24479682 HVAC Handbook CARRIER Block Load v3 Manual

BLOCK LOAD USER’S MANUAL

811-315

COPYRIGHT  1998 CARRIER CORPORATION

PRINTED IN USA

Block Load User’s Manual

Carrier Corporation Software Systems Network

Manual Published.................................. 7/97 First Revision ........................................ 4/98

Copyright  1998 Carrier Corporation

Table of Contents CHAPTER 1

GETTING STARTED

1.0 WHAT THIS CHAPTER CONTAINS ........................................................................................... 1-1 1.1 WHAT THE BLOCK LOAD PROGRAM DOES ......................................................................... 1-1 1.2 INSTALLING BLOCK LOAD....................................................................................................... 1-1 1.2.1 Check Hardware and System Requirements ......................................................................................... 1-2 1.2.2 Run SETUP.EXE ................................................................................................................................ 1-2

1.3 STARTING BLOCK LOAD .......................................................................................................... 1-2 1.3.1 Starting Block Load For The First Time .............................................................................................. 1-2 1.3.2 Navigating The Splash Screen............................................................................................................. 1-3

1.4 OVERVIEW OF PROGRAM OPERATION .................................................................................. 1-3 1.4.1 Preparing Your Data ........................................................................................................................... 1-3 1.4.2 Entering Your Data ............................................................................................................................. 1-3 1.4.3 Running HVAC Load Calculations...................................................................................................... 1-4 1.4.4 Analyzing Your Results....................................................................................................................... 1-4

1.5 ASSISTANCE WHILE YOU WORK ............................................................................................ 1-4 1.5.1 On-line HELP ..................................................................................................................................... 1-4 1.5.2 Block Load User’s Manual .................................................................................................................. 1-4 1.5.3 Local Carrier Sales Representative ...................................................................................................... 1-5 1.5.4 Technical Support Line ....................................................................................................................... 1-5

1.6 HOW TO LEARN MORE ABOUT THIS PROGRAM .................................................................. 1-5 1.6.1 Information on Program Operation...................................................................................................... 1-5 1.6.2 Information on Program Calculations .................................................................................................. 1-5

CHAPTER 2

MANAGING YOUR PROJECT DATA

2.0 WHAT THIS CHAPTER CONTAINS ........................................................................................... 2-1 2.1 BLOCK LOAD PROJECTS ........................................................................................................... 2-1 2.2 PROJECT DATA FILES................................................................................................................ 2-1 2.2.1 Project Registration Data File (PRJXX___.MDB)................................................................................ 2-1 2.2.2 User Configuration Data File (CFGXX___.MDB) ............................................................................... 2-1 2.2.3 Master Project Data File (BLK30___.MDB) ........................................................................................ 2-2 2.2.4 Individual Project Data File (BLK30PRJ.MDB)................................................................................... 2-2

2.3 THE FILE MENU .......................................................................................................................... 2-2 2.3.1 Starting New Projects .......................................................................................................................... 2-2 2.3.2 Opening Existing Projects ................................................................................................................... 2-2 2.3.3 Deleting Projects ................................................................................................................................. 2-3 2.3.4 Saving Projects.................................................................................................................................... 2-4 2.3.5 Making Project Notes .......................................................................................................................... 2-5 2.3.6 Controlling The Printed Page Margins ................................................................................................ 2-5 2.3.7 Selecting The Printer And Printing Options ........................................................................................ 2-6 2.3.8 Retrieving Project Data From Earlier Version Of Block Load .............................................................. 2-6 2.3.9 Archiving Project Data ........................................................................................................................ 2-7 2.3.10 Retrieving Project Data...................................................................................................................... 2-8 2.3.11 Compacting Project Data ................................................................................................................... 2-8

CHAPTER 3

NAVIGATING THE MAIN WINDOW

3.0 WHAT THIS CHAPTER CONTAINS ........................................................................................... 3-1 3.1 OVERVIEW OF THE MAIN WINDOW ....................................................................................... 3-1 3.1.1 Viewing Your Project Data.................................................................................................................. 3-1 3.1.2 Editing Your Project Data ................................................................................................................... 3-2

3.2 ADVANCED USER INTERFACE FEATURES ............................................................................ 3-2 3.2.1 Selecting A System.............................................................................................................................. 3-3 Block Load User’s Manual

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Table of Contents 3.2.2 Adding New Systems........................................................................................................................... 3-3 3.2.3 Making A Copy Of A System .............................................................................................................. 3-3 3.2.4 Adding New Zones To A System......................................................................................................... 3-3 3.2.5 Attaching Zones To A System ............................................................................................................. 3-4 3.2.6 Moving Zones From One System To Another ...................................................................................... 3-4 3.2.7 Moving Zones To And From The Unattached Zones Region................................................................ 3-4 3.2.8 Making A Copy Of A Zone.................................................................................................................. 3-4 3.2.9 Removing Zones From A System......................................................................................................... 3-4 3.2.10 Removing Zones From The Unattached Zones Region ....................................................................... 3-5

Chapter 4

DEFINING WEATHER DATA

4.0 INTRODUCTION.......................................................................................................................... 4-1 4.1 OVERVIEW OF WEATHER DATA ............................................................................................. 4-1 4.2 EDITING WEATHER DATA ........................................................................................................ 4-1 4.2.1 The Edit City Form ............................................................................................................................. 4-1 4.2.2 Region Selection List........................................................................................................................... 4-2 4.2.3 State/Province Selection List ............................................................................................................... 4-2 4.2.4 City Selection List ............................................................................................................................... 4-3 4.2.5 Latitude Input Box............................................................................................................................... 4-3 4.2.6 Elevation Input Box............................................................................................................................. 4-3 4.2.7 Summer Dry Bulb Input Box ............................................................................................................... 4-3 4.2.8 Summer Wet Bulb Input Box............................................................................................................... 4-3 4.2.9 Daily Range Input Box ........................................................................................................................ 4-3 4.2.10 Winter Dry Bulb Input Box................................................................................................................ 4-3 4.2.11 Atmospheric Clearness Number Input Box ........................................................................................ 4-3 4.2.12 Data Source Text Box........................................................................................................................ 4-4

4.3 CHOOSING WEATHER DATA FOR THE DEFAULT PROJECT ............................................... 4-4

Chapter 5

ZONES

5.0 INTRODUCTION.......................................................................................................................... 5-1 5.1 OVERVIEW OF ZONES ............................................................................................................... 5-1 5.1.1 Types Of Zones ................................................................................................................................... 5-1 5.1.2 Manipulating Zone Data...................................................................................................................... 5-1

5.2 THE ZONE MENU ........................................................................................................................ 5-2 5.2.1 New Zone............................................................................................................................................ 5-2 5.2.2 Edit Zone ............................................................................................................................................ 5-2 5.2.3 Delete Zone ......................................................................................................................................... 5-2 5.2.4 Copy Zone........................................................................................................................................... 5-3 5.2.5 Move Zone .......................................................................................................................................... 5-3 5.2.6 Global Changes ................................................................................................................................... 5-3

5.3 THE NEW ZONE TOOLBAR BUTTON ....................................................................................... 5-4 5.4 THE ZONE INFORMATION FORM ............................................................................................ 5-5 5.4.1 Zone Data 1 Tab.................................................................................................................................. 5-6 5.4.2 Zone Data 2 Tab.................................................................................................................................. 5-7 5.4.3 Building Materials Tab........................................................................................................................ 5-9 5.4.4 Exposure Tab .................................................................................................................................... 5-12 5.4.5 Partitions Tab.................................................................................................................................... 5-14

Chapter 6

HVAC SYSTEMS

6.0 INTRODUCTION.......................................................................................................................... 6-1 6.1 OVERVIEW OF HVAC SYSTEMS ............................................................................................... 6-1 ii


Table of Contents 6.1.1 Types Of HVAC Systems..................................................................................................................... 6-1 6.1.2 Manipulating HVAC Systems.............................................................................................................. 6-2

6.2 THE SYSTEM MENU ................................................................................................................... 6-2 6.2.1 New System......................................................................................................................................... 6-2 6.2.2 Edit System ......................................................................................................................................... 6-2 6.2.3 Delete System...................................................................................................................................... 6-2 6.2.4 Copy System........................................................................................................................................ 6-2

6.3 THE NEW SYSTEM TOOLBAR BUTTON .................................................................................. 6-3 6.4 THE HVAC SYSTEM INFORMATION FORM ............................................................................ 6-3 6.4.1 HVAC System Data 1 Tab................................................................................................................... 6-3 6.4.2 HVAC System Data 2 Tab................................................................................................................... 6-7 6.4.3 Zones Tab............................................................................................................................................ 6-8

Chapter 7

REPORTS

7.0 INTRODUCTION.......................................................................................................................... 7-1 7.1 OVERVIEW OF INPUT REPORTS .............................................................................................. 7-1 7.2 OVERVIEW OF OUTPUT REPORTS .......................................................................................... 7-1 7.3 SELECTING AN HVAC SYSTEM ............................................................................................... 7-2 7.4 CHOOSING THE CALCULATION TIMES .................................................................................. 7-2 7.5 SELECTING REPORTS ................................................................................................................ 7-3 7.6 THE BLOCK LOAD REPORT FORM .......................................................................................... 7-4 7.6.1 Printing A Report ................................................................................................................................ 7-4 7.6.2 Paging Through A Report.................................................................................................................... 7-4 7.6.3 Selecting Other Reports....................................................................................................................... 7-4 7.6.4 Exiting The Report Form..................................................................................................................... 7-4

CHAPTER 8

COOLING DESIGN CALCULATIONS

8.0 INTRODUCTION.......................................................................................................................... 8-1 8.1 ZONE COOLING LOAD CALCULATIONS ................................................................................. 8-1 8.2 COOLING COIL LOAD CALCULATIONS - SINGLE-ZONE SYSTEMS ................................... 8-2 8.3 COOLING ANALYSIS FOR MULTIPLE-ZONE SYSTEMS ...................................................... 8-11

CHAPTER 9

HEATING DESIGN CALCULATIONS

9.0 INTRODUCTION.......................................................................................................................... 9-1 9.1 ZONE HEATING LOAD CALCULATIONS ................................................................................. 9-1 9.2 SIZING CALCULATIONS FOR WARM AIR HEATING SYSTEMS .......................................... 9-2 9.3 SIZING CALCULATIONS FOR HYDRONIC BASEBOARD HEATING SYSTEMS .................. 9-5 9.4 SIZING CALCULATIONS FOR ELECTRIC BASEBOARD HEATING SYSTEMS .................... 9-6

APPENDIX A


INDEX

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Getting Started

CHAPTER 1

Chapter 1

GETTING STARTED

1.0 WHAT THIS CHAPTER CONTAINS This chapter summarizes the basic information required to use the E20-II Block Load program. The chapter explains what the program does, how to use the program to design HVAC systems, how to operate the program and how to use this manual. This chapter takes 5 to 10 minutes to read. Program users are strongly encouraged to read this chapter before using the program. 1.1 WHAT THE BLOCK LOAD PROGRAM DOES Block Load is an engineering tool which helps HVAC engineers and designers size and select cooling and heating equipment. It calculates design cooling and heating loads for commercial buildings. It also determines required sizes for terminals, fans, and cooling and heating equipment. More than its name implies, Block Load is a fully featured load estimating program. In addition to computing "block" loads for buildings, the program can determine diversified zone loads and coil loads, all according to user specifications. Further, the program can easily analyze projects involving: •

One single-zone HVAC unit

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Several separate single-zone units

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Multiple-zone central air handler systems

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Constant volume equipment

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Variable volume systems

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DX or chilled water cooling coils

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Systems with warm air heating

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Systems with hydronic baseboard heating

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Systems with electric baseboard heating.

In all cases appropriate load and sizing information is provided as output. 1.2 INSTALLING BLOCK LOAD You install Block Load on your computer using the Setup program. The Setup program installs all the files you need in order to run the Block Load program. Note: you cannot simply copy files from the Block Load disks to your hard disk. You must run the Setup program to have all the Block Load files installed in the appropriate directories on your hard disk. To install Block Load, follow the steps outlined below. Block Load

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Getting Started

1.2.1 Check Hardware and System Requirements Before you install Block Load, make sure that your computer meets the minimum requirements listed below. Do not proceed with Block Load installation if your computer does not meet the minimum requirements. System requirements for running Block Load include: •

Microsoft Windows 3.11 or later, or Microsoft Windows 95, or Microsoft Windows NT 3.51 or later.

•

80386 or higher microprocessor.

•

A hard disk with a minimum of 4 megabytes of available space.

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VGA or higher resolution monitor.

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8 MB of RAM

•

A mouse.

1.2.2 Run SETUP.EXE This section describes how to run SETUP.EXE from drive A: of your computer. If you are installing Block Load from a drive other than A:, simply substitute the actual drive letter for A: in these instructions. To begin, insert Program Disk 1 into drive A:. From the File Menu of Windows Program Manager, choose the Run command, then type A:SETUP. At this point, the install process will commence. At the beginning of the install process, you will be asked to specify the drive letter where you want Block Load installed. You may enter any valid hard disk drive designation available to your computer. If you enter an invalid hard disk drive letter, the Install program will display a message stating “ Invalid Drive Specification “, You will have to answer OK then input the correct drive letter. Continue to follow the directions on the screen. The Install program will prompt you to insert the remaining program disks as needed. During installation, a “Carrier E20-II” group will be created, if one does not already exist. Within the Carrier E20-II group, a “Block Load” icon will be created. At any point in the Install process, you may choose to stop the installation by pressing the Cancel button. If you press the Cancel button, the Block Load install will terminate, but will not remove any files already installed. You are strongly encouraged to leave your system with the partial install until you can finish it later. Do not attempt to remove any installed files or directories without first consulting Carrier Software Systems technical support. 1.3 STARTING BLOCK LOAD To start the Block Load program, double-click on the Block Load icon in the Carrier E20-II group. 1.3.1 Starting Block Load For The First Time The first time you run Block Load, you will be prompted to enter your company name. The company name will appear on all Block Load output reports.

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Getting Started

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1.3.2 Navigating The Splash Screen At program startup, the Block Load splash screen is displayed. The splash screen contains three buttons: Help, Continue and Config. In order to proceed, you must push one of these buttons. Each is explained below. Help Button. Choose this button for an explanation of Block Load Continue Button. Choose this button when you’re ready to begin using Block Load. This takes you to the Block Load Main Window, and a new, default project (named Untitled) will be loaded. If you are starting a new project, you may begin entering data into the Untitled project. If you want to work with an existing project, you can use the File:Open, File:Retrieve or File:Convert DOS Data file options to load an existing project, or you may select an existing project from the list of “most recently used” projects shown on the File Menu. Refer to Chapter 2 for more information on using the File Menu. Config Button. Brings up the Data Storage Drive form. Here you select the drive to which your Block Load project data will be stored. The data drive does not need to be the same drive to which the Block Load program was installed. For example, you may have installed Block Load on a network drive, but wish to store your Block Load project data on your local hard drive. 1.4 OVERVIEW OF PROGRAM OPERATION This section briefly describes how to use Block Load to estimate cooling and heating loads, and to design HVAC systems. It explains basic operating principles for the program. Understanding these principles is one key to using Block Load efficiently. More complete information is available in Chapters 2-9 of this manual. 1.4.1 Preparing Your Data Before design load calculations can be performed, information about the building, its environment and its HVAC system must be gathered. This work involves extracting data from building floor plans and specifications, evaluating building usage, and studying basic HVAC system needs. Some of the specific types of information needed include: Climate data for the building site. This information may be easily obtained by picking a city from Block Load’s weather database. • Construction material data for walls, roofs, windows, floors and interior partitions. • Building size and layout data including wall, roof, window and floor areas, exposure orientations and characteristics of external shading features. • Internal load characteristics for occupancy, lighting systems, office equipment, appliances and machinery within the building. • HVAC system data concerning equipment and controls. 1.4.2 Entering Your Data •

Once the required project information has been gathered and organized, Block Load can be used to determine maximum cooling and heating loads for the building and to size the cooling and heating equipment. There are three basic steps in entering your project information into Block Load. Each is described below. Step 1: Enter Weather Data. First a city must be selected so that design temperature, humidity and solar radiation profiles can be computed. This weather data forms the basis for all cooling and heating load calculations. More information on this step is provided in Chapter 4.

Block Load

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Chapter 1

Getting Started Step 2: Enter Zone Data. You must enter data for each of the zones in your building. A "zone" is a region of a building served by one thermostatic control. It is often convenient to think of a zone as a room of your building, though a zone can be a group of several zones (or even the entire building) or it can be only a portion of a room. A zone is defined by its characteristics such as wall areas and properties, roof area and properties and the zone’s internal load characteristics. Refer to Chapter 5 for more detailed information on entering zone data. Step 3: Enter HVAC System Data. The "HVAC System" is the equipment and controls used to provide cooling and heating to your building. It includes such things as the supply fan, cooling and heating coils, thermostats, ventilation and exhaust dampers, and the controls that tie them together. Chapter 6 provides further information on HVAC System input.

1.4.3 Running HVAC Load Calculations Once weather, zone and HVAC system data has been defined, design cooling and heating loads can be computed, and the system can be sized. Design cooling calculations are performed for a range of calculation months and hours. By default, Block Load calculates a full 24-hour design day for all twelve months. You have the option to limit the calculations to any other range of months and hours. Chapter 7 describes how to run load calculations in greater detail. 1.4.4 Analyzing Your Results Once load and sizing calculations have been completed, Block Load’s reports can assist you in refining your HVAC system design and, ultimately, allow you to select proper cooling and heating equipment from HVAC manufacturers’ product catalogs. Block Load’s output reports include central fan sizing information, central coil sizing information (including sensible and total capacity, entering and leaving air conditions), duct and terminal sizing data, and space heating capacities. 1.5 ASSISTANCE WHILE YOU WORK If you need assistance with Block Load while you are running the program, there are several sources of help for you. Each is outlined below. 1.5.1 On-line HELP It is important when using Block Load to understand how the data that you enter will be used by the program. The fastest way to get this information is to use Block Load’s on-line Help system. Block Load provides context-sensitive help throughout the program. To get Help in any area of the program, simply press the F1 key; the Help system will appear on your screen with information pertinent to the data you are entering. 1.5.2 Block Load User’s Manual You are encouraged to become familiar with this manual. It contains a lot of useful information - often of a more general nature - not contained in the on-line Help. Typically, you can find the answers to your questions in this manual within a few minutes of searching.

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1.5.3 Local Carrier Sales Representative If you haven’t been able to locate the information you need in the on-line Help system or the Block Load User’s Manual, you may want to call your local Carrier sales representative. In many cases, your Block Load questions can be answered by your local Carrier sales representative. 1.5.4 Technical Support Line Carrier Software Systems provides a toll-free telephone technical support line to help you with your Block Load questions and problems. A staff of HVAC specialists are available to assist you during normal business hours (8:00am - 4:45pm ET, Monday through Friday). The toll-free technical support number is 800/253-1794. 1.6 HOW TO LEARN MORE ABOUT THIS PROGRAM The discussions in this chapter only provide an introduction to the Block Load Program. More detailed information on program operation is provided in the remainder of this User's Manual, and in other publications. These sources of information are described below: 1.6.1 Information on Program Operation 1. Block Load User's Manual Chapter 2 describes the concept of projects and how they can be managed in Block Load. Chapter 4 describes the Block Load user interface, and provides insight on how to use it most effectively. 2. Block Load User's Manual Chapters 4, 5, 6 and 7 describe how to work with the four basic steps in the load calculation process. Chapter 4 describes how to define weather data; Chapter 5 discusses entry of zone data; Chapter 6 deals with HVAC system inputs; Chapter 7 describes the load calculation step and the generation of output reports. 1.6.2 Information on Program Calculations 1. Block Load User's Manual Chapter 8 and 9 describe load and sizing procedures used for cooling and heating systems. 2. The E20/TF Load Manual describes the transfer function load calculation procedures used in this program in greater detail. Contact Carrier Software Systems technical support, or your local Carrier sales representative to obtain a copy. 3. The E20-II Weather Data Guide discusses procedures used to calculate temperature, humidity and solar radiation profiles. Contact Carrier Software Systems technical support, or your local Carrier sales representative to obtain a copy. 4. The ASHRAE Handbook of Fundamentals (1993) provides general background material on the Transfer Function Methodology for load calculations.

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CHAPTER 2

MANAGING YOUR PROJECT DATA

2.0 WHAT THIS CHAPTER CONTAINS Block Load data is organized into projects. This chapter explains the concept of a project, where the Block Load project data is stored, and explains the features built into Block Load to help you manage all of the data that make up your Block Load projects. 2.1 BLOCK LOAD PROJECTS A project is a related collection of data (weather data, building physical characteristics, and HVAC specifications) which reside within the file structure of Block Load. This data makes up the information needed to calculate a building’s design cooling and heating loads, and to properly size the required HVAC equipment to maintain comfort in the building. Other Carrier E20-II and Electronic Catalog programs written for Microsoft Windows® also deal with projects. While Block Load maintains your Block Load project data separate from any project data you may create in these other Carrier applications, Block Load is “aware” of these other projects. In some cases, it may be possible to ‘share’ some of this project data among the different applications. For example, if you create a project in Block Load named “New Office Complex”, it may be possible to pass the resulting equipment sizing output data to a Carrier equipment selection program (Rooftop Selection, for example) which has a project of the same name. Refer to the documentation for each Carrier application to determine if project data can be shared with other Carrier programs. 2.2 PROJECT DATA FILES Block Load uses four standard files in managing your project data. This section documents the name, content and location of these files. 2.2.1 Project Registration Data File (PRJXX___.MDB) This file contains a list and description of all projects created by any Carrier E20-II or Electronic Catalog program written for Windows. It also cross-references each project with all of the Carrier programs which have project data of the same name. The project registration data file is located in the ...\E20II\ENVIRO directory. For network installations, the “___” in PRJXX___.MDB is replaced by a three letters identifying the network user. 2.2.2 User Configuration Data File (CFGXX___.MDB) This file contains user-configurable settings. These include a list of the most recently used projects, the data storage drive letter, and whether projects are stored in English or SI Metric units. The user configuration data file is located in the ...\E20-II\ENVIRO directory. Block Load

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Chapter 2

Managing Your Project Data

For network installations, the “___” in CFGXX___.MDB is replaced by a three letters identifying the network user. 2.2.3 Master Project Data File (BLK30___.MDB) This file contains the names of your Block Load projects, and the names of the directories in which the project data is found (see section 2.2.4). This file is located in the ...\E20-II\BLK30\WORK directory. For network installations, the “___” in BLK30___.MDB is replaced by a three letters identifying the network user. 2.2.4 Individual Project Data File (BLK30PRJ.MDB) This file contains your Block Load project data. This includes weather data, zone data, HVAC data and all output data. This file is located in the ...\E20-II\BLK30\WORK\PJxxx directory, where ‘xxx’ is a reference number (base 36) assigned to the project. Each project is assigned to its own Pjxxx directory. 2.3 THE FILE MENU Most of Block Load’s data management features are built into the File Menu. The File Menu has options to create new projects (New), open existing projects (Open), delete projects (Delete), save projects (Save, Save As), archive projects (Archive), retrieve archived project data (Retrieve), recover project data from Block Load v2.1 (Convert DOS Data), clean up the project database (Compact), and add miscellaneous notes to your project (Properties). In addition, it also has options for setting the printed page margins (Page Setup), managing your printer resources (Print Setup), and contains a list of your most recently used projects for quick access. This section explains the purpose and use of each of these options. 2.3.1 Starting New Projects The New option is used to create (or start) a new project. When this option is chosen, a default project is loaded and displayed onscreen. The default project contains no systems or zones, but does contain a default city [note: you can specify which city is used as the default by using the Save button on the Edit City form. For more details, refer to Chapter 4]. The name of the new project is initially set to “Untitled”. This name is displayed in the program’s title bar. Before a new project is loaded, Block Load will verify that your current project has been saved. If it has not, you will be issued a warning, and given an opportunity to save that project. 2.3.2 Opening Existing Projects The Open option is used to open an existing project. When this option is chosen, the Open Project form is displayed (see Figure 2.1). The Open Project form contains a Project Name list box which is used to select the project to open. Beneath the Project Name text box is a list of all available projects which can be opened. To open a project, click on the desired project from this list, then press the OK button in the upper right-hand corner of the Open Project form. The List Projects Of Type prompt - which appears at the bottom of the form - controls the list of projects appearing beneath the Project Name text box. You may elect to display:

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Chapter 2

•

only those projects for which Block Load data exists (from the current version of Block Load).

•

projects created by any other Carrier E20-II or Electronic Catalog program (Rooftop Selection Program, for example).

•

all projects created by all Carrier E20-II and Electronic Catalog programs.

Figure 2.1 Open Project Form.

2.3.3 Deleting Projects The Delete option is used to delete projects from your current data drive which you no longer need. This is an important way of doing housecleaning on your computer hardware. When the Delete option is chosen, the Delete Project form is displayed (see Figure 2.2).

Block Load

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Managing Your Project Data Figure 2.2 Delete Project Form.

The Delete Project form contains a Project Name list box which is used to select the project to delete. Beneath the Project Name text box is a list of all available projects which can be deleted. To delete a project, click on the desired project from this list, then press the OK button in the upper right-hand corner of the Delete Project form. The List Projects Of Type prompt - which appears at the bottom of the form - controls the list of projects appearing beneath the Project Name text box. You may elect to display: •


•


•


If you choose to delete the currently-loaded project, Block Load will automatically create a new, default project for you. 2.3.4 Saving Projects The Save and Save As options are used to save your project to the current data storage drive. The Save option saves the current project under its current project name. The Save As option allows you to save the current project under a new name. When the Save As... option is chosen, the Save Project As... form is displayed (see Figure 2.3).

Figure 2.3 Save Project As... Form.

The Save Project As… form contains a Project Name list box which is used to enter a name under which the current project will be stored. You may enter a name directly into the Project Name list box, or you may choose to store your project in one of the existing projects listed beneath the Project Name text box. Up to 24 characters are allowed (embedded blanks are permissible). The project name must be unique (ie., you cannot have another project by the same name on the current data storage drive). The List Projects Of Type prompt - which appears at the bottom of the form - controls the list of projects appearing beneath the Project Name text box. You may elect to display:

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•


•


•


If you choose to delete the currently-loaded project, Block Load will automatically create a new, default project for you. 2.3.5 Making Project Notes The Project Properties option allows you to save notes about the project that may not directly affect your Block Load data (see the example in Figure 2.4). The Project Properties form contains a Project Description input box where your notes will be entered. This information is not used within the program, so its purpose is solely to record project-related information. It is not necessary to enter anything into the Project Description box.

Figure 2.4 Project Properties Form.

2.3.6 Controlling The Printed Page Margins The Page Setup option gives you control over the printed margins used when generating reports from Block Load. Figure 2.5

Block Load

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Figure 2.5 Page Setup Form.

2.3.7 Selecting The Printer And Printing Options The Print Setup option allows you standard Windows control over your printer. Refer to your Windows documentation for information on how to use the Print and Print Setup forms. 2.3.8 Retrieving Project Data From Earlier Version Of Block Load The Convert DOS Data command converts a Block Load dataset from its DOS format (Block Load v2.1) to the current program format. When the Convert DOS Data option is chosen, the Convert DOS Data form is displayed (see Figure 2.6). Use the Folders directory tree structure to locate the Block Load v2.1 data directory which contains the data you wish to pull into Block Load For Windows. Double click on the directory. To convert your DOS data, do the following: • Step 1: Use the Folders directory tree structure to locate the Block Load v2.1 data directory which contains the data you wish to pull into Block Load For Windows. Double click on the directory •

Step 2: Highlight the file blk21sys.dat in the list box at the right of the form. If blk21sys.dat does not appear in the list box, then the folder identified in Step 1 does not contain a valid Block Load v2.1 dataset.

•

Step 3: Click the OK button.

The conversion will proceed to completion. All data will be loaded into a new, untitled project on the Main Window.

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Figure 2.6 Convert DOS Data Form.

2.3.9 Archiving Project Data The Archive option is used to store your project data away for future use. When the Archive option is chosen, the Archive Project form is displayed. Use the Archive Project form to choose the project you wish to archive. The Archive Project form operates the same as the Open Project from (refer to Section 2.3.2 for information on how to use this form). Once you have selected a project to archive, the Archive prjname form will be displayed. This is shown in figure 2.7. Use this form to specify a file name for the archived dataset, and a folder in which to put the file. You may choose to store the archived project onto a removable disk or onto a hard disk. Archiving a project does not remove the project from the current data storage drive. If you wish to have the project removed from the data storage drive, you must use the File:Delete option (see section 2.3.3). Archived projects can be retrieved back into Block Load by using the File:Retrieve option (see section 2.3.10).

Figure 2.7 Archive Prjname Form. Block Load

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2.3.10 Retrieving Project Data The Retrieve option is used to restore Block Load data from an archived project dataset. The Retrieve option can only be used on an archived dataset from Block Load v3. When the Retrieve option is chosen, the Retrieve Project form is displayed (see Figure 2.6). Use this form to specify the folder and file name of the archived dataset that you wish to retrieve. When you push the OK button, Block Load will retrieve your archived dataset and make it the current project.

Figure 2.6 Retrieve Project Form.

2.3.11 Compacting Project Data The Compact option is used to compress a project dataset. This is important because the project dataset tends to get filled with unused space as modifications to the project data are made. The Compact option shrinks the size of the project dataset by removing all the unused space. When the Compact option is chosen, the Compact Project form is displayed (see Figure 2.7).

Figure 2.7 Compact Project Database Form.

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CHAPTER 3

NAVIGATING THE MAIN WINDOW

3.0 WHAT THIS CHAPTER CONTAINS Most of your interaction with Block Load will occur in the Main window. It is here that you will perform all your data entry and manipulation, and view all of your output results. The Main window has a rich assortment of features for viewing and manipulating your project data. In order to get the most benefit from Block Load, it is important to understand how to navigate the Main window most efficiently. This chapter explains all of the features and capabilities of the Main window. 3.1 OVERVIEW OF THE MAIN WINDOW Figure 3.1 illustrates the appearance of the Main window. It consists of an all-white background containing icons (pictures) representing your project data. A weather icon (a globe) represents your weather data, HVAC system icons (air handlers) represent your HVAC systems, and zone icons (wall thermostats) represent your zones. 3.1.1 Viewing Your Project Data The most obvious benefit of Block Load’s Main window is its ability to visually summarize your entire project dataset. The weather icon lists the name of the city for which design weather is being used. The name and number of HVAC system icons tells you what systems you’ve entered. And the zone icons communicate the number of zones in your project, and which HVAC systems are serving them. When you first begin a project, the only icon on the Main window is the weather icon, indicating that your project has weather data (but no zone or HVAC system data). The weather icon is always located in the upper left-hand corner of the window. Icons for various zones and HVAC systems will appear as you enter data for new zones and HVAC systems (refer to Chapters 5 and 6 for details on entering zone and HVAC system data). Each HVAC system that you enter into Block Load is represented by its own icon. Each HVAC system icon is contained in a rectangular box, with the name of the system displayed beneath the icon. Each rectangular “system” box is connected by a short vertical branch to the horizontal line extending from the weather icon. If your project contains more HVAC systems than can be displayed on the screen, horizontal scroll bars below the Main window allow you to view the remaining system icons. In addition to this, the dark arrow at the right-hand of the horizontal line is a visual clue that there are more systems which extend off the screen. Referring to Figure 3.1, the current project (named ISC1, as shown on the title bar) has systems named Base: Multiple Zone, Base: Single Zone, Solar and SZ: 100% vent_exh shown on the screen. The horizontal scroll bar and the horizontal arrow (pointing to the right) are visual indications that the project contains other systems. Each zone that you enter is represented by its own zone icon. The zone icons are displayed vertically in a rectangular box underneath the HVAC system icon which serves the zone. The zone’s name is listed to the right of its icon. It is possible to have zones which are not “attached to” (ie., served by) an HVAC system. These zone icons are displayed vertically in the area marked “Unattached Zones”, which is located beneath the weather icon. If any system - or the unattached area - contains more zones than can Block Load

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Navigating The Main Window

fit in its rectangular box, vertical scroll bars will appear at the right side of the box to allow you to view the remaining zones. 3.1.2 Editing Your Project Data The Main window icons do more than just provide a picture of your project data. They also provide a way for you to quickly access the data (to change it, or simply to look at it). This is done by doubleclicking on the icon. For example, double-clicking on the weather icon will display the properties of the design weather data, and allow you to modify it. Double-clicking a zone icon will display the zone’s properties, and allow you to change them. Double-clicking an HVAC system icon will display the system’s input properties, and will allow you to change them.

Figure 3.1 Main Window.

3.2 ADVANCED USER INTERFACE FEATURES The Main window has features beyond just allowing you to view and edit your project data. It has features for easily moving zones from one HVAC system to another, or detaching zones from any systems. This is particularly useful in helping determine the optimum zoning arrangement for a building. This section describes some of the advanced features of the Main window. 3-2

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3.2.1 Selecting A System Block Load allows you to perform several operations on an HVAC system. You can print or edit its input data, create a copy of it, or run design load calculations on the HVAC system. Before performing any of these operations, you must first ‘select’ the system on which you want the operation performed. Selecting a system can be done through the Menu options (refer to Chapter 6), but the Main window allows you a faster and easier way. To select an HVAC system from the Main window, single-click on the HVAC system icon desired In Block Load, only one system can be selected at a time. When you select a new system, the previouslyselected system is automatically de-selected. The Main window provides a visual clue to indicate which HVAC system is currently selected: the rectangular box surrounding the system and its attached zone icons is drawn with thick, dark lines. Note that you may often have situations where no system is currently selected. 3.2.2 Adding New Systems There are three ways to add a new system to your project: 1. Use the System:New System menu option. 2. Click the “Create a new system” button on the toolbar. The “Create A New System” button has a picture of a rectangular blue air handler with a white fan symbol inside of it. 3. Right click on an existing system icon. A pop-up menu will appear with an option to create a new system (New System). Choose this option.

When you choose any of these methods for creating a new system, a form displaying the default properties of your new system will appear. When you press the OK button (you may change any of the system properties first), a system icon for your new system will appear on the Main Window. 3.2.3 Making A Copy Of A System To make a copy of a system, right click on the icon of the system you want to copy. A pop-up menu will appear with an option to copy the system (Copy System). If you choose this option, Block Load will create a new system which is an identical copy of the selected system, except that the name will be modified slightly (since you cannot have two systems with identical names). The new system will appear on the Main Window, and will have the same zones attached to it as the original system. 3.2.4 Adding New Zones To A System There are three ways to add a new zone to a system: 1. Right click on the zone box beneath the system to which you want a zone added. A pop-up menu will appear with an option to add a new zone (New). 2. Select the system to which you want to add a new zone (refer to section 3.2.1 for information on selecting a system). Choose the New option from the Zone Menu. 3. Click the “Create a new zone” button on t he toolbar. The “Create A New Zone” button has a picture of a cube office on it.

When you choose either of these ways to add a new zone to the system, a form displaying the default properties of a new zone will appear. When you press the OK button (you may change any of the zone properties first), a zone icon for your new zone will appear on the Main Window in the zone box attached to the system.

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3.2.5 Attaching Zones To A System In Block Load, you ‘attach’ a zone to a specific HVAC system to indicate that the zone will receive conditioning from that system. Attaching zones to a system can be done on the HVAC System Information form (see Chapter 6). However, it can be done more quickly and easily from the Main window. To do this, drag the zone icon from its current position and drop it on the HVAC system icon to which you want it attached. Block Load will re-position the zone icon to the bottom of the zones attached to the system. In a similar fashion, you can detach a zone from a system by dragging the zone icon from beneath the HVAC system icon and dropping it on another system icon or in the ‘Unattached Zones’ area. 3.2.6 Moving Zones From One System To Another To move a zone from one system to another, drag the zone icon from its currently attached system and drop it onto the system icon to which it is to be attached. This is just a specific case of detaching and reattaching a zone, as described in section 3.2.5. 3.2.7 Moving Zones To And From The Unattached Zones Region In general, the rules for moving zones to and from the Unattached Zones region are the same as for any system, with one exception: Block Load will not allow you to move a zone to the Unattached Zones area if that zone is attached to any other system. If you attempt to do this, a warning message will appear, explaining that you cannot perform that operation, and ask if you want to remove the zone from the system where the original move was attempted. For general rules on moving zones, refer to section 3.2.6. 3.2.8 Making A Copy Of A Zone There are two types of zone copies allowed in Block Load. It is very important to understand the distinction between the two to avoid mistakes or possible loss of data. 1. You may attach the same zone to more than one system. In this case, there is only one zone, but it appears in multiple places. Changing the zone properties in any one of these places will change the properties in all of the places where the zone is attached. To attach a zone to more than one system, right click, drag and drop the zone icon in the zone box of any other system. When you do this, a pop-up menu will appear with an option to attach the zone to the new system (Copy Here). If you choose this option, the zone will be attached to both the original and destination systems. 2. You may create an identical - but unique - copy of a zone. Block Load will create a new zone with the same properties as the original (except for the zone name). Since each zone is unique, changing the properties of one zone doesn’t change the properties of the other. To make a unique copy of a zone, right click and drag the zone icon to another system (or the Unattached Zones area). When you drop the zone icon on a system (or Unattached Zones area), a pop-up menu will appear with an option for creating a new copy of this zone (New Zone Based On Original). If you choose this option, the new zone (with a modified name) will appear. You are permitted to drop the icon on the same system as the original. For example, referring to Figure 3.1, if you want to make a copy of East Zone, from the system Base: Multiple Zone, and keep it in Base: Multiple Zone, then right click on East Zone, drag and drop it somewhere in the zone box for Base: Multiple Zone.

3.2.9 Removing Zones From A System There are three ways to remove a zone from a system. They are: 3-4

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1. You may select the zone (by clicking on its icon), then use the Delete option on the Zone Menu. Note that the zone will not be deleted from your project. If the zone is not attached to any other system, then it will be automatically moved to the Unattached Zones area. 2. You can left drag the zone icon from your system and drop it in the Unattached Zones area. 3. You can select the zone (by clicking on its icon), then right click on it. A pop-up menu will ap pear with an option to delete the zone (Delete). If you choose this option, the zone will be removed from that system. Note that the zone will not be deleted from your project. If the zone is not attached to any other system, then it will be automatically moved to the Unattached Zones area.

3.2.10 Removing Zones From The Unattached Zones Region Removing a zone from the Unattached Zones area deletes the zone from your project. There are two ways to remove a zone from the Unattached Zones area. They are: 1. You may select the zone (by clicking on its icon), then use the Delete option on the Zone Menu. Block Load will ask you to confirm that you want the zone permanently deleted from your project. 2. You can select the zone (by clicking on its icon), the n right click on it. A pop-up menu will appear with an option to delete the zone (Delete). Block Load will ask you to confirm that you want the zone permanently deleted from your project.

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Chapter 4

DEFINING WEATHER DATA

4.0 INTRODUCTION This chapter describes how weather data can be manipulated for use in Block Load’s calculations. In this step the user specifies the design weather conditions for the building site. Separate sections in this chapter provide an overview of Editing City data and describe the use of various options on the Edit City screen. 4.1 OVERVIEW OF WEATHER DATA Weather data refers to the temperature, humidity and solar radiation conditions experienced by your project’s building and its HVAC system. Weather data has a significant effect on building loads and equipment operation. It therefore plays a key role in load estimating and HVAC system design work. Block Load uses design weather data in its design cooling and heating load calculations. Design cooling weather data consists of design day (24-hour) profiles of temperature, humidity and solar radiation for each month of the year. Design heating weather data consists only of a single winter design temperature. A Block Load project dataset always includes weather data. When a project is first created, default data is assigned to it. This data cannot be deleted; it can only be changed. 4.2 EDITING WEATHER DATA Weather data is changed by modifying the data on the Edit City form. You can reach the Edit City form by double-clicking on the globe icon on the Block Load Main window, or by selecting the Weather:Edit option from the Menu bar. When you double-click on the globe icon in the Main window, or select the Weather:Edit option from the Menu bar, the Edit City form appears. This section describes the Edit City form, its contents and its uses. 4.2.1 The Edit City Form The Edit City form is used to specify the location and design weather parameters for a Block Load project. Block Load uses the design weather parameters to generate all of the design weather data used in its load estimating calculations, using a procedure outlined in the Weather Data Guide (Carrier Corp., 1989). Figure 4.1 shows the design weather parameters for Chicago, Illinois displayed on the Edit City form. If the Block Load weather database contains a city matching your project location, then you may only need to specify the correct region, state/province/country and city from the Region, State/Province and City selection lists to specify the correct weather parameters (see sections 4.2.1 - 4.2.3). Otherwise, it may be necessary to determine the correct weather parameters, and enter this data into the appropriate input boxes on the Edit City form.

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The following sections describe each of the input fields on the Edit City form. After you have entered the correct data on the Edit City form, click the OK button to exit the form.

Figure 4.1 Edit City Form

4.2.2 Region Selection List Cities in the Block Load weather database are divided into geographical regions. The Region selection list, located at the top of the Edit City form, is used to select the geographic region in which the Block Load project is located. Your first step in navigating the Edit City form should be to choose the correct region from the Region selection list. 4.2.3 State/Province Selection List Cities in each geographic region are further subdivided into smaller groups by the state, province or country in which they are located. The State/Province selection list, located near the top of the Edit City form, contains the states, provinces or countries which comprise the region chosen in the Region selection list. If the Block Load weather database does not have any cities for a particular state, province or country, then that state, province or country will not appear in the State/Province list. If you do not find the state, province or country in the list, check to make sure that the proper region has been selected in the Region list. Your second step in navigating the Edit City form should be to choose the correct state, province or country from the State/Province selection list. 4-2

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4.2.4 City Selection List The City selection list contains all the cities in the Block Load weather database which fall geographically into the state, province or country selected in the State/Province list. Use this list to choose the city which most closely matches the weather pattern of the project location. Note that this is usually, but not always, the city which is geographically closest to the project location. Whenever you select a new city using the City drop-down list. Block Load automatically displays the design weather parameters for the new city. The Data Source parameter is always listed as “Carrier Defaults” whenever a new city is selected. This is to communicate that the design weather parameters displayed on the Edit City form come from the Block Load weather database. 4.2.5 Latitude Input Box The latitude for the city is used in solar radiation calculations. It has a direct effect on the direction and intensity of solar radiation throughout the year. Positive values are used for cities north of the equator. Negative values are for cities south of the equator. 4.2.6 Elevation Input Box The elevation for the city is required for air property and psychrometric calculations since the properties of air vary with altitude. Positive values indicate the distance above sea level. Negative values define the distance below sea level. 4.2.7 Summer Dry Bulb Input Box This design temperature defines the warmest outdoor air temperature considered for cooling conditions. For U.S. and Canadian cities in Carrier's weather database, ASHRAE 1% values are used. This means the summer dry-bulb is exceeded in only 1% of the hours during summer months. This value is used to derive cooling design temperature profiles. 4.2.8 Summer Wet Bulb Input Box This is the average wet-bulb temperature coincident with the summer design dry-bulb. It is used in generating wet-bulb temperature profiles for cooling design days. 4.2.9 Daily Range Input Box This represents the difference between maximum and minimum temperatures on a typical cooling design day. It is used in deriving temperature profiles for cooling design days. 4.2.10 Winter Dry Bulb Input Box This design temperature defines the coldest outdoor air temperature considered for heating conditions. For U.S. and Canadian cities in Carrier's weather database, ASHRAE 99% values are used. This means the winter design temperature is exceeded in 99% of the hours during the winter (i.e. it is colder 1% of the time). The winter design value is used for heating design calculations, and is indirectly involved in the derivation of cooling design temperature profiles. 4.2.11 Atmospheric Clearness Number Input Box The atmospheric clearness number (ACN) is a factor used to correct clear sky solar radiation estimates for unusually clear or hazy conditions. Values typically range from 1.15 for very clear conditions, to 1.00 for typical conditions, to 0.85 for very hazy conditions. For more information on this factor, please refer to the E20-II Weather Data Guide or the ASHRAE Handbook of Fundamentals.

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4.2.12 Data Source Text Box The data source describes the source of the design weather parameters displayed on the Edit City form. Data from Block Load’s weather database is listed as “Carrier Default”. If you change any of the design parameters, the data source will be listed as “User Defined”. 4.3 CHOOSING WEATHER DATA FOR THE DEFAULT PROJECT You can choose the weather data that will be loaded each time you start a new project (using the File:New option). This is done by using the Save button located on the Edit City form. Whenever you push the Save button, Block Load saves the weather properties - shown on the form with the default project data.

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Chapter 5

ZONES

5.0 INTRODUCTION This chapter deals with Block Load zones. It describes what zones are, what they are used for, and how to enter zone information into Block Load. Section 5.1 provides an overview of zones. The remaining sections in the chapter describe the various zone features available in Block Load. 5.1 OVERVIEW OF ZONES A zone is a region of a building which is served by one thermostat. It is sometimes helpful to think of a zone as a room in a building, although the definition of a zone is much broader than this. A zone can be a portion of a room, a collection of several rooms, or even an entire building. A zone is defined by its physical characteristics such as its floor area, wall areas and U-values, roof area and U-value, window area, orientation (N, S, E, W, etc.), and internal loads. This data is used to determine the cooling and heating loads in the zone. 5.1.1 Types of Zones Many projects involve a single-zone HVAC unit. A small office building which needs packaged rooftop equipment may be such an example. For such projects, you’d only need to enter one zone into Block Load. Often the zone will represent the entire building. For other projects, two or more single-zone HVAC units are used. Examples of these applications include the use of multiple rooftop units for a shopping center or single-story office building, or the use of fan coil or water source heat pump units in hotels and larger office buildings. For these projects, separate zones might be defined for the individual stores in the shopping center, or the different portions of the office building or hotel. Finally, some projects utilize a central air handler which provides conditioning to various regions of a building, each with its own thermostat. A variable air volume (VAV) system in a large office building is a common example of this application. For this situation, separate zones would be defined for the various regions in the building. Block Load allows you to combine zones and equipment in various ways so that all these different applications can be properly analyzed. 5.1.2 Manipulating Zone Data Block Load offers you several ways to manipulate your zone data. You can create a new zone, modify the data for an existing zone, delete a zone, create a copy of a zone, print input data for a zone, attach and detach zones from HVAC systems, and make global changes to zone data. There are three ways to access the zone data manipulation features in Block Load:

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Zones •

Chapter 3 described how to create new zones, modify existing zones, and attach/detach zones using the zone icons on the Main window.

•

The Zone Menu has options for creating new zones, modifying existing zones, deleting zones, copying and moving zones, and making global changes to all zones. These options will be described fully later in this chapter.

•

The toolbar has a New Zone button for creating new zones. Operation of the New Zone button will be described fully later in this chapter.

5.2 THE ZONE MENU The Zone Menu has options for creating new zones, modifying existing zones, deleting zones, copying and moving zones, and making global changes to all zones. Each of these options is described in the following sections. 5.2.1 New Zone The Zone:New menu option allows you to create a new zone. When you select this option, the Zone Information form appears (see Figure 5.2). The Zone Information form allows you to describe the physical characteristics of the zone. It initially contains default zone data. Refer to the section entitled “Zone Information Form” later in this chapter for complete details on the Zone Information form. When you return from the Zone Information form, a new zone icon is added to the Main window with the name you’ve assigned on the Zone Information form. The zone will be attached to the currently selected HVAC system automatically; if there was no currently selected HVAC system when the New Zone option was chosen, then the zone will be assigned to the “Unattached Zones”. 5.2.2 Edit Zone The Zone:Edit menu option allows you to modify existing zone data. This option is only available if you have selected (highlighted) a zone on the Main Window; if no zone is selected, the Edit option will be grayed out. When you select the Edit option, the Zone Information form appears. It contains the current zone data for the selected zone. Refer to the section entitled “Zone Information Form” later in this chapter for complete details on the Zone Information form. 5.2.3 Delete Zone The Zone:Delete option is used to delete zones from your Block Load project. This option is only available if you have selected (highlighted) a zone on the Main Window; if no zone is selected, the Delete option will be grayed out. The Delete option works in slightly different ways, depending on whether the zone you are trying to delete is attached to a system, or whether it is in the Unattached Zones area. Each case is discussed below: Deleting a zone from a system. When you “delete” a zone from a system, the zone is un-attached from the system to which it was attached. However, the zone is not actually deleted from your project. If the zone is attached to any other system, then no other change is made to your project. If, however, the zone is not attached to any other system, then the zone is moved to the Unattached Zones area. To remove the zone from your project, you must delete it from the Unattached Zones area. Deleting a zone from the Unattached Zones area. When you delete a zone from the Unattached Zones area, you are asked to confirm that you want the zone permanently removed from the project. If you 5-2

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respond Yes, the zone is deleted from the project. If you say No, then the zone is left in the Unattached Zones area. 5.2.4 Copy Zone The Zone:Copy option is used to attach the selected zone to another system in your Block Load project, while keeping it attached to its current system(s). This option is only available if you have selected (highlighted) a zone on the Main Window; if no zone is selected, the Copy option will be grayed out. When you select this option, the Copy Zone form appears. The Copy Zone form asks you to select the systems to which you’d like the zone attached. When you press the Copy button, the zone will be attached to the chosen systems. If the zone were originally attached to a system, the zone will remain attached to that system. If the zone were originally in the Unattached Zones area, the zone will be removed from the Unattached Zones area after the copy process is completed (because the zone is no longer unattached). 5.2.5 Move Zone The Zone:Move option is used to un-attach a zone from its current system, and attach it to another system. This option is only available if you have selected (highlighted) a zone on the Main Window; if no zone is selected, the Move option will be grayed out. When you select this option, the Move Zone form appears. The Move Zone form provides a list box of all systems in your project, and asks you to pick the system to which you want the zone attached. When a zone move is executed, the zone will no longer be attached to its original system. 5.2.6 Global Changes The Zone:Global Changes option is used to make changes to many zones simultaneously. Rather than modifying zone data one space at a time, this option allows you to choose a category of data and a group of zones, and then make changes for all zones in the group. This feature is useful when changing common attributes of a zone. Typically, it is used to change a single zone characteristic. For example, you may wish to examine the variation in cooling loads if you were to replace the building’s standard double-pane windows with low-e windows. Using the Global Changes option, you could - in one step change the window glass factor (shade coefficient) for every zone in the building. When you select the Global Changes option, the Global Zone Changes form appears (see Figure 5.1). This form allows you to choose which data item is to be changed and how it is to be changed. The form is divided into three general areas: Data Selection, Global Values and Make Changes To Zones. Each is described below. Data Selection. Located on the left-hand side of this form are listed the various data items which can be globally changed. The items are grouped by category. For example, in the Wall Data category are three items which can be selected: wall U-value, wall weight and wall color. Use this section to choose the data item that you want globally changed. Only one item can be selected at a time. Notice that the information in the Global Values area (discussed below) of the form changes to match the data item you’ve chosen in Data Selection. Global Values. Located beneath the Data Selection area. Use this area to specify what value you want to assign to the data item chosen in the Data Selection area (see above). You have two choices about what data is changed. •

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You can change the selected data item in all selected zones in your project. Check the box in front of the Change All Values prompt, then enter the value for the data item in the input box. 5-3

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You can change only the data which matches a value that you specify. To do this, first make sure the Change All Values box is unchecked. In the Change To input box, enter the value that you want the data changed to. In the remaining input box, enter the value of the data item that you want replaced.

Figure 5.1 The Global Zone Changes Form

Make Changes To Zones. Located on the right-hand side of the form, this area is used to select the zones to which you want the global changes to apply. The global changes will apply only to those zones which are highlighted in this area. 5.3 THE NEW ZONE TOOLBAR BUTTON The New Zone button is located on the toolbar. The New Zone toolbar button behaves exactly as the Zone: New menu option (see section 5.2.1). The New Zone button allows you to create a new zone. When you push this button, the Zone Information form appears (see Figure 5.2). The Zone Information form allows you to enter a description of the zone. It initially contains default zone data. Refer to the section entitled “Zone Information Form” later in this chapter for complete details on the Zone Information form. 5-4

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When you return from the Zone Information form, a new zone icon is added to the Main window with the name you’ve assigned on the Zone Information form. The zone will be attached to the currently selected HVAC system automatically; if there was no currently selected HVAC system when the New Zone option was chosen, then the zone will be assigned to the “Unattached Zones”.

Figure 5.2 The Zone Information Form (Zone Data 1 Tab)

5.4 THE ZONE INFORMATION FORM The Zone Information form (shown in Figure 5.2) contains all the information needed to describe a zone. All entry of new zone data, and editing of existing zone data occurs on the Zone Information form. The form is divided into several tabs. Each tab contains input boxes for a portion of the required zone data. For example, the Exposures tab contains input boxes for defining the wall and roof exposures and areas of a zone. In addition to zone data input boxes, each tab contains an Information bar and a Parameter Limits bar. The Information bar serves as an automatic mini-Help system. As you move the cursor about the Zone Information form, it displays some useful, brief information about the data required in the input boxes. The Parameter Limits bar displays the allowable range of information which can be entered into an input box. For example, if the cursor is located on the Floor Area input box on the Zone Data 1 tab, the Parameter Limits bar notes the minimum allowable floor area is 1.0 square foot (0.1 square meters); the maximum allowable floor area is 9,000,000 square feet (836,100 square meters).

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When you are finished entering zone data, click the OK button to save the data and return to the Main window. You should review the zone data on each of the Zone Information form tabs before clicking the OK button. If you wish to cancel any changes made to your zone data, click the Cancel button. Note that changes cannot be canceled once you click OK. The remainder of this section describes the zone data inputs on each of the Zone Information form tabs. 5.4.1 Zone Data 1 Tab The Zone Data 1 tab contains general zone data, and data to describe the lighting and other electric usage in the zone. Each data item is described below. Zone Name. A reference name, up to 20 characters in length, is used to identify the zone. This name appears on selection screens and on program printouts. The name may have embedded blanks and special characters. Floor Area. This field is used to compute internal loads such as lighting and occupancy which are defined on a per-unit-floor-area basis (per sqft or per sqm). Building Weight. The overall weight of interior walls, floors and ceilings for the building plays a major role in influencing how heat gains are converted into cooling loads. Heavy buildings tend to absorb and store heat for longer periods than light buildings. Thus, there is more of a lag between the time a heat gain occurs and the time it becomes an air-conditioning load. Building weight may be entered as "Light", "Medium" or "Heavy", or as an exact value in weight per unit floor area. Equivalencies for the light, medium and heavy categories are listed in Table 5.1. TABLE 5.1 Wall, Roof and Building Weights Weight (lb/sqft) Very Lt

Light

Medium

Walls

6.0

20.0

60.0

Roofs

NA

10.0

Building

NA

30.0

Weight (kg/sqm) Heavy

Very Lt

Light

Medium

Heavy

140.0

29.3

97.6

292.9

683.5

30.0

55.0

NA

48.8

146.5

268.5

70.0

130.0

NA

146.5

341.8

634.7

Lighting Usage. The lighting use in the zone can be specified in watts per unit floor area (W/ sqft or W/sqm) or in total watts. This input is the total of bulb wattage for all lights in the zone. To switch from one type of units to another use the drop down list. Lighting Unoccupied Diversity Factor . The unoccupied diversity factor is the fraction of lights which are in use during the unoccupied equipment operation period. For example, a diversity factor of 20% means that 20% of the lights are in use during the unoccupied period. Because of the transient nature of lighting loads, lighting heat gains during one hour have an effect on loads during other hours of the day. Consequently, it is important to know the use pattern for lights for all 24 hours in the day. Further, in order to produce realistic load results, realistic diversity factors must be used. Wattage Multiplier. The wattage multiplier describes the additional power required to operate a ballast starter device for fluorescent lights. The actual lighting power draw is computed as fixture watts times the wattage multiplier. When incandescent lights are used a wattage multiplier of 1.00 should be entered. Lighting Fixture Type. The proportions of convective and radiative heat transfer from lights will vary depending on the kind of lighting fixture used. This in turn affects the transient nature of loads due to lighting heat gain. In this program three lighting fixture types are offered: 5-6

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Chapter 5 • • •

Recessed, vented lighting fixtures, Recessed, unvented lighting fixtures, or Free-hanging lighting fixtures.

Other Electric Usage. Use of other electrical equipment such as computers, typewriters, vending machines, etc... is specified in either watts per unit floor area (W/ sqft or W/sqm) or in total watts. To switch from one type of units to the other, select from the drop down list. Other Electric Unoccupied Diversity Factor . Defines the fraction of other electrical equipment in use during the unoccupied equipment operation period. For example, a diversity factor of 10% means that 10% of the other electrical equipment is in use during the unoccupied period. For further information on the diversity factor and its importance, please refer to the discussion of the lighting diversity factor.

5.4.2 Zone Data 2 Tab Figure 5.3 illustrates Zone Data 2 tab. The Zone Data 2 tab contains information on the occupancy of the zone, its infiltration rate, details about basements or slab floors and other miscellaneous loads. Each data item is described below. Occupancy. The number of people present in the zone is either specified directly or on the basis of floor area per person. To switch from one type of units to the other, use the drop down list. People Unoccupied Diversity Factor . This factor defines the fraction of people present in the zone during the unoccupied equipment operation period. For example, a diversity factor of 5% means that 5% of the total people are present during the unoccupied period. Frequently this input is confusing to users because of the term "unoccupied". It is not meant to imply that no people are present. In this program the "unoccupied equipment operation" period refers to the hours when the equipment is off or in a set-up/set-back mode. For an office building, for example, cooling equipment typically operates to ventilate and cool the building during daytime working hours. At night, the equipment operates in set-up/set-back mode, only providing cooling or heating when necessary. However, at night it is possible that custodial or security personnel are present. Hence people can be present in the building during the "unoccupied" period. For further information on the importance of the diversity factor input, please refer to the discussion of the lighting diversity factor. People Activity Level. Sensible and latent heat gains from people vary with the type of activity being performed in the zone. Five common activity levels are offered in the program. When one is chosen, the corresponding sensible and latent heat gains shown in Table 5.2 are used in load calculations. If the values in Table 5.2 are not appropriate, the sixth activity level ("User-Defined") should be used. In this case sensible and latent heat gains are directly specified. To change the activity level, select from the drop down list. Sensible & Latent Heat Gains . If activity level six ("User-Defined") is selected, you are given the opportunity to specify people sensible and latent heat gains on a per person basis (BTU/h/person or W/person). When any of the first five activity levels are selected, the standard heat gains for these levels are displayed on the input screen. In this case, these values may not be changed. Values can only be changed by specifying the activity level as "User-Defined". TABLE 5.2 People Activity Levels And Heat Gains

Activity Level Seated At Rest Block Load

Sensible

Latent

Sensible

Latent

(Btu/hr-person)

(Btu/hr-person)

(W/person)

(W/person)

120.0

67.4

35.2

230.0

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Zones Office Work

245.0

205.0

71.8

60.1

Sedentary Work

280.0

270.0

82.1

79.1

Medium Work

295.0

455.0

86.5

133.4

Heavy Work

525.0

925.0

153.9

271.1

Figure 5.3 Zone Data 2 Tab Miscellaneous Sensible & Latent Loads . Sensible and latent heat gains from other non-electric internal sources can be considered using these inputs. Positive inputs indicate a heat gain; negative inputs indicate a heat loss. Readers should note that miscellaneous internal loads are only considered during design cooling calculations. These inputs are useful for analyzing such things as the presence of refrigeration cases in supermarkets or the use of gas-fired kitchen equipment in restaurants. Miscellaneous Load Unoccupied Diversity Factor . This factor defines the fraction of the specified miscellaneous loads present during the unoccupied equipment operating period. A diversity factor of 25%, for example, means that 25% of the heat gain is present during the unoccupied period. While miscellaneous heat gains are assumed to become cooling loads instantly, the accumulation of heat during a nighttime shutdown period can have a significant effect on pull down loads during the daytime operating period. Hence, it is important to specify a realistic diversity factor in order to obtain reliable cooling load results. Cooling & Heating Infiltration . Infiltration airflow may be specified as either an airflow per unit floor area (CFM/sqft or L/s/sqm) or as a total airflow rate (CFM or L/s). To switch from one type of 5-8

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Chapter 5 units to the other, use the drop down list. The cooling infiltration value is used for design cooling load calculations. The heating value is used for design heating load calculations. Slab. Inputs are used to account for heat transmission losses through floors on grade, or through floors and walls below grade. These heat losses are only considered for design heating load calculations. The slab inputs have slightly different meanings for on-grade and below-grade cases. For slabs on-grade: •

Slab Area is the area of the on-grade slab floor.

•

Slab Perimeter is length of the perimeter of the on-grade slab floor.

•

Slab Depth should be specified as zero for an on-grade slab.

For below-grade floors: •

Slab Area is the area of the below-grade basement floor.

•

Slab Perimeter is the length of the perimeter of the below-grade basement floor.

•

Slab Depth refers to the distance between the grade level and the top of the basement floor surface. This input is used in conjunction with the slab perimeter to determine the area of below-grade walls. The slab depth also influences rates of heat loss through the basement walls.

5.4.3 Building Materials Tab Figure 5.4 illustrates the Bldg. Matl. tab. The Bldg. Matl. tab contains information on the thermal properties of the walls, roofs and glass which are used in the zone construction. Also included on this tab is external shading dimensions. Each data item is described below.

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Figure 5.4 Building Materials Tab Wall U-Value. Wall U-values describe the overall insulating value of the wall assembly. U-values are used in transmission load calculations. Wall Weight. The storage and transmission of heat by building walls depends partly on the weight of the wall. Wall weights may be specified as Very Light, Light, Medium or Heavy, or as an exact value of the wall weight per unit surface area ( lb/sqft or kg/sqm). Equivalencies for the Very Light, Light, Medium and Heavy categories are shown in Table 5.1. Wall Color. The color of the exterior wall surface affects the amount of solar energy absorbed by the wall. Colors are defined as Light, Medium or Dark. According to the ASHRAE Handbook of Fundamentals, the dark color specification should be used for all walls in industrial areas. The other color specifications should only be used when the designer is certain a wall will permanently remain light or medium colored. Roof U-Value. Roof U-values describe the overall insulating value of the roof assembly. U-values are used in transmission load calculations. Roof Weight. The storage and transmission of heat by the roof depends partly on the weight of the roof assembly. Roof weights may be entered as Light, Medium or Heavy, or as an exact value of the roof weight per unit area (lb/sqft or kg/sqm). Equivalencies for the various weight categories are listed in Table 5.1. Roof Color. The color of the exterior roof surface influences the amount of solar energy absorbed by the roof. Colors are defined as Light, Medium or Dark. The ASHRAE Handbook of Fundamentals recommends that the dark specification be used for all roofs in industrial areas. The other color

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Chapter 5 specifications should only be used when the designer is confident a roof will permanently remain light or medium colored. Glass U-Value. The glass U-value defines the insulating value of the window assembly. This U-value is used in glass transmission load calculations. Glass Factor. Defines how solar energy is transmitted through windows. In the ASHRAE Handbook this factor is referred to as a "shading coefficient". The ASHRAE procedure for computing solar gains evaluates solar energy transmission through a single pane of ordinary glass. The glass factor is used to correct solar gains for other types of glass such as double pane windows or reflective glass, or for the use of internal shading devices. Chapter 27 of the ASHRAE Handbook of Fundamentals (1989) contains several tables of glass factors (shading coefficients) for various window designs. Internal Shading. Plays a role in determining how soon a solar gain becomes a load. If internal shading devices such as curtains are used, a portion of the solar gain will be absorbed by the curtain and quickly convected to room air. If no shades are used, more of the solar energy will be absorbed by interior floors and walls and will be convected to the air at a slower rate. Readers should note that the "Internal Shading", "Glass Factor" and "Glass U-Value" inputs are related. If internal shades are specified, glass factors and U- values which are appropriate for the internal shades should also be entered. External Shading. Seven parameters are used to describe external shading features for windows in the zone. Five of these inputs deal with dimensions of overhangs, fins and reveals. External shading inputs are discussed in the paragraphs below. Window Height and Width. Used to describe the dimensions of one window aperture. For example, 200 sqft of glass may be specified for the zone, but may consist of five windows, each 10 ft by 4 ft. To perform external shading calculations, the dimensions of a single window aperture must be known. It is assumed all windows associated with the external shading data have these dimensions. If this is not the case, multiple glass types should be used, and separate shading types should be defined. Reveal Depth. Defines the distance the glass pane is set into the wall of the building. Depth is measured from the wall surface to the outer surface of the glass. Overhang Height. Defines the vertical distance between the top of the window aperture and the bottom of the overhang. Overhang Extension. Defines the horizontal distance from the wall to the outer edge of the overhang. Fin Separation. Defines the distance between the window aperture and the fin. It is assumed that fins are located on both sides of the window. Fin Extension. Defines the distance from the wall to the outer edge of the fin.

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Figure 5.5 Exposure Tab

5.4.4 Exposure Tab Figure 5.5 illustrates the Exposure tab. The Exposure tab is used to describe the orientation of the zone, and its associated wall, roof and window areas. Each data item is described below. Exposures. Defines the direction in which the exterior surface of the wall or roof faces. Block Load offers nine exposures. To enter a vertical wall, select from north, northeast, east, southeast, south, southwest, west and northwest. To enter a horizontal roof, choose the roof exposure. Readers should note that only five exposures can be displayed on the screen at one time. To display the remaining exposures, use the slide bar at the bottom of the form. Wall Type. Specify the wall or roof construction type. This refers to the Type 1, 2 or 3 wall or roof construction listed on the Bldg. Matl. tab. When you’ve chosen one of the eight principal exposures in the Exposure input box, a summary of the three wall construction types will be displayed at the bottom of the form when the cursor is on the Wall Type input. If you’ve chosen the roof exposure, then the three roof construction types will be displayed at the bottom of the form. Gross Area. Wall and roof areas are entered on a gross area basis. This refers to the total surface area of the exposure, including the opaque surface (wall or roof) and the transparent surface (window or skylight). During calculations, the program will automatically subtract glass areas from the gross areas to determine the net wall and roof areas. Glass Type. Enter the glass type which applies to this exposure. This refers to the Type 1, 2 or 3 glass construction listed on the Bldg. Matl. tab. When the cursor is on the Glass Type input box , the three glass types are displayed at the bottom of the Exposure tab. 5-12

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Chapter 5 Glass Area. The total glass surface area for each exposure must be defined. All glass areas for wall exposures are assumed to be vertical windows. The glass area input on the "Roof" line is used to define horizontal skylight areas. Shade Type. If the glass area listed above has any external shading, then enter the appropriate shade type (1, 2 or 3) corresponding to the external shading data defined on the Bldg. Matl. tab. If no external shading is used, simply specify the shade type as zero. When the cursor is on the Shade Type input box, the three external shade types are displayed at the bottom of the Exposure tab. Note that external shading is not considered for horizontal skylights, so only shade type values of zero are permitted in this case.

5.4.5 Partitions Tab Figure 5.6 illustrates the Partitions tab. Partitions refer to walls, floors or ceilings adjacent to an unconditioned region of the building. The Partitions tab is used to enter data for up to three partitions. Each data item is described below. Net Area. Specify the surface area of the wall, floor or ceiling adjacent to the unconditioned region. U-Value. The partition U-value describes the insulating value of the partition. This U-value is used in transmission load calculations. Adjacent Region Temperature (Cooling). In order to compute heat transfer across the partition, the temperature in the adjacent unconditioned region must be known. This input is used for design cooling calculations only. The temperature can be defined in two ways. The drop-down list to the right of the temperature input box allows you to choose whether to input the unconditioned space temperature directly, or define it based on a percentage of the indoor-outdoor temperature difference. A temperature input might be used when modeling a restaurant kitchen adjacent to a refrigerated storeroom in which the storeroom temperature is relatively constant. A percentage input might be used to analyze offices adjacent to an unconditioned warehouse. In this case, the warehouse temperature might vary as a function of outdoor temperature. If for example a 75% value is used, and the indoor and outdoor temperatures are 72 F and 92 F respectively, a temperature of 87 F in the adjacent region would be assumed when calculating partition heat gain. Adjacent Region Temperature (Heating). This input is used to calculate heat transfer across the partition for design heating load calculations. The same adjacent temperature and percentage input options offered for the cooling input are offered for heating.

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Figure 5.6 Partitions Tab

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Chapter 6

HVAC SYSTEMS

6.0 INTRODUCTION This chapter deals with HVAC systems. It describes what systems are, what they are used for, and how to enter system information into Block Load. Section 6.1 provides an overview of systems. The remaining sections in the chapter describe the various system features in Block Load. 6.1 OVERVIEW OF HVAC SYSTEMS An HVAC system is the airside equipment and controls used to provide cooling and heating to one or more zones in a building. The system includes fans, thermostats, coils, ductwork, dampers, terminals, piping and controls which make up an air conditioning system. HVAC system data is needed in order to perform design cooling and heating calculations. These calculations determine how the system must be sized in order to satisfy peak cooling and heating loads in each of the zones. 6.1.1 Types Of HVAC Systems Many projects involve a single-zone HVAC unit. A small office building which needs packaged rooftop equipment may be such an example. For such projects, you’d only need to enter one HVAC system into Block Load. To this system, you would attach a single zone. For other projects, two or more single-zone HVAC units are used. Examples of these applications include the use of multiple rooftop units for a shopping center or single-story office building. For these projects, separate HVAC systems might be defined for the individual stores in the shopping center, or the different portions of the office building. Some projects utilize a central air handler which provides conditioning to various regions of a building, each with its own thermostat. A variable air volume (VAV) system in a large office building is a common example of this application. For this situation, a single HVAC system would be defined, to which would be attached zones for the various regions in the building. Finally, some projects involve many single-zone HVAC units which are similar. Examples of these applications include the use of fan coil or water source heat pump units in hotels and larger office buildings. For projects of this type, you can designate that each zone attached to an HVAC system represents a separate air handling unit. In this way, a single HVAC system can be defined whose characteristics represent one single fan coil or water source heat pump. The many zones attached to the system (representing the individual hotel rooms, for example) would be treated as though each has its own HVAC unit. In effect, Block Load treats this one HVAC system as multiple HVAC units. Block Load provides ways to combine zones and HVAC systems in various ways so that all these different applications can be properly analyzed.

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HVAC Systems

6.1.2 Manipulating HVAC Systems Block Load offers you several ways to manipulate your HVAC system data. You can create a new system, modify the data for an existing system, delete a system, create a copy of a system, print input data for a system, and attach and detach zones from the system. There are three ways to access the system data manipulation features in Block Load: •

Chapter 3 describes how to create new systems, modify existing systems, and attach/detach zones from the system using the zone icons on the Main window.

•

The System Menu has options for creating new systems, modifying existing systems, deleting systems, and copying systems. These options will be described fully later in this chapter.

•

The toolbar has a New System button for creating new systems. Operation of the New System button will be described fully later in this chapter.

6.2 THE SYSTEM MENU The System Menu has options for creating new systems, modifying existing systems, deleting systems, and copying systems. Each of these options is described in the following sections. 6.2.1 New System The System:New System menu option allows you to create a new system. When you select this option, the HVAC System Information form appears (see Figure 6.1). The HVAC System Information form allows you to enter a description of the system and attach zones to the system. It initially contains default system data. Refer to the section entitled “HVAC System Information Form” later in this chapter for complete details on the HVAC System Information form. When you return from the HVAC System Information form, a new system icon is added to the Main window with the name you’ve assigned on the HVAC System Information form. If you attached any zones to the system on the form, those zone icons will be attached to the new system icon automatically. 6.2.2 Edit System The System:Edit System menu option allows you to modify existing system data. This menu option is only available if you have a system selected on the Main Window. When you select this option, the HVAC System Information form will appear. It contains the current system data for the selected system. Refer to the section entitled “HVAC System Information Form” later in this chapter for complete details on the HVAC System Information form. 6.2.3 Delete System The System: Delete System option is used to delete systems from your Block Load project. This menu option is only available if you have a system selected on the Main Window. When you select this option, Block Load asks you to confirm that you want the selected system removed from the project. Note that any zones attached to the system will not be deleted. If they are not attached to any other system , they will be moved to the Unattached Zones area. 6.2.4 Copy System The System: Copy System option is used to create a copy of any system in your Block Load project. When you select this option, Block Load creates a new system which is an exact copy of the original, except that the name is modified. If the original system had any zones attached, the new system will have the same zones attached. 6-2

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To print the System Input report, press the Print button in the upper left-hand corner of the report screen, or choose the File:Print command. Refer to Chapter 7 for more details on the operation of the report screen. 6.3 THE NEW SYSTEM TOOLBAR BUTTON The New System button is located on the toolbar. The New System toolbar button behaves exactly as the System: New System menu option (see section 6.2.1). The New System button allows you to create a new system. When you push this button, the HVAC System Information form appears (see Figure 6.1). The HVAC System Information form allows you to enter a description of the system. It initially contains default system data. Refer to the section entitled “HVAC System Information Form” later in this chapter for complete details on the HVAC System Information form. When you return from the HVAC System Information form, a new system icon is added to the Main window with the name you’ve assigned on the HVAC System Information form. If you attached any zones to the system on the form, those zone icons will be attached to the new system icon automatically. 6.4 THE HVAC SYSTEM INFORMATION FORM The HVAC System Information form (shown in Figure 6.1) contains all the information needed to describe a system. All entry of new system data, and editing of existing system data occurs on the HVAC System Information form. The form is divided into several tabs. Each tab contains input boxes for a portion of the required system data. In addition to system data input boxes, each tab contains an Information bar and a Parameter Limits bar. The Information bar serves as an automatic mini-Help system. As you move the cursor about the HVAC System Information form, it displays some useful, brief information about the data required in the input boxes. The Parameter Limits bar displays the allowable range of information which can be entered into an input box. For example, if the cursor is located on the System Name input box on the HVAC System Data 1 tab, the Parameter Limits bar notes that you may enter up to 24 characters for the name. When you are finished entering system data, click the OK button to save the data and return to the Main window. [Note that the OK button is located on HVAC System Data 1 tab]. You should review the system data on each of the HVAC System Information form tabs before clicking the OK button. If you wish to cancel any changes made to your system data, go to the HVAC System Data 1 tab and click Cancel. Note that changes cannot be cancelled once you click OK. The remainder of this section describes the system data inputs on each of the HVAC System Information form tabs. 6.4.1 HVAC System Data 1 Tab The HVAC System Data 1 tab contains information about when the system operates, fan data, and supply and ventilation air specifications. It is also where you can designate that each zone has its own HVAC unit. Each data item is described below. System Name. A reference name up to 24 characters in length is used to identify the system. This name appears on selection screens and program printouts. System Type. The system type defines the capabilities of the HVAC system and how it provides conditioning. This input also influences how certain sizing calculations are performed. Seven system type options are offered: •

Block Load

Cooling and Warm Air Heating 6-3

Chapter 6

HVAC Systems •

Cooling and Hydronic Heating

•

Cooling and Electric Heating

•

Cooling Only

•

Warm Air Heating Only

•

Hydronic Heating Only

•

Electric Heating Only

Readers should note that hydronic heating refers to the use of hot water baseboard units. Electric heating refers to the use of electric baseboard units. For warm air heating, the heat source (electric, direct-fired, or hot water) does not need to be known. Depending on the system type selected, various sizing calculations will be performed differently:

6-4

•

For warm air heating systems, an airflow rate and supply temperature for heating will be determined.

•

For hydronic heating systems a baseboard unit hot water flow rate will be computed.

•

For electric heating systems, the required baseboard heater wattage will be calculated.

•

For systems which do both cooling and heating, ventilation airflow will be based on the cooling sizing calculation.

•

For a "Cooling and Warm Air Heating" system, the supply airflow rate is based on cooling sizing criteria. This supply airflow rate will also be used in design heating calculations.

Block Load

HVAC Systems

Chapter 6 Figure 6.1 HVAC System Data 1 Tab

System Start Time & Duration . These two inputs define the "occupied" equipment operating period. During this period the equipment provides both ventilation and conditioning. This is referred to as the "occupied" period because it typically coincides with the times people are present in the building. For the remaining hours of the day, it is assumed the equipment operates in a set-up/set-back mode. Because fewer people or no people at all are present during set-up/set-back operation it is often referred to as the "unoccupied period". To define the occupied operating period, specify the hour the period begins, and the number of hours it lasts. A 24-hour clock format is used when defining start times. Hour 0000 corresponds to midnight, for example, 0100 corresponds to 1am, 0200 corresponds to 2am, etc ... Sizing Specification: Supply . Supply air sizing calculations are based on this input. Sizing can be based on: •

An airflow rate per unit floor area (CFM/sqft or L/s/sqm),

•

A specified supply airflow rate (CFM or L/s), or

•

A supply temperature.

If an airflow rate is defined, the program will calculate the required supply temperature. Likewise, if a supply temperature is entered, the program will determine the required airflow rate. To change the type of units for the supply specification, select from the drop down list. Whenever the current HVAC system provides cooling, this input pertains to the sizing of cooling supply air. If the system type is "Warm Air Heating Only", this input defines the heating airflow sizing criteria. Finally, if the system type is either " hydronic" or "electric" baseboard heating only, this supply input is not used in sizing calculations. It is also worth noting that when a cooling supply temperature is specified, it must be less than the occupied cooling thermostat set-point. The parameter limits will change according to the thermostat setpoint. The Max limit will be 5° F less then the setpoint. When a heating supply temperature is entered, it must be greater than the heating thermostat setpoint. The cooling setpoint must always be higher than the heating setpoint, even if you have specified a heating-only system. Ventilation Air Sizing Specification. Sizing can be based on:

Ventilation air sizing calculations are based on this input.

•

An airflow per unit floor area (CFM/sqft or L/s/sqm),

•

A specified ventilation airflow rate (CFM or L/s),

•

A fixed percentage of the supply airflow rate, or

•

An airflow per person value (CFM/person or L/s/person).

To change the type of units for the ventilation specification, select from the drop down list. Whenever the current HVAC system provides cooling, this input defines how ventilation air for cooling will be sized. If the system provides both cooling and heating, the ventilation airflow rate calculated for cooling will also be used for design heating calculations. Finally, for heating-only systems the ventilation inputs are used specifically for heating sizing calculations. Direct Exhaust Air Sizing Specification. "Direct exhaust" refers to air which is exhausted from a zone rather than return to the central air handler through a return duct or plenum. Whether air is exhausted before or after the return plenum can have an important effect on the temperature rise in a plenum and the resulting cooling coil loads. Direct exhaust air sizing calculations can either be based on: Block Load

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HVAC Systems •

A specified direct exhaust airflow rate (CFM or L/s/sqm), or

•

A fixed percentage of the ventilation airflow rate.

Readers should note that this sizing input is only used for cooling load calculations. Hot Water Delta-T. If hydronic baseboard heating is used, a delta-T value for water flowing through the heating coil must be specified. The required hot water flow rate is then calculated based on this sizing value and the design heating load. This input only appears when the "system type" input specifies that hydronic baseboard heating is used. Fan Configuration. The air handling unit may have either a draw- thru or blow-thru configuration. For a draw-thru configuration, the cooling coil is located upstream of the fan. For blow- thru, the cooling coil is downstream of the fan. This input is only used in cooling load calculations. The position of the cooling coil relative to the fan will have an effect on the coil inlet and outlet temperatures. This in turn will influence the coil psychrometrics. Fan Static Pressure, Brakehorsepower or kW. In order to calculate fan heat gain, some characteristic of fan operation must be known. Because fan data is provided in various forms for different types of equipment, users are provided with three alternatives. Users can specify the: •

Fan total static pressure (inches of water gage, or Pascals),

•

Fan brakehorsepower, or

•

Fan kW.

When total static pressure is used as the fan input, an assumed fan efficiency value of 54% is used in heat gain calculations. This is a typical efficiency and is a combined value for the motor, fan drive and fan mechanical efficiencies. When brakehorsepower is used as the fan input, an assumed fan motor efficiency of 90% is used in heat gain calculations. If these assumptions are not appropriate for a job, the fan kW input option should be utilized instead. System Arrangement. Defines how the HVAC system and zone input data are to be combined during load and sizing calculations. Two arrangement options are offered: •

All zones served by a common air handler.

•

Each zone served by a separate air handler.

All Zones Served By A Common Air Handler. Block Load will treat this system as a single air handler serving all attached zones. During load calculations, the HVAC system inputs and inputs for all the zones selected will be put to use together. Required supply airflow rates will be determined for all zones involved, as well as for the central supply fan. The maximum central cooling coil load will also be identified. Depending on the type of heating, either a central heating coil load will be determined for a warm air heating system, or baseboard loads will be computed for each zone when hydronic or electric baseboard heating is used. Each Zone Served By A Separate Air Handler. Block Load will treat this system as a series of single-zone systems, each serving one of the attached zones. This is particularly useful in applications such as hotels, where each room may have its own packaged air conditioner. Rather than force you to run load calculations for each single-zone unit separately, this option provides a way to quickly run calculations for the entire project all at one time. During load calculations, the HVAC system inputs will be used with each zone separately to perform load and sizing calculations. If, for example, the job involved 20 stores in a strip shopping center, the program will generate separate load and sizing printouts for the 20 packaged units used on the job. This feature allows you to complete calculations for a project quickly and efficiently. 6-6

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6.4.2 HVAC System Data 2 Tab Figure 6.2 illustrates the HVAC System Data 2 tab. The HVAC System Data 2 tab contains thermostat setpoint and return air plenum information. It is also where you can designate sensible, latent and heating safety factors. Each data item is described below. Cooling Thermostat Setpoint(Occupied Period). This is the thermostat setpoint for cooling used for the "occupied" equipment operation period.

Figure 6.2 HVAC System Data 2 Tab Cooling Thermostat Setpoint (Unoccupied Period). This is the thermostat setpoint used for the "unoccupied" equipment operation period. Users may either enter the unoccupied setpoint temperature or enter an [N] to specify that cooling is never provided during the unoccupied period. When a setpoint temperature is specified, it must be greater than or equal to the occupied cooling setpoint. The program will not accept values less than the occupied setpoint. While design cooling loads will never occur during the "unoccupied" period, cooling loads for all 24hours in the day must be calculated in order to properly evaluate morning pulldown loads. For example, smaller pulldown loads would typically result when occupied and unoccupied setpoints of 75/78 F are used compared to setpoints of 75/95 F. Heating Thermostat Setpoint. For heating load calculations, the heating thermostat setpoint must be defined. The heating setpoint must be less than or equal to the occupied cooling setpoint. Cooling Coil Bypass Factor is used to evaluate dehumidification occurring at the cooling coil. In general, the bypass factor is a measure of the approach to the apparatus dewpoint (ADP) for air flowing through the coil. Values of coil bypass factors are typically published in product literature. Note that some manufacturers publish a "contact factor" rather than a bypass factor. The bypass factor is simply ( 1 contact factor). Block Load

6-7

Chapter 6

HVAC Systems Cooling Safety Factors (Sensible & Latent). The next two inputs are cooling safety factors. In design calculations, a factor is often introduced to provide a margin of safety. Separate safety factors may be specified for sensible and latent loads. During calculations, zone cooling loads are increased by this safety amount before supply airflow and cooling coil computations are performed. Heating Safety Factor. In design heating calculations, a factor is also often introduced to provide a margin of safety. During heating load calculations the zone heating loads are increased by this factor before airflow or baseboard sizing calculations are performed. Is a Return Plenum Used? If a return plenum is used, a portion of the roof, lighting and wall loads may be removed by air flowing through the plenum. This reduces the room component of the load and can have a significant effect on terminal sizing and system operation. When a plenum is specified, additional questions for roof, lighting and wall plenum loads will be displayed. % of Roof Load to Plenum. When a plenum is used, a portion of the roof transmission load will be carried away by air flowing through the plenum. Therefore, only a portion of the total roof load will reach the zone. The portion of the roof load removed by plenum air is defined as a percentage of the total roof load. % of Lighting Load to Plenum. A portion of the lighting load will also be removed by air flowing through the plenum. This typically happens when the lighting fixtures are recessed into the ceiling so that plenum air flows directly over or through the fixture. Plenum heat gain from lights is estimated as a percentage of the total lighting heat gain. % of Wall Load to Plenum. A portion of wall transmission loads may be removed by plenum air. The fraction of the wall load reaching the plenum can usually be estimated as the ratio of wall area adjacent to the plenum divided by the total wall area.

6.4.3 Zones Tab Figure 6.3 illustrates the Zones tab. The Zones tab contains a list of all zones in your project. It is used to attach or detach zones from the HVAC system. Highlighted zones are attached, while all others are not attached. To attach a previously-unattached zone, click on it; it will immediately become highlighted. To detach a previously-attached zone, click on it; it will immediately become un-highlighted.

6-8

Block Load

HVAC Systems

Chapter 6

Figure 6.3 Zones Tab

Block Load

6-9

Chapter 6

HVAC Systems (This page intentionally left blank)

6-10

Block Load

Chapter 7

REPORTS

7.0 INTRODUCTION This chapter describes the contents and operation of the Reports Menu. The Reports Menu allows you access to all of the input and output reports generated by Block Load. Reports contain the data inputs and results of the design cooling and heating load calculations performed by the program, including all of the information needed to properly select cooling and heating coils, fans and terminals. There are two types of reports offered in Block Load: input reports and output reports. Input reports contain only the project data that you have entered into the program. Output reports contain the results of cooling and heating load calculations which Block Load has performed on your project data. This chapter will describe the various input and output reports available in Block Load, and how you access them. 7.1 OVERVIEW OF INPUT REPORTS Block Load offers two input reports. They are: Zone Input Report. The Zone Input Report contains all of the input data for a single zone. It is found on the Zone:Zone Input Report option from the Reports Menu. To generate a Zone Input Report, you must first select a zone on the Main Window. [If you do not select a zone, the Zone Input Report option will be grayed out on the Reports Menu]. Then select the Reports:Zone:Zone Input Report option. The Block Load Report form will display the Zone Input Report (refer to the Block Load Report Form section in this chapter for features of this report form). System Input Report. The System Input Report contains all of the data for a single system. It is found on the System:System Input Report option from the Reports Menu. To generate a System Input Report, you must first select a system on the Main Window. [If you do not select a system, the System Input Report option will be grayed out on the Reports Menu]. Then select the Reports:System:System Input Report option. The Block Load Report form will display the System Input Report (refer to the Block Load Report Form section in this chapter for features of this report form). 7.2 OVERVIEW OF OUTPUT REPORTS The purposes of Block Load are to compute design cooling and heating loads, and to size the HVAC equipment which will maintain comfort conditions within your project’s building. The load and sizing information generated in Block Load is provided to you in a variety of reports. There are three steps required to generate an output report. They are: 1. Select the HVAC system for which reports are to be generated. Block Load

7-1

Chapter 7

REPORTS

2. Choose the calculation times. 3. Select the reports to view or print. The following sections will cover each of these steps in greater detail. 7.3 SELECTING AN HVAC SYSTEM In order to calculate load or generate reports, you must first choose an HVAC system for which reports are to be generated. The Main Window allows you a fast and easy way to select a system. To select an HVAC system from the Main window, simply single-click on the HVAC system icon desired. Refer to Chapter 3 for more details on selecting systems. In Block Load, only one system can be selected at a time. When you select a new system, the previouslyselected system is automatically de-selected. The Main Window provides a visual clue to indicate which HVAC system is currently selected. The box surrounding the selected system icon and attached zones is drawn with thick, dark lines. Note that you can have situations where no system is currently selected. 7.4 CHOOSING THE CALCULATION TIMES By default, Block Load will calculate loads for an entire 24-hour design day for each month of the year. By doing so, you are guaranteed that Block Load can identify the peak load conditions within your building. However, there may be times when you do not wish to have Block Load “wasting time” performing calculations for months or hours which are of no consequence to you. For example, you may know for certain that none of your zones or the HVAC system peak in winter months such as December, January or February. In these cases, you may wish to exclude those months from Block Load’s calculations. The Reports:Calculation Parameters menu option is used to set the months and hours for which you want calculations run. When this option is chosen, the Calculation Parameters form appears (see Figure 7.1). Each of the required inputs is explained below. The Options:Display Calculation Times menu item can be used to display the currently chosen calculation months and hours on the Main Window.

7-2

Block Load

REPORTS

Chapter 7

Figure 7.1 Calculation Parameters Form First Month and Last Month. These inputs are used to specify the months for which the design cooling calculations will be performed. Months are chosen to ensure that times of year when maximum cooling loads occur are included in the calculations. To be absolutely sure maximum loads are identified, all months should be selected ( eg., select January as the First Month, and December as the Last Month). However, based on prior experience, you may be able to select a smaller range of months and still be sure that peak loads have been identified. At a minimum. it is best to include a range of months encompassing the times when maximum solar gains on the different building exposures occur, and the times when maximum outdoor temperatures occur. Month selections are made by touching the First Month or Last Month drop down boxes, then selecting the month you desire. First Hour and Last Hour. Cooling load calculations can also be performed for any group of consecutive hours during the day. This group is defined by specifying the first and last hours in the group. Hours are specified using a 24-hour clock convention. Hour 0000 corresponds to midnight, 0100 corresponds to 1am, 0200 corresponds to 2am, etc ... Hour selections are made by selecting the appropriate times from the First Hour and Last Hour drop down lists.

7.5 SELECTING REPORTS Results from the load and sizing calculations can be displayed or printed from the Reports menu. When you select an output report from the Reports Menu, Block Load will automatically determine whether load calculations need to be performed (if the calculations have previously been run, then they will not need to be run again). Each output report listed on the Reports Menu is described below. System:System Sizing Summary. The standard program output provides all load and sizing data necessary to select cooling and heating equipment for the job. This includes cooling sizing data such as the required supply temperature and airflow rates, coil loads and coil operating conditions. Heating sizing data describes maximum loads, and required airflow rates, hot water flow rates or baseboard wattages depending on the type of heating used. In addition, useful check figures are also provided. Block Load

7-3

Chapter 7

REPORTS

System:Detailed System Load Report. This printout provides a component-by-component breakdown of loads for the month and hour in which the maximum cooling coil load occurs. Component loads are also provided for the design heating condition. This printout is typically used when detailed information about a job is required for troubleshooting or documentation purposes. System:Design Psychrometric Process. The psychrometric output is a graphical report which plots the air conditioning processes for the entire HVAC system on a psychrometric chart. When you select this output, the Psychrometric Graph form is displayed. This form allows you to customize the psychrometric graph a great deal. In order to access the customizability features of this form, right-click anywhere within the graph area. A menu will appear, containing all of the customizability options allowed. Zone:Detailed Zone Load Report. This printout provides a listing of component loads for each zone served by the HVAC system. Load data is printed for the month and hour in which the maximum sensible load for each zone occurs. A one page printout is generated for each zone involved. Typically, this printout is generated when very detailed information about a job is needed for troubleshooting or documentation purposes. Weather:Design Temperature Report. This output contains a table of the design weather parameters (which are project inputs), and a table of design drybulb and wetbulb temperatures for a selected month. In addition, a graph of the drybulb and wetbulb temperature profiles is contained in the report. Weather:Design Solar Report. This output contains a table of the design weather parameters (which are project inputs), and a table of the maximum solar heat gains on each of the principal exposures for each month of the year. 7.6 THE BLOCK LOAD REPORT FORM All reports, except for the Psychrometric Graph, are displayed on the Block Load Report form. This form has several useful features, documented below. 7.6.1 Printing A Report The Block Load Report form provides two ways to print the currently displayed report. You can select the File:Print option or simply press the Print button located at the top of the form. 7.6.2 Paging Through A Report Four buttons - located in the lower left-hand corner of the form - allow you an easy and convenient way to quickly go to the previous page of the report, the next page, the first page or the last page. A page counter separating the buttons lets you know which page of the report you are viewing. 7.6.3 Selecting Other Reports The Reports list is located at the top of the Block Load Report form. This allows you a quick way to access other available reports. For example, if you are viewing one of the output reports, the Reports list contains the names of all the other input and output reports offered in Block Load. Choosing any of these reports will immediately display that report on the form. 7.6.4 Exiting The Report Form Block Load offers you three ways to close the Block Load Report form. You may:

7-4

•

press the Exit button at the top of the form.

•

press the “Close” button (the “X” in the upper right-hand corner of the form).

•

select the File:Exit menu option. Block Load

CHAPTER 8


8.0 INTRODUCTION This chapter describes design load calculations and equipment sizing procedures for cooling systems. Maximum cooling loads are determined using an hour-by-hour calculation approach. Loads for a number of hours specified are examined. Maximum cooling loads are identified from among this group of hours and are then used to size the cooling system. Cooling analyses for single-zone and multiple-zone systems differ slightly. For single-zone HVAC systems, the analysis involves two stages: 1. Zone Load Calculations. First, zone sensible loads are computed for the months and hours specified by the user. A "zone load" is the amount of heat which must be removed in order to maintain zone air at the cooling setpoint temperature. 2. Cooling Coil Load Calculations. Next, system operation is analyzed in order to determine the system airflow rate and the sensible and latent cooling coil loads. Airflows and coil loads are determined for all the months and hours specified.

The sensible and latent coil loads can then be combined to determine the total cooling coil load. The maximum coil load is identified from among all the months and hours considered. Sections 8.1 and 8.2 describe these calculations for single-zone systems in more detail. Calculations for multiple-zone systems are discussed in section 8.3. 8.1 ZONE COOLING LOAD CALCULATIONS In the first step in the analysis zone sensible cooling loads are calculated. A zone load is the amount of heat which must be removed from a zone in order to maintain zone air at the cooling setpoint temperature. This load is the sum of a number of transmission, infiltration, solar and internal load components: Qs = [ Qw + Qg + Qr + Qp + Qslr + Qlt + Qpe + Qoe + Qms + Qi ] [ 1 + Fss/100 ] .... (Eqn 8-1) where:

Block Load

Qs

=

Zone sensible load (BTU/hr or W).

Qw

=

Wall transmission load (BTU/hr or W).

Qg

=

Glass transmission load (BTU/hr or W).

Qr

=

Roof transmission load (BTU/hr or W).

Qp

=

Partition transmission load (BTU/hr or W).

Qslr

=

Solar load (BTU/hr or W).

Qlt

=

Lighting load (BTU/hr or W). 8-1

Chapter 8

COOLING DESIGN CALCULATIONS Qpe

=

People sensible load (BTU/hr or W).

Qoe

=

Other electrical load (BTU/hr or W).

Qms

=

Miscellaneous sensible load (BTU/hr or W).

Qi

=

Sensible infiltration load (BTU/hr or W).

Fss

=

Sensible cooling safety factor (%).

In this program, zone loads are computed using the Transfer Function methodology. This procedure takes into account the transient heat transfer characteristics of all component loads in the building. Currently, Transfer Functions are recommended by ASHRAE as the preferred means of computing hourly loads. These calculations are described in full detail in the E20/TF Load Manual. Finally, you should note that a "zone load" is different from a "coil load". A coil load is the amount of heat removed at the cooling coil. Heat removed at the coil is a combination of heat removed from the zone plus fan and ventilation heat gains, plus portions of the plenum heat gains. Coil load calculations are described in the next section. 8.2 COOLING COIL LOAD CALCULATIONS - SINGLE-ZONE SYSTEMS In the second step of the process, system operation is analyzed in order to determine cooling coil loads. In this procedure airflow rates, dry-bulb temperatures and humidities at all key points in the system are computed. The ultimate goal is to determine the coil inlet and outlet conditions so that the coil load can be calculated. Coil loads are determined for a number of hours and the maximum coil load among these hours is then identified. This analysis is performed in two parts. The first involves a sensible analysis of the system which leads to a calculation of the sensible cooling coil load. In the second part, system humidities are determined in order to compute the latent cooling coil load. Step-by-step procedures for both the sensible and latent system analyses are described in remainder of this section. A. SENSIBLE ANALYSIS 1. Calculate Supply Air Characteristics. First, the zone sensible load is used to determine either the supply airflow rate or the supply temperature. Different calculations are required depending on which supply characteristic the user defined during HVAC system inputs. a. Supply Airflow Rate Defined as CFM (L/s) or CFM/ sqft (L/s/sqm). In this case the specified airflow rate will be used for all hourly cooling coil load calculations. For each hour, a required supply air temperature is computed by solving equation 8-2 for Ts. Qs = pa Vs Cpa Fu (Tc - Ts) .... (Eqn 8-2) where:

8-2

Qs

=

Zone sensible load (BTU/hr or W).

pa

=

Density of air. Value is adjusted for site elevation.

=

psl Pba / Psl

Vs

=

System supply airflow rate (CFM or L/s). For the case in which supply air is specified as CFM/sqft (L/s/sqm) this value is multiplied by the total floor area served by the HVAC system to obtain the system CFM.

Cpa

=

Specific heat for air (.24 BTU/(lbm-F) or 1004.832 J/(kg-K)). Block Load

COOLING DESIGN CALCULATIONS Fu

Chapter 8

=

Units conversion factor.

=

(60 min)/hr for English units.

=

m3/(1000 L) for S.I. Metric units.

Tc

=

Cooling thermostat setpoint temperature (F or C).

Ts

=

Supply air temperature (F or C).

psl

=

Density of air for standard sea level conditions (0.075 lbm/ft3 or 1.201 kg/m3).

Pba

=

Standard atmospheric pressure at site elevation ( psia or kPa).

=

14.696 (1 - 6.87535x10-6E)5.2561 for English units.

=

101.3 (1 - 2.25569x10-5E)5.2561 for Metric units.

Psl

=

Standard atmospheric pressure at sea level (14.696 psia or 101.3 kPa).

E

=

Site elevation (feet or meters above sea level).

b. Supply Temperature Defined. In this case the temperature will be used for all hourly cooling coil load calculations. For each hour the required supply airflow rate is computed by solving Equation 8-2 for Vs. 2. Calculate Supply Fan Heat Gain. Based on the system supply air flow rate, the fan heat gain can be computed next. Fan heat gain is due to friction between air and the fan blades, energy added to the air by compression, energy lost in the fan drive mechanism, and energy losses in the fan motor. Depending on data supplied by the user, fan heat gain is calculated in one of three different ways: a. If a total static pressure is defined for the fan, heat gain is determined using the equation: Qf = Ffu Vs Tsp / nf .... (Eqn 8-3) where: Qf

=

Fan heat gain (BTU/hr or W).

Vs

=

Supply airflow rate (CFM or L/s).

Tsp

=

Total static pressure across fan (in wg or Pa).

nf

=

Combined fan drive, mechanical and motor efficiency (dimensionless). A value of 0.54 (i.e. 54%) is assumed.

Ffu

=


=

.4003 for English units.

=

(62.3 lbm water/cuft)(ft/12 in)(60 min/hr)(.001285 BTU/ft- lb)

=

m3/(1000 L) for Metric units.

b. If a fan brakehorsepower is specified by the user, heat gain is computed using the equation: Qf = Ffu BHP / nm .... (Eqn 8-4) where:

Block Load

Qf

=


Ffu

=


=

2544.3 for English units.

=

(745.7 W/hp)(3.412 BTU/hr/W) 8-3

Chapter 8

COOLING DESIGN CALCULATIONS =

745.7 W/hp for Metric units.

BHP

=

Fan brakehorsepower specified by user.

nm

=

Fan motor efficiency (dimensionless). A value of 0.90 (i.e. 90%) is assumed.

c. Finally, if fan kW is directly specified by the user, heat gain is computed using the equation: Qf = Ffu Pf .... (Eqn 8-5) where: Qf

=


Ffu

=


=

3412 (BTU/hr)/kW for English units.

=

1000 W/kW for Metric units.

=

Fan kW specified by user.

Pf

3. Calculate Coil Outlet Temperature. Based on the values computed thus far, a coil outlet temperature can be determined next. The coil outlet temperature will be used later to compute the coil sensible load. Two different calculation procedures are used depending on whether the supply fan configuration is blow-thru or draw-thru: a. Blow-Thru Fans. For this fan configuration, the coil outlet temperature, Tco is equal to the supply air temperature, Ts. b. Draw-Thru Fans. For this configuration, the coil outlet temperature is lower than the supply temperature due to fan heat gain. The coil outlet temperature is computed using the equation: Tco = Ts - Qf / (pa Cpa Vs Fu) .... (Eqn 8-6) where: Tco

=

Coil outlet temperature (F or C).

Ts

=


Qf

=

Supply fan heat gain (BTU/hr or W).

pa

=

Air density (lb/ft3 or kg/m3). Values are adjusted for elevation.

Cpa

=

Specific heat of air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vs

=

System supply airflow rate (CFM or L/s).

Fu

=


=

60 min/hr for English units.

=


4. Calculate Ventilation Airflow Rate. This and the following four steps are used to determine the cooling coil inlet temperature. This process involves working forward from the point air exits from the zone to the point where air enters the cooling coil, solving for airflow rates and temperatures at each point along the way. First the ventilation airflow rate must be determined. Airflow is calculated in four different ways depending on how the user has defined ventilation air: a. When the ventilation air per unit floor area (CFM/ sqft or L/s/sqm) has been specified, the airflow rate is calculated as: 8-4

Block Load


Chapter 8 Vv = Vvf Atot .... (Eqn 8-7)

where: Vv

=

Ventilation airflow rate (CFM or L/s).

Vvf

=

Ventilation airflow per unit floor area (CFM/ sqft or L/s/sqm).

Atot

=

Total floor area served by system (sqft or sqm).

b. When the ventilation airflow rate (CFM or L/s) is directly specified, no calculation is necessary. c. When ventilation is specified as a percentage of the supply airflow rate, airflow is calculated as: Vv = Vs Fv/100 .... (Eqn 8-8) where: Vv

=


Vs

=

Supply airflow rate (CFM or L/s)

Fv

=

Percentage value specified by user (%).

d. Finally, when ventilation is specified on an airflow per person basis (CFM/person or L/s/person), the airflow is calculated as: Vv = Vvp P .... (Eqn 8-9) where: Vv

=


Vvp

=

Ventilation airflow rate per person (CFM/person or L/s/person).

P

=

Total number of people occupying zone served by the HVAC system at maximum occupancy.

It is important to note that in some unusual situations, the ventilation airflow rate computed will be larger than the system supply airflow rate. This could occur when a fixed ventilation rate (CFM or L/s) and a supply air temperature are defined. For this combination of inputs, it is possible the required supply airflow rate that is calculated will be less than the ventilation airflow specified. When this happens, the supply airflow rate is increased to equal the ventilation airflow rate. This is done because it is assumed ventilation rates must be maintained to conform to codes. After the supply airflow rate has been adjusted, steps 1 through 3 in the sensible analysis procedure must be repeated. Further, in order to maintain the specified supply air temperature, reheat will be required downstream of the cooling coil. 5. Calculate Direct Exhaust Airflow Rates. In some cases, air may be directly exhausted from the zone before it enters the return duct or plenum. This airflow rate is determined in two different ways depending on the user's HVAC system inputs: a. When the direct exhaust air is defined as a total airflow (CFM o r L/s), no calculations are necessary. b. When direct exhaust is specified as a percentage of the ventilation airflow, the direct exhaust airflow is computed using: Vde = Vv Fde/100 .... (Eqn 8-10) where: Block Load

8-5

Chapter 8

COOLING DESIGN CALCULATIONS Vv

=


Vde

=

Direct exhaust airflow rate (CFM or L/s).

Fde

=

Direct exhaust percentage value specified by user (%).

6. Calculate Return Airflow Rate. Next, knowing the direct exhaust airflow rate, the return airflow rate can be calculated using the equation: Vr = Vs - Vde .... (Eqn 8-11) where: Vr

=

Return airflow rate (CFM or L/s).

Vs

=


Vde

=


7. Calculate Return Air Temperature. If a return air plenum is used, portions of the roof, wall and lighting loads may be carried away by air flowing through the plenum. To calculate the temperature of air after it has passed through the plenum, the following equation is used: Tr = Tc + Qp / (pa Cpa Vr Fu) .... (Eqn 8-12) where: Tr

=

Temperature of air after it has passed through the return plenum (F or C).

Tc

=


Qp

=

Total sensible plenum load (BTU/hr or W).

pa

=

Air density (lb/ft3 or kg/m3). Values are adjusted for elevation.

Cpa

=

Heat capacity for air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vr

=

Return airflow rate (CFM or L/s).

Fu

=


=


=


Note: If no return plenum is used, the return air temperature is assumed to be equal to the zone air temperature. 8. Calculate Mixed Air Temperature. Next, the air temperature resulting from the mixture of return air and outdoor ventilation air can be computed: Tmix = [Vv Ta + (Vs - Vv) Tr] / Vs .... (Eqn 8-13) where: Tmix

=

Mixed air temperature (F or C).

Vv

=


Ta

=

Outdoor air temperature (F or C).

Vs

=


Tr

=

Return air temperature (F or C).

9. Calculate Coil Inlet Temperature. At this point, the coil inlet temperature can be computed. Different calculations are required depending on the supply fan configuration: 8-6

Block Load


Chapter 8

a. Draw-Thru Fans. The coil inlet temperature is equal to the mixed air temperature in this case, so no calculation is necessary. b. Blow-Thru Fans. In this case, fan heat gain must be considered so the inlet temperature is computed as: Tci = Tmix + Qf / (pa Cpa Vs Fu) .... (Eqn 8-14). where: Tci

=

Cooling coil inlet temperature (F or C).

Tmix

=

Mixed air temperature (F or C).

Qf

=


pa

=

Air density (lb/ft3 or kg/m3). Values are adjusted for altitude.

Cpa

=

Heat capacity of air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vs

=


Fu

=

Unit conversion factor.

=


=


10. Calculate Sensible Cooling Coil Load. Finally, we're ready to compute the sensible cooling coil load: Qcs = pa Cpa Vs Fu (Tci - Tco) .... (Eqn 8-15). where: Qcs

=

Sensible cooling coil load (BTU/hr or W).

pa

=


Cpa

=

Heat capacity of air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vs

=


Fu

=


=


=


Tci

=

Coil inlet temperature (F or C).

Tco

=


11. Calculate Sensible Ventilation Load. Based on the previous calculations, the sensible ventilation load can also be determined at this point. This calculation is performed differently for cases in which direct exhaust air is used and is not used. For the case in which no direct exhaust air is used: Qvs = pa Cpa Vv Fu (Ta - Tr) .... (Eqn 8-16) where:

Block Load

Qvs

=

Sensible ventilation load.

pa

=


Cpa

=

Heat capacity of air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)). 8-7

Chapter 8

COOLING DESIGN CALCULATIONS Vv

=


Fu

=


=


=


Ta

=

Outdoor air temperature (F or C).

Tr

=

Return air temperature (F or C).

For the case in which air is directly exhausted from the zone before it flows through a return air duct or plenum: Qvs = pa Cpa Vde Fu (Ta - Tc) + pa Cpa (Vv-Vde) Fu (Ta - Tr) .... (Eqn 8-17) where: Qvs

=

Sensible ventilation load (BTU/hr or W).

Vde

=


Tc

=

Cooling thermostat setpoint (F or C).

B. LATENT ANALYSIS The latent system analysis is somewhat more complicated than the sensible analysis. This is due to the inter-dependence of humidities throughout the system. Background information and a description of the general approach to the latent analysis are provided in the following paragraphs. Afterward, the step-bystep calculation procedure is described. BACKGROUND INFORMATION Humidity calculations are frequently a source of confusion among designers. This confusion seems to result from differences between the way humidity was analyzed in older hand-calculation approaches and the way it is analyzed in computer programs. Typically in the older hand-methods a room relative humidity was assumed (usually around 50%) and was then used as the starting point for calculations. It is important to recognize, however, that this assumed room RH is an approximation. For many applications the true room RH is within 5 to 10 percentage points of 50%, so only small to moderate errors are introduced by the RH assumption. For other applications, the true room RH deviates farther from 50% and therefore, the RH assumption introduces larger errors. Rather than rely on an assumed room RH which leads to errors of varying magnitude, Carrier's load estimating computer programs perform the rigorous calculations necessary to determine the true humidities present in the system. This analysis procedure yields more accurate latent coil load results than previous hand-calculation approximations. GENERAL APPROACH Before humidity calculations begin, a sensible load analysis for the air conditioning system must be completed. This analysis defines the airflow rates and dry-bulb temperatures at all points in the system. Next, the basic humidity equations for the system are formulated. There are five separate equations as shown below. These define the latent ventilation load (Eqn 8-18), the latent coil load (Eqn 8-19), the zone latent load (Eqns 8-20 and 8-21), and the relationship between the bypass factor and coil humidities (Eqn 8-22). Qvl

8-8

= paVvhfgFu(wa-wz)

... (Eqn 8-18)

Block Load


Chapter 8

Qcl

= paVshfgFu(wci-wco)

... (Eqn 8-19)

Qzl

= [Ql+paVihfgFu(wa-wz)](Msl) ... (Eqn 8-20)

Qzl

= paVshfgFu(wz-wco)

... (Eqn 8-21)

BF

= (wco-wadp)/(wci-wadp)

... (Eqn 8-22)

= (Tco-Tadp)/(Tci-Tadp) where: BF

=

Cooling coil bypass factor (dimensionless).

Fsl

=

Latent cooling safety factor (%).

Fu

=

Units correction factor.

=


=


hfg

=

Heat of vaporization for water (1054.8 BTU/ lbm or 2.4535 x 106 J/kg).

Msl

=

Latent cooling safety multiplier.

=

(1 + Fsl/100)

Qcl

=

Latent cooling coil load (BTU/hr or W).

Ql

=

Internal latent heat gains due to people and miscellaneous internal sources (BTU/hr or W).

Qvl

=

Latent ventilation load (BTU/hr or W).

Qzl

=

Latent zone load (BTU/hr or W).

Tci

=

Coil inlet temperature (F or C).

Tco

=


Vi

=

Zone infiltration airflow rate (CFM or L/s).

Vs

=


Vv

=


wa

=

Outdoor air specific humidity (lb/lb or kg/kg).

wadp

=

Specific humidity corresponding to apparatus dewpoint for coil (lb/lb or kg/kg).

wci

=

Specific humidity at coil inlet (lb/lb or kg/kg).

wco

=

Specific humidity at coil outlet (lb/lb or kg/kg).

wz

=

Zone specific humidity (lb/lb or kg/kg).

pa

=

Density of air (lb/ft3 or kg/m3). Values adjusted for site el evation.

To solve for the system humidities, a moisture balance for the system must be formulated. Because the total moisture added to and removed from the system must be equal for steady-state conditions, we know that: Qvl - Qcl + Qzl = 0 ... (Eqn 8-23)

Using equations 8-18, 8-19 and 8-20 from above we can rewrite equation 8-23 as : Block Load

8-9

Chapter 8

COOLING DESIGN CALCULATIONS Vswci - Vswco + (ViMsl+Vv)wz = QlMsl/pahfgFu + (Vv+ViMsl)wa ... (Eqn 8-24)

This single equation contains three unknowns (wco, wci, wz) which reveals an important fact - that all system humidities are interdependent. The room humidity is influenced by the supply air provided with humidity wco; the coil outlet humidity is influenced by the coil inlet humidity; the coil inlet humidity is influenced by return air with humidity wz. Thus, no single humidity can be calculated directly. Because of this, the only way to solve the problem is to develop a set of three equations containing the three unknowns and then solve the equations simultaneously. Equation 8-24 serves as the first of the three equations required. To obtain a second equation, we can set Equations 8-20 and 8-21 equal to one another since both are expressions of the zone latent load, Qzl: [Ql + paVihfgFu(wa-wz)](Msl) = paVshfgFu(wz-wco)

This equation can be rewritten as: -Vswco + (Vs + ViMsl) wz = QlMsl/(pahfgFu) + waViMsl ... (Eqn 8-25)

To obtain the third equation, we can use Equation 8-22. Because the coil inlet and outlet dry-bulb temperatures are already known from a sensible analysis of the system, the apparatus dewpoint temperature, Tadp, can be computed. Further, because the apparatus dewpoint is a saturated condition, the corresponding specific humidity, wadp, can be easily determined. Then Equation 8-22 can be rewritten as: (BF)wci - wco = wadp(BF - 1) ... (Eqn 8-26)

Finally, with the set of equations 8-24, 8-25 and 8-26, we have a system of three equations and three unknowns and the equations can be solved simultaneously to determine wci, wco and wz. First, simultaneous solution of the three equations yields the following expression for wz: wz = [waVvBF+QlMsl/(pahfgFu)+waViMsl+wadpVs(1-BF)] / [(ViMsl+Vs - (Vs-Vv)BF ] ... (Eqn 8-27)

Once wz is known, it can be used in Equation 8-25 to solve for wco: wco = [-QlMsl/(pahfgFu)-waViMsl+(Vs+ViMsl)wz]/Vs ... (Eqn 8-28)

Finally, wz and wco can be used in Equation 8-24 to solve for wci: wci = [QlMsl/(pahfgFu) + (Vv+ViMsl)wa + Vswco - (ViMsl+Vv)wz ] / Vs ... (Eqn 8-29)

From this discussion it is evident that calculation of true system humidities involves a fair amount of mathematics and several complicated equations. This is probably why the procedure was never used in older hand-calculation methods. Using a computer, however, it is no trouble to perform the rigorous analysis in order to determine the correct humidity values. The procedure for using these equations to complete the latent system analysis is outlined in the following paragraphs. STEP-BY-STEP LATENT SYSTEM ANALYSIS PROCEDURE 1. Compute Total Internal Latent Heat Gain. The first step is to add up all the internal latent heat gains from people and miscellaneous sources for the zone served by the system. This quantity is referred to as Ql in the humidity equations. 2. Compute Room Humidity. Next, Equation 8-27 is solved to determine the room specific humid ity, wz. 3. Compute Coil Outlet Humidity. Then solve Equation 8-28 for the coil outlet specific humidity, wco. 4. Compute Coil Inlet Humidity. Solve Equation 8-29 for the coil inlet specific humidity, wci. 8-10

Block Load


Chapter 8

5. Calculate Latent Cooling Coil Load. Once the coil inlet and outlet humidities are known, the latent cooling coil load can be determined using Equation 8-19. 6. Calculate Latent Ventilation Load. At this point, the latent component of the ventilation load can also be computed using Equation 8-18. 7. Calculate Resulting Room Relative Humidity. Finally, the resulting relative humidity can also be determined. The relative humidity is determined using standard psychrometric equations with the known values of the zone cooling setpoint temperature, Tc, and the zone specific humidity, wz.

8.3 COOLING ANALYSIS FOR MULTIPLE-ZONE SYSTEMS Cooling analyses for multiple-zone central air handler systems are slightly more complicated than singlezone analyses. The multiple-zone calculation procedure includes three stages: 1. Zone Load Calculations. Zone sensible loads are computed for all zones in the system for all months and hours specified. 2. Zone Airflow Calculations. Next, required airflow quantities for the zones served by the HVAC system are determined. 3. Cooling Coil Load Calculations. Finally, system operation is analyzed to determine the system airflow rate and the sensible and latent cooling coil loads for all months and hours specified.

Sensible and latent coil loads are then combined to obtain the total coil load. The maximum coil load is identified from among all the months and hours considered. Step-by-step details for these calculations are provided in the remainder of this section. A. ZONE LOAD CALCULATIONS Zone sensible cooling loads are computed using the same procedure described for single-zone systems (section 8.1). The only difference is that loads are computed separately for each zone served by the system. The total of sensible loads for all zones served by the system is also calculated for each hour. B. ZONE AIRFLOW CALCULATIONS Next, the required zone airflow rates are calculated. These computations take one of three forms depending upon the supply air characteristic specified. 1. Given a specified supply airflow per unit floor area (CFM/ sqft or L/s/sqm), zone airflow quantities are computed as shown in Equation 8-30. Note that these airflows are not related to a specific system supply temperature, or even to the zone loads. The airflow rates are therefore of questionable use for multiple-zone HVAC systems. Vsz = Vsf Az .... (Eqn 8-30) where: Vsz

=

Zone supply airflow rate (CFM or L/s).

Vsf

=

Supply flow rate per unit floor area (CFM/ sqft or L/(s-sqm)).

Az

=

Zone floor area (sqft or sqm).

2. If a total supply airflow rate is specified for the system, the zone supply air flow rates are determined using zone sensible load ratios: Vsz = Vs (Qsz / Qs) .... (Eqn 8-31) where: Block Load

8-11

Chapter 8

COOLING DESIGN CALCULATIONS Vsz

=


Vs

=

System supply airflow rate defined by user (CFM or L/s).

Qsz

=

Zone sensible load, calculated for hour when maximum cooling coil load occurs (BTU/h or W).

Qs

=

Sum of zone sensible loads for all zones, calculated for hour when maximum cooling coil load occurs (BTU/h or W).

Note that this calculation relies partly on data for the month and hour during which the maximum cooling coil load occurs. Therefore, the zone supply airflow rates cannot be determined in this case until after the cooling coil load analysis has been completed. 3. Finally, given the supply temperature, the zone supply flow rate is computed by solving the following equation for Vsz. Qsz = pa Vsz Cpa Fu (Tc - Ts) .... (Eqn 8-32) where: Qsz

=

Maximum zone sensible cooling load (BTU/hr or W).

pa

=

Density of air (lb/ft3 or kg/m3). Value is adjusted for site elevation.

Vsz

=


Cpa

=


Fu

=

Units conversion factor:

=


=


Tc

=


Ts

=


C. COOLING COIL LOAD CALCULATIONS - SENSIBLE ANALYSIS 1. Calculate Supply Air Characteristics. First, the total zone sensible load is used to determine either the supply airflow rate or the supply temperature. Different calculations are required depending on which supply characteristic has been defined by the user. a. Supply Airflow Rate Defined as CFM (L/s) or CFM/ sqft (L/s/sqm). In this case, the same specified airflow rate will be used for all hourly cooling load calculations. For each hour, a required supply temperature will be computed by solving Equation 8-5. This approach is appropriate for the analysis of constant volume multiple-zone HVAC systems. b. Supply Temperature Defined. In this c ase the specified temperature will be used for all hourly load calculations. For each hour, the required supply airflow rate will be computed using Equation 8-5. This approach is appropriate for the analysis of variable volume multiple-zone HVAC systems.

For the remaining steps in the sensible analysis procedure: 2. Calculate Supply Fan Heat Gain. 3. Calculate Coil Outlet Temperature. 4. Calculate Ventilation Airflow Rate. 5. Calculate Direct Exhaust Airflow Rate. 8-12

Block Load


Chapter 8

6. Calculate Return Airflow Rate. 7. Calculate Return Air Temperature. 8. Calculate Mixed Air Temperature. 9. Calculate Coil Inlet Temperature. 10. Calculate Sensible Cooling Coil Load. 11. Calculate Sensible Ventilation Load.

All calculations are the same as for single-zone systems. In these calculations zone sensible and plenum loads represent the total for all zones served by the system. D. COOLING COIL LOAD CALCULATIONS - LATENT ANALYSIS The same latent cooling load analysis described for single-zone systems is used for multiple-zone systems. The only difference is that the internal latent heat gain, Ql, and the infiltration airflow rate, Vi, represent totals for all zones served by the HVAC system rather than the total for a single zone.

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8-13

Chapter 8

COOLING DESIGN CALCULATIONS (This page intentionally left blank)

8-14

Block Load

CHAPTER 9


9.0 INTRODUCTION This chapter describes design load calculations and equipment sizing procedures for heating systems. A "design-point" analysis technique is used to determine design heating loads. With this technique, loads are analyzed assuming outdoor air is at the winter design temperature. The traditional heating design procedure is to consider only transmission and infiltration components when computing the zone heating load. Further, only zone and ventilation loads are considered when determining the total heating coil load. Readers should note that the heating design condition is not associated with any particular month or hour. In this program, heating analyses involve two stages: 1. Zone Load Calculations. First, zone loads are computed. A "zone load" is the amount of heat which must be added in order to maintain zone air at the heating thermostat setpoint. 2. Coil Load and Sizing Calculations. Next system sizing and heating coil load calculations are performed. For a warm air system, the required supply airflow characteristics are determined along with the resulting heating coil load. For hydronic baseboard systems, required hot water flow rates are computed. For electric baseboard systems, required baseboard wattages are calculated.

Zone load calculations are described in section 9.1 below. Sizing of warm air, hydronic baseboard and electric baseboard systems are each dealt with in the remaining sections in the chapter. Readers should note that in these discussions heating loads are presented as positive numbers in order to simplify the discussions and avoid confusion. 9.1 ZONE HEATING LOAD CALCULATIONS The first step in the analysis involves calculating zone heating loads. This procedure is repeated for all zones served by the HVAC system. A zone load is the amount of heat which must be added in order to maintain zone air at a desired temperature. This load is the sum of a number of transmission and infiltration components: Qzh = [Qw + Qr + Qg + Qp + Qi](1+Fsh/100) ... (Eqn 9-1) where:

Block Load

Qzh

=

Zone design heating load (BTU/hr or W).

Qw

=

Wall transmission load (BTU/hr or W).

Qr

=

Roof transmission load (BTU/hr or W).

Qg

=

Glass transmission load (BTU/hr or W).

Qp

=

Transmission load for partitions adjacent to u nconditioned areas (BTU/hr or W). 9-1

Chapter 9

HEATING DESIGN CALCULATIONS Qi

=

Infiltration load (BTU/hr or W).

Fsh

=

Heating safety factor (%).

All transmission load calculations are performed using a simple (UAdelta-T) equation. The infiltration load is computed using the equation: Qi = paCpaViFu(Th - Ta) ... (Eqn 9-2) where: Qi

=

Heating infiltration load (BTU/hr or W).

pa

=

Density of air (lb/ft3 or kg/m3). Values are adjusted for site elevation. See Chapter 9 for details.

Cpa

=


Vi

=

Heating infiltration airflow rate (CFM or L/s).

Fu

=


=


=


Th

=

Heating thermostat setpoint temperature (F or C).

Ta

=

Outdoor air temperature for winter design condi tion (F or C).

Zone heating load calculations are described in greater detail in the E20/TF Load Manual. 9.2 SIZING CALCULATIONS FOR WARM AIR HEATING SYSTEMS In a warm air heating system, a central heating coil and supply fan are used to provide warm air to each zone served by the system. Sizing procedures for warm air heating systems vary slightly depending on whether the equipment provides both cooling and heating, or heating only. Procedures for each case are documented below. WARM AIR HEATING -- COOLING & HEATING SYSTEM At the start of this procedure several basic load and sizing values are known: Qs

=

Sum of zone heating loads, for all zones served by the HVAC system (BTU/hr or W).

Vs

=

Supply airflow rate (CFM or L/s). This value was determined duri ng cooling sizing calculations. See Chapter 8 for details. Because the system provides both cooling and heating, the same supply airflow rate used for cooling is also used for heating.

Vv

=

Ventilation airflow rate (CFM or L/s). This value was also dete rmined during cooling sizing calculations. See Chapter 8 for details. Since the system provides both cooling and heating, the same ventilation airflow rate will be present for both modes of operation.

Using this data, the sizing procedure is as follows: 1. Calculate Required Heating Supply Temperature. Ts = Qs / (paCpaVsFu) + Th ... (Eqn 9-3) where: 9-2

Block Load


Chapter 9

Ts

=

Heating supply temperature (F or C).

Qs

=

Sum of zone heating loads, for all zones served by the HVAC system (BTU/hr or W).

pa

=

Air density (lb/ft3 or kg/m3). Values are adjusted for site elevation.

Cpa

=

Heat capacity of air (.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vs

=

Supply air flow rate (CFM or L/s).

Fu

=


=


=


=

Heating thermostat setpoint (F or C).

Th

2. Calculate Ventilation Load. Qv = paCpaVvFu(Th - Ta) ... (Eqn 9-4) where: Qv

=

Heating ventilation load (BTU/hr or W).

pa

=


Cpa

=


Vv

=


Fu

=


=


=


Th

=


Ta

=

Outdoor air temperature at winter design condition (F or C).

3. Compute Heating Coil Load. Qhc = Qs + Qv ... (Eqn 9-5) where: Qhc

=

Heating coil load (BTU/hr or W).

Qs

=

Sum of zone heating loads for all zones served by the HVAC system (BTU/hr or W).

Qv

=

Heating ventilation load (BTU/hr or W).

WARM AIR HEATING -- HEATING ONLY SYSTEM At the start of this procedure two basic quantities are known. One quantity is: Qs = Sum of zone sensible heating loads, for all zones served by the HVAC system (BTU/hr or W).

The other is either of the following two items, depending on the user's supply air specification: Vs

Block Load

=

Heating supply airflow rate (CFM or L/s). This value may be directly specified by the user, or entered in terms of CFM/ sqft (L/s/sqm). In the latter case, the 9-3

Chapter 9

HEATING DESIGN CALCULATIONS supply airflow rate is determined by multiplying the CFM/ sqft (L/s/sqm) value by the total floor area served by the heating system. Ts

=

Heating supply air temperature (F or C).

Using this data, the sizing procedure is as follows: 1. Calculate Required Supply Airflow Rate or Temperature. If a supply airflow rate has been specified by the user, equation 9-6 is solved to determine Ts. If a supply temperature has been specified, equation 9-6 is solved to determine Vs. Qs = paCpaVsFu(Ts - Th) ... (Eqn 9-6) where: Qs

=

Sum of zone heating loads for all zones served by the HVAC system (BTU/hr or W).

pa

=


Cpa

=


Vs

=


Fu

=

Conversion factor to provide load in proper units.

=


=


Ts

=

Heating supply air temperature (F or C).

Th

=


2. Calculate Ventilation Airflow Rate. The ventilation airflow rate is computed in one of four ways depending on user specifications: a. When the ventilation air per unit floor area (CFM/ sqft or L/s/sqm) has been specified, the airflow rate is calculated as: Vv = Vvf Atot .... (Eqn 9-7) where: Vv

=


Vvf

=

Ventilation airflow per unit floor area (CFM/ sqft or L/s/sqm).

Atot

=

Total floor area in zones served by system ( sqft or sqm).

b. When the ventilation airflow rate (CFM or L/s) is directly specified, no calculation is necessary. c. When ventilation is specified as a percentage of the supply airflow rate, airflow is calculated as: Vv = Vs Fv/100 .... (Eqn 9-8) where:

9-4

Vv

=


Vs

=

Supply airflow rate (CFM or L/s)

Fv

=

Percentage value specified by user (%). Block Load


Chapter 9

d. Finally, when ventilation is specified on an airflow per person basis (CFM/person or L/s/person), the airflow is calculated as: Vv = Vvp P .... (Eqn 9-9) where: Vv

=


Vvp

=

Ventilation airflow rate per person (CFM/person or L/s/person).

P

=

Total number of people occupying zones served by the HVAC system at maximum occupancy.

Note that if the ventilation airflow rate is greater than the calculated supply airflow rate, the supply flow rate will be increased to equal the ventilation flow rate. A new supply temperature will then be determined using Equation 9-6. The reason for this adjustment is that it is assumed ventilation must be maintained for code requirements. 3. Calculate Ventilation Load. Next, the ventilation load is computed using Equation 9-4. 4. Calculate Heating Coil Load. Finally, the design heating coil load is derived using Equation 9-5.

9.3 SIZING CALCULATIONS FOR HYDRONIC BASEBOARD HEATING SYSTEMS For a hydronic heating system it is assumed heat is provided via hot water baseboard units. If the system also provides ventilation air, a separate hot water coil will be sized to heat ventilation air to the heating thermostat setpoint. At the start of this analysis, the following values are known: Qzh

= Zone design heating load (BTU/hr or W).

deltaTw = Temperature drop for water flowing through baseboard heating coil (F or K).

Steps in the sizing procedure for this system are described below: 1. Calculate Required Hot Water Flow Rates for Zone Baseboards. For each zone included in the HVAC system, a required baseboard hot water flow rate is determined: Vw = Qzh / (pwCpwFwudeltaTw) ... (Eqn 9-10) where: Vw

= Hot water flow rate for zone baseboard unit (gallons/min or L/s).

Qzh

= Design heating load for zone (BTU/hr or W).

pw

= Density of water (62.0 lbm/ft3 or 993.1 kg/m3). Conditions for water at 100 F (37.8 C) are used.

Cpw

= Specific heat of water (1.0 BTU/(lbm-F) or 4186.8 J/(kg-K)).

Fwu

= Units conversion factor. = (60 min/hr)(.13668 ft3/gal) for English units. = m3/(1000 L) for S.I. Metric units.

deltaTw = Temperature drop for water flowing through baseboard heating coil (F or K). 2. Determine Ventilation Airflow Rate. If the HVAC system provides both cooling and heating, then the ventilation airflow rate defined during cooling sizing calculations will be used for heating. For a heating-only system, ventilation air is computed in one of four ways, depending on userBlock Load

9-5

Chapter 9

HEATING DESIGN CALCULATIONS specifications. Refer to section 9.2 for details on this calculation. Readers should note that if ventilation air is specified as a "% of supply air" for a heating-only system, a zero airflow will be used for ventilation. This is because no supply airflow exists. 3. Calculate Ventilation Load. Next, the ventilation heating load is computed using Equation 9-4. 4. Calculate Hot Water Flow Rate for Ventilation Coil. The required water flow rate for a coil which heats ventilation air from the outdoor temperature to the heating setpoint temperature is computed as: Vw = Qv / (pwCpwFwudeltaTw) ... (Eqn 9-11) where: Vw

= Hot water flow rate for ventilation coil (gallons/minute or L/s).

Qv

= Ventilation heating load (BTU/hr or W).

pw

= Density of water (62.0 lbm/ft3 or 993.1 kg/m3). Conditions for water a t 100 F (37.8 C) are used.

Cpw

= Specific heat of water (1.0 BTU/(lbm-F) or 4186.8 J/(kg-K)).

Fwu

= Units conversion factor. = (60 min/hr)(.13668 ft3/gal) for English units. = m3/(1000 L) for S.I. Metric units.

deltaTw = Temperature drop for water flowing through baseboard heating coil (F or K). 5. Compute Totals. Finally, the total heating load is computed using the zone heating loads and the ventilation heating load. The required total hot water flow rate is determined using the zone flow rates and the flow rate for the ventilation coil.

9.4 SIZING CALCULATIONS FOR ELECTRIC BASEBOARD HEATING SYSTEMS For an electric heating system it is assumed heat is provided via electric baseboard units. If the system also provides ventilation air, a separate electric heating coil will be sized to heat ventilation air to the heating thermostat setpoint. At the start of this analysis, the following value is known: Qzh

=

Zone design heating load (BTU/hr or W).

Steps in the sizing procedure for this system are described below: 1. Calculate Required Wattages For Zone Baseboards. For each zone included in the HVAC system, a required baseboard wattage is determined: Pbb = Qzh Feu ... (Eqn 9-12) where:

9-6

Pbb

=

Required wattage for zone baseboard heating unit (Watts).

Qzh

=

Design heating load for zone (BTU/hr or W).

Feu

=


=

0.2930711 (W)/(BTU/hr) for English units.

=

1.0 for Metric units. Block Load


Chapter 9

2. Determine Ventilation Airflow Rate. If the HVAC system provides both cooling and heating, then the ventilation airflow rate defined during cooling sizing calculations will be used for heating. For a heating-only system, ventilation air is computed in one of four ways, depending on userspecifications. Refer to section 9.2 for details on this calculation. Readers should note that if ventilation air is specified as a "% of supply air" for a heating-only system, a zero airflow will be used for ventilation. This is because no supply airflow exists. 3. Calculate Ventilation Load. Next, the ventilation heating load is computed using Equation 9-4. 4. Calculate Wattage for Ventilation Coil. The required wattage for a coil which heats ventilation air from the outdoor temperature to the heating setpoint is computed as: Pva = Qv Feu ... (Eqn 9-12) where: Pva

=

Required wattage for ventilation coil (Watts).

Qv

=

Ventilation heating load for zone (BTU/hr or W).

Feu

=


=

0.2930711 (W)/(BTU/hr) for English units.

=

1.0 for Metric units.

5. Compute Totals. Finally, the total heating load is computed using the zone heating loads and the ventilation heating load.

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9-7

Chapter 9

HEATING DESIGN CALCULATIONS (This page intentionally left blank)

9-8

Block Load

APPENDIX A

INDEX

Activity Level ..................................5-7 Atmospheric Clearness Number ....... 4-3 Building Weight............................... 5-6 Button Config....................................... 1-2, 1-3 Continue....................................1-2, 1-3 Help.......................................... 1-2, 1-3 New System .............................. 6-2, 6-3 New Zone..................................5-2, 5-4 Print.......................................... 7-4 Calculation Parameters .................... 7-2 Calculation Times .......................... 7-1, 7-2 choosing....................................7-2 first hour ...................................7-2 first month.................................7-2 last hour ....................................7-2 last month .................................7-2 Daily Range.....................................4-3 Data Source.....................................4-4 Elevation ......................................... 4-3 Equipment cooling ...................................... 1-1 heating ...................................... 1-1 sizing ........................................ 1-1, 2-1, 8-1, 9-1 Exposure ......................................... 5-11, 5-12 External Shading............................ 5-10 fin extension .............................. 5-10 fin separation............................. 5-10 overhang extension .................... 5-10 overhang height ......................... 5-10 reveal depth ............................... 5-9 type........................................... 5-12 window height ........................... 5-10 window width ............................ 5-10

Block Load

A-1

Index

Appendix A

File Menu ....................................... 2-2 Archive option........................... 2-2, 2-6 Compact option ......................... 2-2, 2-8 Convert DOS Data option.......... 1-3, 2-2, 2-6 Delete option ............................. 2-2, 2-3, 2-6 New option................................ 2-2 Open option............................... 1-3, 2-2, 2-3, 2-6 Page Setup option...................... 2-2, 2-5 Print Setup option...................... 2-2, 2-5 Properties option ....................... 2-2, 2-4 Retrieve option .......................... 1-3, 2-2, 2-7 Save As option .......................... 2-2, 2-4 Save option ............................... 2-2, 2-4 Floor Area ....................................... 5-5, 5-6 Form Archive Project.......................... 2-6 Block Load Report .................... 7-1, 7-4 Calculation Parameters .............. 7-2 Compact Project ........................ 2-8 Convert DOS Data .................... 2-6 Copy Zone ................................ 5-3 Data Storage Drive .................... 1-3 Delete Project ............................ 2-3 Edit City ...................................2-2, 4-1 thru 4-4 Global Zone Changes ................ 5-3 HVAC System Information ........ 6-2 thru 6-8 Move Zone ................................ 5-3 Open Project ............................. 2-2, 2-3 Page Setup ................................ 2-5 Print.......................................... 2-5 Print Setup ................................ 2-5 Project Properties ...................... 2-4 Retrieve Project ......................... 2-7 Save Project As ......................... 2-4 Zone Information....................... 5-2 thru 5-5 Glass area........................................... 5-9, 5-12 external shade type .................... 5-10, 5-12 factor ........................................ 5-10 internal shading ......................... 5-10 type........................................... 5-10, 5-12 U-value .....................................5-10 HELP button........................................ see Button, Help on-line....................................... 1-4 HVAC System................................ 6-1 thru 6-9 arrangement .............................. 6-6, 6-7 A-2

Block Load

Appendix A

Index

attaching zones .......................... 3-1, 3-3 thru 3-5, 5-1 thru 5-4, 6-1, 6-2, 6-3, 6-8 cooling coil bypass factor .......... 6-7 cooling safety factor .................. 6-7 cooling thermostat setpoint ........ 6-7 copying .....................................3-2, 3-3, 6-1, 6-2 creating .....................................3-3, 6-1 thru 6-3 definition ...................................6-1 deleting .....................................6-1, 6-2 design........................................ 1-3 direct exhaust sizing spec........... 6-5 duration.....................................6-4, 6-5 entering system data .................. 1-4, 6-3 fan brakehorsepower.................. 6-6 fan configuration ....................... 6-6 fan kW ...................................... 6-6 fan static pressure...................... 6-6 heating safety factor .................. 6-8 heating thermostat setpoint......... 6-7 hot water delta-T ....................... 6-5 icon........................................... 3-1 thru 3-4, 6-2, 6-3, 7-1 modifying ..................................6-1 thru 6-3 name ......................................... 6-3 overview....................................6-1, 6-2 printing .....................................7-1 return plenum ............................ 6-8 selecting ....................................3-2, 3-3, 6-2, 7-1 start time ...................................6-4, 6-5 supply air sizing specification ....6-5 type........................................... 6-1, 6-3, 6-4 vent air sizing specification ........ 6-5 Infiltration ...................................... 5-8 cooling ...................................... 5-8 heating ...................................... 5-8 Information bar................................ 5-5, 6-3 SETUP.EXE ...................................1-2 Installation, system requirements ...... 1-2 Latitude........................................... 4-3 Lighting.......................................... 5-6 fixture type................................ 5-6 unoccupied diversity factor ........ 5-6 usage......................................... 5-6 wattage multiplier ...................... 5-6 Load calculations ............................... 8-1, 8-2, 9-1, 9-2 coil............................................ 1-1, 8-1, 8-2, 8-11 thru 8-13, 9-1, 9-3, 9-5 design cooling............................ 1-1, 2-1, 4-1 design heating............................ 1-1, 2-1, 4-1, 9-1, 9-5 diversified zone.......................... 1-1 Block Load

A-3

Index

Appendix A estimating..................................1-1, 1-3 glass transmission...................... 8-1, 9-1 infiltration .................................8-2, 9-1, 9-2 latent......................................... 8-1, 8-2, 8-9 thru 8-11, 8-13 lighting...................................... 8-1 maximum cooling ...................... 8-1 miscellaneous ............................ 8-2 other electric.............................. 8-2 partition transmission ................ 8-1, 9-1 people ....................................... 8-2 roof transmission ....................... 8-1, 9-1 sensible .....................................8-1, 8-2, 8-7 thru 8-9, 8-11, 8-12, 9-3 solar.......................................... 8-1 wall transmission....................... 8-1, 9-1 ventilation .................................8-8, 8-9, 8-11, 8-13, 9-3, 9-5 thru 9-7 zone .......................................... 8-1, 8-2, 8-9 thru 8-12, 9-1 thru 9-6 Main window..................................1-3, 4-1, 5-1, 5-2, 6-2, 6-3, 7-1, 7-3 advanced features ...................... 3-2 thru 3-5 appearance ................................ 3-1, 3-2 navigating .................................3-1 thru 3-5 Miscellaneous Load ........................ 5-8 latent load .................................5-8 sensible load .............................. 5-8 unoccupied diversity factor ........ 5-8 Other Electric ................................ 5-6, 5-7 unoccupied diversity factor ........ 5-7 usage......................................... 5-6 Parameter Limits bar ....................... 5-5, 6-3 Partition ......................................... 5-12, 5-13 adjacent region temperature ....... 5-12 definition ...................................5-12 net area .....................................5-12 tab ............................................ 5-12 U-value .....................................5-12 People activity level .............................. 5-7 latent heat gain .......................... 5-7 occupancy .................................5-7 sensible heat gain....................... 5-7 unoccupied diversity factor ........ 5-7 Project data files ...................................2-1, 2-2 data storage drive ...................... 1-3 definition ...................................2-1 editing project data .................... 3-1 managing...................................1-5,2-1 thru 2-8

A-4

Block Load

Appendix A

Index

viewing project data................... 3-1 Reports........................................... 7-1 thru 7-4 Design Solar.............................. 7-3 Design Temperature .................. 7-3 Detailed System Loads .............. 7-3 Detailed Zone Loads .................. 7-3 printing .....................................7-4 Psychrometric Graph ................. 7-3 selecting ....................................7-1, 7-3 System Input ............................. 7-1 System Sizing Summary ............ 7-3 Zone Input.................................7-1 Roof area........................................... 5-12 color.......................................... 5-10 type........................................... 5-11 U-value .....................................5-10 weight ....................................... 5-10 Skylight........................................... 5-12 Slab................................................. 5-8, 5-9 Splash Screen ..................................1-2 Summer Dry Bulb............................ 4-3 Summer Wet Bulb ........................... 4-3 System ............................................ see HVAC System Copy System option................... 3-3, 6-2 Delete System option ................. 6-2 Edit System option .................... 6-2 New System option.................... 6-2, 6-3 System Menu ............................ 6-2, 6-3 Technical Support............................ 1-4, 1-5 Terminals ........................................ 1-1 Units, English and SI Metric ............ 2-1, 2-3, 2-8 Wall area........................................... 5-12 color.......................................... 5-10 type........................................... 5-11 U-value .....................................5-10 weight ....................................... 5-10 Weather definition ...................................4-1 design weather parameters ......... 4-1, 4-3 cooling design day ..................... 4-1, 4-3 Block Load

A-5

Index

Appendix A entering weather data ................. 1-3, 4-1 thru 4-3 heating design day ..................... 4-1, 4-3 icon........................................... 3-1, 4-1 overview....................................4-1 printing .....................................4-4 Winter Dry Bulb.............................. 4-3 Zone attaching to a system ................. 3-3 thru 3-5, 5-1 thru 5-3, 6-8 creating new .............................. 5-1, 5-2 definition ...................................1-3, 5-1 editing ....................................... 5-1, 5-2 entering zone data ...................... 1-3 global changes ........................... 5-1 thru 5-4 icon........................................... 3-1, 3-3, 5-1 thru 5-3, 6-2, 6-3 name ......................................... 5-6 overview....................................5-1, 5-2 types ......................................... 5-1 Unattached Zones area............... 3-1, 3-4, 3-5, 5-2 thru 5-4 Zone Menu .....................................5-2 thru 5-4 Copy Zone option ...................... 5-3 Delete Zone option..................... 3-4, 3-5, 5-2 Edit Zone option ........................ 5-2 Global Changes option............... 5-3, 5-4 Move Zone option ..................... 5-3 New Zone option ....................... 3-3, 5-2

A-6

Block Load

24479682 HVAC Handbook CARRIER Block Load v3 Manual

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