amount that must be supplied to the tempering stations for the showers, arm tub, and whirlpool. Storage tank size To determine the tank size required, divide 435 gal (1647 L) of 140°F (60°C) water by the percent usable storage capacity. If we assume 80% usable storage capacity, then we should select a tank with approximately 543.75 gal (2058 L). Note: Percent usable storage capacities vary. Contact your tank manufacturer for specific information.

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Recovery requirements This is determined based on the frequency and duration of the showers plus additional equipment load requirements. If showers are required hour after hour, then minimum recovery must be the shower load demand recovered over a period of 1 h. If the second hour is not required but the third hour is, the recovery can be reduced by 50%. If neither the second nor the third hour is required, then the recovery can be 33% of shower and additional equipment load requirements. energy output = 435 gph × 8.33 lb/gal × (140 – 40°F) = 362,355 Btu/h output [energy output = 1647 L/h × 1 kg/L × (60 – 4.4°C) = 91 573 kJ/h output] If a heater has a thermal efficiency of 80%, then the input must be 452,944 Btu/h (114 467 kJ/h) if 488.25 gph (1848 L/h) are used each hour. Water heater requirements (based on hour after hour for shower operation) recovery = 435 gph (1647 L/h) at 40 to 140°F (4.4 to 60°C) storage = 544 gal (2059 L) Note: Storage requirement capacity remains the same even though peak demand time may vary. The designer may choose to increase or decrease storage or recovery, balancing the two as necessary to arrive at a cost-effective system that will fit into the space available.

Laundries

12

221

LAUNDRIES

INTRODUCTION The objective of this chapter is to guide the designer through the procedure of designing a domestic water heating system for a commercial/institutional/industrial laundry. The designer is charged with identifying the variables and calculating the demand affecting such a system. The procedure presented here will help predict the amount of hot water required to meet both the hourly demand and momentary peak demands of a laundry. Before completing the final design, the designer should verify the laundry equipment requirements with the equipment manufacturers.

SYSTEM DESIGN QUESTIONS 1. Will the laundry hot water system be separate from or combined with other systems? 2. Will the laundry demand occur at the same time as other demands for hot water? 3. What will the laundry’s hot water usage be (gallons per hour [liters per hour] and gallons per pound [liters per kilogram] of laundry)? 4. How many washers will there be and what is the pound (kilogram) capacity of each? 5. What is the maximum flow rate per machine (gallons per minute [liters per second])?


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6. What is the average cycle time of each washer? 7. How many cycles will there be per hour? 8. What hot water temperature is required? 9. What hours does the owner expect to operate the laundry? 10. What fuels are available? 11. What is the minimum temperature of the supply water? 12. Is there a heat recovery system available to preheat the water for the laundry?

STORAGE Unless otherwise directed by the owner, assume that all the washers will operate simultaneously. Provide an amount of hot water storage equivalent to 50 to 75% of the hourly demand. Evaluate the operating characteristics of the washers before deciding on the amount of storage.

RECOVERY The water heating system should be designed for full recovery of the hourly demand.

EXAMPLE 12.1 A hospital laundry has three 135-lb (61-kg) and two 75-lb (34kg) washers which use 160°F (71°C) water for sanitation and blood removal. The washer manufacturer’s data indicate that all washers require 2 gal (7.57 L) of hot water per hour per pound (kilogram). (3 × 135 lb) + (2 × 75 lb) = 555 lb total capacity [(3 · 61 kg) + (2 · 34 kg) = 251 kg total capacity] 555 lb × 2 gph/lb = 1110 gph of 160°F water (251 kg · 7.6 L/h = 1907.6 L/h of 71°C water) The laundry equipment manufacturer suggests usable storage of between 50 and 75% of hourly demand. For this example, we’ll choose 60%. 60% × 1110 gal = 666 gal

Laundries

223

(60% · 1907.6 L = 1145 L) A tank with a percent usable storage volume of 75% is selected. 666 gal = 888 gal 75% L = 1527 L) (1145 75% Select the nearest standard size tank, giving consideration to the space allotted for the tank.

Miscellaneous Facilities

13

225

MISCELLANEOUS FACILITIES

RELIGIOUS FACILITIES Kitchen Many religious facilities have assembly areas, usually with adjacent kitchens. These kitchens range from full, commercial type facilities to minimal rooms where general food warming and preparation will occur. If there will be a dishwasher in the kitchen, it may be a major determinant of the size of the water heater. If there will be a commercial dishwasher and it has a hot water rinse cycle (in lieu of a chemical rinse), a booster heater may be required to provide the sanitizing temperature (180ºF [82ºC]) required (residential and some institutional type dishwashers have a built-in heater). If the capacity of the dishwasher is not available, the hot water requirements for the dishwasher can be estimated from Chapter 4, Table 4.5. If the kitchen will have a utensil cleaning sink (sometimes called a “pots and pan sink”) and a hand washing sink, Table 4.4 in Chapter 4 can be used to determine the kitchen demand.

Baptistries Baptismal fonts that range in size from 400 to 1200 gal (1514 to 4543 L) are required to be maintained at near skin temperature, between 94 and 105ºF (34 and 41ºC); use 100ºF (38ºC) for design purposes. Depending on the use of the font, the water will either be maintained in the font or filled and drained for each use. Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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When the water is maintained in the font, the application is similar to a small swimming pool. The water is circulated between the font and the heater by a small pump. The size of the water heater is dependent on the time required to raise the water to the desired temperature; due to heat loss, the water heater will also have to maintain the temperature. When the font is drained and filled for each use, the application is similar to the filling of a large tub. The hot water can be provided by the building’s domestic water heating system or a dedicated water heating system. A dedicated system can have a variety of designs, such as an instantaneous heater, a storage tank combination or a dedicated tank. The critical element is the recovery capacity required to meet temperature requirements and fill rate. When one water heater is used for kitchen use and the baptismal font, the recovery rate for these functions may not be concurrent. These functions normally happen at different times; therefore, the higher of the two recovery rates can be used to select the water heater.

Toilet Rooms The toilet room usage can be sporadic but will produce intermittent heavy loads. Depending on the size and location of the toilet room, hot water can be supplied by the building’s domestic water heating system or from a point-of-use heater.

Other Considerations The designer needs to evaluate additional hot water usage, such as gymnasiums, pools, activity rooms, meeting rooms, classrooms, day-care facilities, residences, and administrative offices.

GROCERY AND CONVENIENCE STORES There are many sizes and types of grocery and convenience store. Grocery stores are defined to include a selection of the following departments: bakery; deli; meat; produce; and specialty areas, such as floral or food service. The designer, working with the owner or architect, must identify all the potential uses of hot water. Grocery and convenience


227

stores have the usual facilities, such as kitchens, toilets, and cleaning areas. Some special areas the designer should be aware of include: • Food preparation, • Utensil cleaning, • Thawing of food, • Tray cleaning, • Can wash, • Cleanup, • Hand washing, • Wash down, and • Sanitizing of food preparation areas. The cleaning process is usually done in the late afternoon or evening and must be able to remove the fat, grease, flour, etc. Each food preparation department will usually have at least one hot water hose bibb or mixing faucet to use for wash down. Because the wash down hot water load is significant, it is important to obtain the specifications for the wash down equipment (e. g., water hose, mixing faucet, flow rate, and pressure) and the wash down procedures. The hot water demand load for wash down and cleanup is generally not concurrent with the other hot water demand loads in the building. Based on the location and layout of the different departments, consideration should be given to using smaller water heaters for each department.

Toilet Rooms Many times toilet rooms are located in remote areas of the grocery story, away from the food preparation areas. Consideration should be given to providing a point-of-use water heater.

Other Considerations Due to the quantity of refrigeration equipment in this type of facility, the designer should consider the opportunity for heat reclamation. This is a common method of preheating water in a grocery store and can be a substantial energy saving factor.

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RETAIL CENTERS There are two primary considerations for retail centers or shopping malls: the large anchor or department store and the smaller general retail establishments. For determining hot water demand in large anchor stores, the designer needs to consider the inclusion of a restaurant, administrative offices, and general facilities. Concepts for many of these areas can be found throughout this manual. For the general retail establishment, hot water is primarily for use in toilet rooms and demand is driven by hand washing. The number and type of plumbing fixtures, including those using hot water, are governed by local building codes. Each tenant will usually have, and be responsible for, his/her own domestic hot water system. For general public use toilet rooms, a point-ofuse water heater may be appropriate.

FAST FOOD RESTAURANTS The designer is encouraged to consult the owner to determine the exact hot water requirements. There are usually one or two 3-compartment stainless steel sinks for either food preparation or utensil cleaning. Many times the 3-compartment stainless steel sinks are used for both food preparation and utensil cleaning. Often the utensil cleaning sink has special size bowls to allow cleaning of the large trays. The size of the bowl and the size of each stainless steel sink vary greatly. Most health departments require one or two hand washing sinks, one in the customer service area and one in the food preparation area. There are many sizes and types of fast food establishment. These establishments have the usual requirements, such as kitchens, toilets, and cleaning areas. Areas the designer should be aware of include: • Food preparation, • Utensil cleaning, • Thawing of food, • Cleanup, and • Hand washing. The cleaning process is conducted after business hours and


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must be able to remove the fat, grease, flour, etc. The food preparation area usually has at least one hot water hose bibb or mixing faucet to use for wash down and cleanup. The hot water demand load for wash down and cleanup is generally not concurrent with the other hot water demands.

Toilet Rooms Typically all hot water demands are met by a single heater. However, a point-of-use water heater should be considered for the public toilet rooms in fast food establishments.

OFFICE BUILDINGS The number and type of plumbing fixtures required for an office building are governed by local building codes. Hot water demand is usually determined by the quantity of hand washing fixtures. Based on the location and size of loads in a building, a single water heater can serve an individual fixture, a toilet room, multiple toilet rooms, or the entire building. Special tenant requirements (e.g., mini health clubs, food service, day care, cleaning, retail shops, medical and/or dental offices) should be considered individually. In many instances, the tenant is responsible for his or her own domestic hot water system.

Section

II

EQUIPMENT The material presented in the majority of chapters in this section is drawn from information and documents received from numerous manufacturers. In order to provide balanced, unbiased, and complete coverage, ASPE made every effort possible to solicit information from all applicable equipment manufacturers. The chapters reflect that effort to the extent that manufacturers responded. For some chapters, such as Chapter 17, there was only limited manufacturer input, and the limitations of the material in these chapters are obvious. Manufacturers may submit additional information, data, documents, and new innovations for this section at any time. All submitted materials will be considered and incorporated as appropriate. As new editions of this “work in progress” are issued in future years, this equipment section will develop into a complete compendium of domestic water heating equipment possibilities to assist the design engineer.

Recirculating Domestic Hot W ater Systems Water

14

233

RECIRCULATING DOMESTIC HOT WATER SYSTEMS

INTRODUCTION It has been determined through field studies that the correct sizing and operation of water heaters depend on the appropriateness of the hot water maintenance system. If the hot water maintenance system is inadequate, the water heater sizing criteria are wrong and the temperature of the hot water distributed to the users of the plumbing fixtures is below acceptable standards. Additionally, a poorly designed hot water maintenance system wastes large amounts of energy and potable water and creates time delays for those using the plumbing fixtures. This chapter addresses the criteria for establishing an acceptable time delay in delivering hot water to fixtures and the limitations of the length between a hot water recirculation system and plumbing fixtures. It also discusses the temperature drop across a hot water supply system, types of hot water recirculation system, and pump selection criteria, and gives extensive information on the insulation of hot water supply and return piping.

BACKGROUND In the past, the plumbing engineering community considered the prompt delivery of hot water to fixtures either a requirement for a project or a matter of no concern. The plumbing engineer’s decision was based primarily on the type of facility under consideration and the developed length from the water heater to the farthest fixture. Previous reference material and professional common practices have indicated that, when the distance from the water heater to the farthest fixture exceeds 100 ft (30.48 m) water should Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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be circulated. However, this recommendation is subjective, and, unfortunately, some engineers and contractors use the 100-ft (30.48-m) criterion as the maximum length for all uncirculated, uninsulated, dead-end hot water branches to fixtures in order to cut the cost of hot water distribution piping. These long, uninsulated, dead-end branches to fixtures create considerable problems, such as a lack of hot water at fixtures, inadequately sized water heater assemblies, and thermal temperature escalation in showers. The 100-ft (30.48-m) length criterion was developed in 1973 after the Middle East oil embargo, when energy costs were the paramount concern and water conservation was given little consideration. Since the circulation of hot water causes a loss of energy due to radiation and convection in the circulated system and such energy losses have to be continually replaced by water heaters, the engineering community compromised between energy loss and construction costs and developed the 100-ft (30.48-m) maximum length criterion.

LENGTH AND TIME CRITERIA Recently, due to concern about not only energy conservation but also the extreme water shortages in parts of the country, the 100ft (30.48-m) length criteria has changed. Water wastage caused by the long delay in obtaining hot water at fixtures has become as critical an issue as the energy losses caused by hot water temperature maintenance systems. To reduce the wasting of cooled hot water significantly, the engineering community has reevaluated the permissible distances for uncirculated, dead-end branches to periodically used plumbing fixtures. The new allowable distances for uncirculated, dead-end branches represent a trade-off between the energy utilized by the hot water maintenance system and the cost of the insulation, on the one hand, and the cost of energy to heat the excess cold water makeup, the cost of wasted potable water, and extra sewer surcharges, on the other hand. Furthermore, engineers should be aware that various codes now limit the length between the hot water maintenance system and plumbing fixtures. They also should be aware of the potential for liability if an owner questions the adequacy of their hot water system design. What are reasonable delays in obtaining hot water at a fixture? For anything beside very infrequently used fixtures (such as those in industrial facilities or certain fixtures in office buildings), a delay of 0 to 10 sec is normally considered acceptable for most


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residential occupancies and public fixtures in office buildings. A delay of 11 to 30 sec is marginal but possibly acceptable, and a time delay longer than 31 sec is normally considered unacceptable and a significant waste of water and energy. Therefore, when designing hot water systems, it is prudent for the designer to provide some means of getting hot water to the fixtures within these acceptable time limits. Normally this means that there should be a maximum distance of approximately 25 ft (7.6 m) between the hot water maintenance system and each of the plumbing fixtures requiring hot water, the distance depending on the water flow rate of the plumbing fixture at the end of the line and the size of the line. (See Tables 14.1, 14.2, and 14.3.) The plumbing designer may want to stay under this length limitation because the actual installation in the field may differ slightly from the engineer's design, and additional delays may be caused by either the routing of the pipe or other problems. Furthermore, with the low fixture discharge rates now mandated by national and local laws, it takes considerably longer to obtain hot water from nontemperature maintained hot water lines than it did in the past, when fixtures had greater flow rates. For example, a public lavatory with a 0.50 or 0.25 gpm (0.03 or 0.02 L/sec) maximum discharge rate would take an excessive amount of time to obtain hot water from 100 ft (30.48 m) of uncirculated, uninsulated hot water piping. (See Table 14.3.) This table gives conservative approximations of the amount of time it takes to obtain hot water at a fixture. The times are based on the size of the line, the fixture flow rate, and the times required to replace the cooled off hot water, to heat the pipe, and to offset the convection energy lost by the insulated hot water line.

Table 14.1 Water Contents and Weight of Tube or Piping per Linear Foot Nominal Diameter (in.)a ½ ¾ 1 1¼ 1½

Copper Pipe Type L

Copper Pipe Type M

Steel Pipe Schedule 40

CPVC Pipe Schedule 40

Water (gal/ft)

Wgt. (lb/ft)

Water (gal/ft)

Wgt. (lb/ft)

Water (gal/ft)

Wgt. (lb/ft)

Water (gal/ft)

Wgt. (lb/ft)

0.012 0.025 0.043 0.065 0.093

0.285 0.445 0.655 0.884 1.14

0.013 0.027 0.045 0.068 0.100

0.204 0.328 0.465 0.682 0.940

0.016 0.028 0.045 0.077 0.106

0.860 1.140 1.680 2.280 2.720

0.016 0.028 0.045 0.078 0.106

0.210 0.290 0.420 0.590 0.710

aPipe sizes are indicated for mild steel pipe sizing.

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Table 14.1(M) Water Contents and Weight of Tube or Piping per Meter Copper Pipe Type L

Nominal Diameter (mm)a

Water (L)

Wgt. (kg)

Copper Pipe Type M Water (L)

Steel Pipe Schedule 40 Wgt. (kg)

Water (L)

CPVC Pipe Schedule 40 Wgt. (kg)

Water (L)

Wgt. (kg)

DN15

0.045

0.129

0.049

0.204

0.061

0.390

0.061

0.099

DN20 DN25 DN32 DN40

0.095 0.163 0.246 0.352

0.202 0.297 0.401 0.517

0.102 0.170 0.257 0.379

0.328 0.465 0.682 0.940

0.106 0.170 0.291 0.401

0.517 0.762 1.034 1.233

0.106 0.170 0.295 0.401

0.132 0.191 0.268 0.322


Table 14.2 Approximate Fixture and Appliance Water Flow Rates Maximum Flow Ratesa Fittings Lavatory faucet Public non-metering Public metering Sink faucet Shower head Bathtub faucets Single-handle Two-handle Service sink faucet Laundry tray faucet Residential dishwasher Residential washing machine aUnless otherwise noted.

GPM

L/Sec

2.0 0.5 0.25 gal/cycle 2.5 2.5

1.3 0.03 0.946 L/cycle 0.16 0.16

2.4 minimum 4.0 minimum 4.0 minimum 4.0 minimum 1.87 aver 7.5 aver



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Table 14.3 Approximate Time Required to Get Hot Water to a Fixture Delivery Time (sec) Fixture Flow Rate (gpm) Piping Length (ft)

0.5

1.5

2.5

4.0

10

25

10

25

10

25

10

25

Copper Pipe

½ in. ¾ in.

25 48a

63a 119a

8 16

21 40a

5 10

13 24

3 6

8 15

Steel Pipe Sched. 40

½ in. ¾ in.

63a 91a

157a 228a

21 30

52a 76a

13 18

31a 46a

8 11

20 28

CPVC Pipe Sched. 40

½ in. ¾ in.

64a 95a

159a 238a

21 32

53a 79a

13 19

32a 48a

8 12

20 30

Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on water temperature of 140°F and an air temperture of 70°F. aDelays longer than 30 sec are not acceptable.

Table 14.3(M) Approximate Time Required to Get Hot Water to a Fixture Delivery Time (sec) Fixture Flow Rate (L/sec) Piping Length (m)

0.03

0.10

0.16

3.1

7.6

3.1

7.6

3.1

7.6

0.25 3.1

7.6

Copper Pipe

DN15 DN22

25 48a

63a 119a

8 16

21 40a

5 10

13 24

3 6

8 15


DN15 DN20

63a 91a

157a 228a

21 30

52a 76a

13 18

31a 46a

8 11

20 28

CPVC Pipe Sched. 40

DN15 DN20

64a 95a

159a 238a

21 32

53a 79a

13 19

32a 48a

8 12

20 30

Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on water temperature of 60°C and an air temperture of 21.1°C. aDelays longer than 30 sec are not acceptable.

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RESULTS OF DELAYS IN DELIVERING HOT WATER TO FIXTURES As mentioned previously, when there is a long delay in obtaining hot water at the fixture, there is significant wastage of potable water as the cooled hot water supply is simply discharged down the drain unused. Furthermore, plumbing engineers concerned about total system costs should realize that the cost of this wasted, previously heated water must include: the original cost for obtaining potable water, the cost of previously heating the water, the final cost of the waste treatment of this excess potable water, which results in larger sewer surcharges (source of supply to end disposal point), and the cost of heating the new cold water to bring it up to the required temperature. Furthermore, if there is a long delay in obtaining hot water at the fixtures, the faucets are turned on for long periods of time to bring the hot water supply at the fixture up to the desired temperature. This can cause the water heating system to run out of hot water and make the heater sizing inadequate, because the heater is unable to heat all the extra cold water brought into the system through the wastage of the water discharged down the drain. In addition, this extra cold water entering the hot water system reduces the hot water supply temperature. This exacerbates the problem of insufficient hot water because to get a proper blended temperature more lower temperature hot water will be used to achieve the final mixed water temperature. (See Chapter 1, Table 1.1.) Additionally, this accelerates the downward spiral of the temperature of the hot water system. Another problem resulting from long delays in getting hot water to the fixtures is that the fixtures operate for longer than expected periods of time. Therefore, the actual hot water demand is greater than the demand normally designed for. Therefore, when sizing the water heater and the hot water piping distribution system, the designer should be aware that the lack of a proper hot water maintenance system can seriously impact the required heater size.

METHODS OF DELIVERING REASONABLY PROMPT HOT WATER SUPPLY Hot water maintenance systems are as varied as the imaginations of the plumbing engineers who create them. They can be grouped into three basic categories, though any actual installa-


239

tion may be a combination of more than one of these types of system. The three basic categories are 1. Circulation systems. 2. Self-regulating heat trace systems. 3. Point-of-use water heaters (include booster water heaters).

Circulation Systems for Commercial, Industrial, and Large Residential Projects A circulation system is a system of hot water supply pipes and hot water return pipes with appropriate shutoff valves, balancing valves, circulating pumps, and a method of controlling the circulating pump. The diagrams for six basic circulating systems are shown in Figures 14.1 through 14.6.

Fixture 14.1 Upfeed Hot Water System with Heater at Bottom of System. * See text for requirements for strainers.

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Figure 14.2 Downfeed Hot Water System with Heater at Top of System. * See text for requirements for strainers.

Figure 14.3 Upfeed Hot Water System with Heater at Bottom of System. * See text for requirements for strainers.


241


Figure 14.5 Combination Upfeed and Downfeed Hot Water System with Heater at Bottom of System. Note: This piping system increases the developed length of the HW system over the upfeed systems shown in Figures 14.1 and 14.3. * See text for requirements for strainers.

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Figure 14.6 Combination Downfeed and Upfeed Hot Water System with Heater at Top of System. Note: This piping system increases the developed length of the HW system over the downfeed systems shown in Figures 14.2 and 14.4. * See text for requirements for strainers.

Self-Regulating Heat Trace Over approximately the last 20 years, self-regulating heat trace has come into its own because of the problems of balancing circulated hot water systems and energy loss in the return piping. For further discussion of this topic, see Chapter 15.

Point-of-Use Heaters This concept is applicable when there is a single fixture or group of fixtures that is located far from the temperature maintenance system. In such a situation, a small, instantaneous, point-of-use water heater—an electric water heater, a gas water heater, or a small under-fixture storage type water heater of the magnitude of 6 gal (22.71 L)—can be provided. (See Figure 14.7.) The pointof-use heater will be very cost-effective because it will save the cost of running hot water piping to a fixture that is a long distance away from the temperature maintenance system. The


243

plumbing engineer must remember, however, that when a water heater is installed there are various code and installation requirements that must be complied with, such as those pertaining to T & P relief valve discharge. Instantaneous electric heaters used in point-of-use applications can require a considerable amount of power, and may require 240 or 480 V service.

POTENTIAL PROBLEMS IN CIRCULATED HOT WATER MAINTENANCE SYSTEMS The following are some of the potential problems with circulated hot water maintenance systems that must be addressed by the plumbing designer.

Figure 14.7 Instantaneous Point-of-Use Water Heater Piping Diagram. Source: Courtesy of Chronomite Laboratories, Inc.

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Water Velocities in Hot Water Piping Systems For copper piping systems, it is very important that the circulated hot water supply piping and especially the hot water return piping be sized so that the water is moving at a controlled velocity. High velocities in these systems can cause pinhole leaks in the copper piping in as short a period as six months or less.

Balancing Systems It is extremely important that a circulated hot water system be balanced for its specified flows, including all the various individual loops within the circulated system. Balancing is required even though an insulated circulated line usually requires very little flow to maintain satisfactory system temperatures. If the individual hot water circulated loops are not properly balanced, the circulated water will tend to short-circuit through the closest loops, creating high velocities in that piping system. Furthermore, the short-circuiting of the circulated hot water will result in complaints about the long delays in getting hot water at the remotest loops. If the hot water piping is copper, high velocities can create velocity erosion which will destroy the piping system. Because of the problems inherent in manually balancing hot water circulation systems, many professionals incorporate factory preset flow control devices in their hot water systems. While the initial cost of such a device is higher than the cost of a manual balancing valve, a preset device may be less expensive when the field labor cost for balancing the entire hot water system is included. When using a preset flow control device, however, the plumbing designer has to be far more accurate in selecting the control device's capacity as there is no possibility of field adjustment. Therefore, if more or less hot water return flow is needed during the field installation, a new flow control device must be installed and the old one must be removed and discarded.

Isolating Portions of Hot Water Systems It is extremely important in circulated systems that shutoff valves be provided to isolate an entire circulated loop. This is done so that if individual fixtures need modification, their piping loop can be isolated from the system so the entire hot water system does not have to be shut off and drained. The location of these shutoff valves should be given considerable thought. The shutoff valves should be accessible at all times, so they should not be located in


245

such places as the ceilings of locked offices or condominiums.

Maintaining the Balance of Hot Water Systems To ensure that a balanced hot water system remains balanced after the shutoff valves have been utilized, the hot water return system must be provided with a separate balancing valve in addition to the shutoff valve or, if the balancing valve is also used as the shutoff valve, the balancing valve must have a memory stop. (See the discussion of "balancing valves with memory stops" below.) With a memory stop on the valve, plumbers can return a system to its balanced position after working on it rather than have the whole piping system remain unbalanced, which would result in serious problems.

Providing Check Valves at the Ends of Hot Water Loops The designer should provide a check valve on each hot water return line where it joins other hot water return lines. This is done to ensure that a plumbing fixture does not draw hot return water instead of hot supply water, which could unbalance the hot water system and cause delays in obtaining hot water at some fixtures.

A Delay in Obtaining Hot Water at Dead-End Lines Keep the delay in obtaining hot water at fixtures to within the time (and branch length) parameters given previously to avoid unhappy users of the hot water system and to prevent lawsuits.

FLOW BALANCING DEVICES The following are the more common types of balancing device.

Fixed Orifices and Venturis These can be obtained for specific flow rates and simply inserted into the hot water return piping system. (See Figure 14.8.) However, extreme care should be taken to locate these devices so they can be removed and cleaned out, as they may become clogged with the debris in the water. It is recommended, therefore, that a strainer with a blowdown valve be placed ahead of each of these

246


Figure 14.8 Fixed Orifices and Venturi Flow Meters. Source: Courtesy of Gerand Engineering Co.


247

devices. Additionally, a strainer with a fine mesh screen can be installed on the main water line coming into the building to help prevent debris buildup in the individual strainers. Also, a shutoff valve should be installed before and after these devices so that an entire loop does not have to be drained in order to service a strainer or balancing device.

Factory Preset Automatic Flow Control Valves The same admonition about strainers and valves given for "fixed orifices and venturis" above applies to the installation and location of these devices. (See Figure 14.9.)

Figure 14.9 Preset Self-Limiting Flow Control Cartridge. Source: Courtesy of Griswold Controls.

248


Flow Regulating Valves These valves can be used to determine the flow rate by reading the pressure drop across the valve. They are available from various manufacturers. (See Figure 14.10.)

Figure 14.10 Adjustable Orifice Flow Control Valve. Source: ITT Industries. Used with permission.

Balancing Valves with Memory Stops These valves can be adjusted to the proper setting by installing insertable pressure measuring devices (Pete’s Plugs, etc.) in the piping system, which indicate the flow rate in the pipe line. (See Figure 14.11.)


249

Figure 14.11 Adjustable Balancing Valve with Memory Stop. Source: Courtesy of Milwaukee Valve Co.

SIZING HOT WATER RETURN PIPING SYSTEMS AND RECIRCULATING PUMPS The method for selecting the proper size of the hot water return piping system and the recirculating pump is fairly easy, but it does require engineering judgment. First, the plumbing engineer has to design the hot water supply and hot water return piping systems, keeping in mind the parameters for total developed length,1 prompt delivery of hot water to fixtures, and velocities in pipe lines. The plumbing engineer has to make assumptions about the sizes of the hot water return piping. After the hot water supply and hot water return systems are designed, the designer should make a piping diagram of the hot 1See American Society of Plumbing Engineers, 2000, Cold-water systems, Chapter 5 in ASPE Data Book, Volume 2, for piping sizing methods.

250


water supply system and the assumed return system showing piping sizing and approximate lengths. From this piping diagram the hourly heat loss occurring in the circulated portion of the hot water supply and return systems can be determined. (See Table 14.4 for minimum required insulation thickness and Table 14.5 for approximate piping heat loss.) Next determine the heat loss in the hot water storage tank if one is provided. (See Table 14.6 for approximate tank heat loss.) Calculate the total hot water system energy loss (tank heat loss plus piping heat loss) in British thermal units per hour (watts). This total hot water system energy loss is represented by q in Equation 14.1 below. Note: Heat losses from storage type water heater tanks are not normally included in the hot water piping

Table 14.4 Minimum Pipe Insulation Thickness Required Insulation Thickness for Piping (in.) Runouts 2 in. or Lessa

1 in. or Less

1¼–2 in.

2½–4 in.

5 & 6 in.

8 in. or Larger

½

1

1

1½

1½

1½

Note: Data based on fiberglass insulation with all-service jacket. Data will change depending on actual type of insulation used. Data apply to recirculating sections of hot water systems and the first 3 ft from the storage tank of uncirculated systems. aUncirculated pipe branches to individual fixtures (not exceeding 12 ft in length). For lengths longer than 12 ft, use required insulation thickness shown in table.

Table 14.4(M) Minimum Pipe Insulation Thickness Required Insulation Thickness for Piping (mm) Runouts DN32 or Lessa

DN25 or Less

DN32–DN50

DN65–DN100

DN125 & DN150

DN200 or Larger

13

25

25

40

40

40

Note: Data based on fiberglass insulation with all-service jacket. Data will change depending on actual type of insulation used. Data apply to recirculating sections of hot water systems and the first 0.9 m from the storage tank of uncirculated systems. aUncirculated pipe branches to individual fixtures (not exceeding 3.7 m in length). For lengths longer than 305 mm, use required insulation thickness shown in table.


251

Table 14.5 Approximate Insulated Piping Heat Loss and Surface Temperature Nominal Pipe Size (in.) ½ ¾ 1 1¼ 1½ 2 or less 2 2½ 3 4 6 8 10

Insulation Thickness (in.)

Heat Loss (Btu/h/ linear ft)

1 1 1 1 1 ½a 1 1½ 1½ 1½ 1½ 1½ 1½

8 10 10 13 13 24 or less 16 12 16 19 27 32 38

Surface Temperature (°F) 68 69 69 70 69 74 70 67 68 69 69 69 69

Note: Figures based on average ambient temperature of 65°F and annual average wind speed of 7.5 mph. aUncirculating hot water runout branches only.

Table 14.5(M) Approximate Insulated Piping Heat Loss and Surface Temperature Nominal Pipe Size (mm) DN15 DN20 DN25 DN32 DN40 DN50 or less DN50 DN65 DN80 DN100 DN150 DN200 DN250

Insulation Thickness (mm) 25 25 25 25 25 13a 25 38 38 38 38 38 38

Heat Loss (W/m) 7.7 9.6 9.6 12.5 12.5 23.1 or less 15.4 11.5 15.4 18.3 26.0 30.8 36.5

Surface Temperature (°C) 20 21 21 21 21 23 21 19 20 21 21 21 21

Note: Figures based on average ambient temperature of 18°C and annual average wind speed of 12 km/h. aUncirculating hot water runout branches only.

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Table 14.6 Heat Loss from Various Size Tanks with Various Insulation Thicknesses Insulation Thickness (in.) 1 1 2 3 3

Tank Size (gal) 50 100 250 500 1000

Approx. Energy Loss from Tank at Hot Water Temperature 140°F (Btu/h)a 468 736 759 759 1273

Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data. aFor unfired tanks, federal standards limit the loss to no more than 6.5 Btu/h/ ft2 of tank surface.

Table 14.6(M) Heat Loss from Various Size Tanks with Various Insulation Thicknesses Insulation Thickness (mm) 25.4 25.4 50.8 76.2 76.2

Tank Size (L) 200 400 1000 2000 4000

Approx. Energy Loss from Tank at Hot Water Temperature 60°C (W)a 137 216 222 222 373

Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data. aFor unfired tanks, federal standards limit the loss to no more than 1.9 W/m2 of tank surface.

system heat loss because the water heater capacity takes care of this loss, whereas pumped hot water has to replace the piping convection losses in the piping system. (14.1)

q = 60rwc∆T [q = 3600rwc∆T]


253

where 60 3600 q r w c ∆T

= = = = = = =

min/h sec/h piping heat loss, Btu/h (kJ/h) flow rate, gpm (L/sec) weight of heated water, lb/gal (kg/L) specific heat of water, Btu/lb/°F (kJ/kg/K) change in heated water temperature (temperature of leaving water minus temperature of incoming water, represented in this manual as Th – Tc, °F [K])

Therefore = c (gpm × 8.33 lb/gal)(60 min/h)(°F temperature drop) = 1(gpm) × 500 × °F temperature drop [q = c (L/sec • 1kg/L)(3600 sec/h)(K temperature drop) = 1(L/sec) • 15 077 kJ/L/sec/K • K temperature drop] q

(14.2) gpm ≈

[

system heat loss (Btu/h) 500 × °F temperature drop

L/sec ≈

]

system heat loss (kJ/h) 15 077 • K temperature drop

In sizing hot water circulating systems, the designer should note that the greater the temperature drop across the system, the less water is required to be pumped through the system and, therefore, the greater the savings on pumping costs. However, if the domestic hot water supply starts out at 140°F (60°C) with, say, a 20°F (6.7°C) temperature drop across the supply system, the fixtures near the end of the circulating hot water supply loop could be provided with a hot water supply of only 120°F (49°C). In addition, if the hot water supply delivery temperature is 120°F (49°C) instead of 140°F (60°C), the plumbing fixtures will use greater volumes of hot water to get the desired blended water temperature (see Chapter 1, Table 1.1). Therefore, the recommended hot water system temperature drop should be of the magnitude of 5°F (3°C). This means that if the hot water supply starts out from the water heater at a temperature between 135 and 140°F (58 and 60°C), the lowest hot water supply temperature provided by the hot water supply system could be between 130 and 135°F (54 and 58°C). With multiple temperature distri-

254


bution systems, it is recommended that the recirculation system for each temperature distribution system be extended back to the water heating system separately and have its own pump. Using Equation 14.2, we determine that, if there is a 5°F (3°C) temperature drop across the hot water system, the number to divide into the hot water circulating system heat loss (q) to obtain the minimum required hot water return circulation rate in gpm (L/sec) is 2500 (500 × 5°F), (45 213 [15 071 • 3°C]). For a 10°F (6°C) temperature drop that number is 5000 (from Equation 14.2, 500 × 10°F = 5000) (90 426 [from Equation 14.2, 15 071 • 6°C = 90 426]). However, this 10°F (6°C) temperature drop may produce hot water supply temperatures that are lower than desired. After Equation 14.2 is used to establish the required hot water return flow rate, in gpm (L/sec), the plumbing designer can size the hot water return piping system based on piping flow rate velocities and the available pump heads. It is quite common that a plumbing designer will make wrong initial assumptions about the sizes of the hot water return lines to establish the initial heat loss figure (q). If that is the case, the plumbing engineer will have to correct the hot water return pipe sizes, redo the calculations using the new data based on the correct pipe sizing, and verify that all the rest of the calculations are now correct.

EXAMPLE 14.1—CALCULATION TO DETERMINE REQUIRED CIRCULATION RATE 1. Assume that the hot water supply piping system has 800 ft (244 m) of average size 1 ¼ in. (DN32) pipe. From Table 14.5, determine the heat loss per linear foot (meter). To find the total heat loss, multiply length times heat loss per foot (meter): 800 ft × 13 Btu/h/ft = 10,400 Btu/h supply piping losses (244 m • 12.5 W = 3050 W supply piping losses) 2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) piping and 100 ft (30.5 m) of average ¾ in. (DN20) pipe. From Table 14.5 determine the heat loss per linear foot (meter): 100 ft × 8 Btu/h/ft = 800 Btu/h piping loss


255

(30.5 m • 7.7 W/m = 235 W piping loss) 100 ft × 10 Btu/h/ft =

(

30.5 m • 9.6 W/m =

1000 Btu/h piping loss 1800 Btu/h piping loss

293 W piping loss 528 W piping loss

)

3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage tank. From Table 14.6 determine the heat loss of the storage tank @ 759 Btu/h (222 W). 4. Determine the hot water system’s total heat losses by totaling the various losses: A. Hot water supply piping losses B. Hot water return piping losses C. Hot water storage tank losses Total system heat losses

10,400 Btu/h 1,800 Btu/h 759 Btu/h 12,959 Btu/h

Total system piping heat losses (A + B) = 12,200 Btu/h [A. Hot water supply piping losses B. Hot water return piping losses C. Hot water storage tank losses Total system heat losses

3050 W 527 W 222 W 3799 W

Total system piping heat losses (A + B) = 3577 W] From Equation 14.2, using a system piping loss of 12,200 Btu/h (3577 W) and a 5°F (3°C) temperature drop, 12,200 Btu/h = 4.88 gpm (say 5 gpm) 5°F temperature difference × 500 required hot water return circulation rate

[

3577 W

3°C temp. difference • 4188.32 kJ/m3

]

= 0.29 (say 0.3) L/sec required hot water return circulation rate

Recalculation of Hot Water System Losses 1. Assume that the hot water supply piping system has 800 ft (244 m) of average size 1¼ in. (DN32) pipe. From Table 14.5 determine the heat loss per linear foot (meter):

256


800 ft × 13 Btu/h/ft = 10,400 Btu/h piping loss (244 m

•

12.5 W/m = 3050 W piping loss)

2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) pipe, 25 ft (7.6 m) of average ¾ in. (DN22) pipe, and 75 ft (22.9 m) of average 1 in. (DN28) pipe. From Table 14.5, determine the heat loss per linear foot (meter): 100 ft × 8 Btu/h/ft = 800 Btu/h piping loss 25 ft × 10 Btu/h/ft = 250 Btu/h piping loss 75 ft × 10 Btu/h/ft = 750 Btu/h piping loss 1800 Btu/h piping loss [30.5 m • 7.7 W/m = 7.6 m • 9.6 W/m = 22.9 m • 9.6 W/m =

235 W piping loss 73 W piping loss 220 W piping loss 528 W piping loss]

3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage tank. From Table 14.6 determine the heat loss of the storage tank @ 759 Btu/h (222 W). 4. Determine the system’s total heat losses: A. Hot water supply losses B. Hot water return losses C. Hot water storage tank losses

10,400 Btu/h 1,800 Btu/h 759 Btu/h

Total system heat losses

12,959 Btu/h

Total system piping heat losses (A + B) = 12,200 Btu/h [A. Hot water supply losses B. Hot water return losses C. Hot water storage tank losses Total system heat losses

3050 W 528 W 222 W 3800 W

Total system piping heat losses (A + B) = 3578 W] Note: The recalculation determined that the hot water system heat losses remained unchanged and that 4.88 (say 5) gpm (0.29 [say 0.3] L/sec) is the flow rate that is required to maintain the 5°F (3°C) temperature drop across the hot water supply system.


257

It should be stated that engineers use numerous rules of thumb to size hot water return systems. These rules of thumb are all based on assumptions, however, and are not recommended. It is recommended that the engineer perform the calculations for each project to establish the required flow rates because, with all the various capacities of the pumps available today, exact sizing is possible, and any extra circulated flow caused by the plumbing engineer using a rule of thumb equates to higher energy costs, to the detriment of the client.

ESTABLISHING THE HEAD CAPACITY OF THE HOT WATER CIRCULATING PUMP The hot water return circulating pump is selected based on the required hot water return flow rate (in gpm [L/sec]), calculated using Equation 14.2, and the system’s pump head. The pump head is normally determined by the friction losses through only the hot water return piping loops and any losses through balancing valves. The hot water return piping friction losses usually do not include the friction losses that occur in the hot water supply piping. The reason for this is that the hot water return circulation flow is needed only to keep the hot water supply system up to the desired temperature when there is no flow in the hot water supply piping. When people use the hot water at the fixtures, there is usually sufficient flow in the hot water supply piping to keep the system hot water supply piping up to the desired temperature without help from the flow in the hot water return piping. The only exception to the rule of ignoring the friction losses in the hot water supply piping is a situation where a hot water return pipe is connected to a relatively small hot water supply line. "Relatively small" here means any hot water supply line that is less than one pipe size larger than the hot water return line. The problems created by this condition are that the hot water supply line will add additional friction to the head of the hot water circulating pump, and the hot water circulating pump flow rate can deprive the last plumbing fixture on this hot water supply line from obtaining its required flow. It is recommended, therefore, that in such a situation the hot water supply line supplying each hot water return piping connection point be increased to prevent these potential problems, i.e., use ¾ in. (DN22) hot water supply piping and ½ in. (DN15) hot water return piping, or 1 in. (DN28) hot water supply piping and ¾ in. (DN22) hot water return piping, etc.

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When selecting the hot water circulating pump’s head, the designer should be sure to calculate only the restrictions encountered by the circulating pump. A domestic hot water system is normally considered an open system (i.e., open to the atmosphere). When the hot water circulating pump is operating, however, it is assumed that the piping is a closed system. Therefore, the designer should not include static heads where none exists. For example, in Figure 14.1, the hot water circulating pump has to overcome only the friction in the hot water return piping not the loss of the static head pumping the water up to the fixtures because in a closed system the static head loss is offset by the static head gain in the hot water return piping.

HOT WATER CIRCULATING PUMPS Most hot water circulating pumps are of the centrifugal type and are available as either in-line units for small systems or basemounted units for large systems. Because of the corrosiveness of hot water systems, the pumps should be bronze, bronze fitted, or stainless steel. Conventional, iron bodied pumps, which are not bronze fitted, are not recommended.

CONTROL FOR HOT WATER CIRCULATING PUMPS There are three major methods commonly used for controlling hot water circulating pumps: manual, thermostatic (aquastat), and time clock control. Sometimes more than one of these methods are used on a system. 1. A manual control runs the hot water circulating pump continuously when the power is turned on. A manual control should be used only when hot water is needed all the time, 24 h a day, or during all the periods of a building's operation. Otherwise, it is not a cost-effective means of controlling the circulating pump because it will waste energy. Note: The method for applying the “on demand” concept for controlling the hot water circulating pump is a manual control. It can be used very successfully for residential and commercial applications. 2. A thermostatic aquastat is a device that is inserted into the hot water return line. When the water in the hot water return system reaches the distribution temperature, it shuts off the


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circulating pump until the hot water return system temperature drops by approximately 10°F [5.5°C]. With this method, when there is a large consumption of hot water by the plumbing fixtures, the circulating pump does not operate. 3. A time clock is used to turn the pump on during specific hours of operation when people are using the fixtures. The pump would not operate, for example, at night in an office building when nobody is using the fixtures. 4. Often an aquastat and a time clock are used in conjunction so that during the hours a building is not operating the time clock shuts off the circulating pump, and during the hours the building is in use the aquastat shuts off the pump when the system is up to the desired temperature.

AIR ELIMINATION In any hot water return circulation system it is very important that there be a means of eliminating any entrapped air from the hot water return piping. Air elimination is not required in the hot water supply piping because the discharge of water from the fixtures will eliminate any entrapped air. If air is not eliminated from the hot water return lines, however, it can prevent the proper circulation of the hot water system. It is imperative that a means of air elimination be provided at all high points of a hot water return system. The plumbing engineer must always give consideration to precisely where the air elimination devices are to be located and drained. For example, they should not be located in the unheated attics of buildings in cold climates. If the plumbing engineer does not consider the location of these devices and where they will drain, the result may be unsightly piping in a building or extra construction costs.

INSULATION The use of insulation is very cost-effective. It means paying one time to save the later cost of significant energy lost by the hot water supply and return piping system. Also, insulation decreases the stresses on the piping due to thermal expansion and contraction caused by changes in water temperature. Furthermore, the proper use of insulation eliminates the possibility of someone getting burned by a hot, uninsulated water line. See Table 14.5 for the surface temperatures of insulated lines (versus 140°F [60°C] for bare piping).

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It is recommended that all hot water supply and return piping be insulated. This recommendation exceeds some code requirements. See Table 14.4 for the minimum required insulation thicknesses for all systems. If the insulated piping is installed in a location where it is subjected to rain or other water, the insulation must be sealed with a watertight covering that will maintain its tightness over time. Wet insulation not only does not insulate, it also releases considerable heat energy from the hot water piping, thus wasting energy. Furthermore, the insulation on any outdoor lines that is not sealed watertight can be plagued by birds or rodents, etc., pecking at the insulation to use it for their nests. In time, the entire hot water supply and/or return piping will have no insulation. Such bare hot water supply and/or return piping will waste considerable energy and can seriously affect the operation of the hot water system and water heaters. The minimum required insulation thicknesses given in Table 14.4 are based on insulation having thermal resistivity (R) in the range of 4.0 to 4.6 ft2 × h × (°F/Btu) × in. (0.028 to 0.032 m2 • [°C/W] • mm) on a flat surface at a mean temperature of 75°F (24°C). Minimum insulation thickness shall be increased for materials having R values less than 4.0 ft2 × h × (°F/Btu) × in. (0.028 m2 • [°C/W] • mm) or may be reduced for materials having R values greater than 4.6 ft2 × h × (°F/Btu) × in. (0.032 m2 • [°C/ W] • mm). 1. For materials with thermal resistivity greater than 4.6 ft2 × h × (°F/Btu) × in. (0.032 m2 • [°C/W] • mm), the minimum insulation thickness may be reduced as follows:

(

4.6 × Table 14.4 thickness = New minimum thickness Actual R

)

0.032 • Table 14.4 thickness = New minimum thickness Actual R

2. For materials with thermal resistivity less than 4.0 ft2 × h × (°F/Btu) × in. (0.028 m2 • [°C/W] • mm), the minimum insulation thickness shall be increased as follows:

(

4.0 × Table 14.4 thickness = New minimum thickness Actual R 0.028 • Table 14.4 thickness

)

= New minimum thickness


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Actual R

CONCLUSION In conclusion, an inappropriate hot water recirculation system can have serious repercussions for the operation of the water heater and the sizing of the water heating system. In addition, it can cause the wastage of vast amounts of energy, water, and time. Therefore, it is incumbent upon the plumbing designer to design a hot water recirculation system so that it conserves natural resources and is in accordance with the recommendations given in this chapter.

BIBLIOGRAPHY 1.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. 1993. Pipe sizing. Chapter 33 in Fundamentals Handbook.

2.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. 1993. Thermal and water vapor transmission data. Chapter 22 in Fundamentals Handbook.

3.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. 1995. Service water heating. Chapter 45 in Applications Handbook.

4.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. Energy conservation in new building design. ASHRAE Standards, 90A–1980, 90B–1975, and 90C–1977.

5.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. Energy efficient design of new low rise residential buildings. ASHRAE Standards, 90.2–1993.

6.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. New information on service water heating. Technical Data Bulletin. Vol. 10, No. 2.

7.

American Society of Mechanical Engineers. Plumbing fixture fittings. ASME A112.18.1M–1989.

8.

American Society of Plumbing Engineers. 2000. Cold water systems. Chapter 5 in ASPE Data Book, Volume 2.

9.

American Society of Plumbing Engineers. 1989. Piping systems. Chapter 10 in ASPE Data Book.

10. American Society of Plumbing Engineers. 1989. Position paper on hot water temperature limitations. 11. American Society of Plumbing Engineers. 1989. Service hot water

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systems. Chapter 4 in ASPE Data Book. 12. American Society of Plumbing Engineers. 1990. Insulation. Chapter 12 in ASPE Data Book. 13. American Society of Plumbing Engineers. 1990. Pumps. Chapter 11 in ASPE Data Book. 14. American Society of Plumbing Engineers. 2000. Energy conservation in plumbing systems. Chapter 7 in ASPE Data Book, Volume 1. 15. American Water Works Association. 1985. Internal corrosion of water distribution systems. Research Foundation cooperative research report. 16. Cohen, Arthur. Copper Development Association. 1978. Copper for hot and cold potable water systems. Heating/Piping/Air Conditioning Magazine. May. 17. Cohen, Arthur. Copper Development Association. 1993. Historical perspective of corrosion by potable waters in building systems. Paper no. 509 presented at the National Association of Corrosion Engineers Annual Conference. 18. Copper Development Association. 1993. Copper Tube Handbook. 19. International Association of Plumbing and Mechanical Officials. 1985. Uniform Plumbing Code Illustrated Training Manual. 20. Konen, Thomas P. 1984. An experimental study of competing systems for maintaining service water temperature in residential buildings. In ASPE 1984 Convention Proceedings. 21. Konen, Thomas P. 1994. Impact of water conservation on interior plumbing. In Technical Proceedings of the 1994 ASPE Convention. 22. Saltzberg, Edward. 1988. The plumbing engineer as a forensic engineer. In Technical Proceedings of the 1988 ASPE Convention. 23. Saltzberg, Edward. 1993. To combine or not to combine: An in– depth review of standard and combined hydronic heating systems and their various pitfalls. Paper presented at the American Society of Plumbing Engineers Symposium, October 22–23. 24. Saltzberg, Edward. 1996. The effects of hot water circulation systems on hot water heater sizing and piping systems. Technical presentation given at the American Society of Plumbing Engineers convention, November 3–6. 25. Saltzberg, Edward. 1997. In press. New methods for analyzing hot water systems. Plumbing Engineer Magazine. 26. Saltzberg, Edward. 1997. In press. Prompt delivery of hot water at fixtures. Plumbing Engineer Magazine. 27. Sealine, David A., Tod Windsor, Al Fehrm, and Greg Wilcox. 1988. Mixing valves and hot water temperature. In Technical Proceedings of the 1988 ASPE Convention.


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28. Sheet Metal and Air Conditioning Contractors National Association. 1982. Retrofit of Building Energy Systems and Processes. 29. Steele, Alfred. Engineered Plumbing Design. 2d ed. 30. Steele, Alfred. 1988. Temperature limits in service hot water systems. In Technical Proceedings of the 1988 ASPE Convention. 31. Wen-Yung, W. Chan, and Milton Meckler. 1983. Pumps and pump systems. In American Society of Plumbing Engineers Handbook.

Section

II

EQUIPMENT The material presented in the majority of chapters in this section is drawn from information and documents received from numerous manufacturers. In order to provide balanced, unbiased, and complete coverage, ASPE made every effort possible to solicit information from all applicable equipment manufacturers. The chapters reflect that effort to the extent that manufacturers responded. For some chapters, such as Chapter 17, there was only limited manufacturer input, and the limitations of the material in these chapters are obvious. Manufacturers may submit additional information, data, documents, and new innovations for this section at any time. All submitted materials will be considered and incorporated as appropriate. As new editions of this “work in progress” are issued in future years, this equipment section will develop into a complete compendium of domestic water heating equipment possibilities to assist the design engineer.


14

233

RECIRCULATING DOMESTIC HOT WATER SYSTEMS

INTRODUCTION It has been determined through field studies that the correct sizing and operation of water heaters depend on the appropriateness of the hot water maintenance system. If the hot water maintenance system is inadequate, the water heater sizing criteria are wrong and the temperature of the hot water distributed to the users of the plumbing fixtures is below acceptable standards. Additionally, a poorly designed hot water maintenance system wastes large amounts of energy and potable water and creates time delays for those using the plumbing fixtures. This chapter addresses the criteria for establishing an acceptable time delay in delivering hot water to fixtures and the limitations of the length between a hot water recirculation system and plumbing fixtures. It also discusses the temperature drop across a hot water supply system, types of hot water recirculation system, and pump selection criteria, and gives extensive information on the insulation of hot water supply and return piping.

BACKGROUND In the past, the plumbing engineering community considered the prompt delivery of hot water to fixtures either a requirement for a project or a matter of no concern. The plumbing engineer’s decision was based primarily on the type of facility under consideration and the developed length from the water heater to the farthest fixture. Previous reference material and professional common practices have indicated that, when the distance from the water heater to the farthest fixture exceeds 100 ft (30.48 m) water should Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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be circulated. However, this recommendation is subjective, and, unfortunately, some engineers and contractors use the 100-ft (30.48-m) criterion as the maximum length for all uncirculated, uninsulated, dead-end hot water branches to fixtures in order to cut the cost of hot water distribution piping. These long, uninsulated, dead-end branches to fixtures create considerable problems, such as a lack of hot water at fixtures, inadequately sized water heater assemblies, and thermal temperature escalation in showers. The 100-ft (30.48-m) length criterion was developed in 1973 after the Middle East oil embargo, when energy costs were the paramount concern and water conservation was given little consideration. Since the circulation of hot water causes a loss of energy due to radiation and convection in the circulated system and such energy losses have to be continually replaced by water heaters, the engineering community compromised between energy loss and construction costs and developed the 100-ft (30.48-m) maximum length criterion.

LENGTH AND TIME CRITERIA Recently, due to concern about not only energy conservation but also the extreme water shortages in parts of the country, the 100ft (30.48-m) length criteria has changed. Water wastage caused by the long delay in obtaining hot water at fixtures has become as critical an issue as the energy losses caused by hot water temperature maintenance systems. To reduce the wasting of cooled hot water significantly, the engineering community has reevaluated the permissible distances for uncirculated, dead-end branches to periodically used plumbing fixtures. The new allowable distances for uncirculated, dead-end branches represent a trade-off between the energy utilized by the hot water maintenance system and the cost of the insulation, on the one hand, and the cost of energy to heat the excess cold water makeup, the cost of wasted potable water, and extra sewer surcharges, on the other hand. Furthermore, engineers should be aware that various codes now limit the length between the hot water maintenance system and plumbing fixtures. They also should be aware of the potential for liability if an owner questions the adequacy of their hot water system design. What are reasonable delays in obtaining hot water at a fixture? For anything beside very infrequently used fixtures (such as those in industrial facilities or certain fixtures in office buildings), a delay of 0 to 10 sec is normally considered acceptable for most


235

residential occupancies and public fixtures in office buildings. A delay of 11 to 30 sec is marginal but possibly acceptable, and a time delay longer than 31 sec is normally considered unacceptable and a significant waste of water and energy. Therefore, when designing hot water systems, it is prudent for the designer to provide some means of getting hot water to the fixtures within these acceptable time limits. Normally this means that there should be a maximum distance of approximately 25 ft (7.6 m) between the hot water maintenance system and each of the plumbing fixtures requiring hot water, the distance depending on the water flow rate of the plumbing fixture at the end of the line and the size of the line. (See Tables 14.1, 14.2, and 14.3.) The plumbing designer may want to stay under this length limitation because the actual installation in the field may differ slightly from the engineer's design, and additional delays may be caused by either the routing of the pipe or other problems. Furthermore, with the low fixture discharge rates now mandated by national and local laws, it takes considerably longer to obtain hot water from nontemperature maintained hot water lines than it did in the past, when fixtures had greater flow rates. For example, a public lavatory with a 0.50 or 0.25 gpm (0.03 or 0.02 L/sec) maximum discharge rate would take an excessive amount of time to obtain hot water from 100 ft (30.48 m) of uncirculated, uninsulated hot water piping. (See Table 14.3.) This table gives conservative approximations of the amount of time it takes to obtain hot water at a fixture. The times are based on the size of the line, the fixture flow rate, and the times required to replace the cooled off hot water, to heat the pipe, and to offset the convection energy lost by the insulated hot water line.

Table 14.1 Water Contents and Weight of Tube or Piping per Linear Foot Nominal Diameter (in.)a ½ ¾ 1 1¼ 1½

Copper Pipe Type L

Copper Pipe Type M

Steel Pipe Schedule 40

CPVC Pipe Schedule 40

Water (gal/ft)

Wgt. (lb/ft)

Water (gal/ft)

Wgt. (lb/ft)

Water (gal/ft)

Wgt. (lb/ft)

Water (gal/ft)

Wgt. (lb/ft)

0.012 0.025 0.043 0.065 0.093

0.285 0.445 0.655 0.884 1.14

0.013 0.027 0.045 0.068 0.100

0.204 0.328 0.465 0.682 0.940

0.016 0.028 0.045 0.077 0.106

0.860 1.140 1.680 2.280 2.720

0.016 0.028 0.045 0.078 0.106

0.210 0.290 0.420 0.590 0.710


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Table 14.1(M) Water Contents and Weight of Tube or Piping per Meter Copper Pipe Type L

Nominal Diameter (mm)a

Water (L)

Wgt. (kg)

Copper Pipe Type M Water (L)

Steel Pipe Schedule 40 Wgt. (kg)

Water (L)

CPVC Pipe Schedule 40 Wgt. (kg)

Water (L)

Wgt. (kg)

DN15

0.045

0.129

0.049

0.204

0.061

0.390

0.061

0.099

DN20 DN25 DN32 DN40

0.095 0.163 0.246 0.352

0.202 0.297 0.401 0.517

0.102 0.170 0.257 0.379

0.328 0.465 0.682 0.940

0.106 0.170 0.291 0.401

0.517 0.762 1.034 1.233

0.106 0.170 0.295 0.401

0.132 0.191 0.268 0.322


Table 14.2 Approximate Fixture and Appliance Water Flow Rates Maximum Flow Ratesa Fittings Lavatory faucet Public non-metering Public metering Sink faucet Shower head Bathtub faucets Single-handle Two-handle Service sink faucet Laundry tray faucet Residential dishwasher Residential washing machine aUnless otherwise noted.

GPM

L/Sec

2.0 0.5 0.25 gal/cycle 2.5 2.5

1.3 0.03 0.946 L/cycle 0.16 0.16




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Table 14.3 Approximate Time Required to Get Hot Water to a Fixture Delivery Time (sec) Fixture Flow Rate (gpm) Piping Length (ft)

0.5

1.5

2.5

4.0

10

25

10

25

10

25

10

25

Copper Pipe

½ in. ¾ in.

25 48a

63a 119a

8 16

21 40a

5 10

13 24

3 6

8 15


½ in. ¾ in.

63a 91a

157a 228a

21 30

52a 76a

13 18

31a 46a

8 11

20 28

CPVC Pipe Sched. 40

½ in. ¾ in.

64a 95a

159a 238a

21 32

53a 79a

13 19

32a 48a

8 12

20 30

Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on water temperature of 140°F and an air temperture of 70°F. aDelays longer than 30 sec are not acceptable.

Table 14.3(M) Approximate Time Required to Get Hot Water to a Fixture Delivery Time (sec) Fixture Flow Rate (L/sec) Piping Length (m)

0.03

0.10

0.16

3.1

7.6

3.1

7.6

3.1

7.6

0.25 3.1

7.6

Copper Pipe

DN15 DN22

25 48a

63a 119a

8 16

21 40a

5 10

13 24

3 6

8 15


DN15 DN20

63a 91a

157a 228a

21 30

52a 76a

13 18

31a 46a

8 11

20 28

CPVC Pipe Sched. 40

DN15 DN20

64a 95a

159a 238a

21 32

53a 79a

13 19

32a 48a

8 12

20 30

Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on water temperature of 60°C and an air temperture of 21.1°C. aDelays longer than 30 sec are not acceptable.

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RESULTS OF DELAYS IN DELIVERING HOT WATER TO FIXTURES As mentioned previously, when there is a long delay in obtaining hot water at the fixture, there is significant wastage of potable water as the cooled hot water supply is simply discharged down the drain unused. Furthermore, plumbing engineers concerned about total system costs should realize that the cost of this wasted, previously heated water must include: the original cost for obtaining potable water, the cost of previously heating the water, the final cost of the waste treatment of this excess potable water, which results in larger sewer surcharges (source of supply to end disposal point), and the cost of heating the new cold water to bring it up to the required temperature. Furthermore, if there is a long delay in obtaining hot water at the fixtures, the faucets are turned on for long periods of time to bring the hot water supply at the fixture up to the desired temperature. This can cause the water heating system to run out of hot water and make the heater sizing inadequate, because the heater is unable to heat all the extra cold water brought into the system through the wastage of the water discharged down the drain. In addition, this extra cold water entering the hot water system reduces the hot water supply temperature. This exacerbates the problem of insufficient hot water because to get a proper blended temperature more lower temperature hot water will be used to achieve the final mixed water temperature. (See Chapter 1, Table 1.1.) Additionally, this accelerates the downward spiral of the temperature of the hot water system. Another problem resulting from long delays in getting hot water to the fixtures is that the fixtures operate for longer than expected periods of time. Therefore, the actual hot water demand is greater than the demand normally designed for. Therefore, when sizing the water heater and the hot water piping distribution system, the designer should be aware that the lack of a proper hot water maintenance system can seriously impact the required heater size.

METHODS OF DELIVERING REASONABLY PROMPT HOT WATER SUPPLY Hot water maintenance systems are as varied as the imaginations of the plumbing engineers who create them. They can be grouped into three basic categories, though any actual installa-


239

tion may be a combination of more than one of these types of system. The three basic categories are 1. Circulation systems. 2. Self-regulating heat trace systems. 3. Point-of-use water heaters (include booster water heaters).

Circulation Systems for Commercial, Industrial, and Large Residential Projects A circulation system is a system of hot water supply pipes and hot water return pipes with appropriate shutoff valves, balancing valves, circulating pumps, and a method of controlling the circulating pump. The diagrams for six basic circulating systems are shown in Figures 14.1 through 14.6.

Fixture 14.1 Upfeed Hot Water System with Heater at Bottom of System. * See text for requirements for strainers.

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Figure 14.3 Upfeed Hot Water System with Heater at Bottom of System. * See text for requirements for strainers.


241


Figure 14.5 Combination Upfeed and Downfeed Hot Water System with Heater at Bottom of System. Note: This piping system increases the developed length of the HW system over the upfeed systems shown in Figures 14.1 and 14.3. * See text for requirements for strainers.

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Figure 14.6 Combination Downfeed and Upfeed Hot Water System with Heater at Top of System. Note: This piping system increases the developed length of the HW system over the downfeed systems shown in Figures 14.2 and 14.4. * See text for requirements for strainers.

Self-Regulating Heat Trace Over approximately the last 20 years, self-regulating heat trace has come into its own because of the problems of balancing circulated hot water systems and energy loss in the return piping. For further discussion of this topic, see Chapter 15.

Point-of-Use Heaters This concept is applicable when there is a single fixture or group of fixtures that is located far from the temperature maintenance system. In such a situation, a small, instantaneous, point-of-use water heater—an electric water heater, a gas water heater, or a small under-fixture storage type water heater of the magnitude of 6 gal (22.71 L)—can be provided. (See Figure 14.7.) The pointof-use heater will be very cost-effective because it will save the cost of running hot water piping to a fixture that is a long distance away from the temperature maintenance system. The


243

plumbing engineer must remember, however, that when a water heater is installed there are various code and installation requirements that must be complied with, such as those pertaining to T & P relief valve discharge. Instantaneous electric heaters used in point-of-use applications can require a considerable amount of power, and may require 240 or 480 V service.

POTENTIAL PROBLEMS IN CIRCULATED HOT WATER MAINTENANCE SYSTEMS The following are some of the potential problems with circulated hot water maintenance systems that must be addressed by the plumbing designer.

Figure 14.7 Instantaneous Point-of-Use Water Heater Piping Diagram. Source: Courtesy of Chronomite Laboratories, Inc.

244


Water Velocities in Hot Water Piping Systems For copper piping systems, it is very important that the circulated hot water supply piping and especially the hot water return piping be sized so that the water is moving at a controlled velocity. High velocities in these systems can cause pinhole leaks in the copper piping in as short a period as six months or less.

Balancing Systems It is extremely important that a circulated hot water system be balanced for its specified flows, including all the various individual loops within the circulated system. Balancing is required even though an insulated circulated line usually requires very little flow to maintain satisfactory system temperatures. If the individual hot water circulated loops are not properly balanced, the circulated water will tend to short-circuit through the closest loops, creating high velocities in that piping system. Furthermore, the short-circuiting of the circulated hot water will result in complaints about the long delays in getting hot water at the remotest loops. If the hot water piping is copper, high velocities can create velocity erosion which will destroy the piping system. Because of the problems inherent in manually balancing hot water circulation systems, many professionals incorporate factory preset flow control devices in their hot water systems. While the initial cost of such a device is higher than the cost of a manual balancing valve, a preset device may be less expensive when the field labor cost for balancing the entire hot water system is included. When using a preset flow control device, however, the plumbing designer has to be far more accurate in selecting the control device's capacity as there is no possibility of field adjustment. Therefore, if more or less hot water return flow is needed during the field installation, a new flow control device must be installed and the old one must be removed and discarded.

Isolating Portions of Hot Water Systems It is extremely important in circulated systems that shutoff valves be provided to isolate an entire circulated loop. This is done so that if individual fixtures need modification, their piping loop can be isolated from the system so the entire hot water system does not have to be shut off and drained. The location of these shutoff valves should be given considerable thought. The shutoff valves should be accessible at all times, so they should not be located in


245

such places as the ceilings of locked offices or condominiums.

Maintaining the Balance of Hot Water Systems To ensure that a balanced hot water system remains balanced after the shutoff valves have been utilized, the hot water return system must be provided with a separate balancing valve in addition to the shutoff valve or, if the balancing valve is also used as the shutoff valve, the balancing valve must have a memory stop. (See the discussion of "balancing valves with memory stops" below.) With a memory stop on the valve, plumbers can return a system to its balanced position after working on it rather than have the whole piping system remain unbalanced, which would result in serious problems.

Providing Check Valves at the Ends of Hot Water Loops The designer should provide a check valve on each hot water return line where it joins other hot water return lines. This is done to ensure that a plumbing fixture does not draw hot return water instead of hot supply water, which could unbalance the hot water system and cause delays in obtaining hot water at some fixtures.

A Delay in Obtaining Hot Water at Dead-End Lines Keep the delay in obtaining hot water at fixtures to within the time (and branch length) parameters given previously to avoid unhappy users of the hot water system and to prevent lawsuits.

FLOW BALANCING DEVICES The following are the more common types of balancing device.

Fixed Orifices and Venturis These can be obtained for specific flow rates and simply inserted into the hot water return piping system. (See Figure 14.8.) However, extreme care should be taken to locate these devices so they can be removed and cleaned out, as they may become clogged with the debris in the water. It is recommended, therefore, that a strainer with a blowdown valve be placed ahead of each of these

246


Figure 14.8 Fixed Orifices and Venturi Flow Meters. Source: Courtesy of Gerand Engineering Co.


247

devices. Additionally, a strainer with a fine mesh screen can be installed on the main water line coming into the building to help prevent debris buildup in the individual strainers. Also, a shutoff valve should be installed before and after these devices so that an entire loop does not have to be drained in order to service a strainer or balancing device.

Factory Preset Automatic Flow Control Valves The same admonition about strainers and valves given for "fixed orifices and venturis" above applies to the installation and location of these devices. (See Figure 14.9.)

Figure 14.9 Preset Self-Limiting Flow Control Cartridge. Source: Courtesy of Griswold Controls.

248


Flow Regulating Valves These valves can be used to determine the flow rate by reading the pressure drop across the valve. They are available from various manufacturers. (See Figure 14.10.)

Figure 14.10 Adjustable Orifice Flow Control Valve. Source: ITT Industries. Used with permission.

Balancing Valves with Memory Stops These valves can be adjusted to the proper setting by installing insertable pressure measuring devices (Pete’s Plugs, etc.) in the piping system, which indicate the flow rate in the pipe line. (See Figure 14.11.)


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Figure 14.11 Adjustable Balancing Valve with Memory Stop. Source: Courtesy of Milwaukee Valve Co.

SIZING HOT WATER RETURN PIPING SYSTEMS AND RECIRCULATING PUMPS The method for selecting the proper size of the hot water return piping system and the recirculating pump is fairly easy, but it does require engineering judgment. First, the plumbing engineer has to design the hot water supply and hot water return piping systems, keeping in mind the parameters for total developed length,1 prompt delivery of hot water to fixtures, and velocities in pipe lines. The plumbing engineer has to make assumptions about the sizes of the hot water return piping. After the hot water supply and hot water return systems are designed, the designer should make a piping diagram of the hot 1See American Society of Plumbing Engineers, 2000, Cold-water systems, Chapter 5 in ASPE Data Book, Volume 2, for piping sizing methods.

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water supply system and the assumed return system showing piping sizing and approximate lengths. From this piping diagram the hourly heat loss occurring in the circulated portion of the hot water supply and return systems can be determined. (See Table 14.4 for minimum required insulation thickness and Table 14.5 for approximate piping heat loss.) Next determine the heat loss in the hot water storage tank if one is provided. (See Table 14.6 for approximate tank heat loss.) Calculate the total hot water system energy loss (tank heat loss plus piping heat loss) in British thermal units per hour (watts). This total hot water system energy loss is represented by q in Equation 14.1 below. Note: Heat losses from storage type water heater tanks are not normally included in the hot water piping

Table 14.4 Minimum Pipe Insulation Thickness Required Insulation Thickness for Piping (in.) Runouts 2 in. or Lessa

1 in. or Less

1¼–2 in.

2½–4 in.

5 & 6 in.

8 in. or Larger

½

1

1

1½

1½

1½

Note: Data based on fiberglass insulation with all-service jacket. Data will change depending on actual type of insulation used. Data apply to recirculating sections of hot water systems and the first 3 ft from the storage tank of uncirculated systems. aUncirculated pipe branches to individual fixtures (not exceeding 12 ft in length). For lengths longer than 12 ft, use required insulation thickness shown in table.

Table 14.4(M) Minimum Pipe Insulation Thickness Required Insulation Thickness for Piping (mm) Runouts DN32 or Lessa

DN25 or Less

DN32–DN50

DN65–DN100

DN125 & DN150

DN200 or Larger

13

25

25

40

40

40

Note: Data based on fiberglass insulation with all-service jacket. Data will change depending on actual type of insulation used. Data apply to recirculating sections of hot water systems and the first 0.9 m from the storage tank of uncirculated systems. aUncirculated pipe branches to individual fixtures (not exceeding 3.7 m in length). For lengths longer than 305 mm, use required insulation thickness shown in table.


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Table 14.5 Approximate Insulated Piping Heat Loss and Surface Temperature Nominal Pipe Size (in.) ½ ¾ 1 1¼ 1½ 2 or less 2 2½ 3 4 6 8 10

Insulation Thickness (in.)

Heat Loss (Btu/h/ linear ft)

1 1 1 1 1 ½a 1 1½ 1½ 1½ 1½ 1½ 1½

8 10 10 13 13 24 or less 16 12 16 19 27 32 38

Surface Temperature (°F) 68 69 69 70 69 74 70 67 68 69 69 69 69

Note: Figures based on average ambient temperature of 65°F and annual average wind speed of 7.5 mph. aUncirculating hot water runout branches only.

Table 14.5(M) Approximate Insulated Piping Heat Loss and Surface Temperature Nominal Pipe Size (mm) DN15 DN20 DN25 DN32 DN40 DN50 or less DN50 DN65 DN80 DN100 DN150 DN200 DN250

Insulation Thickness (mm) 25 25 25 25 25 13a 25 38 38 38 38 38 38

Heat Loss (W/m) 7.7 9.6 9.6 12.5 12.5 23.1 or less 15.4 11.5 15.4 18.3 26.0 30.8 36.5

Surface Temperature (°C) 20 21 21 21 21 23 21 19 20 21 21 21 21

Note: Figures based on average ambient temperature of 18°C and annual average wind speed of 12 km/h. aUncirculating hot water runout branches only.

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Table 14.6 Heat Loss from Various Size Tanks with Various Insulation Thicknesses Insulation Thickness (in.) 1 1 2 3 3

Tank Size (gal) 50 100 250 500 1000

Approx. Energy Loss from Tank at Hot Water Temperature 140°F (Btu/h)a 468 736 759 759 1273

Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data. aFor unfired tanks, federal standards limit the loss to no more than 6.5 Btu/h/ ft2 of tank surface.

Table 14.6(M) Heat Loss from Various Size Tanks with Various Insulation Thicknesses Insulation Thickness (mm) 25.4 25.4 50.8 76.2 76.2

Tank Size (L) 200 400 1000 2000 4000

Approx. Energy Loss from Tank at Hot Water Temperature 60°C (W)a 137 216 222 222 373

Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data. aFor unfired tanks, federal standards limit the loss to no more than 1.9 W/m2 of tank surface.

system heat loss because the water heater capacity takes care of this loss, whereas pumped hot water has to replace the piping convection losses in the piping system. (14.1)

q = 60rwc∆T [q = 3600rwc∆T]


253

where 60 3600 q r w c ∆T

= = = = = = =

min/h sec/h piping heat loss, Btu/h (kJ/h) flow rate, gpm (L/sec) weight of heated water, lb/gal (kg/L) specific heat of water, Btu/lb/°F (kJ/kg/K) change in heated water temperature (temperature of leaving water minus temperature of incoming water, represented in this manual as Th – Tc, °F [K])

Therefore = c (gpm × 8.33 lb/gal)(60 min/h)(°F temperature drop) = 1(gpm) × 500 × °F temperature drop [q = c (L/sec • 1kg/L)(3600 sec/h)(K temperature drop) = 1(L/sec) • 15 077 kJ/L/sec/K • K temperature drop] q

(14.2) gpm ≈

[

system heat loss (Btu/h) 500 × °F temperature drop

L/sec ≈

]

system heat loss (kJ/h) 15 077 • K temperature drop

In sizing hot water circulating systems, the designer should note that the greater the temperature drop across the system, the less water is required to be pumped through the system and, therefore, the greater the savings on pumping costs. However, if the domestic hot water supply starts out at 140°F (60°C) with, say, a 20°F (6.7°C) temperature drop across the supply system, the fixtures near the end of the circulating hot water supply loop could be provided with a hot water supply of only 120°F (49°C). In addition, if the hot water supply delivery temperature is 120°F (49°C) instead of 140°F (60°C), the plumbing fixtures will use greater volumes of hot water to get the desired blended water temperature (see Chapter 1, Table 1.1). Therefore, the recommended hot water system temperature drop should be of the magnitude of 5°F (3°C). This means that if the hot water supply starts out from the water heater at a temperature between 135 and 140°F (58 and 60°C), the lowest hot water supply temperature provided by the hot water supply system could be between 130 and 135°F (54 and 58°C). With multiple temperature distri-

254


bution systems, it is recommended that the recirculation system for each temperature distribution system be extended back to the water heating system separately and have its own pump. Using Equation 14.2, we determine that, if there is a 5°F (3°C) temperature drop across the hot water system, the number to divide into the hot water circulating system heat loss (q) to obtain the minimum required hot water return circulation rate in gpm (L/sec) is 2500 (500 × 5°F), (45 213 [15 071 • 3°C]). For a 10°F (6°C) temperature drop that number is 5000 (from Equation 14.2, 500 × 10°F = 5000) (90 426 [from Equation 14.2, 15 071 • 6°C = 90 426]). However, this 10°F (6°C) temperature drop may produce hot water supply temperatures that are lower than desired. After Equation 14.2 is used to establish the required hot water return flow rate, in gpm (L/sec), the plumbing designer can size the hot water return piping system based on piping flow rate velocities and the available pump heads. It is quite common that a plumbing designer will make wrong initial assumptions about the sizes of the hot water return lines to establish the initial heat loss figure (q). If that is the case, the plumbing engineer will have to correct the hot water return pipe sizes, redo the calculations using the new data based on the correct pipe sizing, and verify that all the rest of the calculations are now correct.

EXAMPLE 14.1—CALCULATION TO DETERMINE REQUIRED CIRCULATION RATE 1. Assume that the hot water supply piping system has 800 ft (244 m) of average size 1 ¼ in. (DN32) pipe. From Table 14.5, determine the heat loss per linear foot (meter). To find the total heat loss, multiply length times heat loss per foot (meter): 800 ft × 13 Btu/h/ft = 10,400 Btu/h supply piping losses (244 m • 12.5 W = 3050 W supply piping losses) 2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) piping and 100 ft (30.5 m) of average ¾ in. (DN20) pipe. From Table 14.5 determine the heat loss per linear foot (meter): 100 ft × 8 Btu/h/ft = 800 Btu/h piping loss


255

(30.5 m • 7.7 W/m = 235 W piping loss) 100 ft × 10 Btu/h/ft =

(

30.5 m • 9.6 W/m =

1000 Btu/h piping loss 1800 Btu/h piping loss

293 W piping loss 528 W piping loss

)

3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage tank. From Table 14.6 determine the heat loss of the storage tank @ 759 Btu/h (222 W). 4. Determine the hot water system’s total heat losses by totaling the various losses: A. Hot water supply piping losses B. Hot water return piping losses C. Hot water storage tank losses Total system heat losses

10,400 Btu/h 1,800 Btu/h 759 Btu/h 12,959 Btu/h

Total system piping heat losses (A + B) = 12,200 Btu/h [A. Hot water supply piping losses B. Hot water return piping losses C. Hot water storage tank losses Total system heat losses

3050 W 527 W 222 W 3799 W

Total system piping heat losses (A + B) = 3577 W] From Equation 14.2, using a system piping loss of 12,200 Btu/h (3577 W) and a 5°F (3°C) temperature drop, 12,200 Btu/h = 4.88 gpm (say 5 gpm) 5°F temperature difference × 500 required hot water return circulation rate

[

3577 W

3°C temp. difference • 4188.32 kJ/m3

]

= 0.29 (say 0.3) L/sec required hot water return circulation rate

Recalculation of Hot Water System Losses 1. Assume that the hot water supply piping system has 800 ft (244 m) of average size 1¼ in. (DN32) pipe. From Table 14.5 determine the heat loss per linear foot (meter):

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800 ft × 13 Btu/h/ft = 10,400 Btu/h piping loss (244 m

•

12.5 W/m = 3050 W piping loss)

2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) pipe, 25 ft (7.6 m) of average ¾ in. (DN22) pipe, and 75 ft (22.9 m) of average 1 in. (DN28) pipe. From Table 14.5, determine the heat loss per linear foot (meter): 100 ft × 8 Btu/h/ft = 800 Btu/h piping loss 25 ft × 10 Btu/h/ft = 250 Btu/h piping loss 75 ft × 10 Btu/h/ft = 750 Btu/h piping loss 1800 Btu/h piping loss [30.5 m • 7.7 W/m = 7.6 m • 9.6 W/m = 22.9 m • 9.6 W/m =

235 W piping loss 73 W piping loss 220 W piping loss 528 W piping loss]

3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage tank. From Table 14.6 determine the heat loss of the storage tank @ 759 Btu/h (222 W). 4. Determine the system’s total heat losses: A. Hot water supply losses B. Hot water return losses C. Hot water storage tank losses

10,400 Btu/h 1,800 Btu/h 759 Btu/h

Total system heat losses

12,959 Btu/h

Total system piping heat losses (A + B) = 12,200 Btu/h [A. Hot water supply losses B. Hot water return losses C. Hot water storage tank losses Total system heat losses

3050 W 528 W 222 W 3800 W

Total system piping heat losses (A + B) = 3578 W] Note: The recalculation determined that the hot water system heat losses remained unchanged and that 4.88 (say 5) gpm (0.29 [say 0.3] L/sec) is the flow rate that is required to maintain the 5°F (3°C) temperature drop across the hot water supply system.


257

It should be stated that engineers use numerous rules of thumb to size hot water return systems. These rules of thumb are all based on assumptions, however, and are not recommended. It is recommended that the engineer perform the calculations for each project to establish the required flow rates because, with all the various capacities of the pumps available today, exact sizing is possible, and any extra circulated flow caused by the plumbing engineer using a rule of thumb equates to higher energy costs, to the detriment of the client.

ESTABLISHING THE HEAD CAPACITY OF THE HOT WATER CIRCULATING PUMP The hot water return circulating pump is selected based on the required hot water return flow rate (in gpm [L/sec]), calculated using Equation 14.2, and the system’s pump head. The pump head is normally determined by the friction losses through only the hot water return piping loops and any losses through balancing valves. The hot water return piping friction losses usually do not include the friction losses that occur in the hot water supply piping. The reason for this is that the hot water return circulation flow is needed only to keep the hot water supply system up to the desired temperature when there is no flow in the hot water supply piping. When people use the hot water at the fixtures, there is usually sufficient flow in the hot water supply piping to keep the system hot water supply piping up to the desired temperature without help from the flow in the hot water return piping. The only exception to the rule of ignoring the friction losses in the hot water supply piping is a situation where a hot water return pipe is connected to a relatively small hot water supply line. "Relatively small" here means any hot water supply line that is less than one pipe size larger than the hot water return line. The problems created by this condition are that the hot water supply line will add additional friction to the head of the hot water circulating pump, and the hot water circulating pump flow rate can deprive the last plumbing fixture on this hot water supply line from obtaining its required flow. It is recommended, therefore, that in such a situation the hot water supply line supplying each hot water return piping connection point be increased to prevent these potential problems, i.e., use ¾ in. (DN22) hot water supply piping and ½ in. (DN15) hot water return piping, or 1 in. (DN28) hot water supply piping and ¾ in. (DN22) hot water return piping, etc.

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When selecting the hot water circulating pump’s head, the designer should be sure to calculate only the restrictions encountered by the circulating pump. A domestic hot water system is normally considered an open system (i.e., open to the atmosphere). When the hot water circulating pump is operating, however, it is assumed that the piping is a closed system. Therefore, the designer should not include static heads where none exists. For example, in Figure 14.1, the hot water circulating pump has to overcome only the friction in the hot water return piping not the loss of the static head pumping the water up to the fixtures because in a closed system the static head loss is offset by the static head gain in the hot water return piping.

HOT WATER CIRCULATING PUMPS Most hot water circulating pumps are of the centrifugal type and are available as either in-line units for small systems or basemounted units for large systems. Because of the corrosiveness of hot water systems, the pumps should be bronze, bronze fitted, or stainless steel. Conventional, iron bodied pumps, which are not bronze fitted, are not recommended.

CONTROL FOR HOT WATER CIRCULATING PUMPS There are three major methods commonly used for controlling hot water circulating pumps: manual, thermostatic (aquastat), and time clock control. Sometimes more than one of these methods are used on a system. 1. A manual control runs the hot water circulating pump continuously when the power is turned on. A manual control should be used only when hot water is needed all the time, 24 h a day, or during all the periods of a building's operation. Otherwise, it is not a cost-effective means of controlling the circulating pump because it will waste energy. Note: The method for applying the “on demand” concept for controlling the hot water circulating pump is a manual control. It can be used very successfully for residential and commercial applications. 2. A thermostatic aquastat is a device that is inserted into the hot water return line. When the water in the hot water return system reaches the distribution temperature, it shuts off the


259

circulating pump until the hot water return system temperature drops by approximately 10°F [5.5°C]. With this method, when there is a large consumption of hot water by the plumbing fixtures, the circulating pump does not operate. 3. A time clock is used to turn the pump on during specific hours of operation when people are using the fixtures. The pump would not operate, for example, at night in an office building when nobody is using the fixtures. 4. Often an aquastat and a time clock are used in conjunction so that during the hours a building is not operating the time clock shuts off the circulating pump, and during the hours the building is in use the aquastat shuts off the pump when the system is up to the desired temperature.

AIR ELIMINATION In any hot water return circulation system it is very important that there be a means of eliminating any entrapped air from the hot water return piping. Air elimination is not required in the hot water supply piping because the discharge of water from the fixtures will eliminate any entrapped air. If air is not eliminated from the hot water return lines, however, it can prevent the proper circulation of the hot water system. It is imperative that a means of air elimination be provided at all high points of a hot water return system. The plumbing engineer must always give consideration to precisely where the air elimination devices are to be located and drained. For example, they should not be located in the unheated attics of buildings in cold climates. If the plumbing engineer does not consider the location of these devices and where they will drain, the result may be unsightly piping in a building or extra construction costs.

INSULATION The use of insulation is very cost-effective. It means paying one time to save the later cost of significant energy lost by the hot water supply and return piping system. Also, insulation decreases the stresses on the piping due to thermal expansion and contraction caused by changes in water temperature. Furthermore, the proper use of insulation eliminates the possibility of someone getting burned by a hot, uninsulated water line. See Table 14.5 for the surface temperatures of insulated lines (versus 140°F [60°C] for bare piping).

260


It is recommended that all hot water supply and return piping be insulated. This recommendation exceeds some code requirements. See Table 14.4 for the minimum required insulation thicknesses for all systems. If the insulated piping is installed in a location where it is subjected to rain or other water, the insulation must be sealed with a watertight covering that will maintain its tightness over time. Wet insulation not only does not insulate, it also releases considerable heat energy from the hot water piping, thus wasting energy. Furthermore, the insulation on any outdoor lines that is not sealed watertight can be plagued by birds or rodents, etc., pecking at the insulation to use it for their nests. In time, the entire hot water supply and/or return piping will have no insulation. Such bare hot water supply and/or return piping will waste considerable energy and can seriously affect the operation of the hot water system and water heaters. The minimum required insulation thicknesses given in Table 14.4 are based on insulation having thermal resistivity (R) in the range of 4.0 to 4.6 ft2 × h × (°F/Btu) × in. (0.028 to 0.032 m2 • [°C/W] • mm) on a flat surface at a mean temperature of 75°F (24°C). Minimum insulation thickness shall be increased for materials having R values less than 4.0 ft2 × h × (°F/Btu) × in. (0.028 m2 • [°C/W] • mm) or may be reduced for materials having R values greater than 4.6 ft2 × h × (°F/Btu) × in. (0.032 m2 • [°C/ W] • mm). 1. For materials with thermal resistivity greater than 4.6 ft2 × h × (°F/Btu) × in. (0.032 m2 • [°C/W] • mm), the minimum insulation thickness may be reduced as follows:

(

4.6 × Table 14.4 thickness = New minimum thickness Actual R

)

0.032 • Table 14.4 thickness = New minimum thickness Actual R

2. For materials with thermal resistivity less than 4.0 ft2 × h × (°F/Btu) × in. (0.028 m2 • [°C/W] • mm), the minimum insulation thickness shall be increased as follows:

(

4.0 × Table 14.4 thickness = New minimum thickness Actual R 0.028 • Table 14.4 thickness

)

= New minimum thickness


261

Actual R

CONCLUSION In conclusion, an inappropriate hot water recirculation system can have serious repercussions for the operation of the water heater and the sizing of the water heating system. In addition, it can cause the wastage of vast amounts of energy, water, and time. Therefore, it is incumbent upon the plumbing designer to design a hot water recirculation system so that it conserves natural resources and is in accordance with the recommendations given in this chapter.

BIBLIOGRAPHY 1.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. 1993. Pipe sizing. Chapter 33 in Fundamentals Handbook.

2.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. 1993. Thermal and water vapor transmission data. Chapter 22 in Fundamentals Handbook.

3.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. 1995. Service water heating. Chapter 45 in Applications Handbook.

4.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. Energy conservation in new building design. ASHRAE Standards, 90A–1980, 90B–1975, and 90C–1977.

5.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. Energy efficient design of new low rise residential buildings. ASHRAE Standards, 90.2–1993.

6.

American Society of Heating, Refrigerating, and Air Conditioning Engineers. New information on service water heating. Technical Data Bulletin. Vol. 10, No. 2.

7.

American Society of Mechanical Engineers. Plumbing fixture fittings. ASME A112.18.1M–1989.

8.

American Society of Plumbing Engineers. 2000. Cold water systems. Chapter 5 in ASPE Data Book, Volume 2.

9.

American Society of Plumbing Engineers. 1989. Piping systems. Chapter 10 in ASPE Data Book.

10. American Society of Plumbing Engineers. 1989. Position paper on hot water temperature limitations. 11. American Society of Plumbing Engineers. 1989. Service hot water

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systems. Chapter 4 in ASPE Data Book. 12. American Society of Plumbing Engineers. 1990. Insulation. Chapter 12 in ASPE Data Book. 13. American Society of Plumbing Engineers. 1990. Pumps. Chapter 11 in ASPE Data Book. 14. American Society of Plumbing Engineers. 2000. Energy conservation in plumbing systems. Chapter 7 in ASPE Data Book, Volume 1. 15. American Water Works Association. 1985. Internal corrosion of water distribution systems. Research Foundation cooperative research report. 16. Cohen, Arthur. Copper Development Association. 1978. Copper for hot and cold potable water systems. Heating/Piping/Air Conditioning Magazine. May. 17. Cohen, Arthur. Copper Development Association. 1993. Historical perspective of corrosion by potable waters in building systems. Paper no. 509 presented at the National Association of Corrosion Engineers Annual Conference. 18. Copper Development Association. 1993. Copper Tube Handbook. 19. International Association of Plumbing and Mechanical Officials. 1985. Uniform Plumbing Code Illustrated Training Manual. 20. Konen, Thomas P. 1984. An experimental study of competing systems for maintaining service water temperature in residential buildings. In ASPE 1984 Convention Proceedings. 21. Konen, Thomas P. 1994. Impact of water conservation on interior plumbing. In Technical Proceedings of the 1994 ASPE Convention. 22. Saltzberg, Edward. 1988. The plumbing engineer as a forensic engineer. In Technical Proceedings of the 1988 ASPE Convention. 23. Saltzberg, Edward. 1993. To combine or not to combine: An in– depth review of standard and combined hydronic heating systems and their various pitfalls. Paper presented at the American Society of Plumbing Engineers Symposium, October 22–23. 24. Saltzberg, Edward. 1996. The effects of hot water circulation systems on hot water heater sizing and piping systems. Technical presentation given at the American Society of Plumbing Engineers convention, November 3–6. 25. Saltzberg, Edward. 1997. In press. New methods for analyzing hot water systems. Plumbing Engineer Magazine. 26. Saltzberg, Edward. 1997. In press. Prompt delivery of hot water at fixtures. Plumbing Engineer Magazine. 27. Sealine, David A., Tod Windsor, Al Fehrm, and Greg Wilcox. 1988. Mixing valves and hot water temperature. In Technical Proceedings of the 1988 ASPE Convention.


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28. Sheet Metal and Air Conditioning Contractors National Association. 1982. Retrofit of Building Energy Systems and Processes. 29. Steele, Alfred. Engineered Plumbing Design. 2d ed. 30. Steele, Alfred. 1988. Temperature limits in service hot water systems. In Technical Proceedings of the 1988 ASPE Convention. 31. Wen-Yung, W. Chan, and Milton Meckler. 1983. Pumps and pump systems. In American Society of Plumbing Engineers Handbook.

Self-Regulating Heat TTrace race Systems

15

265

SELF-REGULATING HEAT TRACE SYSTEMS

INTRODUCTION A hot water self-regulating heat trace system can be used for prompt delivery of hot water at the fixtures. A heating cable system is one of several accepted methods of providing prompt delivery of hot water. (See Chapter 14.) Today’s buildings are more architecturally complex than those built a decade ago and make ever increasing demands on the interstitial space occupied by HVAC ductwork, mechanical piping, communication wiring, and electrical conduits. This, combined with the need to conserve energy and water, challenge engineers to provide cost-effective, energy-efficient domestic hot water systems. Maintaining the temperature of a domestic hot water system may entail establishing a means to continuously recirculate the water via pumps, valves, and additional piping. An alternative method is to use self-regulating heat trace systems. Water conservation has become a major concern in the past few years. The need to conserve water has led to requirements for the use of low-flow fixtures, including faucets, showers, and water closets. The water wastage that occurs when cooled water is dumped down the drain while the user is waiting for hot water to flow can no longer be tolerated. In addition to wasting a precious resource, this practice incurs extra energy costs to heat the water and waste treatment costs to process the wasted water. The ability to keep a pipe warm close to the point of use is of particular interest with the low-flow fixtures used today.


266


Variables affecting the performance of a heat trace system include: the system temperature range, time to tap, water wastage, and energy efficiency. Designers should consider these factors along with installation and life-cycle costs when selecting the proper hot water self-regulating heat trace system for a particular building.

SYSTEM DESCRIPTION Electric heat tracing systems replace heat lost through the thermal insulation on hot water supply piping to maintain the water at desired nominal temperatures, eliminating the need for insulated recirculation lines, pumps, and balancing valves. Preventing the hot water from cooling also ensures that hot water is readily available when it is needed. An electrical heat tracing system is not a substitute for a complete, efficient domestic hot water system. It does not eliminate the need for an efficient water heater. What a heat tracing system does is provide another approach to the design and installation of a hot water system. It does this by simplifying the hot water distribution system, thereby minimizing the amount of piping required. Items such as additional piping and balancing valves are unnecessary. In a heat trace system, a self-regulating heating cable is attached directly to the hot water supply piping and insulated. A self-regulating heating cable adjusts its power at each point along its length to maintain nominal temperature throughout the piping system. Electrical energy input is controlled by the cable’s construction to maintain the required water temperature at the fixtures. No return piping or circulation pump is required. Successful installation of a heat tracing system requires coordination among the various tradespeople involved. Plumbers and electrical and insulation contractors must be made aware of the specific requirements affecting each other’s work. The information in this chapter will help the designer understand electric heat tracing as it applies to hot water systems. With this information, a designer should be able to: 1. Compare the merits of heat tracing and a recirculation system based on the requirements of a specific project. 2. Identify the extent of piping requiring heat tracing.


267

3. Understand the role of thermal insulation in hot water heat tracing. 4. In coordination with an electrical engineer, determine the circuit breaker/power requirements based on the estimated heat tracing circuit lengths. 5. Translate the design requirements into a complete design for a project. All examples and descriptions in this chapter are based on copper water piping with fiberglass thermal insulation and other typical design conditions. While design parameters may differ and pipe and insulation materials other than those discussed can be and frequently are equipped with heat tracing, such jobs should be undertaken with the design assistance of a qualified manufacturer’s representative.

PRODUCT DESCRIPTION Only Underwriters Laboratories, Inc., listed electric heat tracing systems for hot water temperature maintenance should be used. (Note: Thirty mA ground fault equipment protection is to be used for all hot water heat tracing circuits.) These tested and approved systems are based on self-regulating heating cables that are specifically designed for hot water temperature maintenance. (See Figure 15.1.) Heat is delivered through a carbon matrix heating element that responds to temperature changes. Whenever the temperature in the heat traced piping begins to rise, the cable automatically reduces its heat output. Conversely, when the water temperature begins to drop the cable reacts by increasing its heat output. This self-regulating feature occurs along the entire length of a heat tracing circuit to ensure that each point receives the amount of heat necessary to maintain thermal equilibrium. Heating cables, self-regulating or otherwise, intended for pipe freeze protection or general temperature maintenance should not be used for hot water temperature maintenance, since their performance has not been matched to the requirements of hot water applications.

268


Figure 15.1 Construction of a Typical Heating Cable for Hot Water Temperature Maintenance. Source: Courtesy of Raychem Corporation.


269

SYSTEM COMPONENTS A hot water temperature maintenance system (such as the one shown in Figure 15.2) typically includes the following components: 1. Self-regulating heating cable. 2. Power connection kit.1 3. Tee/inline splice kit (permits 2 or 3 cables to be spliced together). 4. Cable end termination. 5. Attachment tape (secures cable to pipe, use at 12 to 24 in. [305 to 610 mm] intervals). 6. Electric heat tracing label (peel and stick label that attaches to insulation vapor barrier at 10 ft [3.05 m] intervals, or as required by code or specification). 7. Fiberglass thermal insulation and vapor barrier.2

Figure 15.2 Components of a Hot Water Temperature Maintenance System. Source: Courtesy of Thermon Manufacturing Co. Note: See “System Components,” above, for identification of numbered parts.

1Power connection kits do not include electrical junction boxes. 2All heat traced lines are to be thermally insulated with fiberglass. Refer to the

manufacturer’s insulation schedule for insulation information.

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IDENTIFYING THE PIPING REQUIRING HEAT TRACING Typically, main and branch lines that are ¾ inch (DN22) and larger are the primary locations for the application of a hot water heat tracing system. A heat traced line can maintain hot water to every point of use. Systems with different pressure or temperature zones can easily be accommodated in the design and layout of heating circuits. Deciding how close to the point of use the heat tracing should be installed depends on the following conditions: 1. The gallons per minute (liters per second) of the fixture. 2. The diameter of the runout line. 3. The number of times per day the fixture will be used. 4. The acceptable period of time to wait for hot water. 5. The acceptable level of water waste per fixture per use. 6. Any special requirements at the point of use. Most new facilities require fixtures that limit the gpm (L/sec) used by lavatories and showers. As a result, the length of uncirculated, non-heat traced piping has become increasingly important. Table 15.1 shows the correlation of time to get hot water (in seconds), to fixture flow rate, to length of ¾ in. (DN22) diameter runout piping that is not temperature maintained.

Table 15.1 Time for Hot Water to Reach Fixture (sec) Fixture Flow Rate

Distance from End of Heat Tracing Circuit to Point of Use (ft)

(gpm)

15

20

25

30

40

1 1.5 2 2.5 3 3.5 4

23 15 11 9 8 6 6

30 20 15 12 10 9 8

38 25 19 15 13 11 9

45 30 23 18 15 13 11

60 40 30 24 20 17 15

Source: Courtesy of Thermon Manufacturing Co. Note: Numbers based on use of ¾ in. nominal diameter type L copper tubing. Calculations are based on the heat loss from the piping and do not include the amount of heat required to heat the piping or the water in the piping. See Chapter 14 for these values.

Table 15.1(M) Time for Hot Water


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to Reach Fixture (sec) Fixture Flow Rate (L/sec) 0.06 0.1 0.13 0.16 0.19 0.22 0.25

Distance from End of Heat Tracing Circuit to Point of Use (m) 4.6

6.1

7.6

9.1

12.2

23 15 11 9 8 6 6

30 20 15 12 10 9 8

38 25 19 15 13 11 9

45 30 23 18 15 13 11

60 40 30 24 20 17 15

Source: Courtesy of Thermon Manufacturing Co. Note: Numbers based on use of DN22 nominal diameter type L copper tubing. Calculations are based on the heat loss from the piping and do not include the amount of heat required to heat the piping or the water in the piping. See Chapter 14 for these values.

While considering the time factor may be important for the purposes of keeping users satisfied, there is a more critical issue. Even with low-flow fixtures, the amount of water wasted by dumping water until the desired temperature is reached can be significant. (See Table 15.2.)

Table 15.2 Water Wasted While Waiting for Hot Water to Reach Fixture (oz) Distance from End of Temperature Maintenance Nom. Diam. to Point of Use (ft) Type L Copper (in.) 15 20 25 30 40 ¾

48

64

80

97

129

Source: Courtesy of Thermon Manufacturing Co. Notes: 1. Remember to add up all the fixtures in a facility and to multiply by both the waste number shown and the expected number of usages per day. 2. Numbers based on line diameter and distance from end of temperature maintenance.

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Table 15.2(M) Water Wasted While Waiting for Hot Water to Reach Fixture (mL) Nom. Diam. Type L Copper DN22

Distance from End of Temperature Maintenance to Point of Use (m) 4.6

6.1

7.6

9.1

12.2

1420

1895

2365

2870

3815

Source: Courtesy of Thermon Manufacturing Co. Notes: 1. Remember to add up all the fixtures in a facility and to multiply by both the waste number shown and the expected number of usages per day. 2. Numbers based on line diameter and distance from end of temperature maintenance.

DESIGN CONSIDERATIONS Heating cable systems do not require system balancing. Often they are used in buildings with significant lengths of return piping relative to the lengths of supply piping or in hot water systems requiring multiple circulation loops. Heating cable systems may not be economical in buildings with doughnut configurations and small amounts of return piping. Such systems still may be selected, however, if the designer wishes to eliminate flow balancing.

Multiple Temperature Systems For systems requiring multiple temperatures, heating cable can be installed on the supply piping after the mixing valve to maintain the different temperatures independently.

Remodels and Additions For buildings with existing return systems, heating cable systems can be installed in the additions so that hot water temperature is maintained in the new piping without affecting the performance of the existing hot water systems.


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COORDINATING DESIGN INFORMATION To get the most from each heat tracing circuit, the designer should establish the maximum circuit length based on the number of circuit breakers available for the project. (Note: Maximum circuit lengths vary according to the voltage and temperature selection.) Regardless of a building’s shape and size, it is recommended that the heat tracing circuits be organized to follow the layout of the cable. For ease of identification during the layout process and for effective communication, the designer should identify the piping requiring heat tracing on the plumbing drawings. While indication of the heating cable, power connection, end termination, and tee splice kits is given on the plumbing drawings, only the power connection points need to be referenced on the electrical drawings. The symbols shown in Figure 15.3 are routinely used to indicate components of a heat traced hot water supply system.

Figure 15.3 Symbols Used to Indicate Components of a Heat Traced Hot Water Supply System. Source: Courtesy of Thermon Manufacturing Co. Note: The numerals inside the symbols refer to circuit numbers.

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DETERMINING THE TEMPERATURE TO MAINTAIN The desired temperatures for most applications are given in Table 15.3 along with the ambient temperature ranges of the space surrounding the insulated pipe. The appropriate self-regulating cable is chosen based on the desired maintenance temperature. If temperatures differ from those shown, contact the manufacturer.

Table 15.3 Nominal Maintenance Temperatures, °F (°C) Ambient Range, °F (°C) 75–80

Hospitals, Nursing Homes, Prisons

Hospitals, Hotels, Condos, Prisons, Schools

Kitchens, Laundries

105 (42)

(24–27) 72–80

120 (49)

140 (60)

(22–27) Source: Courtesy of Thermon Manufacturing Co.

CHOOSING THE RIGHT CABLE After determining the extent of the hot water supply piping to be heat traced, the designer should decide the lengths to be maintained at 105, 120, and/or 140°F (42, 49, and/or 60°C). At this point, the total length of each type of heating cable can be determined. Using the manufacturer’s published maximum circuit length for the desired temperature cable, the designer can figure the required number of circuits. These maximum circuit lengths should not be exceeded; otherwise, there will be excessive electrical currents in the bus wires of the heating cable. The maximum circuit length is the total length of cable that can be fed from a single power connection point, inclusive of all splices, including tees. Note that circuit lengths that are longer than these maximum lengths may require larger circuit breakers. The designer must be sure to check with the electrical engineer the available amperages of the branch circuit breakers supplying power to the heat tracing. After the required number of circuits is determined, that information should also be checked with the electrical engineer. This will ensure that the proper number of circuits has been allotted in the power distribution system.


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THERMAL INSULATION While frequently overlooked, thermal insulation plays a critical role in ensuring that hot water is available at the point of use. This is true for both recirculation and heat traced hot water systems. The standard design for heat traced piping (the design that manufacturers’ design guides are based on) utilizes fiberglass thermal insulation with a kraft paper vapor barrier. Thicknesses range from 1 to 2 in. (25.4 to 50.8 mm) based on line diameter. If a heat traced hot water system is designed to use only one cable for each temperature range, the thickness of the insulation will vary. Manufacturers of hot water heat tracing systems have established insulation schedules that outline the thicknesses required to keep the heat loss within the desired range. Note that in these schedules the insulation on piping 1 ¼ in. (DN35) in diameter and smaller is oversized to allow space for the heating cable. After the installation of the heating cable and thermal insulation is completed, the piping is identified with stick-on labels to note the presence of electric heat tracing. This labeling gives notice to facility maintenance workers that heating cable has been installed under the insulation should any pipe maintenance or renovations be required.

HEAT TRACING HOT WATER PIPING The design of a heat tracing temperature maintenance system for mains and branch lines can be done on the plumbing drawings. (See Figure 15.4.) By referring to the manufacturer’s heating cable selection chart for the desired maintenance temperature, the designer can determine the maximum heating cable circuit length for circuit breakers of different sizes. Taking this information into account when laying out the hot water lines will ensure optimum use of the circuit lengths. Note, in Figure 15.4, that the main and branch lines are heat traced and insulated while the short runouts are only insulated. (Runouts that feed individual points of use typically contain less than ½ gal [1.89 L] of water. If the faucet flow rate is above 1½ gpm [0.1 L/sec], hot water will reach the point of use within 10 sec.) If the distance between the branch line and the point of use is much longer than 40 ft (12.19 m) or the flow rate is lower, the potential for water wastage and the time required for hot water to

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Figure 15.4 Partial Simplified System Typical of Hospitals, Correctional Facilities, and Hotels. Source: Courtesy of Thermon Manufacturing Co.

reach the point of use may be beyond the levels considered acceptable for the facility. To remedy this situation, simply heat trace closer to the point of use.

COMBINING HORIZONTAL MAINS WITH SUPPLY RISERS Designers of multilevel facilities often duplicate floor plans over several levels, which simplifies the layout of electrical, HVAC, and mechanical equipment. This practice also simplifies the layout of hot water supply lines, unless there is a maze of recirculation piping and balancing valves are required. Figure 15.5 shows a layout typical of two to four-story facilities, such as hospitals, research labs, correctional facilities, and campus dormitories.


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In this example, the supply main is located in the interstitial space between the first-story ceiling and the second-story floor. Because each story has roughly the same layout and water use points are stacked, a riser and drop are used to supply water at each plumbing location. Electric heat tracing is installed on the horizontal mains and the risers. Since the distance between the horizontal piping and the first-story runouts is minimal (less than 15 ft [4.57 m]), heating cable is not required beyond the horizontal line connecting the main to the riser. Since this example is of a four-story facility, it is recommended that heating cable be installed up to the feed point for the third story. The line feeding from level three to level four again is less

Figure 15.5 Typical Layout for 2 to 4-Story Hospitals, Research Labs, Correctional Facilities, and Dormitories. Source: Courtesy of Thermon Manufacturing Co.

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than 15 ft (4.57 m), and under most conditions a line of this length does not require heat tracing. Untraced lines should be installed so as to prevent rapid heat loss between uses. While this example is somewhat simplistic, the design principles it demonstrates can be applied to a project of any size.

HOT WATER HEAT TRACING TERMS The following terms apply to all hot water heat tracing systems and may aid in the selection of the appropriate system for each project. 1. System temperature range. For a return system, this is the allowable temperature drop to the end of the system plus any additional variability caused by improper system balancing. With return systems, there is a trade-off between desired system performance and the life-cycle cost of the system. For a heating cable system, the system temperature range is the range around the nominal maintenance temperature. 2. Unheated distance. This is the distance in feet (meters) between the last maintained leg of hot water piping and the point of use. For example, if hot water temperature is maintained only for the main run, the distance from the main to the point of use is the unheated distance. 3. Time to tap. This is the time required for hot water to reach the fixture when the fixture is turned on. If the hot water temperature is not maintained all the way to the fixture, the cold water in the pipe must be drawn out before the user gets hot water. The length of the wait is called time to tap. It is a function of the unheated distance, the gpm (L/sec) flow rate, and the diameter of the pipe.

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HEAT EXCHANGERS

INTRODUCTION The basic process behind the heating of water is heat exchange, whereby heat from a hot substance (the heating medium) is given to a colder substance or medium, in this case water. This heat exchange between a heating medium and water usually takes place in a piece of equipment called a “heat exchanger” that is specifically designed and manufactured to efficiently and costeffectively transfer heat from one medium to another. This section discusses the basic construction, operation, configuration, and selection of various types of heat exchanger and offers insights into their advantages, disadvantages, and application.

CODES AND STANDARDS Plumbing Codes Over the last few years, some plumbing codes have been revised to require double-wall protection in potable water systems. These revisions address concern over the contamination of potable water during normal use or as a result of excess pressure by any fluid that is flooded in a tank or heat exchanger. The possibility of such contamination has led to the introduction of double-wall heat exchangers to generate domestic hot water.


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Tubular Exchanger Manufacturers Association The Tubular Exchanger Manufacturers Association (TEMA), of Tarrytown, New York, has established heat exchanger standards and nomenclature for industrial applications. It has assigned every shell and tube device a three-letter designation, the letters referring to the specific type of stationary head at the front end, the shell type, and the rear end head type, in that order. (A fully illustrated description of all the shell and tube devices can be found in the TEMA standards).

DEFINITIONS Heating Medium A “heating medium” is any substance used to heat another substance to a higher temperature. In the case of heat exchangers used to heat domestic hot water, the heating mediums are generally fluids or fuels. There are exceptions to this rule, however, such as electrical energy, which is used to heat a solid wire, or element, which then directly transfers heat to the water by contact. Examples of heating mediums include: 1. 2. 3. 4. 5. 6. 7. 8.

Steam. Water. Gas. Oil. Electricity. Solar energy. Geothermal energy. Refrigerants.

Approach The term “approach” is used to describe how close the outlet temperature of the water to be heated comes to (or approaches) the inlet temperature of a fluid heating medium.

Heat Exchanger This term refers to a device specifically designed and constructed to efficiently transfer heat energy from a hot substance to a colder one.

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281

Countercurrent This term is used to describe a situation where the liquid heating medium in a heat exchanger flows in a direction opposite to that of the fluid to be heated.

Temperature Cross A “temperature cross” occurs when the liquid being heated has an outlet temperature that falls between the inlet and outlet temperatures of the heating medium; this is possible only when flows are 100% countercurrent.

TYPES OF HEAT EXCHANGER Heat exchangers have been used to heat water for domestic and other purposes in commercial and industrial facilities for years. In fact, the ever-increasing cost of energy has led to the increased use of heat exchangers to extract and conserve energy that previously was wasted. Commonly used types of heat exchanger include: plate type, shell and tube, tube-in-tube, and tube-on-tube. However, only the plate type and the shell and tube are discussed below. Operating conditions, ease of access for inspection and maintenance, and compatibility with heating medium are some of the variables engineers must consider when assessing heat exchanger options. Others include: 1. 2. 3. 4. 5.

Maximum pressure and temperature. Heating or cooling applications. Compatibility of the material with process fluids. Cleanliness of the streams. Approach temperature.

Certain exchangers operate better than others at different temperature approaches. Plate and frame exchangers, for example, work well at a very close approach, in the order of 2°F (1°C). For shell and tube exchangers, however, the lowest possible approach is in the order of 10°F (5.5°C). As for cleanliness, shell and tube exchangers have tube diameters that can accommodate a certain amount of particulate matter with very little clogging or fouling. Plate and frame exchangers, however, have narrow passageways, making them more susceptible to damage from precipitation or particulate fouling.

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The most common type of heat exchanger, the shell and tube, can be found in almost every type of application. In recent years, the plate and frame has emerged as a viable alternative to the shell and tube.

Shell and Tube Mechanically simple in design and relatively unchanged for more than 60 years, the shell and tube offers a low-cost method of heat exchange. The shell and tube heat exchanger has the following advantages: 1. 2. 3. 4.

The greatest flexibility of design and configuration. A large choice of shell and tube materials. High temperature and pressure characteristics. Ability to handle large amounts of particulate material.

U-tube, removable bundle The U-tube heat exchanger is made by bending straight tubes into the shape of a “U,” hence the name. The U-shaped tubes are then mechanically rolled into a common header or tubesheet. Depending on the fluid outside the tubes, this bundle is fitted with either tube supports or flow baffles along its length. The tubesheet, tubes, and tube supports/flow baffles make up the bundle assembly. The bundle assembly is then placed in a shell (a length of pipe that contains inlet and outlet connections and a pipe sized flange at one end for insertion of the tube bundle; and a cap at the other end), which will contain the fluid heating medium outside the tube bundle. A head assembly (usually a casting that contains inlet and outlet connections for directing a fluid into the tube bundle) is then bolted to the shell flange to complete the heat exchanger. The head assembly contains one or more pass partitions for controlling tube velocity, hence the tube side heat transfer coefficient and pressure drop. If a condensing vapor (such as steam) is to be the heating medium, the tube bundle will have supports designed to support the tubes along their length and provide for the proper flow and drainage of the condensate from the shell. If a liquid is to be circulated outside the tube bundle, flow baffles will be used to support the tubes and direct the flow across the bundle. In such a case, the number and spacing of the flow baffles will control the shell side heat transfer coefficient and its pressure drop.

Heat Exchangers

283

The U-tube heat exchanger is well suited for large domestic water heating applications that use either boiler water or steam as the heating medium. It is in the nature of the U-tube construction to allow for large temperature differences between the tube side and shell side fluids because the U-tubes expand and contract independently of the shell assembly. In addition, the tube bundle assembly is removable, allowing for easy and economical replacement of the heat transfer surface should a failure or leak develop in the bundle. The U-tube design does, however, have its limitations. First, because of the U-bends, the tube side fluid must make multiple passes down the length of the unit. This makes it less economical to use the U-tube for close temperature approaches and eliminates the possibility of its use (i.e., a single U-tube unit) for temperature-cross applications such as those found in energy reclamation projects. Also, because of the U-bend, the unit cannot be completely cleaned by mechanical means, which could be a problem if the tube side fluid is dirty or prone to scaling/fouling. The basic U-tube design can be modified to meet a number of special applications. Tank heater Replacing the shell assembly of a U-tube heat exchanger with a tank mounting collar will allow the exchanger to function as a storage heater for large domestic water systems. In such an application, the tank heater uses hot water as a heating medium. The hot water is pumped through the tubes, thus maintaining the tank system water at a set temperature. Steam can also be used as the heating medium if a special head assembly that allows for proper condensate drainage of the unit is installed. The tank heater uses natural convection as the means for transferring heat to the tank side system. Most heat exchangers use forced convection. This is a significant difference in that natural convection produces much lower rates of heat transfer. Consequently, for a given capacity, tank heaters require more heat transfer surface area than heat exchangers utilizing forced convection. In addition, it is very important for proper natural convection that the relationship between the size of the tank heater and the size of the tank be within specific limits. The guideline for this relationship is to have the tube bundle extend into the tank for a distance of from 50 to 75% of the tube bundle’s length for a horizontal tank and a distance nearly equal to its full diameter for a tank that is to be installed vertically.

284


A steel tank for a domestic water system requires a lining. Consequently, the manufacturer of the tank heater must take care to ensure that the tube bundle fits inside the tank mounting collar. Finally, every tank heater should have adequate support inside the tank to eliminate stress on the tube-tubesheet rolled joint. Inadequate support can lead to leaks of the tube bundle in this area. Double-wall heat exchanger The purpose of double-wall protection is to warn of a tube failure before cross-contamination between the tube-side and shell-side fluids can occur. Such cross-contamination could occur, for instance, where treated water from a boiler in a closed loop system is utilized to produce heat. A number of manufacturers now produce double-wall units in a U-tube design. Although some of the design features of these units may differ, the basic design is fairly common among double-wall manufacturers. The double-wall U-tube unit has a tube-within-a-tube design. Fins or grooves are used on one of the tubes to create a leak path between the tubes when they are mechanically bonded to enhance heat transfer. The outside tube is machined back at each end, bent into the U-tube, and either mechanically rolled or brazed into a double-tubesheet arrangement. Should either of the tubes fail, its fluid would be channeled through the leak path between the tubes to the space between the tubesheets. The appearance of fluid between the tubesheets is evidence of tube failure. While the double-wall design is very expensive compared to the single-wall unit, its use is increasing, due in large part to revisions to local plumbing codes. Double-wall exchangers are used for applications where a failed tube bundle would result in a health hazard. A disadvantage of the double-wall design is the loss of efficiency in transferring heat from the heating medium to the water.

Plate Type Heat Exchanger In recent years, the plate type heat exchanger has emerged as an alternative to the shell and tube. With its ability to optimize thermal performance, the plate type exchanger has made possible a number of close approach and temperature-cross applications that would not have been economical or practical with a shell and tube exchanger. A plate type unit is efficient, easy to maintain, and less susceptible to fouling, and it takes up little space.

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A plate type heat exchanger is characterized by having heat transfer occur via metal, plastic, glass, or ceramic barriers between fluids. One stream heats the other by means of conduction (or radiation) through the barrier. Inside the heat exchanger, the fluids are heated by convection. There are two types of plate type unit: prime surface and plate and frame. In general, the prime surface units are best suited to small heat loads and batch operations and the plate and frame are most efficient when used for large heat loads and continuous duty. Prime surface heat exchanger A prime surface heat exchanger is fabricated from two die-formed sheets, which are welded together. One or both of the sheets are die or pressure formed (cold formed) to create a series of welldefined passages through which the heating medium flows. Any common metal that can be cold worked and resistance welded could be used, the most typically used being carbon steel, stainless steel, monel, titanium, and hastelloy. A prime surface heat exchanger has a single circuit design and can be used as a shelf or immersed, clamped on, or built into a tank or used otherwise where a plate and frame exchanger would not be suitable—even given the same media. Maximum operating parameters are generally a temperature of 650°F (343°C) and a pressure of 500 psig (3450 kPa). Plate and frame heat exchanger A plate and frame unit is fabricated from a series of channel plates, which are pressed together to form a plate pack, with the holes at the corners of the plates forming a continuous passage or manifold. This manifold distributes the heat transfer media from the inlet of the heat exchanger into the plate pack for each fluid. The media are then distributed into the narrow channels formed by the plates. The gasket arrangement on each plate distributes the hot and cold media into alternating flow channels throughout the plate pack. In all cases, hot and cold media flow countercurrent to each other. The most common plate and frame type heat exchanger is the gasketed plate unit, in which a series of channel plates are mounted on a frame and clamped together. Each plate is made from pressable materials, such as stainless steel, and is corrugated. The most common pattern of corrugation is the herringbone or chevron. In-

286


cluded with each plate is an elastomer gasket. This gasket is used for sealing purposes and for the proper distribution of fluids in the plate heat exchanger. The spaces between adjacent plates form flow channels for the hot and cold fluids. A corrugated herringbone or chevron pattern is pressed into each plate to produce highly turbulent fluid flows. The high degree of turbulence results in high heat transfer coefficients and keeps fouling to a minimum. In addition, the corrugations add rigidity to each channel plate. This allows the use of thinner plate material and improves heat transfer. The basic design of the gasketed plate exchanger allows for the opening of the frame to add or remove channel plates to optimize heat exchanger performance or to service and maintain the channel plates, all with a minimum of downtime. The benefits of a plate and frame heat exchanger (100% countercurrent flow, high turbulence, and thin plate material) make it a highly efficient device that typically yields heat transfer rates three to five times greater than those of other types of heat exchanger. Because of these high heat transfer rates, it is possible to use a plate and frame exchanger that is compact relative to other types of heat exchanger for a given application. Ideal operating conditions include temperature crosses and close approach temperatures for the hot and cold media. While a gasketed plate and frame heat exchanger can be used in almost any application, it has limitations, which must be considered. These limitations have to do primarily with the unit’s design pressures and temperatures. Practical design pressures are limited to 800 psig (5516 kPa), while design temperatures are a function of the gasket material used in the exchanger. The most popular and widely used gasket material is nitrile rubber (NR), which has a temperature limit of 280°F (138°C). NR is followed in popularity by ethylene propylene diene monomer (EPDM), which has a temperature limit of 820°F (438°C). EPDM gaskets can be used to substitute for NR gaskets (for higher temperature ratings) on all applications except those involving oil heating or cooling, since EPDM swells in the presence of most oils. Other gasket materials, such as hypalon and viton, are also available. These gasket materials are more prevalent in industrial applications. Gasketed exchangers have benefited from improvements in the quality and diversity of elastomer materials and gasket designs. The use of exchangers with welded connections, rather than gaskets, reduces the likelihood of process fluid escape.

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Other limitations of the gasketed plate and frame exchanger are due to the narrow channels between adjacent plates. If a fluid that will enter the plate heat exchanger has suspended solids or is likely to deposit large amounts of scale on the plate surfaces, careful consideration should be given to the free channel space between the plates. Also, the narrow channels and resultant high turbulence of the fluid flows produce high pressure drops, making the plate exchanger incompatible with low-pressure applications. Until recently, a major limitation to the gasketed plate and frame heat exchanger was caused by the method of attaching the gaskets to the channel plates. In the past, gaskets were glued to the channel plates. Since gaskets are a replaceable part, this made removing old gaskets and installing new ones a very timeconsuming and labor-intensive procedure. Most manufacturers now use a glueless gasket design. Clip and snap are the two most common types of glueless gasket. Both simplify the re-gasketing procedure, making on-site service possible and thus reducing downtime. Recent advances in plate design and technology have produced two variations to gasketed plate and frame heat exchangers: double-wall and welded plate. Double-wall plate and frame exchanger In a double-wall plate and frame exchanger, two standard channel plates are welded together at the four corner ports to form one assembly. An air space or leak path is created between the plates for the passage of a fluid should a plate fail. The appearance of this fluid is evidence of plate failure. The purpose of the double-wall plate and frame exchanger, like that of the double-wall shell and tube heat exchanger (discussed earlier in this chapter), is to warn of a plate failure before cross-contamination can occur between the heating medium and potable water. Welded plate and frame exchanger In welded plate and frame exchangers, two standard channel plates are welded together at their peripheries. These welded plates (usually called a “cassette”) form a flow channel where the elastomer gasket has been replaced by the welded joint. This configuration may be necessary if there is no elastomer gasket compatible with the fluid or if more positive containment is re-

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quired. Typical applications include refrigerant evaporators/condensers, ammonia refrigeration, and cases where aggressive or corrosive fluids are present.

SELECTING HEAT EXCHANGERS When it comes to selecting a type of heat exchanger for a particular application, one of the questions asked most frequently is, “Which is best—shell and tube or plate type?” Assuming that the application is within the pressure and temperature limits of both designs, the issues come down to initial cost, maintenance costs, and future operating conditions. The initial cost is usually dictated by the approach temperatures of the application. Close approach temperatures and temperature crosses favor the plate heat exchanger while wide temperature approaches favor the shell and tube. Construction materials can influence initial cost too, especially if the application requires the use of stainless steel. With the computerized selection programs now used extensively, little effort is required to obtain prices for each type of unit for the quick comparison of initial costs. With respect to maintenance costs, much depends on the properties of the fluids involved. If the fluids have a tendency to foul, the plate heat exchanger may be a better choice, since it offers somewhat easier and more direct access to the heat transfer surface for the purpose of cleaning. In addition, because of the high turbulence in plate units, they tend to scale or foul less than shell and tube exchangers. If the plate and frame heat exchanger has a weakness compared to the shell and tube, it is the amount of gasketing in the unit. Compared to the shell and tube, the plate and frame has a much greater amount of gasketing, and therefore a much higher potential for leakage. In addition, since the gaskets are elastomers, they have a service life. On average, the life of a gasket on a plate and frame heat exchanger is approximately 6 to 7 years, with operating temperatures having a significant effect on actual performance. Units operating close to the temperature limit of the gasket will experience shorter gasket life. There is one other aspect of an elastomer gasket that must be considered: the phenomenon of cold leakage. Cold leakage is caused by the cooling down of a plate heat exchanger from high operating temperatures when there is a pressure differential between the

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hot and cold media in the unit. The plate and frame unit has a tendency to weep through the gasket interface. The weeping normally stops after the gaskets reset or the unit is brought back up to operating temperatures. Basically, if the application requires a low probability of leakage, the better choice is a prime surface or shell and tube design rather than a plate and frame. While gaskets may be a weakness in a plate and frame unit, being able to expand its thermal capacity merely by adding channel plates to an existing unit is one of its major strengths. If it is known that a particular application will be expanded in the future, a plate unit is by far the easiest and most economical design to use.

Indirect Fired W ater Heaters Water

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INDIRECT FIRED WATER HEATERS

INTRODUCTION An indirect water heater is a fluid-to-fluid heat exchanger that uses one hot fluid to heat a second colder fluid. The hot fluid can be anything, such as freon or ammonia from an air conditioning compressor, but most often is water heated by a boiler or a direct fired unit. In homes and offices, the liquid heated is usually potable domestic cold water, but indirect water heaters can also be used to heat pool water or melt snow. Since they do not contain a firebox or electrical element for heating, they have no need of a separate flue or fuel line, which reduces related installation and construction costs.

PRODUCT DESCRIPTION There are two basic types of indirect water heater on the market today, which are distinguished primarily by the location of the boiler water.

Storage Tank Type Indirect Water Heaters The first kind of indirect water heater to appear in the marketplace, the storage tank type is very similar to its direct fired cousins in that its tank contains potable domestic water to be heated by boiler water flowing through a single coil. (See Figure 17.1.) The advantage of this type of indirect water heater is its ability to deliver a large amount of heated water. However, as hot water is delivered, the tank must constantly be refilled with incoming cold Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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Figure 17.1 Indirect Water Heater Designs. Source: Courtesy of Group Thermo, Inc.

water, which reduces the temperature of the remaining stored water. This type of indirect water heater needs sufficient time to recover (reheat) its contents once they are cooled. Therefore, its capacity to deliver hot water during short intervals of high demand may be limited. In such instances as a residential application requiring large amounts of hot water within 5 to 10 min, for the purposes of filling a large spa or a whirlpool bathtub or the concurrent operation of several appliances needing hot water, installation of a commercial size storage indirect water heater tank of at least 80 to 100 gal (303 to 379 L) would be necessary. This tactic would meet the demand for the availability of more hot water but would significantly increase the cost to the consumer. Another kind of storage tank type indirect water heater is the double-tank or “tank-within-a-tank” design. The potable domestic water is held in an inner tank while the boiler water circulates around it.


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This design innovation has led to considerably improved performance and faster recovery due to the larger heat transfer surface. However, the same “dump” limitation applies. Early models of this type of water heater were prone to corrosion at the top of the tank due to oxygen accumulation, but current versions are vented to prevent this problem. Nevertheless, the constant refilling of the tank with fresh water makes all storage indirect water heaters susceptible to two other major causes of tank failure—thermal stress and scaling. Thermal stress results because the 90 to 100°F (32 to 38°C) temperature fluctuations that occur on a daily basis cause tank linings and dissimilar metals to expand and contract at different rates. This expansion and contraction eventually leads to cracking. Over time, oxygen contained in the fresh water attacks these cracks and corrodes the tank. Fresh water also contains mineral salts, which precipitate out as the water is heated and attach themselves to the hottest surface available. Regardless of whether the hottest surface is the coil containing the boiler water or a portion of the tank wall, scale buildup steadily erodes heat transfer efficiency. The chart in Figure 17.2 illustrates how dramatically the rate of scale formation increases as temperatures rise above 140°F (60°C). At this temperature in residential use, their average lifespan ranges anywhere from 7 to 12 years, depending on water conditions. For water heaters in commercial use, the life expectancy is considerably shorter. In summary, while both of these storage tank designs are capable of delivering water at high temperatures, their consistent operation at temperatures above 140°F (60°C) will result in significantly faster scale formation, rapidly deteriorating heat transfer efficiency, and much shorter life expectancies.

Instantaneous Indirect Water Heaters The second type is the instantaneous indirect water heater. Its tank is filled with boiler water that heats potable domestic water that passes through multiple, small diameter coils as it is needed. Provided that the boiler continues to produce enough heat, the instantaneous indirect water heater will provide an unending supply of hot water for as long as it is needed. This type of water heater needs no recovery time.

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The instantaneous indirect water heater is a descendant of the well-known instantaneous coil in a boiler water heater. Several simple design innovations make the modern version better.

Figure 17.2 Purdue Bulletin 74 Chart, Showing the Relationship Between Lime Deposits and Water Temperature. Source: Chart developed by Purdue University. Reprinted courtesy of Group Thermo, Inc. Notes: 1. Chart is based on 10 grains of hardness. For any other hardness, multiply the “pounds of lime deposited per year” data by the new grain hardness converted by a multiple of 10. For example, 20 grain hardness = 2 times the data. (1 grain hardness = 17.1 ppm hardness.) 2. A very important fact demonstrated by this figure is that almost 7 times more lime is deposited when the water temperature is 180°F (82°C) as opposed to 140°F (60°C). The factor of 7 translates into a very short life expectancy for tank type heaters in services that require sanitizing (180°F [82°C]) water temperatures.


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First, the potential for scaling and corrosion in the boiler water tank has been virtually eliminated because it is filled with “dead” boiler water circulating in a closed loop. Once the loop is filled, the small amount of makeup water added over time is not enough to cause problems, provided the loop is properly vented. Scaling inside the coils is prevented by the accelerated flow of the potable water whenever hot water is drawn. By using several coils of relatively small diameter, high output levels are possible with little pressure drop. Since this type of indirect water heater does not develop scale, even at higher temperatures, it is often used in applications where 180°F (82°C) water is needed for sanitizing (e.g., automatic dishwashers, hospital laundries, and food processing equipment). Second, a tankless coil typically used a single, finned coil immersed in the boiler water. Since both sides of each fin or rib on the coil were considered part of the available heat transfer surface, efficiency was expected to be high. In reality, the fins and ribs trapped pockets of static water which acted like a layer of insulation and hindered the heat transfer process. Scale collected in the “valleys,” compounding the problem. Wherever coils were tightly wrapped or touching, heat transfer surfaces were either unavailable or starved of boiler water. In comparison, the new instantaneous water heater design makes use of multiple smooth coils in loosely overlapping bundles to maximize the amount of available heat transfer surface. The addition of turbulent flows inside and outside the coil boosts the heat transfer efficiency into the high 90% range and raises the overall operating efficiency to new levels. The turbulence also scrubs the coils clean of any scale buildup. As a result, instantaneous indirect water heaters are projected to last 20 or more years.

WATER CONDITIONS Obviously, the quality and condition of the potable water supply will affect the performance of a water heater, direct or indirect. In general, if the water supply has a pH value close to 7, neither highly acidic nor heavily alkaline, any indirect water heater will function properly. However, when high acidity is encountered and cannot be modified using water treatment equipment, indirect water heaters with copper coils may be adversely affected. Conversely, very alkaline water will cause storage tank type indirect water heaters to accumulate scale much more rapidly. Particulate matter in suspension or otherwise contained in the potable water supply

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should be filtered out before the water enters either type of indirect water heater. Sediment will quickly accumulate in and clog up the storage tank type or sandblast the coils of the instantaneous indirect water heater, causing damage.

Electri ater Heaters —Storage and Booster Electricc W Water Heaters—

18

297

ELECTRIC WATER HEATERS— STORAGE AND BOOSTER

INTRODUCTION An electric water heater is an appliance for heating water that is to be used for purposes other than space or central heating (for instance, cooking, dish and cooking utensil washing, clothes washing, lavatories, baths, and showers).

PRINCIPAL TYPES OF ELECTRIC WATER HEATER Water heaters are classified as residential or commercial, based on their size as well as their intended use. Residential water heaters that meet UL Standard 174 generally include those with inputs of 600 volts (V) or fewer, no more than 12 kW, and with tanks at capacities of between 1 and 120 gal (3.79 and 454 L). Commercial storage tank water heaters and electric booster water heaters that meet UL Standard 1453 are those that have inputs of 600 V or fewer and satisfy at least one of the following conditions: 1. Have a capacity of more than 120 gal (454 L). 2. Are rated over 12 kW. 3. Are equipped with one or more temperature regulating controls permitting a water temperature higher than 185°F (85°C). For medium and heavy-duty commercial applications, hot water with temperatures of 180°F (82°C) and above generally must be available to meet the dish and utensil washing requirements of restaurant installations. For equipment to be classified as a


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water heater instead of a boiler, it must have provisions that guard against water temperatures exceeding 210°F (99°C).

COMPONENTS Other than controls, the following are the principal components of an electric water heater.

The Tank In electric tank type water heaters, the tank serves the purpose of hot water storage. Linings are generally used in steel tanks to protect the steel and to prolong tank life. (Tank materials other than steel are also available.) An additional means of protecting a tank against corrosion is the use of a sacrificial anode. With the insertion of a sacrificial anode, such as an aluminum or magnesium rod in the tank, the primary electrolytic reaction occurs between the anode and the other exposed dissimilar metals within the tank. The anode is consumed first, thereby protecting the tank. The anode should be replaced as it approaches decomposition to ensure continued protection of the tank.

Tank Fittings Tanks require fittings for cold water inlet and hot water outlet connections. These connections normally are threaded nipples welded to openings in the tank to provide for the water pipe inlet and outlet connections. A fitting that enables the replacement of the sacrificial anode also is usually provided. In addition to the inlet and outlet fittings, there are threaded nipples for the insertion of immersion type elements, thermostats, temperature-pressure relief valves, and high limits. Residential and light-duty commercial tanks have brackets on the outside for surface-mounted thermostats and high limits. A fitting for the insertion of a drain cock is required on all domestic and commercial water heater tanks to allow easy drainage of the tank and removal of foreign matter that may accumulate on the tank bottom. Figure 18.1 illustrates a typical residential or commercial electric water heater and shows the location of some of the fittings on the tank.


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Figure 18.1 A Typical Electric Water Heater. Source: Courtesy of A.O. Smith Water Products. Note: Cover of electric water heater shown removed to reveal fittings at tank top.

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Dip Tube A dip tube is used with all tank water heaters that have the cold water inlet located at the top of the tank. The dip tube directs the cold water toward the bottom of the tank to prevent excessive mixing of cold and hot water as the hot water is used. The relationship between the length of the dip tube and the height of the tank determines the amount of usable hot water that can be drawn from the tank at any one time (the tank draw efficiency). A dip tube that is too short will cause excessive mixing of cold water at the top of the tank, which can cause the hot water to be delivered at a lower than desired temperature. In the past, dip tubes were made of metal, but presently most dip tubes are made of high-temperature-resistant, nontoxic, high-density plastic. A dip tube has a small hole, located near the top of the tank, that expels a small amount of cold water into the top of the tank under operating conditions. This “anti-siphoning” feature prevents the tank from being siphoned in case the cold water supply is cut off. In such a situation, the tank would be siphoned only to the level of the anti-siphon hole, where the siphoning action would be stopped.

Elements Electric water heating technology has been through only minor changes since its inception. That is because immersion elements are considered 100% efficient. Only the wattage of the elements has been increased over the years to shorten recovery times. Two types of element—wraparound and immersion—have been used, with immersion type elements representing the overwhelming majority. Wraparound elements, as their name implies, wrap around the outside of the tank in a channel. This type of element heats from the outside and is used primarily in high lime areas to prevent scaling and premature element failure. Immersion elements, as their names implies, are immersed in the water and are made in several styles: blade, single-loop, and multi-loop. (Figure 18.2 shows the types of electric water heater element.) Element construction Element construction is essentially the same, regardless of wattage or sheath surface area. As Figure 18.3 illustrates, the principle components of an element are the electrical terminals, flanges, sheath, magnesium oxide, and resistance wire.


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Figure 18.2 Electric Water Heater Element Types. Source: Courtesy of A.O. Smith Water Products.

Figure 18.3 Electric Water Heater Element Construction. Source: Courtesy of A.O. Smith Water Products.

The magnesium oxide is used as an electrical insulator between the resistance wire and sheath as well as a conductor of heat. The resistance wire is made of nichrome (nickle chrome) and is of an appropriate length and diameter (ohm rating) to draw a certain wattage (producing a predictable amount of heat) at a given voltage. (Table 18.1 charts the relationship among the watt-

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age, voltage, and resistance of an element.)

Table 18.1 Resistance of Element (in ohms) (± 7.5%) Rated Wattage

Rated Voltage

600

750

1000

1250

1500

2000

2500

120 208 240 277

23.2 72.1 92.8 128

18.6 57.7 74.3 102

13.9 43.3 55.7 76.7

11.1 34.6 44.6 61.4

9.28 28.6 37.1 51.2

6.96 21.6 27.8 38.4

5.57 17.3 22.3 30.7

Rated Wattage

Rated Voltage

3000

3500

4000

4500

5000

5500

6000

120 208 240 277 480

4.64 14.4 18.6 25.6 76.8

12.4 15.9 21.9 65.7

10.8 13.9 19.2 57.5

9.61 12.4 17.1 51.1

8.65 11.1 15.3 45.7

7.85 10.1 14.0 41.8

7.2 9.28 12.8 38.4

Source: Courtesy of A.O. Smith Water Products.

Element operation In an electric element, thermal energy is produced when voltage is applied to the nichrome wire. The heat energy produced is conducted through the magnesium oxide and copper or incoloy sheath into the water. Once the thermal energy enters the water, it is distributed throughout the tank by convection. Residential electric water heaters are normally furnished with dual elements that are wired for non-simultaneous operation (only one element operates at a time; the upper element operates first on a cold start). Electric water heaters may be specified with the elements wired for simultaneous operation (both elements operate at the same time). The designer should be sure to check the total connected load with the electrical engineer. Most electric water heaters currently produced use immersion type electric elements, which are considered 100% efficient. There are two kinds of such element, distinguished by the material used in their sheathing.


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Copper sheathed element This consists of a nichrome resistance wire surrounded by magnesium oxide and sleeved in a copper sheath. Standard equipment on residential models, this element features: 1. High to medium watt density. 2. UL listing. 3. Zinc plating for corrosion protection. Note: Copper sheathed elements must be immersed in water when energized or they will “dry fire” (melt down). The dry firing of water heaters usually occurs during initial installation when the heaters are not completely filled with water and the power is switched on. Incoloy sheathed element This consists of a nichrome resistance wire surrounded by magnesium oxide and sleeved in an incoloy iron-based super alloy sheath. Standard equipment on top-of-the-line residential models, this element features: 1. Low to medium watt density. 2. UL listing.

CONTROLS FOR RESIDENTIAL AND LIGHT-DUTY, COMMERCIAL ELECTRIC WATER HEATERS Thermostat This regulates the temperature of the water in the tank. Usually one snap-action, surface-mounted thermostat is used per element. Temperatures are adjustable from 110 to 170°F, ± 10°F (43 to 77°C, ± 6°C). (See Figure 18.4 for location.)

High Limit This safety device limits the maximum water temperature in the tank. Usually one snap-action, surface-mounted high limit safety device is used. It is set to open at 190°F, ± 5°F (88°C, ± 3°C).

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Figure 18.4 Location of Controls—Residential and Light-Duty, Commercial Electric Water Heaters. Source: Courtesy of A.O. Smith Water Products.


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CONTROLS FOR MEDIUM-DUTY, COMMERCIAL ELECTRIC WATER HEATERS Surface-Mounted Controls Thermostat This regulates the temperature of the water in the tank. Usually one snap-action, surface-mounted thermostat is used per element. Temperatures generally are adjustable from approximately 120 to 180°F (49 to 82°C). Surface-mounted thermostats have a differential of between 8 and 15°F (4 and 7°C). High limit This safety device limits the maximum water temperature in the tank. Usually one snap-action, surface-mounted high limit safety device is used. It is set to open at 200°F (93°C) but can be manually adjusted to open. Wiring circuits Voltages commonly available are 208, 240, 277, and 480. Many of the circuits are field convertible between single and three-phase voltages. Also, these heaters have internal fusing.

Immersion Controls Thermostat An immersion well, remote bulb thermostat is used to regulate the temperature of the water in the tank. Temperatures generally are adjustable from approximately 120 to 180°F (49 to 82°C). Immersion thermostats have a differential of ±5°F (±3°C) and are excellent units to use when precise temperatures are important. Multiple thermostats may be used. High limit This safety device limits the maximum water temperature in the tank. Usually an immersion well, remote bulb high limit is used. It is set to open at 200°F (93°C) but can be manually adjusted to open.

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Wiring circuits Voltages commonly available are 208, 240, 277, and 480. Many of the circuits are field convertible between single and three-phase voltages. Also, these heaters have internal fusing and contactors to link control (120 V) and power circuits (line voltage).

CONTROLS FOR HEAVY-DUTY, COMMERCIAL ELECTRIC WATER HEATERS Immersion Thermostat A direct immersion bulb thermostat is used to regulate the temperature of the water in the tank. Temperatures generally are adjustable from approximately 95 to 180°F (35 to 82°C). Immersion thermostats have a differential of ±5°F (±3°C) and are excellent units to use when precise temperatures are important. The control of groups of elements is done by the use of multiple thermostats, time-delay sequencers, or a solid-state progressive sequencer. (See Figure 18.5.)

Immersion High Limit This safety device limits the maximum water temperature in the tank. Usually one snap-action, surface-mounted high limit is used per thermostat. An immersion well, remote bulb high limit may be used. It is set to open at 200°F (93°C) but can be manually reset to open at 180°F (82°C).

Wiring Circuits Voltages commonly available are 208, 240, 277, and 480. Many of the circuits are field convertible between single and three-phase voltages. Also, these heaters have internal fusing and contactors to link control (120 V) and power circuits (line voltage).

Options There are many options available with this category of heater.

CONTROLS FOR BOOSTER TYPE, COMMERCIAL ELECTRIC WATER HEATERS These heaters typically are low storage type heaters, with capacities generally ranging from 6 to 20 gal (23 to 76 L).


Figure 18.5 Location of Controls—Commercial Electric Water Heaters. Source: Courtesy of A.O. Smith Water Products.

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308


Immersion Thermostat A direct immersion bulb thermostat is used to regulate the temperature of the water in the tank. Temperatures generally are adjustable from approximately 140 to 185°F (60 to 85°C). Immersion thermostats have a differential of ±2°F (±1°C) and are excellent units to use when precise temperatures are important. (See Figure 18.6.)

Immersion High Limit This safety device limits the maximum water temperature in the tank. Usually one snap-action, surface-mounted high limit is used per thermostat. An immersion well, remote bulb high limit may be used. It is set to open at 200°F (93°C) but can be manually reset to open at 180°F (82°C).

Wiring Circuits Circuits are convertible between single and three-phase voltages. Also, these heaters have internal fusing and contactors to link control (120 V) and power circuits (line voltage).

Ratings All heaters shall be rated according to the following standards: 1. Underwriters’ Laboratories, Inc. 2. American Society of Mechanical Engineers.

Options There are many options available with this category of heater.


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Figure 18.6 Location of Controls—Booster Type, Commercial Electric Water Heaters. Source: Courtesy of A.O. Smith Water Products.

Ga ater Heater —Instantaneous With Separate TTank ank Gass W Water Heater—

19

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GAS WATER HEATERS— INSTANTANEOUS WITH SEPARATE TANK

The direct or indirect, instantaneous water heater coupled with a separate hot water storage tank, which can be of various volumes, is a water heating system that is well suited for many applications. (For the purposes of this chapter, an instantaneous water heater will be defined as a gas fired heating device with no storage.) Because of its ability to handle a high peak water heating load, this type of system is used in a variety of applications. It is frequently found in such facilities as hotels, motels, restaurants, food processing plants, laundries, garment manufacturing and dye houses, and chemical processing facilities. In this type of system, a gas fired water heater is used to heat the domestic water, and a pump moves this water through the water heater and transfers it to the storage tank. The pump circulates the water between the tank and the heater when there is a demand for heat, thereby keeping the tank at a relatively uniform temperature. With some systems this pump can be turned off during periods of no demand. The storage tank is sized to meet the demands of a particular application. The criteria that need to be evaluated in order to select the size of the heater, the circulating pump, and the storage tank vary from application to application. Please refer to Section I of this manual for information on sizing domestic water heating systems. The more that is known about the exact operation of a facility, the more intelligently the designer can match the input of the heater (Btu [W]) to the storage tank volume. In this type of system, cold water is introduced to the system per the manufacturer’s recommendations, and hot water is drawn from the storage tank. This type of system has the flex-


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ibility to allow the designer to balance the heater recovery with the storage tank. The size, flow rate (gpm [L/sec]), and head of the pump to be utilized depend upon the total dynamic head of the system loop. It is important that the designer consult the manufacturer to select a pump that will maintain the proper velocity in the heater tubes, which will reduce the effects of scaling and overheating the water as it is routed through the heater. When this type of water heater is used in areas with hard water, softening the water or selecting a heat exchanger material other than copper (such as cupro-nickel) will increase the longevity of the heater and system components.

Gas W ater Heate Water Heaterrs—Storage

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GAS WATER HEATERS— STORAGE

TYPES OF GAS WATER HEATERS Water heaters are classified as residential (domestic) or commercial based on their size as well as their intended use. Residential water heaters are generally considered to include those with input rates up to and including 75,000 Btu/h (21 975 W), and commercial water heaters are those with input rates over 75,000 Btu/h (21 975 W). The most common type of gas water heater is the storage (tank) type heater in which a single tank is used for both heating and storing the water. The heaters most commonly used for residential purposes are those with 30, 40, and 50-gal (115, 150, and 190-L) tanks. Large heaters have capacities ranging from 120 up to as many as several thousand gallons (455 up to as many as several thousand liters).

FLUES AND HEAT EXCHANGERS Storage type heaters are classified according to the placement of the gas flue. With respect to this classification, types include the internal (center) flue, the external channel flue, the floating tank external flue, and the multiple flue. (See Figure 20.1.) The internal (center) flue type has the most economical construction. The external channel flue increases the bottom heating surface and tends to promote heating from the bottom, which improves efficiency. The floater has the greatest heat transfer area of the three types, with the whole bottom and the full surface of the tank available for heat transfer. Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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The internal (center) flue tends to be smaller in diameter than the external and floating type flues for the same capacity tank. Flues serve as the primary means for disposing of the products of combustion and also as heat exchangers. Because commercial water heaters have higher gas inputs and need even greater heat transfer areas than residential heaters, many are constructed with multiple flues to both increase the heat transfer area and provide a cross-sectional flue area sufficient for properly disposing of the products of combustion. (Figure 20.1 illustrates a multiple flue commercial water heater.)

TANKS As previously explained, the tank in a tank type water heater serves the dual purposes of heat exchange and hot water storage. Also, it must be able to withstand water pressure in compliance with the codes and regulations of whatever authority has jurisdiction. The storage of hot water in the tank accelerates corrosion. Linings are generally used with steel tanks to protect the steel and to prolong tank life. Tank materials other than steel are also available. A second method of protecting the tank is the sacrificial anode. When a sacrificial anode such as a magnesium rod is inserted in the tank, corrosive action occurs between the anode and any exposed metals in the tank. The anode, being higher on the galvanic scale, is consumed first, thereby protecting the tank. In some instances, anode rods are not installed because they have a detrimental effect on the tank lining. Figure 20.2 illustrates a residential gas water heater containing one type of sacrificial anode. An anode such as this should be replaced as it approaches decomposition to ensure continued protection of the tank. One disadvantage of the underfired tank is its propensity for depositing sediment on the bottom of the tank. The harder the water, the greater the potential for this problem.

TANK FITTINGS Tanks require fittings for cold water inlet and hot water outlet connections. These connections are normally threaded nipples welded to openings in the tank to provide for the water pipe inlet and outlet connections. A fitting enabling the replacement of the


315

sacrificial anode is also normally provided. In addition, most tanks are provided with one or more threaded nipples for the insertion of immersion type thermostats, temperature-pressure relief valves, and automatic gas shut-off devices. A fitting for the insertion of a drain cock is found on most residential and commercial water heater tanks to allow easy drainage of the tank and removal of foreign matter that may accumulate on the tank bottom. Although infrequently done in practice, the periodic draining of tanks is highly recommended (the frequency depending on water conditions in the area) because the removal of foreign matter improves heat transfer, provides for cleaner hot water, and eliminates any noises caused by the accumulated foreign matter. Commercial tanks have, or can be fitted with, a handhole cleanout. ASME rated tanks over a certain size require a manhole. See Figure 20.3 for possible locations of some of the residential and commercial water heater fittings described. These are examples only; many variations of location and gas water heater are encountered.

DIP TUBES A dip tube is used on all tank water heaters in which the cold water inlet is at the top of the tank. The dip tube directs the incoming cold water toward the bottom of the tank to prevent the mixing of cold and hot water. In all tank water heaters, the water at the top of the tank, under cycling and intermittent standby conditions, attains a higher temperature than water at the bottom of the tank. The variation between the two temperatures depends on heater design and dip tube length. A dip tube that is too short will cause excessive mixing of the cold and hot water, which will reduce the tank draw efficiency. In the past, dip tubes were made of metal, but presently most dip tubes are made of high-temperature-resistant, nontoxic, highdensity plastic. A dip tube has a small hole, located near the top of the tank, that expels a small amount of cold water into the top of the tank under operating conditions. This “anti-siphoning” feature prevents the tank from being siphoned. Figure 20.4 shows the operation of the dip tube under normal operating conditions and under conditions—such as occur when the cold water supply is shut off or a line breaks—necessitating anti-siphoning action.

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(A)

(B)


317

(C)

(D) Figure 20.1 Location and Types of Flue: (A) Internal Flue Tank, (B) External Channel Flue Tank, (C) “Floating” Tank—External Flue, (D) Multiple Flue— Multiple Burner, Commercial Water Heater. Source: Courtesy of Uni-Line North America, Robertshaw.

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Figure 20.2 Sacrificial Anode Installation in a Residential Gas Water Heater Tank. Source: Courtesy of Uni-Line North America, Robertshaw.

Figure 20.3 Example of Water Heater Fittings. Source: Courtesy of Uni-Line North America, Robertshaw.


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Figure 20.4 The Principle of Operation of the Dip Tube. Source: Courtesy of Uni-Line North America, Robertshaw.

BURNERS Burner assemblies are designed to ensure that gas and air are properly mixed for combustion. Burners vary greatly in design and construction, but all have: 1. An inlet air orifice. Varies with the type of gas and the normal range of gas pressure. 2. A means of controlling air intake. For primary air burners, air intake control may be fixed or variable (air shutter). 3. A mixing tube or mixing area. Allows gas and air to mix before or during burning. 4. Ports. Control the gas flame pattern to improve burning characteristics and distribute the flame in relation to the tank and/or heat exchanger area. A few of the more common types of burner found in gas water heaters are illustrated in Figure 20.5.

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Figure 20.5 Types of Gas Burner. Source: Courtesy of Uni-Line North America, Robertshaw.

Issues to consider when selecting a burner design include the overall physical dimensions of the burner, type of burner head and port, and flame pattern. A burner’s gas input rating governs its orifice and total port areas. Ports that are too large encourage flashback of the flame to the burner orifice. Ports that are too small encourage the blowing of flames. The number and size of the ports necessary to give the proper flame characteristics can be calculated. Ports must be properly spaced for good flame travel and ignition. Flame characteristics are affected by: 1. The form of the ports (slotted, drilled, ribbon, raised, or flush). 2. Port size, depth, and spacing. 3. Type of burner head. 4. Air-gas mixture temperatures.


321

Air inlets must cover a range wide enough to allow the airgas mixture to be properly adjusted for different gas, pressure, and altitude conditions. Note: Designers should be sure to consult the manufacturers’ recommendations for derating burners as necessitated by high altitudes.

VENTING SYSTEMS A venting system is required to transfer the products of combustion to the outside. The venting system of a water heater consists of: 1. 2. 3. 4.

Water heater flues. A draft diverter or draft regulator. Vent pipe connections to the outside or chimney. Vent caps.

Proper venting generally is covered by local codes. Improper venting results from a lack of understanding of how and why a venting system functions. The basic principle behind venting appliances is that flue gases rise because they are lighter than the surrounding ambient air. It is the heat content of the gases that lightens them and causes them to rise. A venting system that uses the natural tendency of hot gases to rise could be essentially a vertical path. Other considerations include using: 1. Vents of a diameter sufficient to carry the gases. 2. Controlled mixtures of flue gases with dilution air from the draft diverter to prevent excessive cooling of the gases. 3. Insulation on the vent pipe to maintain sufficient flue gas temperatures in excessively long or high vents (to avoid condensation and maintain draft). 4. Mechanical draft inducers with a double-acting barometric damper.

Draft Hoods A draft hood is used with almost every water heater not equipped with a draft regulator or power vent (positive pressure) system. The draft hood is designed to minimize the effects of: 1. Updrafts. It prevents excessive updrafts through the burner compartment.

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2. Downdrafts. It prevents a downdraft from blowing out the pilot flame or causing it to flash back. 3. Blocked flues. If the vent becomes blocked, it minimizes the concentration of carbon monoxide by diluting the spilling flue gases. 4. Spillage. It ensures that flue gases do not “spill” from the bottom of the diverter if the water heater is installed with a minimum amount of venting. Some of the draft hoods commonly used on gas water heaters are shown in Figure 20.6.

Figure 20.6 Commonly Used Draft Hoods. Source: Courtesy of Uni-Line North America, Robertshaw.


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The operation of a vertical draft hood under downdraft conditions is illustrated in Figure 20.7.

Vent Connections The ideal venting system has vent pipe connections that rise vertically from the draft hood through the roof to the outside and terminate in a vent cap, which protects the vent from stoppage and minimizes the effects of downdraft.

Figure 20.7 Downdraft Conditions in a Vertical Draft Hood. Source: Courtesy of Uni-Line North America, Robertshaw.

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Where lateral runs are required to connect with chimney installations, the lateral runs should be kept to the minimum required length. They should slant upward, at a minimum of ¼ in./linear ft (a 2% angle), in the direction of normal flue gas flow. The connection of a vent to a chimney should be smooth on the interior surface. The vent pipe should not project into the chimney interior. Consult local codes or National Fuel Gas Code NFPA 54 for details. (See Figure 20.8.)

Figure 20.8 Vent Connection to a Chimney. Source: Courtesy of Uni–Line North America, Robertshaw.

Heat Pump W ater Heaters Water

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HEAT PUMP WATER HEATERS

INTRODUCTION The heat pump water heater uses modern refrigeration technology. In both residential and commercial applications, this type of water heater can heat water more efficiently and thus is more cost-effective than an electrical resistance heater. In the right commercial applications, the energy savings can be significant. A residential heat pump water heater has a refrigeration system much like that of a refrigerator. The heat pump water heater uses this system to transfer heat from a warm airstream to water. A typical residential heat pump water heater can heat water to a temperature of 130°F (54°C). A typical commercial heat pump water heater can heat water to a temperature of 160°F (71°C). Heat pump water heaters operate on the principle of recovering heat from an air source. For this type of water heater to operate, there must be a warm air source (35°F [1.7°C] or higher). The heat pump water heater consists of two heat exchangers and a refrigeration compressor. The first heat exchanger is usually located in the airstream with the waste heat and acts to recover this wasted heat. The compressor pumps the recovered heat from the airstream to the other heat exchanger, which is associated with a storage tank, for the heating or preheating of domestic hot water. This is where the heater gets its name—heat is pumped from one location to another. The refrigeration compressor uses the refrigeration system’s hot gas for pumping. In the right locations, a heat pump system can provide simultaneous water heating and space cooling or refrigeration. Heat pump water heaters use a vapor compression cycle similar to that of a refrigerator to remove heat from an airstream Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

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flowing through the evaporator and transfer it to water. Hot, highpressure refrigerant gas is routed from the compressor to the heat exchanger associated with the storage tank. This exchanger is either one that the entering cold water flows through (remote type) or one at the water storage tank to which entering cold water is piped (integral type). The temperature of the hot gas in commercial refrigeration systems is usually around 200°F (93°C) or higher and is ideal for heating domestic water. There are several combined heat exchanger and tank designs. Some have less of a pressure drop through the heat exchanger than others. Some have coils immersed in the tank while others have coils that wrap around the tank, and one has a heat exchanger plate that surrounds the water storage tank. The refrigerant is cooled and condensed when it heats the water. The refrigerant liquid then passes through capillary tubing (an expansion device), which causes the pressure and temperature of the refrigerant to drop. The refrigerant gas then enters the evaporator coil where it absorbs heat from the air passing through the coil and evaporates. The compressor evacuates the cool, evaporated refrigerant gas and compresses it to a high pressure and temperature to repeat the process.

TYPES OF HEAT PUMP WATER HEATER There are two main types of heat pump water heater. In the integral type, the heat pump and water storage tank are assembled together. In the remote type, the heat pump is located at a distance from the water storage tank and connected by tubes or piping. Integral type heat pump water heaters are available in residential and small commercial sizes (approximately 8000 to 60,000 Btu/h [2345 to 17 580 W]) with storage tank sizes ranging from 50 to 120 gal (190 to 455 L). Remote type heat pump water heaters are available in these same sizes, as well as in much larger sizes for commercial and industrial applications (approximately 8000 to 180,000 Btu/h [2345 to 52 740 W]). With a remote type heat pump water heater a separate storage tank must be added to complete the water heating system.

Integral Heat Pump Water Heaters Integral heat pump water heaters are assembled with the main refrigeration components attached to the hot water storage tank.


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The water storage tank of this type of water heater is essentially an electric resistance hot water heater. It has electric resistance heating elements to provide additional heating capability for periods of peak hot water usage. Some integral heat pump water heaters are available with remote evaporators, which can be located near specific heat sources to provide spot cooling. Remote evaporators are often used in areas such as a hot kitchen and the space above an ice machine to remove heat directly.

Remote Heat Pump Water Heaters Remote type heat pump water heaters are separate from water storage tanks and can be located at a distance from them. In most residential and small commercial remote heat pump water heater installations, an electric resistance water heater is used for the storage tank. In large commercial remote heat pump water heater installations, a heat pump water heater is used in combination with a gas or electric resistance water heater to provide enough heating capability for periods of peak hot water usage, and all the water heaters are connected to a large storage tank. Remote heat pump water heaters are located inside or outside a structure depending on available space and whether or not there is an application for the heat pump’s space cooling ability.

ENERGY SOURCES Electricity is the primary source of energy for the refrigeration system components of a heat pump water heater, for instance, the compressor, pumps, and fans. Air is the heat source for the heat pump water heater. All integral type and most remote type heat pump water heaters use a water storage tank equipped with backup electric resistance elements to meet peak hot water demand. If electricity rates are excessive, the tank can be ahead of a gas fired water heater. Heat pump water heaters remove heat from an airstream and put it, along with heat from the electrical power they consume, into water. A heat pump water heater can produce the same amount of hot water as an electric resistance water heater using only one quarter to one half the electrical power. The heat pump water heater also provides space cooling and dehumidification as a result of the water heating, a result that is often beneficial to the customer.

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BENEFITS OF THE HEAT PUMP WATER HEATER The main benefit of the heat pump water heater is its efficiency. It is much more efficient than an electric resistance water heater and may be cheaper to operate than a gas water heater, depending on local costs for gas and electricity. Also the heat pump water heater provides cool, dehumidified air as a byproduct of water heating. If there is a need for space cooling or the existing air conditioning system is inefficient, the space cooling effect of the heat pump water heater should be taken into account in an economics analysis. Another benefit of the heat pump water heater is that it allows the user to reduce the peak water heating load by spreading it over a long period of time. With adequate storage, a heat pump water heater with electric backup enables a large part of the water heating load to be shifted to off-peak hours for electricity usage, thereby providing additional savings. Because of this, heat pump water heaters may qualify users for utility rebates or tax credits. Heat pump water heaters have lower instantaneous electricity demands than electric resistance water heaters do. If a heat pump water heater cannot meet peak hot water demand, the backup electric resistance elements in the storage tank will be energized until the demand is met. When the backup electric resistance elements are energized, the heat pump water heater has a higher rate of recovery, but it also has the high electric power demand of an electric resistance water heater. The combination of a heat pump water heater and electric resistance heating elements offers redundancy so that hot water heating ability will be maintained in the case of partial equipment failure.

DRAWBACKS OF THE HEAT PUMP WATER HEATER The heat pump water heater may be more expensive than a conventional water heater. A heat pump water heater has a slower rate of recovery than a conventional water heater. It may require the engineering and field installation of additional plumbing or refrigeration piping. If the space cooling is to be distributed, ductwork may need to be field installed. An air source heat pump water heater will not operate if the temperature of the evaporator falls below freezing. Also if the evaporator temperature falls below freezing, the airstream can become blocked as ice forms on the evaporator coil.


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If a heat pump is used for supplemental cooling, the building must be able to handle the space cooling year-round. The engineer should not have to supply additional ambient heat during the cold season in order for the heat pump water heater to continue operating—unless it can be supplied in a cost-efficient manner. Heat pump water heaters are not as widely available as conventional electric or gas water heaters. Also, heat pump water heaters are available in only a limited number of capacities and sizes, so the designer may have to compromise or manifold units when sizing a heat pump water heater for a particular application. Heat pump water heaters require maintenance and service technicians who have an understanding of heating, ventilation, and air-conditioning systems as well as the conventional plumbing systems associated with water heaters.

HEAT RECOVERY SYSTEMS Some engineers use heat pump water heater technology in an engineered system referred to as a “heat recovery system.” Basically this type of system is similar to a heat pump water heater system except that its refrigeration compressor is usually part of the refrigeration system and is used to pump hot gas to the heat exchangers in the storage tanks. Heat recovery systems may or may not have electric heating elements. Sometimes a separate gas water heater is provided downstream of the heat recovery water heaters. Heat recovery systems are used in supermarkets, restaurants, convenience stores, dairy farms, and indoor ice rinks. Such buildings have large demands for warm water for washing down food preparation, meat processing, dairy, and other areas from hot and cold hose stations. They also have large refrigeration rooms full of compressors to keep refrigerator/freezer systems cold. The waste heat produced by such applications is ideal for a heat recovery water heater. In a study done in a supermarket in Michigan, the waste heat from the refrigeration equipment heated the domestic water stored in three 120-gal (455-L) storage tanks, then the preheated water passed through a gas fired water heater before being distributed to the domestic hot water system. A meter on the gas line serving the water heater showed that over an extended period of time the water heater burner was never turned on.

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For supermarket applications, engineers sometimes use a large single-circuit heat recovery unit that can accommodate high refrigerant flow rates with low pressure drops. Sometimes multiple heat recovery units are installed in parallel or in series (a two-stage system) for a single application. Note: Caution should be used when working with heat recovery units. A separate condenser still must be installed with the refrigeration system. When manifolding heat recovery units for large refrigeration systems, the designer must take care to lay out the piping for the units in such a way that, during periods of low refrigeration demand, condensed liquid refrigerant is prevented from forming a trap and blocking the flow of refrigerant gas through the units. Some manufacturers have designed special refrigerant drain tubes on their units to prevent this from happening.

APPLICATIONS The heat pump is an excellent choice for a water heater when certain conditions are met. The building should have a use for simultaneous water heating and space cooling or refrigeration. The concurrence of the water heating and space cooling loads is important. In a good heat pump water heater application, the water heating load occurs over a long period of time, giving the heat pump water heater an extended run time. There should be a use for the space cooling or refrigeration load throughout the year, and the temperature of the heat pump water heater’s evaporator must be maintained above freezing. If natural gas is expensive or unavailable locally, the heat pump water heater may be the most cost-efficient choice for heating water. A heat pump water heater makes the most economic sense when natural gas, liquid petroleum gas (LPG), oil, and electric resistance heat are expensive. A poor heat pump water heater application is one in which all or some of the above conditions are not met. The customer has no use or only limited use for the space cooling byproduct. The building has a water heating load that occurs over a short period of time, giving the heat pump water heater a limited run time and requiring that the backup electric elements be energized during most of the run time. When the backup electric resistance elements are energized most of the time, the advantages of a heat pump water heater are limited. Also, if low-cost


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natural gas, LPG, oil, or electric resistance heat are readily available, the heat pump water heater loses its relative cost-efficiency. Possible commercial heat pump/heat recovery water heater applications are restaurants, grocery stores, and other buildings with large refrigeration loads and high demands for hot water. The commercial refrigeration units of such buildings usually have condensing units, located on the roof or beside the building, that reject the heat produced by the refrigeration process. In a commercial heat recovery application, the refrigeration hot gas line has a bypass valve that sends the refrigeration hot gas to the double-wall heat exchanger in the water storage tank. When the thermostat in the water storage tank indicates that the water has reached its set point, the bypass valve sends the hot gas to the condenser on the roof where the excess heat is rejected.

CRITERIA FOR SELECTING HEAT PUMP WATER HEATERS If a natural gas or electric water heater is being replaced, the designer should take into account the efficiency of the old water heater or the heat pump water heater will be oversized. If space cooling is desired, the heat pump water heater should be slightly undersized to allow maximum run time and prevent overcooling of the conditioned space. The designer can contact the water heater’s manufacturer or the office of the local utility for engineering assistance for a particular application.

SPECIAL REQUIREMENTS FOR HEAT PUMP WATER HEATERS The installation procedures for a heat pump water heater are the same as the those for a conventional electric resistance water heater with some additions. A drain must be provided to remove condensate from the evaporator. Installation of ductwork for the evaporator to direct the conditioned air may be desired. The installer must connect refrigeration or additional water lines between the heat pump water heater and the storage tank if a remote type heat pump water heater is being installed. Remote type heat pump water heaters also should have unions, strainers, and isolation valves installed on the water lines. Integral type heat pump water heaters require a greater height clearance than conventional water heaters if the refrigeration components are mounted on top of the storage tank.

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The maintenance procedures for a heat pump water heater are the same as those for a conventional water heater with a few additions. The anodes and backup electric elements of integral type water heaters should be checked regularly. The scaling of the heat exchanger and the accumulation of sediment are concerns and should be dealt with using the same procedures used for a conventional water heater. The strainers on remote heat pump water heater piping should be checked regularly. Additionally, heat pump water heaters require regular maintenance of the refrigeration system. The pump or fan motors may need lubrication. The air filter on the evaporator should be regularly cleaned or replaced, and the evaporator coil may need to be cleaned for the heat pump water heater to operate at a high efficiency. The evaporator condensate drain must remain open and should not have any biological growth in it if the conditioned air is supplied to an inhabited space. Finally, the refrigeration system should be checked to ensure that it is operating efficiently.

INCOMING WATER QUALITY Heat pump water heaters have the same requirements for incoming water quality as conventional residential and commercial water heaters. Special heat exchangers can be used to accommodate extremely poor quality incoming water. Scale and sediment have the same effect on the heat exchangers of heat pump water heaters that they have on conventional water heaters and should be handled with the same procedures. In hard water areas water softeners should be installed ahead of the water heating system.

SAFETY CONTROLS AND DEVICES Heat pump water heaters use the same safety controls as conventional electric or gas water heaters, such as temperature/ pressure relief valves and thermostats with manual reset overloads. Heat pump water heaters also use the same safety controls as HVAC systems, such as refrigeration pressure and temperature controls. Heat pump water heaters with remote components should have fuses or circuit breakers for remote components on branch circuits.

Steam W ater Heater Water Heaterss

22

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STEAM WATER HEATERS

INTRODUCTION Instantaneous Water Heaters A steam, instantaneous water heater is a device that utilizes steam to heat water to a specific temperature. It is able to supply this tempered water without delay in volumes up to the water heater’s maximum capacity. Because of its ability to supply hot water instantly, storage tanks usually are not required with this type of water heater, providing the water heater is sized to handle the maximum demand. A steam, instantaneous water heater can be used for any application that requires domestic or process hot water and has steam as an available energy source. Such applications include: shower rooms, washrooms, dishwashing areas, laundries, and food processing plants. The types of facility these applications are found in include: industrial plants, petrochemical plants, schools, universities, apartments, hotels, motels, and restaurants. Generally speaking, there are two main types of steam, instantaneous water heater available today: the feedback unit and the feed-forward unit.

Storage Water Heaters The storage heater is a type of water heater in which heat is transferred to water through tubes or coils. The hot water is then held, ready to supply demand, in a tank. The heating assembly can be either separate from or incorporated with the tank.


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A storage type water heating system requires more floor space than an instantaneous system to accommodate the storage tank. Also there must be adequate floor support to hold the weight of the water stored in the tank. Water hardness can be a problem with a storage type system. Scale from hard water can have a degrading effect on any heater, unless the unit is designed to remove scale buildup. Some heaters reduce scale buildup by expanding and contracting metal parts, others by properly scouring with high water velocities. If there is any hardness in the water, a heater that is designed to counter scale formation and can be easily maintained should be selected. Systems with welded plates or other similarly sealed assemblies are best reserved for use with scale-free water. Storage heaters can generate hot water over a period of time and hold it, ready for use, in large volumes. Because of this, boilers with relatively small capacities can be used and the peak demands for fuel are reduced. Storage heaters can meet high demands for such things as periodic showers without increasing peak energy demands. With a steam, storage water heating system, water is heated either in the tank or at a remotely located heater. The tanks of storage heating systems are large, maybe holding thousands of gallons (liters) of water. Energy is supplied to a storage system at a rate determined by the design of the system. In a steam, storage system, heat exchangers are used in conjunction with storage tanks. Temperature controls located on the storage tanks maintain uniform outlet temperatures. A steam system is operated by boiler- or district-supplied steam. A steam boiler is operated by oil, gas, or another fuel source. Electricity is often available for generating steam or directly heating water but is usually a costly source of energy. “District-supplied steam” refers to overseas use, where steam is created in a central location then distributed to the buildings in a district.

FEEDBACK UNITS A feedback unit is a water heater that controls hot water temperature by sensing hot water in either a tank or exit piping and feeding back a signal to the steam control device. Such units are reactive, depending on a change in water temperature for their control. This need to react to change causes a lag in the control


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of the temperature. Lag time is greatly affected by the quality of a unit’s controls. Another way of thinking of the term “feedback” is that control of the unit is accomplished behind or in back of the operation of the heat exchanger. There are generally two types of feedback system: 1. Storage tank feedback system. 2. Tankless, instantaneous feedback system. Storage tank feedback systems are used more often than tankless systems. The following are the main components of the storage tank feedback system: 1. 2. 3. 4.

Bayonet type U-tube heat exchanger. Temperature controlled steam valve. Storage tank. Recirculation pump. The U-tube heat exchanger is located in the bottom portion of the storage tank, and the steam flowing to it is controlled by the temperature controlled steam valve. A gas or liquid-filled temperature sensing bulb is located in the midsection of the tank and is connected via a capillary to the temperature controlled steam valve, which modulates the flow of steam to the heat exchanger based on the temperature of the water in the tank. The function of a recirculation pump (in a large tank) is to keep the water in the tank turbulent to prevent stratification and to allow for more accurate temperature readings by the sensing bulb. A storage tank feedback system is capable of supplying a large volume of water (the volume depending on the size of the storage tank). It is not an instantaneous system, however, so its recovery rate can be slow. Also because the storage tank can be very large, it may require a large floor space. Because these units are usually located in a basement or mechanical room, replacing the storage tank is impossible without either making major modifications to the building or replacing the large tank with multiple smaller tanks. The tankless, instantaneous feedback system operates exactly the way the storage tank feedback system does. Because there is no tank, however, the temperature sensing bulb is mounted in the outlet water line. Because of the bulb location and the slow response time associated with self-contained temperature regulators, inaccurate control is a characteristic of this type of unit when hot water demand fluctuates the way it does in a domestic hot water system. In the transition from low to heavy

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load, there is a lag time before the temperature regulator reacts, which causes a temperature drop in the water. Conversely, when demand changes from heavy to low load the lag time causes overheating of the outlet water. Another shortcoming of this type of feedback system is the thermostatic capillary system. Domestic hot water systems usually have demands from 10 to 20% of the time. The other 80 to 90% of the time they stand idle. Under no load conditions, the water radiates heat, thus cooling down. As this happens, the temperature regulator opens and allows steam into the heat exchanger, elevating the water temperature, which in turn causes the temperature regulator to close. While the system is idle, this cycling goes on continuously. Such cycling can cause the bellows of the thermostatic capillary system to fail, causing severe overheating of the outlet water. In summary, the storage tank feedback system offers large volumes of constant temperature water but has storage tanks that take up valuable floor space. Because of the size of such a system, maintenance or replacement is very difficult and very expensive. Also this type of unit wastes more energy than a tankless system because it heats and maintains the temperature of water that is not being used. On the other hand, the tankless, instantaneous feedback system can fit into very small areas and uses no tank that would require service or replacement. It does not waste energy keeping unused water hot, but rather heats water instantly on demand. Because it does not use a large stored volume of water as a temperature heat sink, however, it is prone to large temperature swings and temperature system failures. Both systems, being thermostatically controlled, have modulating steam pressures within the heat exchanger. If they are not piped and trapped properly, water hammer and corrosion can occur in the heat exchanger, causing premature failure.

FEED-FORWARD UNITS A feed-forward unit is a water heater that controls hot water temperature by sensing the difference between the inlet and outlet water pressures. This differential pressure is an indication of demand. The greater the differential pressure, the greater the demand for hot water. Such units are proactive, rather than reactive, in terms of their control of outgoing water temperature. There is no lag time associated with this method of control because with it a unit responds to demand rather than to something


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affected by demand, such as water temperature. Another way of thinking of the term “feed-forward” is that, in such a unit, control is accomplished in front of or forward of the operation of the heat exchanger. Feed-forward control eliminates the need for the temperature controlled valve associated with feedback systems. Instead a specially designed differential pressure diaphragm mixing valve is used to regulate the flow of water in the unit and to maintain temperature control. This valve is combined with a shell and tube heat exchanger to complete the system. As hot water demand downstream of the valve increases, it creates a pressure drop that is sensed by the differential pressure diaphragm, causing it to position a series of valves to allow flow of makeup water into the heat exchanger as well as bypass water around the heat exchanger. The concept is to overheat the water in the heat exchanger and then blend cold water as needed with the overheated water so the unit delivers the proper temperature water over a broad range of flows. Because the differential pressure is associated with and proportional to demand, a feed-forward unit can respond immediately to demand by positioning its valves to control output temperature. There is no lag time. The greatest benefit of the feed-forward system is safety. First, because it has proactive control, such a system provides much better temperature control than its feedback instantaneous counterpart. Second, if its operator, the differential pressure diaphragm, fails, the unit cannot pass water to the heat exchanger. Only cold water may exit the unit. This prevents a scalding situation, such as would occur with a feedback instantaneous system, which fails uncontrolled. The feedback unit cycles its controls on and off under no load conditions, ultimately wearing them out. The feed-forward unit does not operate unless there is demand, meaning that it can sit idle for prolonged periods of time, not cycling and wearing out its controls. Feed-forward units operate on low-pressure steam, usually no greater than 15 psig (103 kPa). This steam pressure remains on the unit throughout its operation. The water in the unit does not boil because its pressure is greater than the steam’s. Because the steam pressure is constant, condensate drainage from the feed-forward unit is more assured than it is with the modulating pressure of the feedback system. If low-pressure steam is readily available at the point of installation, the installer need only make the connection to the steam main and include an isolation valve. If steam pressures are higher than 15 psig (103 kPa),

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a pressure reducing valve must be used and sized to supply adequate volumes of steam at delivery pressures between 2 and 15 psig (14 and 103 kPa). Steam volume requirements must be studied to determine whether the steam available at the unit’s location is adequate. Steam mains are sized to handle the maximum volume of steam required by any instantaneous device experiencing substantial pressure drops due to equipment and valve restrictions. Steam volume requirements are provided in the manufacturer’s feed-forward capacity charts and depend on the sizes and condensing rates of the units used. For all the benefits of a feed-forward unit, there also are a few shortcomings. First, because the differential pressure control valve on a feed-forward unit is not temperature activated, the unit requires that two things delivered to the unit remain constant. One is steam pressure, which ensures a constant temperature in the shell of the heat exchanger. The other is entering water temperature. A constant steam pressure is generally not difficult to maintain, but a constant inlet water temperature may be. This means that preheating the inlet water with a heat recovery system or energy conservation device, as is is done with a feedback system, cannot be done. Sudden changes in inlet water temperature can affect the output water temperatures of the feed-forward unit once it has been adjusted. Seasonal temperature changes of the water are generally not a problem. These changes occur so slowly that they are not noticed by the user. If, however, seasonal changes are undesirable to the user, a quick and simple readjustment of the unit will solve the problem. With a typical domestic hot water temperature of 120 to 140ºF (49 to 60ºC), for every 3ºF (2ºC) inlet water temperature change, the outlet temperature change with a feed-forward unit will be 1ºF (1ºC) in the same direction.

RECIRCULATION SYSTEM PIPING AND OPERATION Because a feed-forward system is relatively small and compact, it can easily be installed close to the point of usage. This usually eliminates the need for a recirculation system. In applications where the unit is located in a basement or utility room and feeds an entire building or the wing of a building, a recirculation system or loop is desirable to ensure delivery of instantaneous hot water at all points of usage.


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The feed-forward recirculation system is composed of several different components designed to work together to maintain the temperature of the water in the loop during times of no or very low demand. (See Figure 22.1.) The recirculation pump runs continuously, regardless of the hot water demand. Its function is to constantly recirculate the water in the loop to maintain the temperature during times of no or low demand. The size of the pump is determined by the maximum capacity of the feed-forward unit used. As a rule of thumb, the pump flow rate should be approximately 10 to 15% of the maximum capacity of the feed-forward unit. The recirculation pump can be larger than 15%, but when a larger pump is used, the installer must pipe a full size balancing line with globe valves around the thermostatic capsule to balance the flow going to the diverting valve. Failure to do this can cause overheating of the

Figure 22.1 Recirculation System Piping and Operation. Source: Courtesy of Armstrong-Yoshitake, Inc.

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system due to the large volume of diverted water going back to the unit for reheating. The three-way diverting valve is a device with a nominal set point that is roughly 15 to 20ºF (8 to 11ºC) below the set point of the feed-forward unit or a diverting temperature that is roughly 5 to 10ºF (3 to 6ºC) below the unit’s set point. The capsule senses the temperature of the recirculated water and compares it with its diverting temperature. If the temperature in the return piping drops below the three-way valve’s diverting temperature because of radiation loss from the piping and there is no hot water demand from the loop, the valve begins to divert some of the loop’s flow to the inlet of the feed-forward unit (ports A to B in Figure 22.1). There it is reheated to bring the temperature of the loop back up to its required level. Once the temperature in the loop is above the capsule’s diverting temperature, all flow from the recirculation pump is directed straight through the valve (ports A to C in Figure 22.1) and the return water is fed back out to the hot water system. This diverting recirculation system eliminates the need for aquastats and electrical wiring. It is a self-contained, self-regulating system that controls the temperature of the water in the loop during periods of no or low hot water demand. When there is a demand for hot water, the temperature of the water introduced into the system is instantly controlled by the feed-forward unit. Note: Failure to install the diverting valve in the feed-forward unit’s recirculation system will result in the eventual overheating of the system due to the constant elevation of inlet water temperatures.

DESIGN CONSIDERATIONS The following are system design criteria: • The heat exchanger must be sized on gpm not gph when a storage tank is not provided. The maximum instantaneous flow, not the diversified flow, must be used. • The heat exchanger should have the domestic water in the shell and the steam in the bundle. This will provide for the load/ lag flywheel required to maintain a uniform delivery temperature. • Heat exchanger selection should include local, state, and federal code provisions.


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• A recirculating hot water pump should be provided. • Since most steam control valves are not good for finite control less than 30%, two steam valves should be provided for, sized at 0–30% and 25–100% of the load. For other design considerations, please refer to American Society of Plumbing Engineers, 2001, Steam and condensate systems, Chapter 8 in ASPE Data Book, Volume 3.

Example 22.1 A hot water system is required for 1110 gph (4202 L/h) of 160ºF (71ºC) water from a 50ºF (10ºC) cold water system. The maximum fixture demand is 43 gpm (2.7 L/sec). Gph method (with storage tank) 1110 gph × 8.33 × (160 – 50ºF) = 1017.5 Mbh [4202 L/h × 4.186 × (71 – 10ºC) = 1 073 519 kJ/h] Gpm method (using maximum connected flow) 43 gpm × 500 × (160 – 50ºF) = 2365 Mbh [2.7 L/sec × 15 071 × (71 – 10ºC) = 2 495 207 kJ/h]

Expansion TTanks anks

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EXPANSION TANKS

INTRODUCTION The objective of this chapter is to show the designer how to size an expansion tank for a domestic hot water system and to explain the theory behind design and the calculations. The following discussion is based on a diaphragm or bladder type expansion tank, which is the one most commonly used in the plumbing industry. This type of expansion tank does not allow the water and air to come in contact with each other. When water is heated, it expands. If this expansion occurs in a closed system, dangerous water pressures can be created. A domestic hot water system can be a closed system. When hot water fixtures are closed and the cold water supply piping has backflow preventers or any other device that can isolate the domestic hot water system from the rest of the domestic water supply, a closed system can be created. (See Figure 23.1[a].) The water pressures can quickly rise to a point at which the relief valve on the water heater will unseat, hence relieving the pressure but also compromising the integrity of the relief valve. (See Figure 23.1[b].) A relief valve installed on a water heater is not a control valve but a safety valve. It is not designed or intended for continuous usage. Repeated excessive pressures can lead to equipment and pipe failure and personal injury. An expansion tank, when properly sized and connected to a closed system, provides additional system volume for water expansion while ensuring a maximum desired pressure in a domestic hot water system. It does this by utilizing a pressurized cushion of air. (See Figure 23.2[a] and [b].)

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(a)

(b)

Figure 23.1 A Closed Hot Water System Showing the Effects as Water and Pressure Increase from (a) P1 and T1 to (b) P2 and T2.


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(a)

(b)

Figure 23.2 Effects of an Expansion Tank in a Closed System as Pressure and Temperature Increase from (a) P1 and T1 to (b) P2 and T2.

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EXPANSION OF WATER A pound of water at 140°F (60°C) has a larger volume than the same pound of water at 40°F (4.4°C). To look at it another way, the specific volume of water increases with an increase in temperature. Specific volume data show the volume of 1 lb (1 kg) of water for a given temperature and are expressed in ft3/lb (m3/ kg). When the volume of water at each temperature condition is known, the expansion of water can be calculated. (23.1) Vew = Vs2 – Vs1 where Vew = expansion of water, gal (L) Vs1 = system volume of water at temperature 1, gal (L) Vs2 = system volume of water at temperature 2, gal (L) Vs1 is the initial system volume and can be determined by calculating the volume of the domestic hot water system. This entails adding the volume of the water heating equipment with the volume of piping and any other part of the hot water system. Vs2 is the expanded system volume of water at the design hot water temperature. Vs2 can be expressed in terms of Vs1. To do that, we must look at the weight of water at both conditions. The weight of water at temperature 1 (T1) equals the weight of water at temperature 2 (T2), or W1 = W2. At T1, W1 =

Vs1 VSP1

where VSP = specific volume of water at a specified temperature condition (see Table 23.1 for specific volume data). Similarly, at T2, W2 =

Vs2 VSP2

Since W1 = W2, then


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Table 23.1 Thermodynamic Properties of Water at a Saturated Liquid Temp., °F (°C)

Specific Volume, ft3/lb (m3/kg)

40 (4.4) 50 (10)

0.01602 (0.0010013) 0.01602 (0.0010013)

60 (15.55) 70 (22.1)

0.01604 (0.0010027) 0.01605 (0.0010032)

80 (26.7) 90 (32.2)

0.01607 (0.0010045) 0.01610 (0.0010064)

100 (37.8) 110 (43.3)

0.01613 (0.0010082) 0.01617 (0.0010107)

120 (48.9) 130 (54.4)

0.01620 (0.0010126) 0.01625 (0.0010157)

140 (60) 150 (65.6)

0.01629 (0.0010181) 0.01634 (0.0010214)

160 (71.1)

0.01639 (0.0010245)

Vs1 = VSP1

Vs2 VSP2

Solving for Vs2: Vs2 = Vs1

(VSP VSP ) 2

1

Earlier it was stated that the expansion of the water (Vew) = Vs2 – Vs1. Substituting Vs2 from above, we can now say that: Vew = Vs2 – Vs1 Since Vs2 = Vs1

, then (VSP VSP ) 2

1

Vew = Vs1

–V (VSP VSP ) 2

1

(23.2) Vew = Vs1

VSP – 1) (VSP 2

1

, or

s1

348


Example 23.1 A domestic hot water system has 1000 gal (3785.4 L) of water. How much will the 1000 gal (3785.4 L) expand from a temperature of 40°F (4.4°C) to a temperature of 140°F (60°C)? From Table 23.1: VSP1 = 0.01602, at 40°F (0.0009, at 4.4°C) VSP2 = 0.01629, at 140°F (0.001017, at 60°C) Using Equation 23.2: Vew = 1000

0.01629 –1 ( 0.01602 )

Vew = 16.9 gal [Vew = 3785.4

0.0010181 – 1) ( 0.0010013

Vew = 64.0 L] Note: This is the amount of expansion of the water and should not be confused with the size of the expansion tank needed.

EXPANSION OF MATERIALS Does the expansion tank receive all of the water expansion? The answer is no because not just the water is expanding. The piping and water heating equipment expand with increased temperature as well. So any expansion of material results in less of the water expansion being received by the expansion tank. Another way of looking at it is as follows: (23.3) Venet = Vew – Vemat where Venet = net expansion of water seen by the expansion tank, gal (L) Vew

= expansion of water, gal (L)

Vemat = expansion of material, gal (L)


349

To determine the amount of expansion each material will experience per a certain change in temperature, look at the coefficient of linear expansion for each material. For copper, the coefficient of linear expansion is 9.5 × 10–6 in./in.°F (1.7 × 10-5 mm/mm°C); for steel, it is 6.5 × 10–6 in./in.°F (1.2 × 10–5 mm/mm°C). From the coefficient of linear expansion we can determine the coefficient of volumetric expansion of material. The coefficient of volumetric expansion is three times the coefficient of linear expansion. β = 3α

(23.4) where β

= volumetric coefficient of expansion

α

= linear coefficient of expansion

βsteel = 19.5 × 10–6 gal/gal°F (3.6 × 10–5 L/L°C) βcopper = 28.5 × 10–6 gal/gal°F (5.1 × 10–5 L/L°C) The material will expand proportionally with an increase in temperature. (23.5) Vemat = Vmat × β (T2 – T1) Making the above substitution and solving for Venet: (23.6) Venet = Vew – [Vmat1 × β1 (T2 – T1) + Vmat2 × β2 (T2 – T1)]

Example 23.2 A domestic hot water system has a water heater with a volume of 900 gal (3406.86 L) and is made of steel. It also has 100 ft (304.8 m) of 4 in. (101.6 mm) piping, 100 ft (304.8 m) of 2 in. (50.8 mm) piping, 100 ft (304.8 m) of 1½ in. (38.1 mm) piping and 300 ft (91.44 m) of ½ in. (12.7 mm) piping. All the piping is copper. Assuming that the initial temperature of water is 40°F (4.4°C) and the final temperature of water is 140°F (60°C), (A) how much will each material expand, and (B) what is the net expansion of water that an expansion tank would see? A. Utilizing Equation 23.5, for the steel (material no. 1): Vmat1 = 900 gal

350


Vemat1 = 900 (19.5 × 10–6)(140 – 40) = 1.8 gal [Vmat1 = 3406.86 L Vemat1 = 3406.86 (3.6 × 10–5)(60 – 4.4) = 6.81 L] For the copper (material no. 2) we first look at Table 23.2 to determine the volume of each size of pipe. 4 in. (101.6 mm):

100 × 0.67 = 67 gal (30.48 × 8.32 = 253.6 L)

2 in. (50.8 mm):

100 × 0.17 = 17 gal (30.48 × 2.113 = 64.4 L)

1½ in. (38.1 mm):

100 × 0.10 = 10 gal (30.48 × 1.243 = 37.99 L)

½ in. (12.7 mm):

300 × 0.02 = 6 gal (91.44 × 0.249 = 22.7 L)

Total volume of copper piping = 100 gal (378.69 L) Utilizing Equation 23.5 for copper: Vmat2

= 100 gal (378.69 L)

Table 23.2 Nominal Volume of Piping Pipe Size, in. (mm) ½ ¾

Volume of Pipe, gal/l ft (L/m)

(12.7) (19.1)

0.02 0.03

(0.249) (0.472)

1 (25.4) 1¼ (32.5)

0.04 0.07

(0.495) (0.869)

1½ (38.1) 2 (50.3)

0.10 0.17

(1.243) (2.113)

2½ (63.5) 3 (76.2)

0.25 0.38

(3.104) (4.718)

4 (101.6) 6 (152.4)

0.67 (8.32) 1.50 (18.629)

8 (203.2)

2.70 (33.533)


351

Vemat2 = 100 (28.5 x 10–6)(140 – 40) = 0.3 gal [Vemat2 = 378.69 (5.1 × 10–5)(60 – 4.4) = 1.07 L] B. The initial system volume of water (Vs1) equals Vmat1 + Vmat2, or 900 gal + 100 gal (3406.86 L + 378.69 L). From Example 23.1, we already determined that 1000 gal (3785.4 L) of water heated from 40 to 140°F (4.4 to 60°C) will expand 16.9 gal (64.0 L). So, utilizing Equation 23.6, we find that Venet = 16.9 – (1.8 + 0.3) = 15 gal [Venet = 60.4 – (6.81 + 1.07) = 56.12 L]. This is the net amount of water expansion that the expansion tank will see. Again, please note that this is not the size of the expansion tank needed.

BOYLE’S LAW We have determined how much water expansion will be seen by the expansion tank. Now it is time to look at how the cushion of air in an expansion tank allows us to limit the system pressure. Boyle’s Law states that, at a constant temperature, the volume occupied by a given weight of perfect gas (including, for practical purposes, atmospheric air) varies inversely as the absolute pressure (gage pressure + atmospheric pressure). It is expressed by: P1V1 = P2V2 How does this law relate to sizing expansion tanks in domestic hot water systems? The air cushion in the expansion tank allows a space for the expanded water to go. The volume of air in the tank will decrease as the water expands and enters the tank. As the air volume decreases the air pressure increases. Utilizing Boyle’s Law, we can determine what the initial volume of air (size of expansion tank) needs to be based on (A) the initial water pressure, (B) the desired maximum water pressure, and (C) the change in the initial volume of air. In using the above equation, we realize that the pressure of the air equals the pressure of the water at each condition and we make the assumption that the temperature of the air remains constant at condition 1 and condition 2. This assumption is reasonably accurate if the

352


expansion tank is installed on the cold water side of the water heater. Remember, to size an expansion tank you are sizing a tank of air, not a tank of water. Referring to Figure 23.3, you see that at condition 1 the tank has its initial air pressure charge, P1, which equals the incoming water pressure on the other side of the diaphragm. V1 is the initial volume of air in the tank and is also the size of the expansion tank we are solving for. V2 is the final volume of air in the tank, which also can be expressed as V1 less the net expansion of water (Venet). P2 is the pressure of the air at condition 2. P2 will be the same pressure as the maximum desired pressure of the domestic hot water system at T2. P2 should always be less than the relief valve setting on the water heater (approximately 10% less than the relief valve setting). Utilizing Boyle’s law, P1V1 = P2V2, since V2 = V1 – Venet P1V1 = P2 (V1 – Venet) P1V1 = P2V1 – P2Venet (P2 – P1) V1 = P2Venet V1 =

P2Venet (P2 – P1)

Multiplying both sides of the equation by (1/P2)/(1/P2) or by “1” we have: Venet (23.8) V1 = (1 – P1/P2) where V1 P1

= size of expansion tank required to maintain the desired system pressure (P2), gal (L) = incoming water pressure (in absolute pressure), psia (kPa)

(Note: Absolute pressure is the gage pressure, psig, plus atmospheric pressure, e.g., 50 psig = 64.7 psi in absolute pressure [344.5 kPa = 445.78 kPa].) Venet = net expansion of water, gal (L) P2

= maximum desired pressure of water (in absolute pressure), psia (typically 10% less than the relief valve setting)


353

Figure 23.3 Sizing the Expansion Tank.

Example 23.3 Looking further at the domestic hot water system described in Example 23.2, if the cold water supply pressure is 50 psig (344.5 kPa) and the maximum desired water pressure is 110 psig (757.9 kPa) (the relief valve setting is 125 psig [861.25 kPa]), what size expansion tank is required? In example 23.2 we determined that Venet equals 15 gal (56.78 L). Converting the given pressures to absolute and utilizing Equation 23.8 we can determine the size of expansion tank needed: V1 =

15 = 31 gal (1 – 64.7/124.7)

[V

56.78 = 117.3 L (1 – 445.78/859.18)

1

=

]

Note: When selecting the expansion tank, make sure the tank’s diaphragm or bladder can accept 15 gal (56.78 L) of water (Venet).

354


SUMMARY Earlier in this chapter the following was established, Equation 23.2: Vew = Vs1

VSP – 1) ( VSP 2

1

Equation 23.6: Venet = Vew – [Vmat1 × β1 (T2 – T1) + Vmat2 × β2 (T2 – T1)] In Equation 23.2, Vs1 was defined as the system volume at condition 1. Vs1 can also be expressed in terms of Vmat. Vs1 = Vmat1 + Vmat2 Making this substitution and combining the equations, we get the following: (23.9) Venet = (Vmat1 + Vmat2)

VSP – 1) – [V ( VSP 2

mat1

× β1 (T2 – T1) +

1

Vmat2 × β2 (T2 – T1)] (23.8)

V1 =

Venet (1 – P1/P2)

where Venet

= net expansion of water seen by the expansion tank, gal (L)

Vmat

= volume of each material, gal (L)

VSP

= specific volume of water at each condition, ft3/lb (m3/kg)

β

= volumetric coefficient of expansion of each material, gal/gal°F (L/L°C)

T

= temperature of water at each condition, °F(°C)

P

= pressure of water at each condition, psia (kPa)

V1

= size of expansion tank required, gal (L)

These two equations are required to size an expansion tank for a domestic hot water system properly.

INDEX

Index Terms

Links

1-bedroom apartments retirement homes water demand

157 26

1 -compartment sinks hospital example work-sheets

hospital sizing example

84

86

100

108

115

123

112

hospital usage factors

79

80

hourly demand

65

87

jailusage kitchen requirements

103

183 50

87

151

142

147

149

165

168

171

175

103

nursing/intermediate care/retirement homes nursing/intermediate care worksheet examples 2-bedroom apartments retirement homes water demand

157 26

2 -compartment sinks central sterile supply

95

high school usage

55

hospital example

112

hospital example work-sheets

113

84

86

100

106

108

115


79

80

hospital utility rooms

73

This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

2 -compartment sinks (Cont.) hourly demand

65

87

kitchen requirements

50

87

151

142

147

149

care worksheet examples

165

168

173

sports arenas and stadiums

211

103

119

52

53

87

147

149

nursing/intermediate care/retirement homes nursing/intermediate

3-compartment sinks booster heaters for

187

fast-food restaurants

228

high schools hospital example

55 112

hospital worksheet examples

84

86

hospital worksheets

79

80

hourly demand

65


50 151

nursing/intermediate care/retirement homes

142

nursing/intermediate care worksheet examples

168

3-way diverting valves (thermostatic capsules) 4-compartment sinks

339

340

65

5-min peak demand guideline

30

30/3 guideline 30 mA ground fault equipment

33

30 267


Index Terms

Links

32-bed hospitals example worksheets

93 100

48-bed nursing/intermediate care/retirement home example

158

gathering information

161

worksheet example totals

176

worksheets

164

100-ft length criterion

234

300-bed hospital example

111

A absolute pressures equations

352

gases

351

access to equipment

281

ACEEE (American Council for Energy Efficient Economy)

xxi

acidity of water, indirect fired water heaters and

295

activity rooms in religious facilities ADA (Americans with Disabilities Act)

226 xxi

192

additions to buildings, heat trace systems and

272

adjustable orifice flow control valves

248


Index Terms

Links

administration areas hospitals

77

82

83

157

163

99 nursing/intermediate care facilities

138

religious facilities

226

retirement homes

140


204

advanced high-efficiency water heating systems considerations

17

multifamily buildings and

30

after-hours at schools

47

after-work crowd at spas and health clubs

130

afternoon peak demand multifamily buildings

21

spas and health clubs

130

AGA. See American Gas Association (AGA) aggressive fluids, heat ex-changers and

288

air air intake control in burners

319

321

343

351

cushions in expansion tanks entrapped in recirculating systems

259

as heat source in heat pumps

327


93

Index Terms

Links

air filters in heat pump systems

332

alkalinity of water heat pump systems and

332

indirect fired water heaters and

295

steam storage water heaters

334

altitudes DSH systems and gas burners and

4 321

ambient heat, heat pumps and

329

American Council for Energy Efficient Economy (ACEEE)

xxi

American Gas Association (AGA)

xxi

15

16

American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)

xxi

Energy Conservation in New Building Design

261

Energy Efficient Design of New Low Rise Residential Buildings IEW 90.1 standard

261 16

New Information on Service Water Heating

261

Pipe Sizing

261

Service Water Heating

261

Thermal and Water Vapor Transmission Data

261


Index Terms

Links

American Society of Mechanical Engineers (ASME)

15

code for fired and unfired pressure vessels

16

code for relief valves

16

Plumbing Fixture Fittings

261

American Society of Plumbing Engineers (ASPE)

xxi

Cold Water Systems

261

Energy Conservation in Plumbing Systems

262

Insulation

262

Piping Systems

261

Position Paper on Hot Water Temperature Limitations

261

Pumps

262

Service Hot Water Systems

57

261

Steam and Condensate Systems

341

American Water Works Association Internal Corrosion of Water Distribution Systems

262

Americans with Disabilities Act (ADA)

xxi

192

ammonia in indirect fired water heaters

291

refrigeration

288

anchor department stores

228


Index Terms

Links

Anding, Craig

xix

Andrews, Steven M.

xix

animal facilities in pharmaceutical plants

195

anodes. See also sacrificial anodes heat pump systems

332

anti-siphoning features

300

antibacterial cleaners

195

315

319

apartment buildings. See multifamily buildings apartments in retirement homes. See retirement homes appliance flow rates table

236

approach temperature defined

280

heat exchangers

281

plate-type heat exchangers and

284

U-tube removable bundles and

283

aquastat controls

288

258

340

arms/hips/leg/back tubs

94

112

art rooms

46

arenas. See sports arenas 159

ASHRAE. See American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) ASME. See American Society of Mechanical Engineers (ASME) This page has been reformatted by Knovel to provide easier navigation.

214

Index Terms

Links

ASPE. See American Society of Plumbing Engineers (ASPE) assisted bathing

73

athletic centers calculating demand

130


127

hot water requirements

128

laundry and food service demand

130

shower rooms

129

athletic teams. See sports teams atmospheric pressures equations

352

gases

351

attachment tape in heat trace systems

269

automatic flow control valves

247

automatic gas shut-off valves

315

318

77

91

autopsy rooms considerations

93


99

user group totals work-sheets

82

83

average demand calculating for apartment building example

32

vs. peak demand

26

average occupancy per hotel guest room

61


Index Terms

Links

B backflow preventers in closed systems

343

backup electric elements in heat pump systems

332

bacteria biological growth on drains

332

Legionnaires’ Disease

14

pharmaceutical plants

195

baffles gas water heaters

316


282

balancing devices. See flow balancing devices and valves Balliet, James L.

xix

ballrooms in hotels

59

baptistries

225

bar sinks demand

87

high school

55


151


209

barber shops in prisons

185

barometric dampers

321

211

bars in sports arenas and stadiums

204


Index Terms

Links

base-mounted centrifugal circulating pumps

258

baseball stadium example

214

batch loads, heat exchangers and

285

bathing. See also central bathing areas compared to showering

37

bathroom groups hospital example work-sheets

84

86


79

80

100

107

115

142

147

149

hospital worksheet examples nursing/intermediate care/retirement homes nursing/intermediate care worksheet examples

173

bathtubs delivered hot water temperatures faucet flow rates

12 236

fill times

74

136


79

80


84

86

100

91

94

112

142

147

149

170

173

obstetrics areas

77

93

in patient rooms

73

91

107

115 hydrotherapy nursing/intermediate care/retirement homes nursing/intermediate care worksheet examples

95


156

Index Terms

Links

bathtubs (Cont.) therapy tubs

73

whirlpool baths. See whirlpool baths bayonet type U-tube heat exchangers

335

bedpan washers

73

biological growth on drains

95

113

332

biological laboratories. See laboratories birthing rooms

77

93

black and white photo processing

198

bladder-type expansion tanks

343

blade immersion elements

300

blocked flues

322

blood removal hospital laundry example

222

on prison uniforms

188

Bloodborne Pathogen law

188

blowdown valves for fixed orifices and venturis body showers

245 128

boilers combination heating/ DHW boilers

33


334


135

Index Terms

Links

booster heaters controls

306

defined

297

308

dishwashers

48

64

hospital food services

74

112

nursing/intermediate care facilities

137

prison kitchens

185

recovery times and

187

67

Boyle’s law

351

bradley wash fountains

211

See also wash fountains branches in heat trace systems

270

break rooms in sports arenas and stadiums

209

Breese, James L.

xix

bronze pump fittings

258

Btu/h ratings

33

building management systems in sports arenas building movement

205 207

building occupants. See populations bundle assemblies approach temperature and

283

U-tube removable bundles

282

burners for water heaters

319

burns from hot pipes

259


Index Terms

Links

burns from hot water. See scalding business travelers’ hotels

60

bypass systems, considerations for

69

Byrley, Tom

14

Byron, R. C.

xix

61

C cable end termination. See termination cafeterias in schools

52

calculations. See equations can washers grocery stores

227


92


79

80


84

86

103

119

122

123

142

147

149

168

171

hourly demand

65

nursing/intermediate care/retirement homes nursing/intermediate care worksheet examples school kitchens

48

capillary tubing for heat pump water heaters car washes in schools carbon matrix heating elements

326 46 267

carbon monoxide, blocked flues and

322


108

Index Terms

Links

carbon steel sheets in heat exchangers

285

Carpenter, S. C.

37

cart washers hospital example work-sheets

84

86

103

119

122

123


74

92

96


79

80

137

142

108


147

149

154

156

157 nursing/intermediate care worksheet examples

168

171

prison kitchens

187

cassettes (welded plates)

287

CCUs (critical care units)

xxi

111

cell pods in jails

181

185

center flues

313

central bathing areas 48-bed nursing care facility example

159


162

hospitals

73

91

137

152


157 nursing/intermediate care worksheet examples obstetrical use

170

176

77


Index Terms

Links

central hot water systems sports arenas and stadiums central hot water temperature

207

212

206

central sterile supply areas 32 -bed hospital example

95


113

considerations

76


92

usage factors

90


82

83

106

122

worksheet examples central systems for schools central utility generating facilities

98

109

47 190

197

centrifugal circulating pumps

258

ceramic barriers in plate-type heat exchangers channel flues

285 316

check valves on loops

245

steam water heater piping systems

339

chemical laboratories. See laboratories chemical processing plants

190

196

12

187

chemical sanitizing dishwashers chevron corrugation

285

children locker rooms for

129

peak demand and

22


124

Index Terms

Links

chimneys

324

churches

225

circuit breakers heat pump systems

332

heat trace systems

267

273

273

274

circuit length in heat trace systems circular wash stations

191

circulating pumps baptistries

226

centrifugal circulating pumps

258

in circulation systems

239

controls

258

flow rates

257

head capacity of

257

in-line centrifugal circulating pumps

258

lack of in heat trace systems

266

return pipes and

257

sizing

249

steam water heater systems

341

for vertical storage tanks

207

circulation rate examples

339

254

circulation systems. See recirculating hot water systems Cix, J. B.

37

classrooms religious facilities schools

226 46

49

52


Index Terms

Links

clean rooms in pharmaceutical plants

195

clean utility rooms hospitals

73

94

111

nursing/intermediate care facilities “clean” work

135 191

194

74

92

cleaning hydrotherapy tubs therapy rooms

128


283

cleanliness of streams in heat exchangers cleanouts on storage tanks

281 315

cleanup activities fast-food restaurants

228

grocery stores

227

kitchen cleanup time periods office buildings

64

66

229

clinic sinks. See flushing rim sinks clip gaskets

287

closed systems dangerous water pressures

343

recirculating systems

258

clothes washers. See also laundries baseball team locker room examples

214

capacity

221

high schools

215

217

54


Index Terms

Links

clothes washers (Cont.) hospital example work-sheets

84

hotel laundries

68

jailusage

86

183

nursing/intermediate care facilities schools sport arenas and stadiums student dormitories

138 49 209 41

club house laundries

203

coal processing plants

196

codes. See standards and codes coefficient of linear expansion

349

coefficient of volumetric expansion

349

Cohen, Arthur

262

coin-operated laundries

39

354

40

cold formed sheets in heat exchangers

285

cold leakage

288

cold showers

197

cold water. See incoming cold water supply Cold Water Systems

261

color photo processing

198

column showers

209

combination aquastat/time clock controls

259

combination heating/DHW boilers

33


Index Terms

Links

combination upfeed/downfeed circulation systems

241

combustion air requirements thermal efficiency and

207 4

commercial dishwashers commercial spray-type dishwashers

12

conveyor dishwashers

50

demand

65


79

80


84

142

55

65

67

86

103

119

147

149

50

55

nursing/intermediate care/retirement homes nursing/intermediate care worksheet examples

168

recovery and

67

school kitchens

48


211

commercial facilities, circulation systems for

239

commercial heat pump water heaters

325

326

commercial laundries gathering information

221


208

211

12

206

water temperatures commercial water heaters defined

297

storage tank gas water heaters

313


Index Terms

Links

Comparison of Collected and Compiled Existing Data on Service Hot Water Use Patterns

38

57

compatibility of heating mediums

281

compressors electric

327

heat pump water heaters

325

concessions areas in arenas

203

concrete plants

198

205

206

concurrent usage hospital areas

77

schools

49

condensation dew points and

206

drains for, in heat pump systems

331

gas-fired water heaters and

15


282

condensors heat pump systems

331

heat recovery systems

330

condo hotels

61

condos. See multifamily buildings connection points, storage volume and

16

conservation laws

37

contaminated laundry

76

188


209

Index Terms

Links

contamination cross-contamination in heat exchangers

284

in nuclear power plants

197

continuous duty systems, heat exchangers and

285

continuous flow demand

6

contraction indirect fired water heaters

293


283

control circuits

306

controls booster heaters coverage in this manual domestic hot water systems

306

308

1 15

electric water heaters

303

heat pump systems

332

recirculating pumps

258

convection plate-type heat exchangers

285

tank heaters and

283

convenience stores

226

329

convention hotels and motels average occupancy

61

considerations

70

defined

59

food service example

65

guest room example

62

conventional, iron bodied pumps

258


Index Terms

Links

conventional water heating systems

17

conveyor dishwashers. See commercial dishwashers cooling functions of heat pumps copper coils, pH values and

327

328

329

295

Copper Development Association Copper Tube Handbook

262

Historical Perspective of Corrosion by Potable Waters in Building Systems

262

copper piping expansion

349

hard water and

312

in heat trace systems

267

time delays and

235

water velocity and

244

copper sheaths

302

Copper Tube Handbook

262

237

303

correctional facilities. See prisons corrosion indirect fired water heaters

293

instantaneous indirect water heaters

295

pump fixtures

258

steam feedback systems

336


330

Index Terms

Links

corrosion (Cont.) storage tanks

314

welded plate and frame exchangers corrugation in plate units

288 285

costs delays in hot water and

238

heat exchangers

284

288

heat pumps

328

331

life-cycle costs

278

oversizing and

37

payment for hot water and demand

25

countercurrent

281

CPVC piping

235

237

critical care units (CCUs)

xxi

111

cross-contamination in heat exchangers

284

crossover bypass systems

69

CT scan rooms

95

cupro-nickel components

114

312

customized sizing for multi-family buildings

28

D daily water demand multifamily buildings

19

peak flows and

26

dairies. See food product facilities This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

Danenhauer, Greg

xix

dark rooms

112

Daugherty, Larry

xix

198

204

day-care facilities office buildings

229


226

dead-end hot water branches Decioco, J.

234

245

37

decontamination chemical processing plants

196

nuclear power plants

197

dehumidification, heat pumps and

327

328

delays in hot water. See also lag time dead-end branches and

245

heat trace systems and

266

hospital user group information low flow fixtures and

270

275

72 235

piping types and diameters table

237

recirculating hot water systems and

234

results of

238

steam water heaters and

333

time to tap defined

278

delivered hot water temperature recommendations

12


Index Terms

Links

demand commercial laundries

221

delays in hot water and

238

football stadium example

211

heat trace system fixtures

270

high school systems

57

hotel guest rooms

60

monitoring in existing systems

28

multifamily building determination

24

patterns in multifamily buildings

19

pay-as-you-go systems and

25

school calculations

49

special use facilities

35

demographic profiles. See populations density of population

23

dental clinics in office buildings

229

department stores desk phones in hotels

228 60

dew points condensation and

206

gas-fired water heaters and

15

DeWerth, D. W.

38

DHW (domestic hot water)

xxi

DHW Modeling

37

57


Index Terms

Links

DHW System Sizing Criteria for Multifamily Buildings

37

diameters of piping, time delays and

237

Diamond, R.

38

diaphragm expansion tanks

343

diaphragm mixing valves

337

352

dietary and food services grocery stores

227

hospitals 32-bed hospital example

94


112

considerations

74


92

requirements table

87

usage factors

89

worksheet examples

82

83

119

124

59

64

136

151

hotels

97

103


156

48-bed nursing care facility example

159


162

worksheet examples

168

office buildings

229

schools

47


130

water temperatures for

75

176

50

206


109

Index Terms

Links

differential pressure diaphragm mixing valves

337

steam feed-forward systems

336

diluting flue gases

321

dip tubes

300

direct fired water heaters “dirty work

315

316

194

196

318

4 191

dishwasher prerinse. See pre-rinse sinks dishwashers apartments in retirement homes delivered hot water temperatures flow rates

139 12 236

high schools

54

55


84

86

103


74

92

112

instantaneous indirect water heaters and

295

jail usage

182

manufacturer’s data

64


136

156

prison kitchens

185

187


225

retirement apartments

158

school classrooms

49

school kitchens

47

small hospital example

94


209

steam water heaters

333

50

52


53

Index Terms

Links

dishwashers (Cont.) student dormitories disinfectors

41 95

113

122


84

86

106


79

80

disposable tableware

48

distances from water heater to fixtures

233

distributed hot water systems

208

district-supplied steam

334

diverting valves

340

Domestic Hot Water Consumption in Four Low Income Apartment Buildings domestic hot water (DSH)

38 xxi

codes and standards

16

controls

15

delivered hot water temperature

12

high altitudes and

4

mixed water temperatures

6

recovery. See recovery periods relief valves

15

safety and health concerns

13

specific applications. See under names of specific applications (i.e., hospitals, jails, hotels and motels) steady-state heat balance formula

3


Index Terms

Links

domestic hot water (DSH) (Cont.) storage and recovery

15

system alternative considerations

17

thermal efficiency

4

thermal expansion

15

Domestic Hot Water Loads, System Sizing and Selection for Multifamily Buildings

37

Domestic Hot Water Service in Lumley Homes

37

donut configurations, heat trace systems and

272

door types of dishwashers

50

dormitories heat trace system plans

277

institutional dormitories

42

student dormitories

39

double bunking in jails

181

186

double compartment sinks. See 2-compartment sinks double tank indirect fired water heaters

292

double-wall heat exchangers defined

284

double-wall plate and frame exchangers

287

double-wall protection

279

heat pump systems

331

doughnut configurations, heat trace systems and

272


Index Terms

Links

downdrafts draft hoods and

323

gas venting systems and

322

downfeed hot water systems

240

draft diverters

321

draft hoods

321

draft regulators

321

drain cocks

298

draining tanks

315

drains for heat pump systems

331

241

315

332

drawdowns laundry equipment

68

sinks

66

drawings

273

drilled port burners

320

dry firing

303

DSH. See domestic hot water PSH) ductwork for heat pump systems

331

“dump” loads indirect fired water heaters

293

showers as

193

dumping water. See water conservation duration shift-end wash-up

192

shower turnaround time

210

showers Dutt, G.

62

181

185

37


Index Terms

Links

E ease of access to equipment

281

educational laboratories. See laboratories The Effects of Hot Water Circulation Systems on Hot Water Heater Sizing and Piping Systems

262

efficiency heat pumps thermal

328 4

260

286

288

75

92

327

330

booster type

297

306

components

298

elastomer gaskets electric flash sterilizers electric heat trace systems. See self-regulating heat trace systems electric resistance hot water heaters electric water heaters

continuous flow controls heat recovery

308

6 303 5

storage type

297

voltage and phase

207

electrical terminals on immersion elements

300


Index Terms

Links

electricity heat pump usage

327

heat trace systems

267

as heating medium

185

280

elementary schools

45

52

Ellis, L. Richard

xix

emergency eyewashes

204

209

emergency medical clinics in prisons

185

emergency operations in surgical suites

75

emergency rooms (ERs)

xxi

95

111

emergency showers in sports arenas

204

end termination

273

energy codes for sports arenas

205

energy conservation 100 ft. length criteria and

234


265

266

problems with inadequate hot water systems

233


336

Energy Conservation in New Building Design

261

Energy Conservation in Plumbing Systems

262

Energy Efficient Design of New Low Rise Residential Buildings

261

Energy Use and DHW Consumption Research Project

37


113

Index Terms

Links

Engineering Plumbing Design

262

entrapped air in recirculating systems

259

EPDM (ethylene propylene diene monomer)

xxi

286

equations absolute pressure

352

circulation rate example

254

demand baseball team locker room examples elementary schools football stadiums

215

218

53 212

high school shower usage

55

hospital laundries

222

hotel guest rooms

62

hotel laundries

68

jail shower usage

181

prisons

186

sports arena shower usage student dormitories

210 41

expansion Boyle’s law

351

materials expansion

349

tank materials

348

354

water expansion

346

354

heat recovery, electric water heaters

5


Index Terms

Links

equations (Cont.) heat transfer mixed water temperatures piping heat loss

68 6 252

probable occupancy rates

31

steady-state heat balance

3

steam water heaters

341

storage tank sizing

183

thermal efficiency (R factor)

4

260

equipment electric water heaters

297

expansion tanks

343

heat exchangers

279


325

indirect fired water heaters

291

instantaneous gas heaters with separate tanks

311

manufacturers’ information

231

recirculating domestic hot water systems

233

self-regulating heat trace systems

265

steam water heaters

333

sterilization

76

93


313

washers and sterilizers

195

equipment ratings

34

erosion, velocity

244

ERs. See emergency rooms This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

(ERs) Estimating Hot Water Use in Existing Commercial Buildings

37

ethylene propylene diene monomer (EPDM) evaporator coils

xxi

286

332

evening peak demand multifamily buildings

22


130

events at sports arenas

204

examples 32-bed hospital

93

48-bed nursing/intermediate care/retirement home

158

300-bed hospital

111

baseball stadium

214

circulation rate

254

continuous flow for electric water heaters

6

direct gas-fired heat input rates elementary school

5 52

expansion tanks

353

football stadium

211

foundry facility

193

high school hospital laundry

54 222

hotel food service

65

hotel guest room

62


Index Terms

Links

examples (Cont.) hotel laundry service

68

institutional dormitory

42

jail

181

materials expansion

349

nursing/intermediate care/retirement home

147

prison

184

shower mixed water temperatures special use housing facility steady state heat balance steam water heaters student dormitory

7 35 4 341 39

traditional multifamily building water expansion

31 348

expansion. See also thermal expansion expansion joints of schools

206 49

expansion tanks Boyle’s law

351

defined

343

examples

349

material expansion

348

types

343

use of

15

water expansion formulas

353

346

experimental laboratories. See laboratories This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

An Experimental Study of Competing Systemsfor Maintaining Service Water Temperature in Residential Buildings external channel flues

262 313

extracurricular activities

48

eyewashes, emergency

204

317

209

F factory preset automatic flow control valves

247

families. See also multifamily buildings family changing areas

129

spas and health club usage

130

heat pumps

327

refrigeration units

332

fans


228

faucets. See also fixtures and fixture outlets infrared faucets

205

metering faucets

205

non-metering faucets

236

FDA (Food and Drug Administration)

236

194

feed-forward units components

336

point of usage installation

338

recirculation systems

339

steam water heaters

333


Index Terms

Links

feedback units steam water heaters

333

types

335

Fehrm, Al

262

fertilizer storage rooms

209

334

fiberglass insulation heat trace systems

267


275

fiberglass insulation thick-nesses

269

275

74

91

156

204

209

250

fill times for hydrotherapy tubs first aid rooms in sports arenas first-degree burns fixed orifices in flow balancing

13 245

fixtures and fixture outlets apartments in retirement homes delivered hot water temperatures

139 12

distances between heater and

233

flow rates table

236

gathering data for requirements

47

hospital user groups

72

kitchens

64

school general purpose

49

78

spas, pools, health clubs, and athletic centers

128


205

temperature at

6

usage patterns

72

130

78


Index Terms

Links

fixtures and fixture outlets (Cont.) worksheets for flanges on immersion elements flash sterilizers

140 300 75

92

313

317

95

112


79

80

111


84

86

100

108

115

142

147

149

165

171

175

floating tank external flues floor receptors

95

nursing/intermediate care/retirement homes nursing/intermediate care worksheet examples flow baffles, U-tube removable bundles and

282

flow balancing devices and valves balancing systems

244

balancing valves

245


239

248

factory preset automatic flow control valves

247

fixed orifices and venturis

245

flow regulating valves

248

friction losses and

257

memory stops

248

as not needed in heat trace systems

272

recirculated hot water systems

244

steam water heater piping systems

339


112

105

Index Terms

Links

flow rates clothes washers

221

daily water patterns in multifamily buildings

21

dormitory fixtures

40


245

fixtures and appliances table

236

head capacity of circulating pumps and in heat balance formula hospital user group information recirculation pumps showers

257 3 72 339 48

51

158

210

sterilization equipment

76

93

storage volume and

16

therapeutic facilities

128

worksheets flow restrictors in prisons

77

78 184

flue gases condensation and

206

mixture control

321

thermal efficiency and

4

flues flue routing

207


313

venting systems

321

fluid treatment facilities

190

198


93

Index Terms

Links

flush port burners

320

flushing rim sinks

73

95

central sterile supply

113


79

80


84

86

100

108

115

121

142

147

149

165

171

93

113

nursing/intermediate care/retirement homes nursing/intermediate care worksheet examples obstetrics area outpatient surgery

113

surgical suites

112

flywheels in steam water heater systems

340

fonts, baptismal

225

Food and Drug Administration (FDA)

194

food kiosks in student dormitories

39

40

food processing facilities and activities design issues

194


228

food product facilities

196


295

steam water heaters

333

food product facilities dairy heat recovery systems

329

defined

190

design issues

196


105

Index Terms

Links

food service. See dietary and food services football stadium example Force, F. forced convection

211 38 283

formulas. See equations fossil fuel plants

190

fouling process in heat ex-changers

288

foundries

190

Frankel, Michael

xix

Freehill, Mina

xx

197

193

freezing areas subject to

207

heat pump installations and

328

heating cables for freeze protection

267

freon in indirect fired water heaters

291

friction loss and circulating pumps

257

full-condensing equipment

17

full-service kitchens

48

fuses for heat pump systems

332

G gage pressures equations

352

gases

351


Index Terms

Links

gallons per hour (gph) in heat recovery equations in


5 88

laundry demand

221

worksheets

140

gallons per minute (gpm) in heat trace system fixtures in


270 88

hospital user group totals worksheets

81


78

worksheets

84

86

140

gallons per pound in laundry demand

221

gas flues. See flues gas input ratings

320

gas shut-off valves

315

gas water heaters burners condensation and

319 15

dip tubes

315

flues and heat exchangers

313

318


311


313

tank fittings

314

tanks

314

venting systems

321

318


Index Terms

Links

gases flame patterns flue gases

319

320

4

as heating medium

280

volume of

351

gasketed plate units

285

288

hospital examples

96

115


74

hospital laundries

75


72

hospital worksheets

78

hotel food service

64

hotel guest rooms

60

hotel laundries

67


jails

181

laundries

221

91


134

156

nursing/intermediate care facility example obstetrics/nursery areas

161 77

prisons

185

retirement homes

157


127


204

general occupancy hotels

60

61

See also hotels and motels This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

general purpose demand in schools

49

53

54

generation rates, capacity and

30

generation systems in apartment buildings geographical variances in demand

34 25

geothermal energy as heating medium glass barriers in heat exchangers glassware sanitizers

280 285 12

195

globe valves

339

glueless gasket designs

287

Goldner, Fredric S.

xix

37

95

113

grocery stores

226

331

grounds services in arenas

203

group wash fountains

192

gph. See gallons per hour (gph) gpm. See gallons per minute (gpm) gravity sterilizers

193

guest rooms examples

62

hotel types

59

multiple systems design

69

gym classes

46

gymnasiums

226

48

55


57

Index Terms

Links

H hand sinks central sterile supply central sterile supply areas

113 95


228

grocery stores

227

high demand hospital areas

73

high schools

55

hospital food service

112

hospital utility rooms

73

kitchens

50

52

53

miscellaneous hospital areas

77

nurses’ stations

89

94

135

138

nursing/intermediate care facilities obstetrics areas prisons temperatures hands/elbows/arms tubs

90 184 75 94

112

159

hard water heat pump systems and

332


312


334

hastelloy

285

HBV (hepatitis B virus)

xxi

188

head. See pressure This page has been reformatted by Knovel to provide easier navigation.

225

Index Terms

Links

head assemblies

282

health clinics. See medical and health clinics health clubs calculating demand

130


127


128

in office buildings

229

health concerns

13

71

approach

280

288

codes and standards

279

countercurrent

281

defined

279

flues as

313

in heat pump water heaters

325

heating mediums

280

indirect fired water heaters as

291

selection factors

288

steam water heaters

334

temperature cross

281

terminology

280

types

281

heat exchangers

340

heat loss equations

252


250

required circulation rate example

254

storage tanks

255

256


Index Terms

Links

heat pump water heaters applications

330

benefits

328

considerations

17

criteria

331

defined

325

drawbacks

328

energy sources for

327


329

incoming water quality

332

integral heat pump water heaters

326

maintenance

332

remote heat pump water heaters

327

requirements

331

safety controls and devices

332

heat recovery. See recovery periods heat trace systems. See self-regulating heat trace systems heat transfer flues and hotel laundry demand plate-type heat exchangers time rates for turbulence and

313 68 285 3 286


Index Terms

Links

heating cable systems approved systems

267

heat trace systems

265

illustrated

268

plumbing drawing indicators

273

selecting cables

274

heating mediums

266

269

280

Henriques, V. C. Jr.

13

hepatitis B virus (HBV)

xxi

herringbone corrugation

285

188

high altitudes DSH systems and gas burners and high-demand facilities

4 321 35

high-efficiency water heating systems considerations

17


30

“high end” hotels high limit safety devices

70 298

303

high population density in multifamily buildings

23

high schools defined

45

examples

54

kitchen demand

55

shower demand

55

system selection factors

56

hip/leg tubs

94

112

159


Index Terms

Links

Historical Perspective of Corrosion by Potable Waters in Building Systems

262

HIV (human immune deficiency virus)

xxi

holding kitchens

48

home team locker rooms

203

horizontal draft hoods

322

188

214

horizontal mains in heat trace systems

276

horizontal slot port case burners

320

horizontal-to-vertical draft hoods

322

horizontal water tanks storage capacity stratification

207 16

hose stations grocery stores

227


79

80


84

86

119

122

142

147

168

171

103


149

nursing/intermediate care worksheet examples hospitals 32-bed example

93

300-bed example

111

heat trace maintenance temperature table

274


108

Index Terms

Links

hospitals (Cont.) heat trace system plans

276

277

instantaneous indirect water heaters kitchen hot water requirements table laundries

295 87 222

safety and health concerns

71

user group example work-sheets

84


81

user group worksheets

78

user groups defined

72

hot tubs

295

61

Hot Water and Energy Usein Apartment Buildings

38

hot water multiplier in hospital worksheets in mixed water temperatures

82

83

109

61

70

7

in nursing/intermediate care worksheets

176

hotels and motels classifications of

59

design considerations

70

food service

64

guest rooms

60


274

heat trace system plans

276

laundry service

67

resorts

60

steam water heaters

333


124

Index Terms

Links

hotels and motels (Cont.) system considerations

69

hourly consumption figures hotel kitchens

65

multifamily buildings

27

hourly number of therapies

74

91

137

154

hours of operation central bathing areas

157

central sterile supply areas

92

food service

64

hospital laundries

92

hydrotherapy units

74

91

136

156

laundries

76

138

139

158

92

222 sterile supply areas

76

surgical suites

75

therapeutic facilities

92

129

human immunodeficiency virus (HIV)

xxi

188

HVAC ductwork, heat trace systems in

265

hybrid systems considerations

17


30

hydro showers

128

hydrotherapy 32-bed hospital example

94


159


112


Index Terms

Links

hydrotherapy (Cont.) gathering information

91

hospital requirements

73

96

161

152

153

nursing/intermediate care/retirement homes school requirements

136 48

sport arenas and stadiums

209

tub temperature

129

usage factors

79

80

89


82

83

109

124

86

102

117

147

149

176 worksheet examples

84 167

hydrotherapy tubs football stadium example

212


142


211

worksheet examples

167

hypalon

286

I ice machines, heat pumps and

327

ice rinks heat recovery systems

329

resurfacing

205

ICVs. See intensive care units (ICUS)


Index Terms IEW 90.1 standard (ASHRAE) immersion controls

Links 16 305

high limit safety devices

305

storage tank fittings

315

318

immersion elements construction and operation

300

storage tanks

298

immersion well remote bulb thermostats

305

Impact of Water Conservation on Interior Plumbing

262

in-line centrifugal circulating pumps

258

incoloy sheaths

302

303

incoming cold water supply heat pump systems laundries and in mixed water temperatures

332 40 6

pressure differences in steam feed-forward systems

336


314

318

in storage tank indirect water heaters

291

temperature and approach

280

temperature of

222

incoming hot water supply in steady-state heat balance formula

3

supply in mixed water temperatures

6


Index Terms

Links

indirect fired water heaters defined

291

as heat exchangers

291


293

storage tank types

291

water conditions

295

indoor ice rinks

329

industrial facilities. See also specific types of facilities areas of demand

191

circulation systems for

239

“clean” and “dirty work

191

defined

188


190

example

193

selecting water heaters

192

showers

192

steam water heaters

333

storage tanks

194

types of

188

wash stations

191

194

194

industrial laundries gathering information

221

in prisons

188

industrial water treatment plants

190

infrared faucets

205

198

initial costs heat exchangers

288


Index Terms

Links

initial costs (Cont.) heat pumps

328

initial fills for sinks

66

initial pressures in expansion tanks

351

initial volumes air cushions in expansion tanks

351

initial system volume of water

346

inlet air orifices in burners

319

inlet fittings

298

inmates double bunking

181

186

lavatories and showers

184

186

redundancy in systems and

185

showers for

180

inns. See hotels and motels input energy in thermal efficiency formulas

4

input water. See incoming cold water supply insertable pressure measuring devices

248

instantaneous systems apartment building example baptistries

32 226

gas heaters with separate tanks

311

group wash fountains

193


293


Index Terms

Links

instantaneous systems (Cont.) industrial facilities usage

192

instantaneous-coil-in-a-boiler water heaters multifamily buildings

294 30

point-of-use heaters

242


335

steam water heaters

333

tankless coil systems

32


295

42

institutional laundries delivered hot water temperatures gathering information

12 221

insulation gas water heaters

316

heat trace systems

267

piping

250


259

269

275

275

sports arena and stadium piping

207

vent pipes

321

Insulation

262

integral heat pump water heaters intensive care units (ICUs) example hand washing demand

326

331

xxi 111 73

intermediate care facilities 48-bed facility example

158

central bathing

137

159


Index Terms

Links

intermediate care facilities (Cont.) defined

133

dietary and food service

136


156

161

hydrotherapy

136

159

kitchen requirements table

151

laundries

138

miscellaneous areas

160

nurse’s stations

135

159

resident areas

135

158

usage factors

152

user group analysis

135

worksheet examples

140

147

worksheet totals

144

176

313

316

internal (center) flues

160

165

Internal Corrosion of Water Distribution Systems

262

internal fusing in wiring circuits

305

306

International Association of Plumbing and Mechanical Officials

262

iron bodied pumps

258

isolation rooms

73

isolation valves feed-forward steam systems

337

heat pump systems

331


Index Terms

Links

J jails auxiliary equipment

182


179

examples

181


181

heat trace system plans

276

life cycle of

180

janitors’ closets

46

277

203

janitors’ receptors. See floor receptors Johnson, Peter J.

xix

junior high schools

45

Justin, Lawrence G.

xix

K kitchen sinks flow rates

40

hospital user group usage factors

79

80

care/retirement homes

142

147


211

nursing/intermediate

student dormitories

41

user group example work-sheets

84

86

103

119

worksheet examples

149

168

kitchens cooling functions of heat pumps

327


Index Terms

Links

kitchens (Cont.) demand hospital requirements table

87


79

hotel example

65

jails and prisons

80

180


136

151

prisons

184

187

schools

46

47

50

205

209

55

57 small hospital example sports arenas and stadiums gathering data for requirements

94 203 47


274

multiple kitchens

64


69

residential

42

water temperature Kokko, J. P. Konen, Thomas

43

206 37 262

L L/h. See liters per hour (L/h) labels in heat trace systems

269

laboratories

197

defined

190

in hospitals

77

91

93


99

Index Terms

Links

laboratories (Cont.) pharmaceutical plants

195

sinks

195

testing laboratories

198


82

83

lag time. See also delays in hot water feed-forward systems

336

instantaneous steam feedback systems

336

steam feedback units

335

large apartment buildings

31

large hospitals

111

lateral runs in vents

324

laundries delivered hot water temperatures

12

demand apartment buildings

36

coin-operated

39

40

hospital considerations

75

92

113

222


79

80

hospital worksheets

84

86

hotels and motels

67


42

hospital example

jails

98

43

180


138

157

160

nursing/intermediate care worksheets

176


295

Index Terms

Links

laundries (Cont.) prison industrial laundries

188

prisons

180

184

185

188


139

155

158

164

208

209

163

221

174 schools

46


130


203

student dormitories

39


98


274


295

manufacturer specifications

68


69

recover requirements

222

steam water heaters

333

storage tanks

222

wash cycles

40

75

222

baseball team locker room examples

214

215

217

flow rates

236

laundry tubs


79

80

142

147


171

174


211


149



Index Terms

Links

lavatories delivered hot water temperatures

12

demand

87

baseball team locker room example hospital usage factors

214

215

79

80

107

115

42

43

180

184

50

151

142

147

88

94

217

hospital worksheet examples institutional dormitories jails and prisons kitchens nursing/intermediate care/retirement homes patient areas

149

resident areas in care facilities

135

schools

49

52

209

211

sport arenas and stadiums staff toilets

73

student dormitories

41

54

user group example worksheets

84

flow rates

40

maximum flow rates

236

steam water heaters

333

86

leaks cold leakage

288

copper piping

244


173

Index Terms

Links

Legionella Pneumophila (Legionnaires’ Disease)

14

length of branches delays in hot water and

234

in non-heat traced systems

270

life cycles costs

278

instantaneous indirect water heaters lime deposits

295 294

300

See also scaling linear expansion

349

linings for storage tanks

284

298

liquid petroleum gas (LPG),

xxi

330

314

liters per hour (L/h) in heat recovery equations

5

laundry demand

221

worksheets

140

LMH factor (low, medium, and high)

xxi

apartment building example

32

applying

26

multifamily building demographics

23

peak and maximum demands

25

33

small, medium and large apartment buildings

31

special use facilities

35

load calculations alternative systems

17


32

load lag flywheels

34

340


Index Terms

Links

loads per hour hospital laundries

75

92

care laundries

138

157

retirement home laundries

139


local plumbing codes

16

locker rooms hospitals

96

114

industrial facilities

191

shower rooms

129


203

214

75

92

surgical suites loops check valves on

245

isolating portions of systems

244

lounges

160

low, medium, and high. See LMH factor (low, medium, and high) low-flow fixtures heat trace systems and

265

hot water delays and

235

low-pressure steam

337

LPG (liquid petroleum gas),

xxi

271

330

M magnesium oxide immersion elements

300

magnetic resonance imaging machines

114


Index Terms

Links

main lines heat trace systems

270

in heat trace systems

276

maintenance accessibility of heat exchangers

281

ease of access to equipment

281


245

gasketed heat exchangers

287

heat pump systems

332

nursing/intermediate care systems planning for repairs sports arenas and stadiums

163 40 207

storage tank draining and cleaning

315

therapy room systems

128

maintenance areas hospitals

77

91

93

99 nursing/intermediate care systems

138

retirement homes

140

157

makeup water for feed-for-ward steam systems malls

337 228

management systems for sports arenas

205

manholes

315

manicures

128

manual pump controls

258

129


96

Index Terms

Links

manufacturing facilities

188

massage therapy

128

194

meals. See also dietary and food services number of

74

92

136

156

nursing/intermediate care facilities meat processing facilities mechanical circulation, stratification and

194 16

mechanical draft inducers

321

Meckler, Milton

262

medical and health clinics first aid rooms in sports arenas

204

office buildings

229

prisons

185

schools

46

shower rooms

209

129

medical patients

72

medication rooms

73

94

111

medium-sized apartment buildings

31

meeting rooms hotel types religious facilities

59 226

melt down in immersion elements

303

memory stops on valves

245

metal barriers in heat ex-changers

285

metering faucets

205

248

236


135

Index Terms

Links

Mettelstaedt, Bernie

xix

Meyer, Randy

xix

mid-sized apartment buildings

31

middle schools

45

Miller, Julius E.

xix

Milligan, N. H.

37

mineral facilities

196

mineral salt baths

129

mining facilities

190

38

miscellaneous areas hospitals 32-bed hospital example

95


113


93

usage factors

91

99

worksheet example totals worksheet examples

82

83

108

123

138

157

109

124

158

164

nursing/intermediate care 48-bed nursing care facility example

160


163

user groups

152

154


176

worksheet examples

171

retirement homes

140

155

175 miscellaneous facilities

225


Index Terms

Links

mixed water temperatures calculating in heat loss equations hydrotherapy jails showers sports arenas and stadiums tables and equations tempering devices

56 253 74 181 51 206 6 69

mixing tubes or areas in burners mixing valves

319 337

Mixing Valves and Hot Water Temperature monel

262 285

mop sinks

41

49

morgues

77

91

considerations

93


99


82

Moritz, A. R.

83

13

morning peak demand multifamily buildings

21


130

22

motels. See hotels and motels movement of buildings

207

MRI machines

114

Mulder, Bernie

xix

multi-loop immersion elements

300


Index Terms

Links

multifamily buildings centralized systems

25

circulation systems for

239

demand determination

24

demographic profiles

23

examples

31

35


274

laundries in

36

LMH factor and

26

patterns of demand

19

peak vs. average demand

26

potential traps

36

retrofitting

28

steam water heaters

333

multifunction full-condensing equipment

17

multilevel facilities

276

multiple flues

313

multiple game events

204

3

17

multiple stamped ribbon ports

320

multiple systems high school considerations

56

hospital user group totals worksheets

81

hotels

69

schools

47

multiple temperature systems

272


Index Terms

Links

N National Board of Boiler and Pressure Vessel Inspectors (NBBPVI)

15

National Electric Code (NEC),

xxi

17

xxi

17

National Fire Protection Association (NFPA) National Fuel Gas Code

324

National Sanitation Foundation (NSF)

xxi

natural convection

283

natural gas heat sources

185

16

330

NBBPVI (National Board of Boiler and Pressure Vessel Inspectors)

15

NEC (National Electric Code),

xxi

Neeck, James T.

xix

neonatal intensive care

113

net expansion of water

354

17

New Information on Seruice Water Heating

261

New Methods for Analyzing Hot Water Systems

262

NFPA (National Fire Protection Association)

xxi

17

nichrome (nickel chrome)

301

302

NICU (neonatal intensive care)

113

nighttime peak demand

22

nitrile rubber (NR)

xxi

non-metering faucets

236

303

286


Index Terms

Links

nonambulatory patients bathing tubs for

137

central bathing areas

157

nonurban hotels noon-time demand in spas

152

154

61 130

nourishment rooms hospitals

73

nursing/intermediate care facilities NR (nitrile rubber)

135 xxi

286

NSF (National Sanitation Foundation)

xxi

nuclear power plants

197

nurseries. See obstetrics/ nursery areas nurses’ stations 32-bed hospital example

94


159


111

characteristics

73


91


89


82

96

156

161

83

101

109

152

153

156

124 nursing/intermediate care/retirement homes

135 159


166

176


Index Terms

Links

nursing care facilities 48-bed facility example

158

central bathing

137

defined

133

dietary and food service

136


156

159

161


274

hydrotherapy

136

159


151

laundries

138

miscellaneous areas

160

nurses’ stations

135

159

resident areas

135

158

usage factors

152

user group analysis

135

worksheet examples

147

165

worksheet totals

144

176

worksheets

140

160

O OB (obstetrics). See obstetrics/nursery areas O’Brien, Tim

xix

obstetrics/nursery areas 32-bed hospital example

95


113


93

obstetrics (OB)

xxi

99


Index Terms

Links

obstetrics/nursery areas (Cont.) usage factors

90


82

83

107

115

worksheet examples

109

occupancy rates in hotels

70

in retirement homes

139

in spas and health clubs

129

occupants. See populations off-peak generation heat pumps multifamily buildings office buildings

328 28 229

OHRD (Ontario Hydro Research Division)

xxi

heat pump applications

330

as heating medium

280

refineries

190

on-call rooms

94

Oil

on-demand controls

111

258

one bedroom apartments. See 1-bedroom apartments one compartment sinks. See 1 -compartment sinks Ontario Hydro Research Division (OHRD) open systems

xxi 258

operating conditions for heat exchangers

281

288


124

Index Terms

Links

ore processing facilities

190

orifices in burners

320

outdoor line insulation

260

outgoing water pressure differences in steam feed-forward systems

336

steady-state heat balance formula

3


298

temperature and approach

280

outlet fittings outpatient surgery output energy in formulas

314

318

298

314

318

95

113

4

output water. See outgoing water overlapping use

49

77

oversizing avoiding in multifamily buildings

25

costs and

37

standard methods and,

xvii

P P. See hot water multiplier pain threshold

13

pantries

185

pantry sinks

214

paper mills

196

215

218


Index Terms

Links

parents at spas and health clubs

130

particulate fouling indirect fired water heaters and

295

plate and frame heat ex-changers and

281

shell and tube devices and

282

patient areas hospitals 32-bed hospital example

93


111


72

91

96

usage factors

88

82

83

109

100

115

worksheet example totals worksheet examples nursing homes worksheet example totals

176

worksheet examples

165

Patterns of Domestic Hot Water Consumptionfor a Multifamily Building payment for hot water, demand and

38 25

37

peak demand alternative systems

17


33

hospital laundries

76


90

hospital worksheets

81


124

Index Terms

Links

peak demand (Cont.) hotels

61


43


19

25

26

remote heat pump water heaters and

327

resort hotels

60


128

sports arenas and stadium fixtures

204

student dormitories

39

surgical suites

75

time of day and

26

vs. average demand

26

Pearlman, M. pedicures

38 128

129

peel and stick labels in heat trace systems

269

pelvic exam rooms

114

perfect gases, volume of

351

Performance of Domestic Hot Water Systems in Five Apartment Buildings

37

pesticide storage rooms

209

Pete’s Plugs

248

petrochemical facilities

333

petroleum refineries

190

pH values

295

See also alkalinity of water; hard This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

pH values (Cont.) water pharmaceutical facilities

188

195

phase, electric water heaters and

207

photographic dark rooms

112

photography labs

196

physical therapy areas

89

198

204

153

physics laboratories. See laboratories pilot plants

188

pinhole leaks in copper piping

244

Pipe Sizing (ASHRAE)

261

piping expansion

259

heat loss

254

heat pump systems

328

heat trace systems

270

heating

235

348

349

331

instantaneous point of use heaters

243

insulation

250

pipe routing in sports arenas

205

steam systems

338

surface temperature

251

time delays tables

237

untraced piping

278

vent pipes

323

volumes table

350

weight of

235

259

339


Index Terms

Links

Piping Systems

261

plastic barriers in heat ex-changers

285

plate and frame heat ex-changers

285

approach temperatures and

281

precipitation and particulates

281

plate-type heat exchangers advantages

284


288

compared to other types

281

double-wall plate and frame exchangers

287

plate and frame heat exchangers

281

285

prime surface heat ex-changers

285

welded plate and frame exchangers

287

plumbing drawings

273

The Plumbing Engineer as a Forensic Engineer Plumbing Fixture Fittings

262 261

point-of-use applications defined

242

grocery stores

227

heat trace systems

270


208

temperature

206


Index Terms

Links

pools calculating demand

130


127


128


130


226

shower rooms

129

populations by apartment size

26

demographic profiles

23

density of population

23

hotel considerations

70


23

schools

47


48

130

working tenants in multi-family buildings ports in gas burners

22 319

320

Position Paper on Hot Water Temperature Limitations

261

post-birthing rooms

77

postsurgery rooms

111

93

potable water treatment plants pots and pans sinks

190

198

225

pounds per square inch gauge (PSIG) power circuits

xxi 306


Index Terms

Links

power connection kits in heat trace systems

269


273

power plants

190

power vent systems

321

197

precipitation, plate and frame heat exchangers and

281

preheating inlet water in feed-forward systems

338

laundry water supply

222

prerinse sinks central sterile supply areas

113

demand

65

food services

92


84

87

86

103

119

122 hospitals

92

112

kitchens

50

52

53

151

147

149

156

55

187 nursing/intermediate care/retirement homes

142


168

prisons

187

schools

50

52

53

prescrapper sinks

50

87

151

preset flow control devices balancing systems

244


Index Terms

Links

preset flow control devices (Cont.) preset automatic flow control valves

247

pressure Boyle's law

351

dangerous water pressures

343

equations

354

head capacity of circulating pumps

257

heat exchangers and

281


326

hospital user group information

72


312


295

kitchen usage and

137

measuring devices

248

sensing in feed-forward steam units sterilization equipment

336 76

93

pressure-balanced shower valves

209

pressure-formed sheets in heat exchangers pressure measuring devices

285 248

pressure relief valves heat pump systems standards storage tanks Price, D. C.

332 15 298

315

37


Index Terms

Links

primary air burners

319

prime surface heat exchangers

285

principal's toilets printing and publishing facilities

46 190

196

prisons design considerations

179

example

184


185

heat trace systems

274

kitchens

187

laundries

188

life cycle of

180

276

277

84

86

100

115

123


79

80


72

redundancy in systems and

185

storage tank sizing

186

work-release programs

186

private lavatories and toilets hospital example work-sheets

105


142

147

149


165


204

209

72

91

private suites in stadiums

203

209

proactive feed-forward systems

336

private patient rooms

135


156

Index Terms

Links

probable occupancy rates calculations sizing and

3

1

26

process fluids

281

professional patrons at spas

130

protective suits at chemical processing plants psig (gage pressure)

196 352

PSIG (pounds per square inch gauge), public laundries

31

public lavatories and toilets hospital example work-sheets

84

86

102

115 hospital usage factors

79


72


42

maximum flow rates

80

43

236


142

147


171

175

public restrooms

160

149


schools sports arenas and stadiums publishing facilities

49 204

209

190

196

Pumps electric

327

head capacity

257

instantaneous gas heaters This page has been reformatted by Knovel to provide easier navigation.

103

Index Terms

Links

Pumps (Cont.) with separate tanks

311

recirculation pumps

257

refrigeration units

332


335

339

types of circulating pumps

258

Pumps

262

Pumps and Pump Systems

262

purified water in sterilization

195

pushbutton self-closing control valves.

180

Q quality of water. See water quality quarter circle wash stations

191

questions. See gathering information

R R factor (thermal resistivity) radiology departments

260 95

rain, insulation and

260

raised port burners

320

raw materials processing

196

re-gasketing maintenance

287

reactive feedback units

334

ready-mix concrete plants

198

rebates, utility

328

114


Index Terms

Links

recirculating hot water systems air elimination

259

circulation systems

239

commercial, industrial, and large residential projects

239

controls

258

delays in hot water

234

flow balancing devices

245

head capacity of pumps

257

heat trace systems

242

insulation

259

length of systems

234

open and closed systems

258

point-of-use heaters

242

problems

233

pump types

258

238

243

required circulation rate example

254

return piping and pumps

249


335

steam water heaters

338

storage volume and

16

stratification and

42

water delivery methods recirculating prerinse sinks

44

238 50

87

216

219

151

recirculating pumps. See cir-culating pumps recovery periods baseball team locker room examples


Index Terms

Links

recovery periods (Cont.) electric water heaters equations football stadiums general design principles

5 63 213 15

grocery stores

227

heat pumps

328


329

hotel kitchens

67

hotels

62

immersion elements and

300

instantaneous gas heaters with separate tanks institutional dormitories laundry requirements

312 43 222

preheating laundry water supply

222

prison laundries

188

sanitizers

194

showers and

57


128


335

storage tank indirect water heaters

292

stratification and

16

recovery rooms in hospitals

112

recovery systems

329

redundancy in systems

185

refrigerants as heating medium

280


Index Terms

Links

refrigerants (Cont.) refrigerant-based water heating systems

17

refrigerant evaporators/ condensers refrigeration heat reclaim systems

288 329

See also heat pump water heaters considerations

17

grocery stores

227

refrigeration pressure/temperature controls regional plumbing codes

332 16

relationships in steady-state heat balance formula

3

relief valves standards unseating of religious facilities

15 343 225

remodeling buildings heat trace systems and

272


28

remote bulb thermostats

305

remote evaporators

327

remote heat pump water heaters

326

327

158

160

331

repairs. See maintenance resident areas 48-bed nursing facility example


Index Terms

Links

resident areas (Cont.) gathering information

161

164

135

152

156

155

157

nursing/intermediate care facilities nursing/intermediate care worksheet examples

176


226

retirement homes

139


205

173

residential dishwashers delivered hot water temperatures flow rates

12 236


79

80

hospital worksheets

84

86

117

142

147

149


173


158

residential heat pump water heaters

325

326

residential laundries delivered hot water temperatures flow rates hospital example work-sheets jails and prisons

12 236 84

86

115

142

147

149

171

174

180



117

Index Terms

Links

residential laundries (Cont.) retirement apartments

139

158

residential water heaters. See domestic hot water (DSH); equipment residents. See populations resistance of elements

302

resistance wires

300

resorts. See hotels and motels response times in steam feedback systems

335

restaurants fast-food food kiosks

228 39

heat pump systems

331


329

in multifunction buildings

40

36

in shopping malls

228

steam water heaters

333

retail spaces in multifunction buildings

36

in office buildings

229

in shopping malls

228

retired patrons at spas

130

retirement homes 48-bed example

160

defined

134


157

161


151


Index Terms

Links

retirement homes (Cont.) laundries

139

155

160

miscellaneous areas

140

155

158

resident areas

139

155

160

worksheet examples

147

173

worksheet totals

144

176

worksheets

140

Retrofit of Building Energy Systems and Processes

262

retrofitting buildings heat trace systems and

272


28

return pipes check valves and

245


239

entrapped air

259

head capacity of circulating pumps

257

insulation

260

lack of in heat trace systems

266

sizing

249

ribbon port burners

320

rinse requirements for dish-washing rise in temperature risers in heat trace systems

48 5 276

runout lines in heat trace systems

270

275


160

Index Terms

Links

S sacrificial anodes

298

314

315

safety concerns feed-forward steam systems

337

hospitals

71

scalding

13

safety controls for heat pump systems safety equipment

332 1

Salisbury, Brian D.

xix

salt baths

129

Saltzberg, Edward

xix

262

same-day surgery

95

113

xviii

xx

Sampler, Donald L. sanitization food processing plants

194

grocery stores

227

hospital laundry example

222

sanitizing dishwashers

12

75

scalding codes and

135

feed-forward steam systems

337

hospital codes and

73

safety concerns

13

scaling heat exchangers

288

heat pump systems

332


293

295

instantaneous indirect This page has been reformatted by Knovel to provide easier navigation.

318

Index Terms

Links

scaling (Cont.) water heaters and

295

lime deposits

294


334

300

schedules. See also hours of operation in prisons

185

schools calculating demand

49

elementary school example

52

expansion

49


47

general considerations

47


274

high school example

54

kitchens and food services

47

50

population

47

48

showers

48

51

steam water heaters

333

system selection factors

56

types of

45

science rooms Scott, J.Joe scraping sinks

46

49

xviii

xx

112

scrub sinks emergency rooms

95

hospital example

112


79

80

nursing/intermediate care/retirement This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

scrub sinks (Cont.) homes obstetrics area outpatient surgery

142 93 113

surgical suites

75

usage factors

90

worksheet examples

113

105

92

108

115

123 worksheets Sealine, David A. seasonal sports arenas

84

86

xviii

xx

262

205

seasonal temperatures of water

338

seasonal usage of heat pumps

330

seasonal water demand

20

secondary schools

45

security type showerheads

205

sediment

296

seismic requirements

207

self-closing valves

180

self-contained photo processors

198

self-limiting flow control car-tridges

247

48

314

332

self-regulating heat trace systems approved systems

267

circuit lengths

273

components

269

defined

242

266


272

273


121

Index Terms

Links

self-regulating heat trace (Cont.) heating cables

266

horizontal mains and supply risers

276

identifying pipes

270

insulation

275

maintenance temperatures

274

overview

265

performance variables to consider

266

piping design

275

selecting cables

274

terminology

278

water and energy conservation

265

semicircular wash stations

191

semiprivate patient rooms

91

semiprivate rooms hospital patient rooms

72

nursing/intermediate care facilities senior high schools sensors for steam water heaters

135

156

45 334

separate systems. See multiple systems Service Hot Water Systems

57

261

room examples

214

215

flow rates

236

service sinks baseball team locker

schools sports arenas and stadiums

218

49 211


Index Terms

Links

Service Water Heating

261

servicing plumbing. See maintenance sewage treatment plants

190

sheaths on immersion elements

300

198

Sheet Metal and Air Conditioning Contractors National Association (SMACNA),xxi Retrofit of Building Energy Systems and Processes

262

shell and tube devices advantages

282


288

cleanliness of stream and

281

compared to other heat exchangers

281

double-wall heat exchangers

284

feed-forward steam systems

337

steam water heater systems

340

tank heaters

283

TEMA (Tubular Exchange Manufacturers Association) standards

280


282

shift changes industrial plants

190

nurses’ stations

89

wash-up duration

153

192


Index Terms shop rooms in schools shopping malls

Links 46 228

short-circuited water in loops

244

showerheads in calculations

51

hotel demand and

62

maximum flow rates

236

security type shower-heads

205


211

showers calculating demand

210

compared to bathing

37

delivered hot water temperatures

12

demand baseball team locker room examples

214

emergency showers

204


212

217

high schools

55

hospital locker rooms

92

112


79

80

90

100

105

107

121

123

hospital worksheets

84

86

hotels

59

61

hydrotherapy areas

74

92


191

192

42

43


institutional dormitories jails and prisons

180


115

Index Terms

Links

showers (Cont.) nursing/intermediate care facilities

142

147

149

156

157 nursing/intermediate care worksheets

170

171

173

obstetrics areas

77

90

93

patient rooms

73

91

94

184

185

prisons

95

resident areas in care facilities

135

schools

46

shower rooms

48

51

206

208

130

181

129


128


204

staff shower rooms in hospitals

77

student dormitories

41

surgical suites

75

“dump” loads

193

duration

62

equations

181

flow rates

40

gathering data for requirements

47

Legionnaires’ Disease and

14

steam water heaters

333

Vichy and swiss showers

129


185

Index Terms

Links

showers (Cont.) water temperature winter vs. summer demand

206 20

shutoff valves in circulation systems

239

for fixed orifices and venturis

247

gas

315

isolating portions of systems

244

silverware washers

318

50

single bedroom apartments. See 1-bedroom apartments single compartment sinks. See 1 -compartment sinks single-loop immersion elements

300

single people at spas

130

single systems

69

sinks. See also specific types of sinks (i.e., kitchen sinks) classrooms faucet flow rates

52 236


84

86


74

92

hourly demand

65

initial fills and draw-downs

66

kitchens

48

laboratories

119

50

195

miscellaneous hospital areas

77


Index Terms

Links

sinks (Cont.) nursing/intermediate care facilities

136

138

156

50

54

315

319

school general purpose usage

49

schools

48

service sinks

49


209

surgical suites

95

siphoning, preventing

300

sitz baths

77

sizing. See also names of specific systems to be sized (i.e., laundries, hospitals) costs and delays in hot water and generator size

37 238 30

heat exchangers

340

heat pump systems

331

instantaneous gas heaters with separate tanks oversizing retrofitting buildings return piping and pumps

312 xvii

25

28 249


3

storage tanks

183

systems baseball team locker room examples

215

218


Index Terms

Links

systems (Cont.) concrete processing water tanks

199

dormitory systems

39

hospital systems

71

hotel and motel systems

59

industrial facility systems

189

jail and prison systems

179

laundries

221

miscellaneous facilities

225


19

25

nursing/intermediate care/retirement home systems

133

school systems

45

spas, pools, health clubs, and athletic center systems

127

sports arenas and stadium systems

203

Sizing of Sewice Water Heating Equipment in Commercial and Institutional Buildings skin damage

38 14

slaughter houses. See food product facilities sleeping quarters in nursing/ intermediate care facilities slotted port burners

135 320


Index Terms

Links

SMACNA (Sheet Metal and Air Conditioning Contractors National Association)

xxi

small apartment buildings

30

small hospitals

93

small hotels

70

Smith, Jean B.

xx

snap-action surface-mounted high limit safety devices

303

snap-action surface-mounted thermostats

303

snap gaskets

287

social areas

160

soiled utility rooms hospitals

73

94

111

95

113

122

79

80

84

86


135

solar energy as heating medium

280

solar water heaters

17

solid-state progressive sequencers sonic cleaners

306

hospital user group usage factors user group example worksheets worksheet examples

106

space cooling functions of heat pumps

327

329

330


Index Terms

Links

spas calculating demand

130


127


128


130

shower rooms

129

special education rooms

46

special needs in therapy services special use housing facilities

128 35

specialized tubs nonambulatory patients

137

worksheet examples

170

specific heat of water specific volume of water Spielvogel, L. G.

3

4

346

354

38

spills flue gas spillage

322

pharmaceutical plants

195

sponge bathing

88

sports arenas baseball stadium example

214

commercial laundries in

208

demand assumptions

208

design traps

206


211


204

sizing systems

210

system design considerations

205

types of systems

207


Index Terms

Links

sports arenas (Cont.) usage areas

203

water temperatures

206

sports teams

46

spot cooling

327

48

55

spray-type dishwashers. See commercial dishwashers stadiums baseball stadium exam-ple

214

commercial laundries in

208

demand assumptions

208

design traps

206


211


204

sizing systems

210

system design considerations

205

types of systems

207

usage areas

203

water temperatures

206

staff shower rooms hospitals

77


138

staff toilets hospitals

73

111


135


209


204


Index Terms

Links

stainless steel in heat exchangers

285

pump fittings

258

288

stamped horizontal port burners stamped mono-port burners

320 320

standards and codes heat exchangers listing sports arenas and stadiums state plumbing codes static head in closed systems

279 16 205 16 258


3

steam as heating medium

185

tank heaters

283


282

Steam and Condensate Systems

341

steam generation plants

185

steam mains

338

steam sterilizers

95

280

112

113

steam water heaters design considerations

340

example

341

feed-forward units

336

feedback units

334

instantaneous water heaters

333

recirculation system piping and operation

338


Index Terms

Links

steam water heaters (Cont.) storage water heaters

333

types

333

steamers

48

steel mills

190

steel piping

235

steel water heaters

349

Steele, Alfred

262

237

sterile areas hospital sterile supply areas pharmaceutical plants

76 195

sterilization pharmaceutical plants requirements for dish-washing

195 48

sterilizers

75

Stevens, Kris

xx

92

95

storage. See also storage tanks general design principles

15

generation rate and capacity research

30

peak vs. average demand and

26

storage rooms

209

storage steam water heaters

333

storage tank electric water heaters commercial and residential

297

dip tubes

300

elements

300

tank fittings

298

tanks

298


197

Index Terms

Links

storage tank feedback systems

335

storage tank gas water heaters burners

319

defined

313

dip tubes

315

flues and heat exchangers

313

tank fittings

314

tanks

314

venting systems

321

318

318

storage tank indirect water heaters

291

295

storage tanks applications apartment building example

34

baseball team locker room example

219


213

high school systems

57

hotel kitchens

66

hotels

62

industrial facilities institutional dormitories

194 43

jail example

183

laundry requirements

222


26

prison example student dormitories

63

185

186

41

corrosion

314

dip tubes

300


Index Terms

Links

storage tanks (Cont.) draining and cleaning

315

electric water heaters

298

expansion formulas

348

expansion tanks

343

fittings

298

gas water heaters

314

heat loss

252


326

314

318

255

256


311

linings

298


335

steam water heaters

333

stratification

16

tank draw efficiency

300

tank mounting collars

283

tank recirculation systems vertical and horizontal tanks

314

42

44

16 207

stores convenience stores

226

329

grocery stores

227

331

malls

228

supermarkets

226

329

330

strainers for fixed orifices and venturis

245

heat pump systems

331

stratification in water tanks eliminating

42

overview

16

44


Index Terms

Links

stresses on indirect fired water heaters

293

on pipes

259

student dormitories

39

student toilets

46

studio apartments

26

suite hotels

61

summer season water de-mand

20

supermarkets

226

329

330

supplemental water heating systems

17

supply. See incoming cold water supply; incoming hot water supply supply pipes check valves and

245


239

insulation

260

risers in heat trace systems

276

surface-mounted high limit safety devices

298

303

surface-mounted thermo-stats

298

303

surface temperature of piping

251

surgical patients

72

92

surgical suites 32-bed hospital example

95


112

considerations

75


97


Index Terms

Links

surgical suites (Cont.) usage factors worksheet examples worksheet totals swimming pools

90 105

121

82

83

109

46

swing care wings in nursing facilities

158

swiss showers

129

symbols in heat trace systems

273

system sizing. See names of specific systems (i.e., laundries, hospitals) system temperature range Szydlowski, R.

278 38

T T & P relief valves tableware tank draw efficiency

243 48 300

tank heaters. See gas water heaters; indirect fired water heaters; storage tank electric water heaters tank mounting collars

283

tank-within-a-tank indirect fired water heaters

292

tankless coil systems apartment building example

32


295


124

Index Terms

Links

tankless systems. See instan-taneous systems tanks. See storage tanks tape in heat trace systems Tarbutton, George B.

269 xx

tax credits

328

Taylor, H.

38

teachers’ lounges

46

teachers’ workrooms

46

49

tee/inline splice kits in heat trace systems

269


273

TEMA (Tubular Exchange Manufacturers Association)

xxi

280

temperature condensation and

15

delivered hot water temperatures

12

differential in heat recovery equations equations at fixture outlet

5 354 6

heat trace systems

266

large differences in

283

lime deposits and

294

mixed water temperatures

64

78

6

requirements concrete gathering requirements

198 47

heat trace maintenance temperature table hospital laundries

274 76

92


Index Terms

Links

temperature (Cont.) hospital user groups

72

78

hospital worksheets

81

84

86

hydrotherapy

74

92

136

156

138

222

jail and prison considerations

179

kitchens

137

187

laundries

76

92

nursing/intermediate care laundries

138

prison kitchens

187

showers

210

special therapeutic needs

128


204

scalding

13

sterilization

76

206

93

system temperature range

278

worksheets

140

temperature controlled steam valves

335

temperature cross defined

281

plate-type heat exchangers and

284


283

temperature differential drops in system temperature range in heat recovery equations

278 5


Index Terms

Links

Temperature Limits in Service Hot Water Systems

262

temperature relief valves heat pump systems standards storage tanks temperature rise temperature sensing bulbs

332 15 298

315

5 335

tempered water. See mixed water temperatures tempering valves temples

69 225

tenants. See populations termination cable end termination in heat trace systems

269

electrical terminals on immersion elements

300

end termination

273


273

terminology heat exchangers

280


278

testing laboratories. See laboratories thawing food fast-food restaurants

228

grocery stores

227


Index Terms

Links

therapy services calculating demand

130


128


128


206

therapy tubs

73

91

Thermal and Water Vapor Transmission Data thermal efficiency (R factor)

261 4

260

thermal expansion allowing for

15


293

piping

259

refrigerant liquids

326

tank materials

348


283

thermal expansion tanks. See expansion tanks thermal insulation. See insulation thermal stress in indirect fired water heaters

293

thermodynamic properties of water

347

thermostatic aquastat controls

258

thermostatic capillary systems

336

thermostatic capsules

339

thermostatic mixing valves

74

112

209


Index Terms

Links

thermostats electric water heaters

303

gas water heaters

316

heat pump systems

332


315

storage tanks

298

thirty mA ground fault equipment

317

318

267

Thrasher, W. H.

38

57

threaded nipples

298

314

339

340

ticket booths

204

209

time clock controls

259

time-delay sequencers

306

three-way thermostatic capsules (diverting valves)

time delays. See delays in hot water time length. See duration time of day, peak flows and

26

time periods for showers

48

time rates for heat transfer

3

time to tap. See delays in hot water timed-control valves

180

titanium

285

To Combine or Not to Combine

262

toilets fast-food restaurants

229

grocery stores

227


191

prisons

184


Index Terms

Links

toilets (Cont.) public

42


226

shopping malls

228

special school facilities

46

staff toilets

73

training rooms

204

trauma rooms

113

travelers’ hotels tray cleaning

60

43

209

61

227

triple compartment sinks. See 3-compartment sinks troubleshooting multifamily building sizing

36

problems with inadequate hot water systems

233

recirculating hot water systems

233

sports arena design

206

truck tanks, concrete tub rooms

243

199 94

tube failures in heat exchangers

284

tube-in-tube heat exchangers

281

tube-on-tube heat exchangers

281

tube velocity

282

tubes, weight of

235

111

157

284

tubs. See bathtubs; hydro-therapy tubs; laundry tubs Tubular Exchange Manufacturers Association (TEMA)

xxi

280


Index Terms

Links

turbulence in heat exchangers

286

instantaneous indirect water heaters turnaround time for showers

295 210

two bedroom apartments. See 2-bedroom apartments

U U-tube bayonet-type heat exchangers

335

U-tube double-wall heat ex-changers

284


282

UL. See Underwriters’ Labo-ratories, Inc. (UL) uncirculated hot water branches

234

Underwriters’ Laboratories, Inc. (UL)

xxi

electrical components listing

16

heat trace systems

267

unheated distances in heat trace systems

278

Uniform Plumbing Code Il-lustrated Training Manual

262

uniforms blood on

188

laundries and

188

uninsulated hot water branches unions in heat pump systems

234 331


Index Terms units of measurement in formulas university steam water systems unrecirculated tanks

Links 3 333 16

untraced piping

278

updrafts, gas venting systems and

321

upfeed hot water systems

239

urban hotels U.S. Food and Drug Administration

240

61 194

user groups hospitals. See also under specific groups (i.e., nurses’ stations, surgical suites) 32-bed hospital example

93

300-bed example

124


111

109

defined

72


72

91

laundries

75

92

98

total worksheets

81

109

124

usage factors

88

worksheet examples

84

worksheets

78

nursing/intermediate care/retirement homes. See also under specific groups (i.e., nurses’ stations, patient areas) 48-bed facility example

158

defined

134


134

161


113

Index Terms

Links

user groups (Cont.) total worksheets

144

usage factors

152

worksheet examples

147

worksheets

140

176

165

users. See populations utensil sinks utensil washers

225

227

228

50

utilities laundries

222

rebates

328


205

utility plants

190

197

V vapor barriers in heat trace systems vapor compression

269 325

vegetable sinks demand

87

high school kitchens

55


151

prison kitchens

187

school kitchens

50

52

53

velocity erosion

244

in recirculating systems

244

vent caps

321

vent pipe connections

321

323


Index Terms

Links

vents gas water heaters

316

pipe connections

323

317


321

venturi flow meters

245

vertical draft hoods

322

323

vertical drilled ports case burners

320

vertical-to-horizontal draft hoods

322

vertical water tanks storage capacity stratification Vichy showers Vine, E.

207 16 128

129

38

visiting team locker rooms

203

viton

286

217

voltage electric water heaters

207

resistance of elements

302

volumes of materials

354

of water

346

volumetric expansion

354

349

W waiting for hot water. See delays in hot water Ward, John R.

xx


Index Terms wards in hospitals warehouses

Links 72 190

197

warm air sources for heat pumps warming kitchens

325 48

wash cycles averages

222

dormitory laundries

40

loads per hour

75

number per hour

222

wash down activities

227

wash fountains baseball team locker room examples

214

example

193


211

215

218

wash rooms. See lavatories wash stations group wash fountains

192


191

193

washing disinfectors. See disinfectors wasting energy. See energy conservation wasting water. See water conservation water expansion formulas

348

as heating medium

280

volume of

346

wastage. See water con-servation This page has been reformatted by Knovel to provide easier navigation.

Index Terms

Links

water (Cont.) weight of

3

4

346

266

270

217

218

water conservation delays in hot water and

238

energy conservation

234


265

laws wastage tables

37 271

water expansion formulas

346

water hammer

336

water heaters applications baseball team locker room examples

215


212


192


43

jail example

183

distances to fixtures

233

expansion

348

types electric water heaters

297

heat exchangers

279


325


291


311


Index Terms

Links

water heaters (Cont.) instantaneous point of use heaters

242

recirculating domestic hot water systems

233

residential and commercial

297


265

steam water heaters

333


313

water lines. See piping water paths (ankle therapy)

129

water quality hospital sterilization

93

instantaneous gas heaters with separate tanks for sterilization equipment water treatment plants

312 76 190

198

water velocities in recirculating systems

244

wattage, resistance of elements and

302

weapons, hot water as

180

weather, insulation and

260

weekday water demand flow patterns

21


19

weekend water demand flow patterns

21

monitoring demand

28


Index Terms

Links

weekend water demand (Cont.) multifamily buildings

19

seasonal demand

20

weeping in plate and frame units

289

weight of heated water of piping or tubes

3

4

346

235

welded connections in heat exchangers

286

welded plates in steam storage water heaters Wen-Yung, W. Chan

334 262

Wentz, Thomas A.

xx

Werden, R. G.

38

wet vacuum equipment

195

whirlpool baths baseball team locker room examples

214


212

hotel demand sports arenas and stadiums Whitworth, Patrick L.

217

61 209

211

xx

Wilcox, Greg

262

Windsor, Tod

262

winter season monitoring demand during

28

water demand

20

wiring circuits for electric water heaters

305


Index Terms

Links

work-release programs in prisons

186

work shifts. See shift changes workforce clients at spas working tenants in multifamily buildings

130 22

worksheets hospitals 32-bed hospital examples

100

109

300-bed examples

115

124

user group examples

84

user group work-sheets

78

worksheet totals

81

nursing/intermediate care/retirement homes 48-bed examples

164

user group examples

147

worksheet totals

144

worksheets

140

retirement home examples

173

wraparound elements

300

Y year-round sports arenas

205

Z Zamboni machines

205

zinc plating

303


07- Domestic Water Heating Design Manual.pdf

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