Manual S
Residential Equipment Selection Seco Se cond nd Ed Edit itio ion, n, Ve Vers rsio ion n 1. 1.00 00 Public
Review Draft 1.00 — April 17, 2013 ISBN # 978-1892 978-1892765-58-6 765-58-6
The Second Edition of ACCA Manual S is the
Air Conditioning Contractors of America guide for selecting and sizing heating heating and cooling equipment for single family homes, and low-rise multi-family dwellings.
Commenters must use the ACCA Response Form -- available from www.acca.org/ansi -- to comment on this document. The completed comment form is to be emailed to
[email protected]; noting "Manual S Public Comment from {your last name}" in the subject line.
The ANSI Public Review period is 10 May through 24 June 2013. Public COMMENTS ARE DUE 24 June 2013
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Copyright and Disclaimer This publication and all earlier working/review drafts of this publication are protected by copyright. By makingthis mak ingthis pub public licati ation on ava availa ilable ble for use use,, ACC ACCA A doe doess notwaive anyright anyrightss in cop copyri yright ghtto to thi thiss pub public licati ation. on. No par partt of thi thiss pub public licati ation on or ear earlie lierr wor workin king/ g/revi review ew dra drafts fts of thi thiss pub public licati ation on may be rep reprod roduce uced, d, sto stored red in a ret retri rieva evall sy syst stem em or tra trans nsmi mitt tted ed in an any y fo form rm by an any y tec techn hnol olog ogy y wi with thou outt wri writt tten en per permi miss ssio ion n fro from m AC ACCA CA.. Address requests to reproduce, store, or transmit to: Chris Hoelzel at the ACCA offices in Arlington, Virginia. © 2013, Air Conditioning Contractors of America 2800 Shirlington Road, Suite 300 Arlington, VA 22206 www.acca.org Adoption by Reference Adoption Public Pub lic aut author horiti ities es and oth others ers are enc encour ourage aged d to refe referen rence ce thi thiss doc docume ument nt in law laws, s, ord ordina inance nces, s, reg regula ulatio tions, ns, admini adm inistr strati ative ve ord orders, ers,or or sim simila ilarr ins instru trumen ments. ts. Anydeleti Anydeletions ons,, add additi itions ons,, and andcha change ngess des desire ired d by the theado adoptpting authority must be noted separately. The term “adoption by reference” means references shall be limited to citing of title, version, date and source of publication. Disclaimer and Legal Notice Dilige Dil igence nce has hasbeen beenexe exerci rcised sed in the pro produc ductio tion n of thi thiss pub public licati ation. on. The con conten tentt is bas based ed on an ind indust ustry ry con con-sensus of recognized good practices drawn from published handbooks, manuals, journals, standards, codes, technical papers, research papers, magazine articles, textbooks used for engineering curriculums, and an d on in info forma rmati tion on pre prese sent nted ed dur during ing co confe nferen rences ces an and d sy sympo mposiu siums. ms. AC ACCA CA ha hass mad madee no att attemp emptt to qu quest estio ion, n, investigate or validate this information, and ACCA expressly disclaims any duty to do so. The commentary, discussion, and guidance provided by this publication do not constitute a warranty, guarantee, or endors end orsemen ementt of any con concept cept,, obs observa ervatio tion, n, reco recommen mmendat dation ion,, pro procedu cedure, re, pro process cess,, form formula ula,, dat data-s a-set, et, pro product duct,, or se serv rvic ice. e. AC ACCA CA,, mem member berss of th thee Manual S Rev Review iew Com Commit mittee tee,, and the doc docume ument nt rev review iewers ers do not war war-rant or guarantee that the information contained in this publication is free of errors, omissions, misinterpretations, or that it will not be modified or invalidated by additional scrutiny, analysis, or investigation. Theentireriskassociatedwiththeuseoftheinformationprovidedbythisstandardisassumedbytheuser.
ACCA do ACCA does es not nottak takee any anypos positi ition on wit with h res respec pectt to the theval validi idity ty of any anypat paten entt or cop copyri yrigh ghtt rig rights htsass assert erted ed in con con-nection with any items, process, procedures, or apparatus which are mentioned in or are the subject of this docume doc ument nt,, and andAC ACCA CAdis discla claimsliabi imsliabilit lity y of th thee inf infrin ringem gementof entof an any y pat patent entres result ultingfrom ingfrom the theuse useof of or rel relian iance ce on th this is doc docume ument nt.. Us Users ers of thi thiss doc docume ument nt are exp expres ressly slyadv advise ised d th that at det determ ermina inatio tion n of th thee val validi idity ty of any anysuc such h patent or copyright, and the risk of infringement of such rights, is entirely their own responsibility. Users of this th is do docum cumen entt sh shoul ould d con consul sultt app applic licabl ablee fed federa eral, l, sta state, te, an and d loc local al law lawss an and d reg regula ulatio tions. ns.ACC ACCA A doe doess not not,, by the publication of this document, intend to urge action that is not in compliance with applicable laws, and this docu do cume ment nt ma may y no nott be co cons nstr true ued d as do doin ing g so so.. No Noth thin ing g in th this is ma manu nual al sh shou ould ld be co cons nstr true ued d as pr prov ovid idin ing g le lega gall advice, and the content is not a substitute for obtaining legal counsel from the reader’s own lawyer in the appropriate jurisdiction or state.
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Acknowledgments The auth author, or, Han Hankk Rutk Rutkowsk owski,i, P.E. P.E.,, ACC ACCA A Tech Technica nicall Cons Consultan ultant, t, grat gratefu efully lly ackn acknowle owledges dges the dive diverse rse expe expertise rtiseembo embodied died in the membership of the ACCA Manual S Advisory Committee:
Manual S, Second Edition, Reviewers and Advisors: Mechanical Contractors Dan Foley, Foley Mechanical Inc.; Lorton, VA Ellis G. Guiles, Jr. P.E., TAG Mechanical Systems, Inc.; Syracuse, Syracuse, NY Jolene O. Methvin, Met hvin, Bay Ba y Area Air Conditioning Co nditioning & Heating; Heati ng; Crystal Cryst al River, Ri ver, FL John D. Sedine, Sed ine, Engineered Eng ineered Heating H eating and Cooling, Inc.; Walker, W alker, MI Daryl F. Senica, Senica Air Corporatio Corporation, n, Inc.; Spring Hill, FL Kenneth B. Watson, Roscoe Brown, Inc.; Murfreesboro, TN
Instructors Jack Bartell, Virginia Air Distributor Distributors, s, Inc.; Midlothian, VA John “Pete” Jackson, Alabama Power Company; Co mpany; Mobile, AL Arthur T. Miller, Community College of Allegheny County; Oakdale, PA Fred G. Paepke, Fitzenrider, Fitzenrider, Inc.; Defiance, OH John F. Parker, P arker, J. J . Parker Park er Consulting Consul ting Services; Clanton, AL Thomas A. Robertson, Baker Distributing Company, Inc.; New Haven, MO David E. Swett, Omaha Public Power District; Omaha, NE
Original Equipment Manufacturer’s Pamela Androff, Mitsubishi Electric Cooling & Heating; Suwanee, Suwanee, GA Tom Fesenmyer, Emerson Climate Technologies, Technologies, AC Division; Sidney, OH Raymond A. Granderson, Rheem Manufacturing Company - A/C Division; Fort Smith, AR J. Kelly K elly Hearnsberger, Goodman Manufacturing Company; Houston, TX Tom Johnson, Lennox Industries Inc.; Dallas, TX Eric Weiss, The Trane Company; Tyler, TX Robert Lambert, Carrier Residential and Commercial Systems; Indianapolis, IN
Consultants Charles S. Barnaby, Wrightsoft Inc.; Lexington, MA Stan Johnson, Consultant; Austin, TX Michael Lubliner, Washington State University - Extension Energy Program; Olympia, WA Jack Rise, Jack J ack Rise R ise HVAC H VAC Technical Techni cal Training; Tampa, FL Henry T. Rutkowski, P.E., HTR Consulting, Inc.; Dover, OH William W. Smith, Elite Software, Inc.; College Station, Station, TX Brent Ursenbach, Ursenbach, Salt Lake County Planning & Development; Salt Lake City, UT
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Richard F. Welguisz, HVAC Consultan Consultant; t; Tyler, TX Jon Winkler, W inkler, National Renewable Energy Laboratory (NREL); Golden, CO
Association and Other Participants Timothy M. Donovan, Sheet Metal Workers Local 265; Carol Stream, IL Glenn C. Hourahan, P.E., Air Conditionin Conditioning g Contractors of America (ACCA); Arlington, VA Edward Janowiak, Eastern Eastern Heating & Cooling Council (EHCC); Mt Laurel, NJ Warren B. Lupson, Air-Conditioning, Air-Conditioning, Heating and Refrigeration Institute (AHRI); Arlington, VA Patrick L. Murphy, Refrigeration Service Engineers Society (RSES); Des Plaines, IL
Extended Reviewer to the Committee Ron Bladen, Fairfax County Building Plan Review Department; Department; Fairfax, VA
Special Thanks and Appreciation John D. Sedine Sedi ne for fo r his guidance and leadership as the Committee Chair.
Staff Liaison — Technical Glenn C. Hourahan, P.E., ACCA; Arlington, VA
Staff Liaison — Production, Publishing, and Editing Christopher N. Hoelzel, ACCA; Arlington, VA
Publishing Consultant Page layout and electronic publishing publishing provided by Carol Lovelady, Lovelady Consulting; Roswell, GA
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Dedication Personal Dedication
Professional Dedication
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This overview is not part of the this standard. It is merely informative and does not contain requirements necessary for conformance to the standard. It has not been processed according to the ANSI requirements for a standard, and may contain material that has not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ACCA or ANSI.”
Overview This manual provides procedures for selecting and sizing residential cooling equipment, heat pumps, furnaces and boilers. These procedures emphasize the importance of using performance data that correlates sensible and latent cooling capacity with all the variables that affect performance. Similar principles apply to heat pump selection and sizing, and to furnace and boiler selection and sizing. All guidance produces installed, design condition capacity that is appropriate for theapplicablebuilding load(s), butis less than, or equal to,the over sizinglimit allowed fora given type of equipment. This manual has been divided into two parts - a 'normative' portion and an 'informative' portion. The two, up-front normative sections provide all the equipment selection and equipment sizing criteria necessary to implement the standard's requirements (there are no additional selection requirements or sizing requirements in the balance of the document): Section N1 - General Requirements Section N2 - Equipment Size Limits The informative sections and informative appendices in the balance of this document provide discussion and guidance related to procedure intent and use; includes example problems that detail application of the procedure. These informative presentations are provided to augment practitioner understanding and application of the normative portion: Sections 1 to 4 - Basic Concepts and Issues Sections 5 to 10 - Central Ducted System and Hydronic Heating Examples Sections 11 to 13 - Ductless Air-Air Equipment Appendix 1 to 5 - Implementation Guidance Appendix 6 to 15 - Related Information Appendix 16 to 21 - Ancillary Pages
Commentary on Over Size Limits for Cooling-Only Equipment and Heat Pumps For Manual S guidance, the target value for equipment size is 100% (1.00 factor) of the smallest defensible value for the Manual J total cooling load (sensible load plus latent load). When indoor humidity control for entire cooling season (the summerdesigncondition, andall part-loadconditions)is an issue,totalcooling capacity must be as close as possible to the target value on the high side, or total cooling capacity may be a little less than the target value (0.90 is the absolute minimum factor). Normative Section N2, Tables N1-1 and N1-2 provides upper and lower limits for the installed cooling capacity of various types of cooling-only equipment and heat pump equipment. If cooling season humidity control is not an issue, and if heating season energy use is an issue, the over size limit for heat pump equipment cooling capacity is equal to the ManualJ total cooling load plus 15,000Btuh.This reduceswinter energy use because it increases the amount of seasonal heat provided by the compressor, and reduces the amount of seasonal heat provided by an electric heating coil. Normative Section N2, Table A1-2 shows this guidance. There is no energy use benefit for over sizing cooling-only equipment, regardless of the summer humidity control issue, or the cold winter weather issue. In other words, the 15,000 Btuh exemption does not apply to any type of cooling-only equipment. Even when there is no latent cooling load, summer comfort is improved by adequate room air motion, so the equipment must run as much a possible. As far as energy use is concerned, compressor cycling degrades seasonal efficiency, so the equipment must be a small as possible. There is no energy use benefit for over sizing heat pump equipment installed in a location that has a mild winter climate. This is because electric coil heat is not an issue when the thermal balance point for equipment that has little or no excess cooling capacity is below, at, or slightly above, the Manual J winter design temperature for outdoor air. Therefore, the plus 15,000 Btuh limit does not apply to any type of heat pump equipment installed in a location that has mild winter weather. Also note that on-offcycling degrades seasonal heating efficiency when theoutdoor airtemperatureis above the thermal balance point, and on-off cycling degrades seasonal cooling efficiency, so excess cooling capacity increases annual energy use. Even if there is no latent cooling load, summer comfort is improved by adequate room air motion, so the equipment must run as much a possible.
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Standard Size Issues Residential HVAC equipment is mass produced for economies of scale. Cooling-only equipment and heat pumps have significant jumps in nominal size. The over size limits specified in Table N2-1 and Table N2-2 allow for substantial deviation from the target value because of the realties of the market place. n
For central ducted equipment, the nominal condenser capacity for single compressor speed equipment may start at 1-1/2 tons, and typically increases in ½ ton steps, but there tends to be a 1 ton jump from 4-tons to 5-tons. Some OEM's do not have a 1-1/2 ton product (2 tons is the smallest size). Effective total cooling capacity may be increased or reduced by a mismatch for nominal condenser-evaporator tonnage values, but this is generally a 2,000 Btuh adjustment, more or less. The primary reason for mismatchingcondenser-evaporator tonnage values is to obtain correspondencebetween the evaporator coil sensible heat ratio and the Manual J sensible heat ratio. OEM expanded performance data may not be readily available for condenser-evaporator combinations that deviate from the basic matched-size product. Product availability and delivery time depends on what is commonly purchased vs. what may possibly be purchased.
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For ducted equipment, the nominal condenser-side capacity for a multi-speed or variable-speed compressor typically increases in 1-ton steps. This type of equipment will cycle or modulate between low and high compressor speed for a large number of part-load hours. Thereis significant latentcapacityfor this mode of operation, sotheundesirableeffectof excesscooling capacity,as faras indoor humidity control is concerned, is somewhat less than what it would be for single-speed equipment. However, there is a low limit to equipment cooling capacity. Whenthe cooling load is belowthislimit, the compressor cycles on and off. So for these part-load hours, indoor humidity control is similar to the control provided by single-speed equipment. In other words, excess cooling capacity is an important issue for a significant number of part-load hours.
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Ductless equipment may be as small as one ton (or less), and may have ½ ton steps (or less) to 5 tons. However, a duct systemis required to distribute capacity among a groupof rooms that arenotpartof a commonopen space. Room cooling loads typically range from less than 1,000 Btuh to less than 4,000 Btuh. Indoor air motion occurs in the space that is near the indoor coil,and less so for a common space that is beyond the throw of the indoor coil's grille, and not at all for remote spaces that have partition walls (with or without partition doors). Some indoorcoilsaredesignedto serve a duct system. However, theavailablestaticpressureof theequipment'sblower, andthe type of duct fittings, establishes the distribution limits (distances) of the duct runs.
Efficiency Issue In general, high SEER valuesare at theexpense of latent capacity and indoor humidity control. Excess cooling capacity, is a bigger issue for contemporary high SEER equipment than it was for older, lower SEER equipment.
Job Economics and Practitioner Talent Proper use of expanded performance data (or the software equivalent) does not require much time, and is relatively simple, providingthe data is readily available. However, practitioneraccess to this data maybe limited to products produced by one OEM, or a few OEM's. In addition, expanded performance data may not be readily available for various condenser-evaporator size matches. n
Business issues typically limit practitioner access to the entire collection of available products.
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Time-is-money issues limit the scope of the available equipment capacity investigation.
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Price-point issues may eliminate classes of equipment that have preferred attributes, as far as excess capacity and humidity control are concerned.
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Fine tuning equipment selection by blower Cfm adjustments, and/or condenser-evaporator size matching, takes time and skill.
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Conclusion The possibility of a comfort problem, humidity problem, or mold-mildew problem increases with the amount of excess cooling capacity. The equipment sizing goal is to have no excess total cooling capacity. Tolerance for upside deviation depends on the Manual J sensible heat ratio (JSHR). For example, a 1.18 over size factor is more compatible with an 0.90 JSHR, and less compatible with an 0.75 JSHR.
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Overview of Size Limits for Residential HVAC Equipment Equipment a Tested and Rated by the AHRI
Attributes of Local Climate
Air-Air and Water-Air Cooling-Only & Heat Pump
Mild Winter or Has a Latent Cooling Load
Air-Air and Water-Air Heat Pump Only
Cold Winter and No Latent Cooling load
Notes b, c
Minimum (deficient) and Maximum(excessive) Capacity Factors. d
Issue Cooling Capacity (Btuh)
Single Speed Compressor GLHP e
Air-Air
Total
Multi- and Variable Speed Compressor
GWHP f
0.90 to 1.15
Air-Air
1.25
GLHP e
GWHP f
0.90 to 1.20
0.90 to 1.25
Latent
Minimum = 1.00. Preferred maximum = 1.50 (may exceed 1.5 if no reasonable alternative).
Sensible
Minimum = 0.90. Maximum determined by total and latent capacities.
Total
Maximum capacity = Manual J total cooling load plus 15,000 Btuh; Minimum factor = 0.90
Latent
Latent capacity for summer cooling is not an issue.
Sensible
Not an issue (determined by the limits for total cooling capacity).
a) Central ducted; ductless single-split; ductless multi-split equipment. AHRI: Air Conditioning, Heating and Refrigeration Institute. b) Mild winter: Heating degree days for base 65 F divided by cooling degree days for base 50 F less than 2.0. Cold winter = 2.0 or more. c) Latent cooling load: Manual J sensible load divided by Manual J total load less than 0.95. No latent load = 0.95 or more. d) Minimum and maximum capacity factors operate on the total, latent, and sensible capacity values produced by an accurate Manual J load calculation (per Section 2 of the Eighth Edition of Manual J , version 2.0 or later). Multiply a size factor by 100 to convert to a percentage. For example, 1.15 excess capacity = 115% excess capacity. e) GLHP: Ground loop heat pump (water in buried closed pipe loop). f) GWHP: Ground water heat pump (ground water from well, pond, lake, river, etc., flows though equipment and is discarded).
Electric Heating Coils
Furnaces; Heat Pump supplement; emergency
Load (Bt uh)
Maximum KW
Minimum Capacity Factor
M aximum Capacity Fact or
15,000
5.0
Satisfy Load
See Maximum KW
> 15,000
See Min and Max
0.95
1.75
Minimum and maximum capacity factors operate on the heating load produced by an accurate Manual J load calculation. Multiply a size factor by 100 to convert to a percentage.
Natural Gas, Oil, Propane Furnaces
Duty
Minimum Output Capacity
Maximum Output Capacity
Heating only Heating-Cooling Preferred
1.40
1.00
Heating-Cooling Allowed
2.00
Minimum and maximum capacity factors operate on the heating load produced by an accurate Manual J load calculation. Multiply a size factor by 100 to convert to a percentage. For heating-cooling duty, blower performance must be compatible with the cooling equipment.
Electric, and Fossil Fuel Water Boilers
Duty
Minimum Output Capacity
Maximum Output Capacity
1.00
1.40
Gravity or forced convection terminals in the space, water coil in duct or air-handler.
Minimum and maximum capacity factors operate on the heating load produced by an accurate Manual J load calculation. Multiply a size factor by 100 to convert to a percentage. Refer to OEM guidance if boiler is used for potable water heat, or snow melting.
Hot Water Coils
Duty
Minimum Factor
Gravity or forced convection terminals in the space.
1.00
Water coil in duct or air-handler.
Maximum Factor
Two-position 1.25
Throttling 1.50
Minimum and maximum capacity factors operate on the heating load produced by an accurate Manual J load calculation. Multiply a size factor by 100 to convert to a percentage. Two-position= open-close valve; Throttling = Full modulating 2-way or 3-way valve.
Electric and Fossil Fuel Water Heaters
The space heating load is the Manual J load. The total load is the space heating load plus the potable water load. Refer to OEM guidance for selection and sizing guidance.
Dual Fuel Systems
Heat pump sizing rules apply, heating equipment sizing rules apply, see Section N2-12.
Ancillary Dehumidification
See Section N2-13. May allow +15,000 Btuh excess cooling capacity for cold winter climate.
Humidifiers
Minimum capacity humidification load, excess capacity dependent on smallest size available
AHAM Cooling and Heat Pump Equipment
See Section N2-15 for sizing rules.
Direct Evaporative Cooling Equipment
See Section N2-15 for sizing rules.
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Prerequisites and Learned Skills Manual S assumes the practitioner is familiarwithresidential comfort conditioning systems and equipment,loadcalculations, procedures for selecting and sizing air distribution hardware, and duct design and airway sizing procedures. The prerequisites for using Manual S procedures are summarized here: n
A general understanding of the concepts, components, arrangements, procedures, requirements and terminology that pertain to residential building construction and residential comfort systems.
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Experience with designing residential heating and cooling systems for comfort applications.
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Mastery of residential load calculation methods and procedures (the full version of ACCA Manual J , Eighth Edition).
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Mastery of air distribution principles, and experience with using manufacturer's performance data to select and size supply air hardware and return air hardware, and associated devices (ACCA Manual T ).
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Mastery of duct designprinciples, andexperience with designingductsystems (ACCA ManualD,ThirdEdition).
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A general understanding of HVAC operating and safety controls, control strategies, and control cycles.
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Experience with designing HVAC systems that adjust performance to maintain space temperature set-points at full-load conditions, and at all part-load conditions (i.e., mastery of capacity control issues and strategies).
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Installing and commissioning refrigerant-cycle equipment and fuel burning equipment; and related power supplies, controls and vents.
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Installing and commissioning HVAC systems and components (per the ACCA HVAC Quality Installation Specification).
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Table of Contents Sections N1 and N2 are normative, and are part of this standard.
1-7 1-8 1-9 1-10 1-11 1-12 1-13 1-14 1-15 1-16 1-17 1-18 1-19 1-20 1-21 1-22
Section N1 Definitions and General Requirements N1-1 N1-2 N1-3 N1-4 N1-5 N1-6 N1-7 N1-8 N1-9 N1-10 N1-11
Definitions Rounding Target Value Determination Altitude Vs. Load Calculations OEM Performance Data Return Duct Load Effect Engineered Ventilation Load Effect Interpolation Altitude Vs. Equipment Performance Air Distribution Requirement Degree Day Data
Section 2
Section N2
Cooling-Only and Heat Pump Equipment Selection
Equipment Size Limits N2-1 N2-2 N2-3 N2-4 N2-5 N2-6 N2-7 N2-8 N2-9 N2-10 N2-11 N2-12 N2-13 N2-14 N2-15 N2-16 N2-17
Scope Compliance with Sizing Limits Alternative Method Climate Sizing Metrics AHRI-Rated Cooling-Only Equipment AHRI Heat Pump Equipment Electric Heating Coils Fossil Fuel Furnaces Water Boilers Water Heater Used for Space Heat Dual Fuel Systems Ancillary Dehumidification Equipment Humidification Equipment AHAM-Rated Appliances Direct Evaporative Cooling OEM Performance Verification Path
2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14 2-15 2-16 2-17 2-18 2-19 2-20 2-21 2-22
Sections 1 through 13 are merely informative, and are not part of the this standard.
Section 1
Load Calculation Equipment Operating Limits Seasonal Efficiency Rating Expanded Performance Data Sizing Cooling Equipment Sizing Heat Pumps Thermal Balance Point Diagram Balance Point Manipulation Balance Point Use Supplemental Heat Emergency Heat Auxiliary Heat High Limit Temperature for Heating Coils Design Blower Cfm for Cooling Design Blower Cfm for Heating Design Blower Cfm for Duct Sizing Blower Data Component Pressure Drop Data Operating and Safety Controls System Start Up and Set Point Recovery Air Zoning Controls Ductless Split Controls
Section 3
Equipment Size Issues and Limits 1-1 1-2 1-3 1-4 1-5 1-6
Heat Pump Equipment Size Interpolation Application Compatibility Caveats Electric Heating Coil Size Fossil Fuel Furnace Size Dual Fuel Systems Hot Water Boilers and Water Heaters AHAM Appliances Ancillary Dehumidification Equipment Humidification Equipment Evaporative Cooling Equipment Over Sizing Authority for Heat Pumps Power Disruptions Set-up and Set-Back Performance Expectations Energy and Op-Cost Calculations
Furnace and Water Boiler Selection
Momentary Loads Excess Capacity vs. Performance Indoor Humidity Issues Summer Dehumidification Equipment Sizing Methods Cooling-Only Equipment Size
3-1 3-2 3-3 3-4 3-5
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Load Calculation Operating Limits Seasonal Efficiency Rating Performance Data Furnace Temperature Limit Calculations
TOC
3-6 3-7 3-8 3-9 3-10 3-11 3-12 3-13 3-14 3-15
Water Temperature Limit Calculations Design Value for Furnace Blower Cfm Furnace Blower Data Component Pressure Drop Data Adequate Blower Pressure Equipment Sizing Fuel Burning and Combustion Venting Operating and Safety Controls Air Zoning Controls System Start Up and Set Point Recovery
6-8 6-9 6-10 6-11
Section 7 Central Ducted Furnace Examples 7-1 7-2 7-3 7-4 7-5 7-6 7-7 7-8 7-9 7-10 7-11 7-12
Section 4 Humidity Control and Evaporative Cooling Equipment 4-1 4-2 4-3 4-4 4-5
Ancillary Dehumidification . . . . . Whole House Dehumidifier Examples Ventilation Dehumidifier Examples Evaporative Cooling Winter Humidification Equipment
Section 5 Central Ducted Air-Air Cooling Examples 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 5-13 5-14 5-15 5-16 5-17 5-18 5-19
Heating Load Maximum Heating Capacity Minimum Heating Capacity Blower Cfm Air Temperature Limits Equipment Selection Examples Attributes of the Example Dwelling Balanced Climate Humid Summer Example Hot-Humid Climate Example Dry Summer Cold Winter Example Oil or Propane Furnace Electric Furnace
Section 8
Latent Cooling Load Issues Sensible Heat Ratio Issues Maximum Capacity for Cooling-Only Equipment Maximum Cooling Capacity for Heat Pump Equipment Minimum Cooling Capacity Total Cooling Capacity Value Latent and Sensible Capacity Values Equipment Selection Examples Attributes of the Example Dwelling Balanced Climate Humid Summer Example Hot-Humid Climate Example Dry Summer Cold Winter Example Moderate Latent Load Applications Multi-Speed Performance Variable-Speed Performance Product Comparison Study Compare Fayetteville Equipment Compare Brunswick Equipment Compare Bosie Equipment
Dual Fuel Heating Guidance and Examples 8-1 8-2 8-3 8-4 8-5 8-6 8-7 8-8 8-9 8-10 8-11 8-12 8-13
Economic Question Heat Pump Outputs and Energy Inputs Furnace Outputs and Energy inputs Economic Balance Point Break-Even COP Water-Air Heat Pump Return on Investment Furnace Sizing Heat Pump Sizing Retrofit Application Economic Balance Points - Fayetteville Economic Balance Points - Brunswick Economic Balance Points - Boise
Section 9 Water-Air Equipment Examples 9-1 9-2 9-3 9-4 9-5 9-6 9-7
Section 6 Central Ducted Air-Air Heat Pump Heating Examples 6-1 6-2 6-3 6-4 6-5 6-6 6-7
Heating Performance for Two-Speed Equipment Heating Performance for Variable-Speed Equipment Entering Air Temperature and Heating Capacity Depend on Blower Cfm Use of Minimum Compressor Speed Data
Balance Point Diagram Electric Coil Heat Heating Performance Examples Balanced Climate Example Hot-Humid Climate Example Dry Summer Cold Winter Example Multi-Speed and Variable-Speed Design
Redundant Guidance Entering Water Temperature Balanced Climate Humid Summer Example Hot-Humid Climate Example Dry Summer Cold Winter Example Multi-Speed Performance Variable-Speed Performance . . . . . . . . .
Section 10 Hydronic Heating Equipment Examples 10-1 10-2
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Hot Water Heating System Design Space Heating Load
TOC
10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12
Appendices 1 through 21, and the Index, are merely informative, and are not part of the this standard.
Maximum Space Heating Capacity Minimum Space Heating Capacity Water Temperature Limits Equipment Selection Examples Attributes of the Example Dwelling Cold Winter Example Mild Winter Humid Climate Example Hydronic Air Handler Engineered Ventilation Freeze Protection
Appendix 1 Basic Concepts for Air System Equipment A1-1 A1-2 A1-3 A1-4 A1-5 A1-6 A1-7 A1-8 A1-9 A1-10 A1-11 A1-12 A1-13 A1-14
Section 11 Ductless Single-Split Equipment 11-1 11-2 11-3 11-4 11-5 11-6 11-7 11-8 11-9 11-10
Applications Design Goals Outdoor Equipment Indoor Equipment Performance Data and Guidance Expanded Performance Data Air Distribution Blower Data Duct System Design Equipment Selection and Sizing
Appendix 2 Entering Air Calculations
Section 12
A2-1 A2-2 A2-3 A2-4
Summary of Procedure Dry-Bulb and Wet-Bulb at the Return Grille Return Duct Loads Dry-Bulb and Wet-Bulb at the Exit of the Return Duct A2-5 Outdoor Air Fraction A2-6 Entering Dry-Bulb and Wet-Bulb Temperatures for Raw Air Ventilation A2-7 Entering Dry-Bulb and Wet-Bulb Temperatures for Heat Recovery Ventilation A2-8 Comprehensive Example A2-9 Entering Air Worksheet for Cooling A2-10 Entering Air Worksheet for Heating A2-11 Entering Air Worksheet Psychrometrics
Ductless Multi-Split Systems 12-1 12-2 12-3 12-4 12-5 12-6 12-7 12-8 12-9 12-10 12-11
Load Calculations Operating Conditions for Cooling Equipment Operating Conditions for Heat Pump Heating Operating Conditions for Forced Air Furnaces Design Values for Supply Air Cfm Sensible Heat Ratio Cooling Cfm Determined by Design Prerequisites for Equipment Selection Expanded Performance Data Blower Performance Data Component Pressure Drop Data Performance Data Formats Standard Formats AHRI Certification Data
Applications Design Goals Outdoor Equipment Indoor Equipment Performance Data and Design Guidance Expanded Performance Data for Cooling Expanded Performance Data for Heating Air Distribution Blower Data Duct System Design Equipment Selection and Sizing
Section 13
Appendix 3
Single-Package Equipment
Searching OEM Data for Candidate Equipment
13-1 13-2 13-3 13-4 13-5 13-6 13-7 13-8 13-9 13-10
Applications Design Goals Equipment Attributes PTAC and PTHP Rating Data Home Appliance Rating Data Expanded Performance Data for Cooling Expanded Performance Data for Heating Air Distribution and Noise Equipment Size Heating Performance
A3-1 Total Capacity Method A3-2 Ballpark Cfm Method A3-3 Ballpark Cfm Calculation
Appendix 4 Requirements for Expanded Performance Data A4-1 A4-2 A4-3 A4-4
xix
Cooling Capacity Values Compressor Heating Capacity Values Temperature Range for Air-Air Cooling Temperature Range for Water-Air Cooling
TOC
A4-5 A4-6 A4-7 A4-8 A4-9 A4-10 A4-11
Temperature Range for Air-Air Heating Temperature Range for Water-Air Heating Compressor Speed for Expanded Cooling Data Compressor Speed for Expanded Heating Data Indoor Blower Speed for Expanded Data Interpolation Additional Reporting Requirements
A8-6 A8-7 A8-8 A8-9 A8-10 A8-11 A8-12 A8-13 A8-14 A8-15
Appendix 5 Altitude Effects A5-1 A5-2 A5-3 A5-4 A5-5 A5-6 A5-7 A5-8 A5-9 A5-10 A5-11 A5-12 A5-13 A5-14 A5-16
Appendix 9
Psychrometric Calculations Altitude Affects Equipment Performance Air-Air Cooling Equipment Water-Air Cooling Equipment Hot Water Coil or Chilled Water Coil Electric Heating Coil Gas Burner Oil Burner Hot-Gas Coil Heat Pump Heating Blower Performance Duct System Performance Duct System Design Effect on Duct System Operating Point Air-to-Air Heat Exchangers and Desiccant Wheels
Water-Loop Issues for Water-Air Heat Pumps A9-1 A9-2 A9-3 A9-4 A9-5 A9-6 A9-10 A9-11 A9-12
Multi-Split Piping A10-1 A10-2 A10-3 A10-4
Energy and Op-Cost Calculations
A6-2 A6-3 A6-4 A6-5 A6-6 A6-7 A6-8
Heat Pump Heating - Reducing Use of Electric Coil Heat Intuitive Indicator Simplified Indicator Alternative to the Degree Day Ratio Method Basic Bin-Hour Calculation Advanced Methods Weather Data for Energy Modeling Proximity Issues for Weather Data Use
Pipe Names Basic Two-Pipe System Two-Pipe Recovery System Three-Pipe Recovery System
Appendix 11 Furnace Cycling Efficiency A11-1 Part-Load Efficiency Curves A11-2 Part-Load Efficiency Equations A11-3 Energy Use and Furnace Over Sizing
Appendix 12 Matching Evaporators and Condensing Units
Appendix 7
A12-1 A12-2 A12-3 A12-4
Moisture and Condensation Issues A7-1 A7-2 A7-3
Once-Through Water Earth-Loop Water Buried Water-Loop Design Piping Geometry Length of Buried Pipe Summary of Design Issues Other Issues Energy Calculations Comprehensive Guidance and Software
Appendix 10
Appendix 6 A6-1
Condensation on Interior Surfaces Condensation on Exterior Glass Winter Condensation in Structural Panels Summer Condensation in Structural Panels Condensation Inside of Duct Runs Condensation Outside of Duct Runs Condensation Software Consequences of Humidity Consequences of Condensation Building Science Software
Design Values for Indoor Humidity Moisture Issues for Winter Moisture Issues for Summer
Evaporator Performance Condensing Unit Performance Refrigerant-Side Operating Point Optimum Refrigerant-Side Balance Point
Appendix 13
Appendix 8 Condensation Calculations
Performance Models for Cooling-Only and Heat Pump Equipment
A8-1 A8-2 A8-3 A8-4 A8-5
A13-1 A13-2 A13-2 A13-3 A13-5
Condensation on Surfaces Dew-Point Temperature Condensation Models Minimum Surface Temperature Minimum R-Value
xx
Performance Model Use Altitude Effects -- General Solution Air-Air Cooling Model Modeling an Exhibit of Air-Air Data Presentation Adjustment
TOC
Appendix 20
A13-6 Air-Air Heating Model A13-7 Water-Air Cooling Model A13-8 Deficient Format for Cooling Data A13-9 Modeling an Exhibit of Water-Air Data A13-10 Error Check A13-11 Water-Air Equation Set Use A13-12 Water-Air Cooling Example A13-13 Water-Air Heating Model A13-14 OEM Data Format Issues A13-15 Modeling Issues and Caveats A13-16 Accuracy of OEM Data
Related Resources
Appendix 21 Blank Forms A21-1 Entering Air Condition A21-2 Friction Rate Worksheet
Appendix 14 Air-Air Heat Pump Supply Air Temperature A14-1 A14-2 A14-3 A14-4 A14-5 A14-6
Balance-point Diagram Supply Air Temperatures Supplemental KW Run Fraction Two Stages Improve Performance Sizing Supplemental Heat Staging Supplemental Heat
Appendix 15 Whole-House Dehumidifier Performance A15-1 Latent Load vs. Month of Year A15-2 Expanded Capacity Data A15-3 Dehumidifier Performance Equations
Appendix 16 Glossary
Appendix 17 Symbols, Acronyms and Abbreviations
Appendix 18 Summary of Tables and Equations A18-1 Psychrometric Equations for Air A18-2 State Point of Air - Altitude Effect
Appendix 19 Supporting Detail For Equipment| Sizing Examples A19-1 A19-2 A19-2 A19-3 A19-4 A19-5 A19-6 A19-7
Dwelling Performance and Attributes Balanced Climate with Summer Humidity Warm and Very Humid Climate Cold Winter Hot Dry Summer Climate Moderate Climate with Some Humidity Cold Winter Hot Humid Summer Hot Dry Climate Bin Weather Data
xxi
TOC
xxii
This section is part of the this standard.
Section N1
Definitions and General Requirements This section defines terminology that is unique to the standard. It also summarizes mandatory requirements and procedures that generally apply to equipment selection and sizing efforts.
Capabilities, Sensitivities and Defaults Capability relates to mathematical modeling. For example, load calculation procedures use mathematical models for fenestration loads, structural surface loads, duct loads and engineered ventilation loads. A credible procedure has a model for outdoor conditions, and for every load producing item associated with thestructure, andits comfort system. Equipment performance data provides an other example of a mathematical model.
N1-1 Definitions Terminology that is directly related to showing compliance equipment sizing limit guidance is defined below, and also appears in the glossary. Total Cooling Load
Sensitivity relates to the variables in a mathematical model. For example, a fenestration model may only apply to clear, single pane, wood frame assemblies, or it may apply to any product listed in the NFRC directory. The credibility of the model depends on how its sensitivities match up with the valuables that affect the fenestration load. An equipment performance model has its own set of sensitivities.
For equipment sizing, the sum of the sensible cooling load and the latent cooling load for the summer design condition. Heating Load
For equipment sizing, the heating load for the winter design condition. Target Value
Fixed defaults are standard inputs for sensitivity values. For example, the Manual J leakage values for a sealed duct system are 0.12 Cfm/SqFt for supply runs and 0.24 Cfm/SqFt for return runs (this is one of five leakage options). Fixed defaults must be technically defensible (based on physical and/or theoretical research). Using one, worst-case compass direction for the front door of a production home is a blatant example of improper use of a fixed default.
The target value is the Manual J total cooling load for the summer design condition, for the space served by cooling-only equipment, or heat pump equipment. n
Section N1-3 summarizes the requirements for producing a target value. Section N1-4 deals with altitude, as it affects load calculations.
n
Thetargetvalue andequipment sizingrulesdetermine the minimum and maximum limits for total (sensible plus latent) cooling capacity. There also are lower and upper limits for latent cooling capacity, for sensible cooling capacity, and for electric coil heating capacity. Section N2 provides related guidance and limit values.
Adjustable defaults simplify model use for common occurrences. For example, if day-to-day work typically relates to dwellings that have clear, doublepane, wood frame fenestration, the practitioner may use a form, or software setting, that is designed or set-up to solve this particular problem. The danger is that such forms and settings are used when they do not apply to the project at hand.
AHRI Equipment
OEM air conditioning and heat pump products tested and rated by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI). AHAM Equipment
Full Compressor Speed
OEM air conditioning and heat pump products that are certifiedby the Association of HomeApplianceManufacturers (AHAM).
For single-speed equipment, full compressor speed is the only available compressor speed. For staged equipment, full compressor speed is the maximum available compressor speed. For variable-speed equipment, full compressor speed is the AHRI rating speed (see next item).
AHRI Rating Test for Cooling
For air-air equipment cooling, the Cooling-A test for 95°F/80°F/67°Fair (perANSI/AHRI Standard 210/240). For water-air equipment cooling, the 85°F water in, 95°F water out, 80°F/67°F air test (AHRI Standard 320-98).
AHRI Rating Speed
Variable-speed compressors (typically by inverter technology) operate over a range of speeds. For this N1-1
Section N1
equipment, full compressor speed is the speed used for the AHRI rating test that produces the advertised value for total cooling Btuh. n
Expanded cooling performance data for full compressor speed is used for equipment sizing.
n
Knowledge of the actual compressor speed value (Rpm, for example) for the AHRI rating test for cooling is not required for equipment sizing.
n
It may be that a compressor can operate at speeds thatexceedthespeedusedfortheAHRIratingtest forcooling, butcooling performance forthis speed or speeds is not used for equipment sizing.
n
Sensible, latent, and total cooling capacity values depend on the blower Cfm, and the summer design condition values for outdoor air temperature or entering water temperature, entering air wet-bulb temperature, and entering air dry-bulb temperature.
n
Heat pump heating capacity depends on blower Cfm, and the winter design condition values for outdoor air temperature or entering water temperature, and entering air dry-bulb temperature.
n
Applied capacity values must be for the entering air condition that corresponds to the circumstances that affect the load calculations for cooling and heating. See Sections N1-6 and N1-7.
n
Applied capacity values cooling and heating must be fully interpolated values when equipment manufacturers's data conditions do not exactly match the operating conditions for the summer or winter designcondition. More detailis provide by Section N1-8.
n
For elevations above 2,500 Feet, applied capacity values for cooling and heating must be adjusted for altitude, or follow OEM guidance if an adjustment is required for 2,500 feet, or less. See Section N1-9.
AHRI Rating Test for Heating
For air-air equipment, the compressor heating test for 47°F outdoors. For water-air equipment , the compressor heating test for 70°F entering water temperature. Enhanced Compressor Speed
Heat pump balance point diagrams, and supplemental electric coil size, are normally based on expanded heating performance data for the compressor speed that is used for the AHRI rating test that produces the advertised compressor heating capacity value for a 47°F outdoor air temperature, or a 70F entering water temperature.
Full Capacity
Forsingle-speed equipment, there isonly onecompressor speed. The maximum available compressor speed applies to staged equipment. For variable-speed equipment, this may be the compressor speedfor the AHRIrating test for heating, or the compressor may be able to operate at a higher speed (enhanced speed).
For single-speed equipment, full capacity refers to operation at the only available compressor speed. For staged equipment, full capacity refers to operation at the maximum available compressor speed. For variable-speed equipment, full capacity refers to performance when the compressor operates at the AHRI rating test speed for cooling, or the AHRI rating test speed for heating.
When applicable, expanded heating performance data for enhanced speed is used for balance point diagrams, and for supplemental electric coil sizing, providing that enhanced speed is continuously available for an unlimited amount of time. Enhanced cooling performance is not used to size equipment (see AHRI Rating Speed).
Maximum and Minimum Capacity
For staged equipment and variable-speed equipment, maximum and minimum capacity refers to the highest and lowest compressor speeds allowed by the OEM's design. For some variable speed equipment, maximum compressor speed may exceed the full-capacity speed (see enhanced speed).
Applied Capacity
Applied capacity is the amount of equipment cooling or compressor heating capacity for the operating circumstances produced by the summer design condition, or the winter design condition. n
n
Over Size Factor
The over size factor (OSF) equals the applied equipment capacity value divided by the target value.
Applied cooling capacity is forthefull compressor speed. For variable speed cooling and heat pump equipment, full compressor speed is theAHRI rating speed, as defined on the next page.
OSF = Applied capacity value / Target value Over Size Limit
Applied compressor heating capacity is normally forthecompressor speed used fortheAHRI rating test for heating, but may be for enhanced speed when enhanced speed is continuously available for an unlimited amount of time.
Theover size limit (OSL) is theacceptable amountof deficient or excess applied capacity, as it relates to the target value. The over size factor must be within the boundaries of the over size limit.
N1-2
Section N1
design load. The dehumidifier may hold a lower indoor humidity set-point whenequipment capacity exceeds the moisture load for 55% RH indoors.
Minimum OSL OSF Maximum OSL Section N2 provides OSL values. Expanded Performance Data
Cooling performance data, or heating performance data that correlates sensible and latent cooling capacity, or heating capacity, with all the operating variables that affect the capacity values. Original equipment manufacturers (OEMs) provide this data in electronic or hard-copyform,or as an interactive computer model.The range of the data, as defined by the available choice of operating variables (compressor speed, burner stage or turndown ratio, blower Cfm, outdoor air temperature, entering water temperature, entering wet-bulb temperature, entering dry-bulb temperature, for example) must be compatible with the summer or winter design conditions used for the load calculation.
N1-2 Rounding There will be occasions where the OSF value is slightly different than the OSL value; a 1.201 to 1.209 OSF vs. a 1.20 limit, or a 0.891 to 0.899 OSF vs. a 0.90 limit, for example. For the purpose of comparing the over size factor to the over size limit, ignore everything after the third decimal place, and round up or down to the second decimal place. For example: 1.201 to 1.205 = 1.20 1.206 to 1.209 = 1.21 0.891 to 0.895 = 0.89 0.896 to 0.899 = 0.90
Excess Latent Capacity
N1-3 Target Value Determination
Excess latent capacity equals the latent capacity value indicated by an OEM's expanded cooling performance data minus the latent load for the summer design conditions.Both valuesare forthe operatingcircumstances that apply to the summer design conditions used to compute the cooling loads.
A target value for equipment size must be provided by an aggressive, accurate load calculation that has the appropriate capabilities and sensitivities. The general requirements are summarized here. n
The load calculation, and all the details of the load calculation, must be for a specific dwelling, its equipment, and its distribution system, for a specific location.
n
In regard to the preceding bullet item, one set of design calculations is sufficient for two or more identical dwellings (floor plan and construction details), providing the dwellings face the same compass direction, and have an identical set of system loads.
n
The ANSI standard for performing a residential load calculation is the latest verison of the unabridged version of Manual J , Eighth Edition.
n
Alternative load calculation methods must have similar capabilities and sensitivities, and defensi ble procedures (see the sidebar on the first page of this section).
n
The abridged version of the Eighth Edition of Manual J may, or may not, be an alternative method. This may be used if the attributes of the dwelling's construction and comfort system comply with the Abridged Edition Check List in front of the abridged manual.
n
Theload calculation must be based on information obtained by a careful and accurate survey of plans and drawings, or a site inspection.
n
The load calculation must account for system loads produced by the HVAC equipment and its
Whole-House Dehumidifier
Ancillarydehumidification equipmentthatis designed to process indoor air (the cabinet has an inlet for indoor air, and an outletfor discharge air). The equipmentmay have a duct interface with the primary equipment's duct system, or may have its own independent duct system, or may be an unducted, movable appliance. Its purpose is to provide a high limit (55% RH) for indoor humidity when the momentary sensible load is significantly less than the design (summer condition) load, and the momentary latent load is relatively large, about equal to, or greater than the summer design load. The dehumidifier may hold a lower indoor humidity set-point when equipment capacity exceeds the moisture load for 55% RH indoors. When outdoor air and indoor air are mixed in a duct tee and used as input to a whole-house dehumidifier, the dehumidifier is a ventilation dehumidifier, as far as equipment selection and sizing guidance is concerned. Ventilation Dehumidifier
Ancillarydehumidification equipmentthatis designed to process indoor air and outdoor air (the cabinet has inlets for indoor air and outdoorair, and an outlet for discharge air). Thedehumidifierwill have a duct runto outdoor air, plus duct runs that interface with the primary equipment's duct system. Its purpose is to provide a high limit (55% RH) for indoor humidity when the momentary sensible load is significantly less than the design (summer condition) load, and the momentary latent load is relatively large, about equal to, or greater than the summer N1-3
Section N1
air or water distribution systems, as applicable to the particular application. n
For the guidance in this standard, boiler and heater size is based on the load calculation heating load. Refer to other guidance if the boiler or water heater provides heat for any other purpose (typicallyforpotablewater,perhaps forsnow melting).
n
There shall be no explicit safety factor applied to any step of the load calculation procedure, or to the final value.
n
There shall be no implicit safety factor (fudging input data) applied to any step of the load calculation procedure.
N1-4 Altitude Vs. Load Calculations
n
When applicable, a complete set of blower Cfmvs. external static pressure data is required for air distributionsystemdesign. Air-side componentsthat were in place (produced a pressure drop) during the blower test must be identified by OEM. Air-side components that are not identified as being in-place for the blower test (by blower table footnotes, or by an OEM letterhead response to a stakeholder request for information), must be treated as a source of external airflow resistance.
n
For air distribution system design, air-side pressure drop data is required for any type of coil, filter, or air-side component that produces air flow resistance that is not accounted for by the OEM's blower data.
n
Refrigeration cycle equipment, fossil fuel heating equipment, electrical resistance heating equipment, and hydronic heating equipment that is selected and sized without the aid of adequate performance data, is not in compliance with Manual S guidance.
n
When adequate performance data is not available to authorized stakeholders, or when the available data is incomplete, the OEM must process design information provided by a stakeholder(typically a practitioner), and return values for total, sensible and latent cooling capacity; for compressor heating capacity; or for fossil fuel, electrical resistance, or hydronic equipment heating capacity, as applicable. When applicable, also provide operating range limits, temperature rise limits, andtemperature drop limits.
Altitude sensitive psychrometrics determine the psychrometric properties of outdoor air and indoor air. Infiltration loads and ventilation loads depend on an altitude adjustment for air density. n
Manual J weather data and related procedures have altitude sensitivity.
n
The load calculations for the example problems in the informative sections of this document are adjusted for altitudes above sea level, even if the effect is small..
n
Load calculation procedures and software must provide altitude sensitivity.
n
Altitude also affects equipment performance, see Section N1-9.
N1-5 OEM Performance Data
Sensitivity to Heat Sink and Heat Source Temperature
Comprehensive (expanded) OEM performance data must be used to select and size equipment, and to design the air distribution system. Appendix 4 summarizes the reportingrequirements for determining applied capacity. Related commentary and exhibits appear at various placesin theinformative sections of this document,and in the example problem sections. n
OEM performance data for air-air equipment shows that refrigeration equipment capacity depends on the temperature ofthe outdoor air. For cooling, this is the designoutdoor air temperature used for the cooling load calculation. For compressor heating, this is the design outdoor air temperature used for the heating load calculation.
Cooling capacity maybe reported as total capacity and sensible capacity, or as total capacity with a coil sensible heat ratio.
n
OEM data provides sensible heating capacity values for compressor heat, furnace heat, boiler heat, water heater heat, electric coil heat, and water-coil heat.
n
OEM data provides, as applicable, operating range limitsfor ambient airtemperature,forentering air or water temperature, for leaving air or water temperature, for air or water temperature rise, and for air or water temperature drop.
OEM performance data for water-air equipment shows that equipment capacity depends on the temperature of the water entering the equipment. For cooling, this is the warmest temperature expected for the cooling season (the local ground water temperature, or a much warmer temperature for a buried, closed-loop system). For compressor heating, this is the coldest temperature expected for the heating season (the local ground water temperature, or a much cooler temperature for a buried, closed-loop system).
N1-4
Section N1
For buried, closed-loop (GLHP) systems, maximum and minimum water temperatures depend on a multitude of variables that affect the water-loop design. Water-loop design requires relevant expertise and software. Section 9-2 provides default guidance for maximum and minimum water temperature, see also Appendix 9. n
For this standard, default guidance for entering water temperature is used forexample problems.
n
Default guidance for entering water temperature may be used for preliminary equipment selection and sizing.
n
Final selection and sizing decisions must be based on the specific details of the water-loop design.
n
This standard defers to water-loop design guidance provided by other authority (local code, industry guidance, OEM guidance, for example).
n
For wet-coil cooling, the total, sensible, and latent capacity values for size limit calculations must be based on the entering air wet-bulb and dry-bulb temperatures for the summer design condition.
n
Fordry-coilcooling (higher elevations, or a dryclimate at a lower elevation), the total and sensible capacity values for size limit calculations must be based on a dry-coil value for entering air wet-bulb and a dry-bulb temperature for the summer design condition.
n
For compressor or water-coil heating, equipment capacity depends on the entering dry-bulb temperature for the winter design condition.
n
The entering air temperature (typically dry-bulb, possibly dry-bulb and wet-bulb) for the summer design condition, or the winter design condition, must comply with OEM limits for entering air temperature, and for leaving air temperature.
n
The condition of the air entering the equipment may be the same as the condition of the room air (no return duct or engineered ventilation load).
n
The condition of the air entering the equipment may just depend on the sensible and latent return duct loads (no engineered ventilation loads).
n
The condition of the air entering the equipment may just depend on the sensible and latent engineered ventilation loads (no return duct loads).
n
The condition of the air entering the equipment may depend on the returnductloadsand the engineered ventilation loads.
Sensitivity to Blower Cfm OEM performance data for cooling-only and heat pump equipment shows that cooling performance, and compressor heating performance, depend on blower Cfm. Any blower Cfm listed in the OEM's performance data may be used for equipment selection, but it is best to use a mid-rangevalue in case a minor performance adjustment is required after the equipment is installed. The heating capacity of a hot water coil depends (in part) on airflow Cfm through the coil. This may, or may not, be equal to the blower Cfm, depending on the location of the coil. The temperature rise through a furnace heat exchanger, electric resistance coil, or hot water heating coil depends on the Cfm flowing through the device.
N1-6 Return Duct Load Effect A sensible duct load affects the dry-bulb and wet-bulb temperatures of theentering air. A latent duct load affects the wet-bulb temperature of the entering air.
Sensitivity to Water GPM OEM performance data for water-air refrigeration cycle equipment shows that cooling performance, and compressor heating performance, depend on the water flow rate(Gpm).The OEM may require a water flowrateforan open (once though water system), and a different flow rate for a water-loop system. Hot water coil performance depends on coil Gpm. Water flow rate is a water temperature rise issue for boilers and water heaters. Sensitivity to Entering Air Condition OEM performance data for cooling-only and heat pump equipment shows that total, sensible and latent capacity depends on thecondition of theentering air. OEMperformance data for hot water coils shows that heating capacity depends on the dry-bulb temperature of the entering air.
n
The condition (dry-bulb and wet-bulb temperatures) of the air entering the return duct is the condition of the air at the return grille (the indoor air design condition used for the load calculation).
n
For cooling, the condition of the air leaving the return duct depends on the sensible and latent loads for the return duct.
n
For heating the dry-bulb temperature of the air leaving the return duct depends on the sensible return duct load.
Implementation Section A2-3 shows how a version of Manual J Worksheet G is used to evaluate return duct loads. Appendix 1 provides tables of default values that may be used to estimate theconditionof theairleaving thereturn duct. Appendix 2 has procedures and equations that N1-5
Section N1
Implementation
provide mathematical solutions to specific problems. The main issues are summarized here: n
Appendix 1 provides tables of default values that may be used to estimate the conditionof theairleaving thereturn duct, and the condition of mixed air. Appendix 2 has procedures and equations that provide mathematical solutions to specific problems. The main issues are summarized here:
The psychrometric equations for duct loads depend on an altitude correction factor (ACF). Sensible Btuh = 1.1 x ACF x Cfm x Temp. Difference Latent Btuh = 0.68 x ACF x Cfm x Grains Difference Figure A5-1 provides ACF values.
n
Altitude sensitive psychrometrics determine the relationship between dry-bulb temperature, wet-bulb temperature, relative humidity, and humidity ratio.
n
For a given location, anoutdoor air Cfm value, or a procedure to determine an outdoor air Cfm value is specified by a local code or governing authority, or local authority may be silent on this issue.
n
For consistency, the procedures and examples in this document have altitude sensitivity, even if the effect is small.
n
A fresh air Cfm value per an industry standard, such as ASHRAE 62.2, may be used if engineered ventilation is not locally mandated by a code or authority.
n
Mixed air psychrometrics determine the relationship between outdoor airCfm, returnairCfm; and the associated dry-bulb temperatures, wet-bulb temperatures, and humidity ratios.
n
Altitude sensitive psychrometrics determine the relationship between dry-bulb temperature, wet-bulb temperature, relative humidity, and humidity ratio.
n
For consistency, the procedures and examples in this document have altitude sensitivity, even if the effect is small.
Related Forms and Software Tools Appendix 21 provides a blank Worksheet G form, and forms for implementing Appendix 2 procedures. Some Manual J software products have an altitude sensitive psychrometrics module. Othersources for psychrometric software are available. These software tools are relatively simple to use.
N1-7 Engineered Ventilation Load Effect For indoor air quality, a relatively small amount of outdoor air may be mixed with a much larger amount of return air before it enters the comfort system equipment. A sensible ventilation load affects the dry-bulb and wet-bulb temperatures of the entering air. A latent ventilation load affects the wet-bulb temperature of the entering air. n
Appendix 21 provides forms for implementing Appendix2 procedures. Some Manual J software products have an altitude sensitive psychrometrics module. Other sources for psychrometric software are available. These software tools are simple to use.
If there are no return duct loads, the return air dry-bulb and wet-bulb temperatures depend on the dry-bulb and wet-bulb temperatures at the return grille.
n
Section N1-6 guidance determines the condition of the return air if the return duct is in an unconditioned space.
n
Outdoor air dry-bulb and wet-bulb temperatures for cooling depend on the summer design values fortheload calculation. Outdoorair dry-bulb temperature forheating depends on the winter design value for the load calculation.
n
The condition of the mixed air depends on the outdoor air cfm and the return air Cfm. Atthe air handler, outdoor air Cfm plus return air Cfm equals blower Cfm.
n
Related Forms and Software Tools
N1-8 Interpolation Published OEM performance data typically has steps in the data set, outdoor air dry-bulb temperature in 10F increments, for example. A full interpolation across the set of relevant variables is required when equipment capacity values are extracted from OEM performance data. This may require two or more simultaneous interpolations. For example, sensible cooling capacity for a given blower Cfm depends on outdoor air temperature, entering wet-bulb temperature, and entering dry-bulb temperature. Exact interpolation is used through out this document, even if the effect is small.
N1-9 Altitude Vs. Equipment Performance
The condition of the outdoor air that is mixed with return air may depend on the use and effectiveness of heat recovery equipment (sensible only, or sensible and latent recovery).
The performance of most types of heating-cooling equipment is affected by altitude. For example, OEM equipment performance data is for sea level air density, so cooling capacity, or furnace heating capacity, is
N1-6
Section N1
somewhat less than indicated by the performance data when the equipment operates at 5,000 feet of elevation. The HVAC industry traditionally ignores this effect for altitudes of 2,500 Feet, or less. The guidance in this standard defers to this habit, because the effect is small.
Degree Day Data Comparison For Bosie, ID, and Vicinity ASHRAE
Unless the guidance in this standard is superceded by specific OEM instructions pertaining to installation at altitude, equipment performance must be adjusted for altitudes above 2,500 feet. Appendix 5 guidance and de-rate factors may be used for this purpose when OEM literature does not provide specific guidance for product use at higher elevations.
n
The critical circulation path is the path that has the largest pressure drop for the path's airflow rate.
Lucky Peak Dam
7N Station
HDD-65
5,658
5,698
~
~
CDD-50
3,036
2,624
~
~
DD Ratio
1.86
2.13
~
~
Boise Air Port
Caldwell
Lucky Peak Dam
7N Station
Note 2
HDD-65
5,727
5,606
5,730
6,325
CDD-50
2,856
3,119
2,840
2,527
2.01
1.80
2.02
2.50
DD Ratio
1) CD-ROM in back of the in the 2009 ASHRAE Handbook of Fundamentals. 2) NOAA: Annual Degree Days to Selected Bases, 1971-2000; Climatography of the United States No. 81; Supplement No. 2
For equipment that serves an air distribution system, blower power mustbe adequate for the air flowresistance produced by all air-side components that are external to the OEM's blower data, and the airflow resistance produced by the duct fittings, and straight duct runs in the critical circulation path. A circulation path is the supply air path from the blower to a space, plus the return path from the space, back to the blower.
Caldwell
NOAA
N1-10 Air Distribution Requirement
n
Boise Air Port
Note 1
Figure N1-1 n
The available static pressure, and the total effective length (fitting equivalentlengths plusstraight run lengths) of the critical circulation path (TEL), determines the friction rate value (pressure drop per 100 feet of duct) for duct airway sizing.
n
The Manual D Friction Rate Worksheet summarizes a procedurethat evaluates theprecedingbullet items and determines when blower power is compatible withreasonable ductairway sizes,and duct air velocity limits.
n
The Friction Rate Worksheet procedure may be performed by hand on any piece of physical or electronic paper.
- The circulation paths are parallel paths. - If the blower has enough power for the path that has most airflow resistance (path pressure drop), it has more than enough power for all other paths. - Adjusted balancing dampers in the lower resistance paths make blower power correct for all paths. n
An external pressure dissipating component may be a filter, cooling coil, or heating coil installed in, or at, an air handler or furnace cabinet. This would be any piece of equipment that was not in place for the blower test that provided the values for the blower performance table.
n
A supply grille, a return grille, a balancing damper, a zone damper, and a duct coil are examples of external pressure dissipating components that may be installed in a circulation path.
n
External static pressure (ESP) is the pressure that moves the air though all pressure dissipating items that are external to the blower data.
n
Available staticpressure (ASP)is the pressure that moves the air though the fittings and straight runs in the critical circulation path.
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Available pressure equals external pressure minus thepressure dissipated by components that are external to the blower data.
N1-11 Degree Day Data Per Table N2-2, the limit for excess cooling capacity for heat pump equipment depends on the ratio of heating degree days to the base 65F (HDD-65) to the cooling degree days to the base 50F (CDD-50). A significant increase in excess total cooling capacity is allowed if this ratio is 2.0, or more, providing that the sensible heat ratio for the total and sensible cooling loads for the summer design condition is less than 0.95. The Condition B sizing rule for heat pump equipment applies when the answer to both questions is yes. Degree day information is provided by the sources listed below. This data is not homogenized. For a given location, there will be differences in the degree day ratio, depending on the source of the data. This is not an issue for locations that are decidedly cold, or decidedly warm, but it is an issue for locations that are at the tipping point for the 2.0 DD-ratio test.
N1-7
Section N1
Figure N1-1 (previous page) provides an example of the degreedayvaluesanddegreedayratios,fortheBosie,ID, area. Note that the results of the degree day ratio test are exactly opposite,dependingon thedata source. Also note that the NOAA data has degree day values for three nearby locations, vs. one location for the ASHRAE data. All of these locations are close to each other, and the consensus per the Figure N1-1 ratios, is that the Boise area qualifies for the Condition B sizing rule. Figure N1-1 thinking is not software friendly. Therefore, the practitioner must specify the HDD-65 and CDD-50 values for the location of interest. Either of the following data sources may be used. ASHRAE Weather Data Climatic design information (including degree day data) for 5,564 locations is provided by a CD-ROM in back of the in the 2009 ASHRAE Handbook of Fundamental (or the latest version of this data base). To access this data, load Chapter 14 from the ASHRAE CD, and click on the following link in the first paragraph of Chapter 14. The complete data tables for all 5,564 stations are contained on the CD-ROM that accompanies this book. Or use the computer's operating system to open CD files. Right-click on the CD, and use Explore command to open the Program Files Folder. Double left-click (DLC) on this folder, DLC on the ASHRAE folder, DLC on the 2009 ASHRAE Handbook folder, DLC on the Stations folder, DLC on the StaList_P.pdf file; then find the state of interest, then DLC on the town of interest.
NOAA Degree Day Data Heating and cooling degree day values for various base temperatures are provided by the following NOAA document. This may be downloaded from the NOAA web site at no cost. Annual Degree Days to Selected Bases, 1971-2000; Climatography of the United States No. 81; Supplement No. 2; National Climate Data Center, Asheville N.C. http://cdo.ncdc.noaa.gov/climatenormals/clim81_supp/CLI M81_Sup_02.pdf.
N1-8
Section N2
Equipment Size Limits Heating-cooling equipment is sized for comfort and efficiency. For climates that have significant summer humidity, excess compressor capacity is minimized for optimum indoor humidity control and refrigeration cycle efficiency. For drysummerclimates, latentcooling capacity is not an issue, so the combined heating season efficiencyof a heat pumpcompressorand theelectricheating coil benefits from excess compressor capacity for cooling. There is no benefit from over sizing electric heating coils and fossil fuel heating equipment. Guidance pertaining to equipmentsizing limitstake these issuesinto account.
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Compressor speed staging or modulation has a dramatic effect on system performance, as far as compressor run time at part-load is concerned.
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Blower/fan speed modulation may have a useful effecton compressor runtime at part-load, butthis is notequivalent to thebenefit offeredby compressor speed control.
Single Compressor Speed Equipment For single-speed equipment, there is one compressor speed anda corresponding data set.Therefore, expanded cooling performance data for the only possible compressor speed must be used for equipment sizing.
N2-1 Scope This section provides sizing limits for the following equipment. See Part 2 and Part 3 of this document for application guidance and example problems.
Multi Compressor Speed Equipment Fortwoor more distinct compressor speeds, there maybe performance data for each compressor speed (typically low, or stage one speed; and high, or stage two speed). The expanded cooling performance data for high-speed (full compressor capacity) must be used for equipment sizing.
AHRI-rated cooling-only equipment AHRI-rated heat pump equipment Electric heating coils Fossil fuel furnaces Hot water boilers and water heaters
Variable Compressor Speed Equipment
Dual fuel systems
At this time (early 2013), data presentation for variable compressor speedequipment (thattypically usesinverter technology), varies with the product. In general, there are data exhibits for maximum capacity, an intermediate capacity, and minimum capacity. An OEM may provide all three sets, a maximum-minimum set, or just the data formaximumcapacity;ornodataatall(justtheAHRIrating values).
Ancillary dehumidification equipment Winter humidification equipment AHAM-certified appliances Direct evaporative cooling equipment
N2-2 Compliance with Sizing Limits
The concepts of maximum capacity and full capacity are defined by this document. Per Section N1-1, full capacity is the capacity for the compressor speed used for the AHRI rating test for cooling. It may be that maximum capacityis the same as fullcapacity, or itmay be that maximum capacity is for a compressor speed that exceeds the value used for a AHRI rating test (i.e., for the maximum compressor speed allowed by the OEM's design).
For refrigeration cycle equipment, acceptable size is demonstrated by showing that a capacity value extracted from OEM performance data is in a limited range when compared to a Manual J load value. There is only one data set for equipment that operates at one compressor speed, so there is no question about which data set to use for equipment sizing. Since multi-speed and variable-speed equipment may have two or more sets of performance data, the data set that must be used for equipment sizing is specified here:
For this document, enhanced speed refers to compressor speeds that exceed the speed used for th e AHRI rating test for heating or cooling. Enhanced speed may, or may not, be available on a continuous basis (i.e., enhanced speed may have a time limit triggered by a monitored refrigeration-side, electric power, or motorheatvariable).
ECM Step and Variable Blower Speed Equipment For the equipment sizing guidance in this standard, equipment that operates at one compressor speed is single-speed equipment, regardless of the technology used to control indoorblower speed,andoutdoor fanspeedfor air-air equipment.
Theexpanded cooling performance data forthecompressor speed used for the AHRI rating test that produces the
N2-1
Section N2
advertised value for AHRI total cooling capacity must be used for equipment sizing. The actual compressor speed value used for the rating test is of interest, but this information is not required for equipment sizing. n
The AHRI rating test is common to all products.
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Product SEER is based on the AHRI rating test.
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This eliminates questions pertaining to what maximum or full capacity terminology actually means.
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This eliminates questions pertaining to enhanced speed availability, and endurance.
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This eliminates questions about actual compressor speed values.
calculation engine that processes operating condition data, and returns capacity values. n
N2-3 Alternative Method The equipment sizing goal is to show that equipment latent and sensible capacities are compatible with ManualJ cooling loads when the equipment operates at summer design conditions. The OEM performance verification path applies when published expanded performance data is not commonly available to an OEM-authorized audience, when available data is incomplete for intended equipment use, or when an authorized party needs help with, and/or confirmation of, available data use (see Section N2-17).
Data Availability Availability of expanded performance data for full-cooling capacity is a mandatory requirement for equipment selection and sizing. This applies to equipment that operates at a single compressor speed, two or more compressor speeds, and to equipment that has the variable-speed feature. n
Figures A1-22, A1-23, A1-24 and A1-26 show examples of expanded performance data for single-speed equipment that has one indoor coil.
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Figures 5-11 and5-12 show examples of expanded performance data for two-speed and variable-speed equipment that has one indoor coil.
N2-4 Climate The over size limit (OSL) for cooling-only equipment and heating-only equipment does not depend on the type of climate. The over size limit for heat pump cooling capacity does depend on the type of climate. For heat pumps, practitioners shouldconsider the energy and economic benefits of excess cooling capacity when the following conditions simultaneously occur:
First stage data, or minimum speed data is very useful to system designers and energy use modelers, but is not used for equipment sizing. n
Figures A1-27,A1-28 andA1-29 showexamplesof expanded performance data for equipment that has two or more indoor coils.
Data Attributes Acceptable cooling data must correlate total capacity and sensible capacity (or sensible heat ratio) with outdoor air temperature or entering water temperature, indoor coil (blower) Cfm, entering air wet-bulb temperature, and entering air dry-bulb temperature.
OEM data presentation formats may be different than the noted exhibits, but the noted sensitivities are a mandatory requirement.
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Data delivery may be by paper or electronic tables similar to the figures cited above, or may be a
n
The Manual J sensible heat ratio (JSHR) for the summerdesigndaycoolingloadis0.95orhigher.
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For the location of interest, the ratio of heating degree days, base 65°F to cooling degree days, base 50.0°F is 2.0 or greater. (For this purpose, 64.4°F data is equivalent to 65°F data.)
N2-5 Equipment Sizing Metrics Accurate Manual J load calculations provide target values for equipment capacity. Manual J , Section 2 defines proper use of Manual J procedures. Comprehensive performance dataprovides heating-coolingcapacityvalues.
Acceptable heat pump heating data must correlate compressor heating capacity with outdoor air temperature or entering water temperature, indoor coil (blower) Cfm, and entering air dry-bulb temperature, plus a defrost cycle adjustment for air-air heat pumps. n
When refrigeration cycle equipment has two or more indoor coils, the expanded performance data must be for the configuration that will be installed (a given set of indoor units served by an outdoor unit), when the compressor is operating at the AHRI rating speed.
Accurate values for the condition of the outdoor air, indoor air, and entering air must be used for equipment selection. Appropriate entering water temperature values for heating and cooling are required for water-air equipment. See Sections A1-2, A1-3, A1-4, A1-10. Expanded performance data must be used for equipment selection and sizing. Such data may be a table that covers an adequate range of operating scenarios, or equipment performance software that processes conditional input for a comprehensive range of operating scenarios. N2-2
