HANDBOOK OF AIR CONDITIONING SYSTEM DESIGN

OTHER McGRAW-HILL HANDBOOKS OF INTEREST

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Engineering TablesMetals Engineering-DesignMetals Engineering-ProcessesMetals Properties

AMERICAN SOCICTY OF TOOL AND MANUFACTURING ENGINEERS:Die Design HandbookManufacturing Planning and

Estimating HandbookHandbook of Fixture DesignTool Engineers Handbook

ARCHITECTURAL RECORD . Time-Saver StandardsBEEn

HANDBOOK OFAIR CONDITIONINGSYSTEM DESIGN

Carrier Air Conditioning Company

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&Ie M C G R A W - H I L L B O O K C O M P A N Y

New York Sara Francisco Toronto London Sydney

HANDBOOK OF AIR CONDITIONING SYSTEM DESIGN

apyright @ 1965 by McGraw-Hill, Inc. All Rights Reserved.

@ 1960, 1963, 1964, 1965 by Carrier Corporation. Printed in the United States of-4merica. This book, or parts thereof, may not be reproduced in any form withoutpermission of the publishers. Lib7ary of Congress Catalog Card Number 65-17650.

.

ISBN 07-010090-X

15 16 17 18 HDHO 8543210

PREFACE

The Handbook of Air Conditioning System Design is the first completepractical guide to the design of air conditioning systems. It embodies all theknowledge and experience gained over the past fifty years by the pioneer in thefield, Carrier Air Conditioning Company.

This handbook is tailored to the specific needs of the man responsible forthe details of design, and, therefore, the foremost consideration has been therequirements of the consulting engineer. In fact, many of the concepts embodythe up-to-date thinking of consulting engineers.

If any one word best describes this work, it is the word practical.

l It is usable at all educational levels. Il It provides practical data for professional designers who need optimum

solutions on a day-to-day basis.l It bridges the gap between air conditioning texts and manufacturers

product catalogs.l It provides proved system design techniques and assures quality of appli-

cation with minimum service requirements.l It provides guidance in simplified form.l It provides a reference source employing the best techniques of indexing

and format.

This Handbook of Air Conditioning System Design is a companion piece tomanufacturers product literature. Together the handbook and product litera-ture make up a complete engineers manual.

Those using this book for study will benefit from clear applicable examplespresented in each of the engineering sections.

In summary, this Handbook of Air Conditioning System Design is a quickreference for those actively engaged in designing air conditioning systems, ateaching work for those studying air conditioning system design, and a refresherfor those engineers with wide experience in the field.

* * *

Grateful appreciation is hereby extended to those hundreds of Carrier engi-neers who generously contributed to the total body of knowledge herein, andto those consulting engineers, mechanica contractors, and architects who sowillingly and enthusiastically contributed their experience to this project.

Carrier Air Conditioning Company

TENAGA EWBANK PRt$CE,LIBRARY

CONTENTS

p fre ace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V

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l-ll-9

l-25l-41l-59l-891-99

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2-l2-172-65

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3-l3-193-433-81

4-l

4-l4-234-55

5-1

5-l5-l 15-195-275-315-47

P a r t 1 LOAD- ESTIMATING . .. .:: . . . . . . . . . . . . .--.-- ..--..:-

1.2 .3 .4 .5 .6 .7 .8 .

1

Building Survey and Load Estimate . . . . . . .Design Conditions . . . . . . . . . . . . . . . . . . . . . . .Heat Storage, Diversity and Stratification .Solar Heat Gain thru Glass . . . . . . . . . . . . . .Heat and Water Vapor Flow thru StructuresInfiltration and Ventilation . . . . . . . . . . . . . .Internal and System Heat Gain . . . . . . . . . . .Applied Psychrometrics . . . . . . . . . . . . . . . . . .

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,Part 2.~ AIR DISTRIBUTION :. . . . . . . . . . . . . . . . . . . .lib_

1. Air Handling Apparatus . . . . . . . . . . . . . . . . . . . . . . . . .2. Air Duct Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Room Air Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . .

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. . . . . .

--Part 3 : PIPING DESIGN .. :: . . . . . . . . . . . . . . . . . . . . . .:- -. -

1. Piping Design-General . . . . . . . . . . . . . . . . . . . . . . . . .2. Water Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Refrigerant Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. Steam Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . ......

......

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

.

: Part 4. REFRIGERANTS; BRINES; OIL.?: : :. :. .L.-.-.-- ..~ I1. Refrigerants . . . . . . .2. Brines . . . .... . . . . . . . . . . . . . . . . . . .3. Refrigeration Oils . . . . . . . .

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.+ Part 5. WATER CONDITIONING . . . . . . . . . , . . . . . . . . .. .

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1. %ter Conditioning-General2. Scale and Deposit Control . . .3. Corrosion Control . . . . . . .4. Slime and Algae Control . . . .5. Water Conditioning Systems .6. Definitions . . . . . . . . . . . . . . . . .

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IPart 6 . AIR HANDLING EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . .

I. Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Air Coriclitioning Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Unitary Equiprncnt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. :l(~rcssory Erlliiprncnt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part 7 . REFRIGERATION EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . .

1. Reciprocating Refrigeration Mnrhine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 . Centrifugal Rcfrigcrntion Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . 3. Absorption Refrigeration Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-1. CombinaGon r\hsorption-Centrifugal System . . . . . . . . . . . . . . . . . . . . . . . .5. ITent Rejection Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part 8. AUXILIARY EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Centrifugal Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Motors and Motor Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Boilers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. Miscellaneous Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part 9. SYSTEMS AND APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . .

1. Systems and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part 10. ALL-AIR SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Convention& Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Constant Volume Induction System 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Multi-zone Unit System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. Dual-duct System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5. Variable Volume; Constant Temperature System . . . . . . . . . . . . . . . . . . . . .6. Dual Conduit System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

\

Part 11. AIR-WATER SYSTEMS ....................................

1. Induction Unit System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Primary Air Fan-coil System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part 12. WATER AND DX SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Fan-coil Unit System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. DX Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6-IG-17G--l 5G-5 1

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7-17-217-337-477-55

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8-l8-178-5 18-61

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10-l10-9

10-17lo-2510-3510-41

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11-l1 l-23

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12-112-11

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HANDBOOK OFAIR CONDITIONINGSYSTEM DESIGN

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Par-t 1LOAD ESTIMATING

CHAPTER 1. BUILDING SURVEY AND LOAD ESTIMATE

The primary function of air conditioning is tomaintain conditions that are (1) conducive tohuman comfort, or (2) required by a product, orprocess within a space. To perform this function,equipment of the proper capacity must be installedand controlled throughout the year. The equipmentcapacity is determined by the actual instantaneouspeak load requirements; type of control is deter-I xd by, the conditions to be maintained duringped~ and partial load. Generally, it is impossible tomeasure either the actual peak or the partial loadin any given space; these loads must be estimated.It is for this purpose that the data contained in Part1 has been compiled.

Before the load can be estimated, it is impera-tive that a comprehensive suruey De made to assureaccurate evaluation of the load components. If thebuilding facilities and the actual instantaneous loadwithin a given mass of the building are carefullystudied, an economical equipment selection and sys-tem design can result, and smooth, trouble free per-formance is then possible.

The heat gain or loss is the amount of heat in-stantaneously coming into or going out of the space.The actual load is defined as that amount of heatwhich is instantaneously added or removed by theenllipment. The instantaneous heat gain and thes. 11 load on the equipment will rarely be equal,because of the thermal inertia or storage effect ofthe building structures surrounding a conditionedspace.

Chapters 2, 4, 5, 6, and 7 contain the data fromwhich the instantaneous heat gain or loss is esti-mated. Chapter 3 provides the data and procedurefor applying storage factors to the appropriate heatgains to result in the actual load. Chapter 8 providesthe bridge between the load estimate and the equip-ment selection. It furnishes the procedure for estab-lishing the criteria to fulfill the conditions requiredby a given project.

The basis of the data and its use, with examples,are included in each chapter with the tables andcharts; also an explanation of how each of the heatgains and the loads manifest themselves.

BUILDING SURVEY

SPACE CHARACTERISTICS AND HEAT LOADSOURCES

An accurate survey of the load components of thespace to be air conditioned is a basic requirementfor a realistic estimate of cooling and heating loads.The completeness and accuracy of this survey is thevery foundation of the estimate, and its importancecan not be overemphasized. Mechanical and archi-tectural drawings, complete field sketches and, insome cases, photographs of important aspects arepart of a good survey. The following physical aspectsmust be considered:

1. Orientation of building - Location of the space to be air conditioned with respect to:a) Compass points -sun and wind effects.b) Nearby permanent structures - shading

effects.c) Reflective surfaces - water, sand, parking

lots, etc.2. Use of space(s) - Office, hospital, department

store, specialty shop, machine shop, factory,assembly plant, etc.

3. Physical dimensions of space(s) - Length,width, and height.

4. Ceiling height - Floor to Hoor height, Hoor toceiling, clearance between suspended ceilingand beams.

5. Columns and beams - Size, depth, also kneebraces.

6. Construction materials - Materials and thick-ness of walls, roof, ceiling, floors and parti-tions, and their relative position in the struc-ture.

7. Surrounding conditions - Exterior color ofwalls and roof, shaded by adjacent buildingor sunlit. Attic spaces - unvented or vented,gravity or forced ventilation. Surroundingspaces conditioned or unconditioned - tem-perature of non-conditioned adjacent spaces,such as furnace or boiler room, and kitchens.Floor on ground, crawl space, basement.

8. Windows - Size and location, wood or metal

l-2 I !ART 1. LOAD ESTIMATING

9 .

10.

11.

12.

1 3 .

14.

sash, single or double hung. Type of glass -single or multipane. Type of shadi-ng device.Dimensions of reveals and overhangs.Doors - Location, type, size, and frequency ofuse.Stairways, elevators, and escalators- Location,temperature of space if open to uncondi-tioned area. Horsepower of machinery, ven-tilated or not.People - Number, duration of occupancy,nature of activity, any special concentration.At times, it is required to estimate the numberof people on the basis of square feet per per-son, or on average traffic.Lighting - Wattage at peak. Type - incan-descent, fluorescent, recessed, exposed. If thelights are recessed, the type of air flow overthe lights, exhaust, return or supply, shouldbe anticipated. At times, it is required to esti-mate the wattage on a basis of watts per sq ft,due to lack of exact information.Motors - Location, nameplate and brakehorsepower, and usage. The latter is of greatsignificance and should be carefully evalu-ated.The power input to electric motors is notnecessarily equal to the rated horsepower di-vided by the motor efficiency. Frequently thesemotors may be operating under a continuousoverload, or may be operating at less thanrated capacity. It is always advisable to meas-ure the power input wherever possible. Thisis especially important in estimates for indus-trial installations where the motor machineload is normally a major portion of the cool-ing load.

APPl iances, business machines, electronicequipment - Location, rated wattage, steamor gas consumption, hooded or unhooded, ex-haust air quantity installed or required, andusage.Greater accuracy may be obtained by measur-ing the power or gas input during times ofpeak loading. The regular service meters mayoften be used for this purpose, provided poweror gas consumption not contributing to theroom heat gain can be segregated.Avoid pyramiding the heat gains from variousappliances and business machines. For exam-ple, a toaster or a waffle iron may not be usedduring the evening, or the fry kettle may notbe used during morning, or not all business

15.

16.

17.

machines in a given space may be used at thesame time.Electronic equipment often requires individ-ual air conditioning. The manufacturersrecommendation for temperature and humid-ity variation must be followed, and these re-quirements are often quite stringent.Ventilation - Cfm per person, cfm per sq Et,scheduled ventilation (agreement with pur-chaser), see Chapter 6. Excessive smoking orodors, code requirements. Exhaust fans-type,size, speed, cfm delivery.Thermal storage - Includes system operatingschedule (12, 16 or 24 hours per day) specifi-cally during peak outdoor conditions, permis-sible temperature swing in space during adesign day, rugs on floor, nature of surfacematerials enclosing the space (see Chapter 3).Continuous or intermittent operation -Whether system be required to operate everybusiness day during cooling season, or onlyoccasionally, such as churches and ballrooms.If intermittent operation, determine durationof time available for precooling or pulldown.

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LOCATION OF EQUIPMENT AND SERVICES ,The building survey should also include informa-

tion which enables the engineer to select equipmentlocation, and plan the air and water distributionsystems. The following is a guide to obtaining thisinformation:

1. Available spaces - Location of all stairwells,elevator shafts, abandoned smokestacks, pipeshafts, dumbwaiter shafts, etc., and spaces forair handling apparatus, refrigeration ma-chines, cooling towers, pumps, and services(also see Item 5).

2. Possible obstructions - Locations 0E all elec-trical conduits, piping lines, and other ob-structions or interferences that may be in theway of the duct system.

3. Location of all jire walls and partitions -Requiring fire dampers (also see Item Ih).

4. Location of outdoor air intakes - In referenceto street, other buildings, wind direction, dirt,and short-circuiting of unwanted contami-nants .

5. Power seruice - Location, capacity, currentlimitations, voltage, phases and cycle, 3 or 4wire; how additional power (if required) maybe brought in ,and where.

6. Water seroice - Location, size of lines, ca-

CHAP-I-El< I . l\LJII,DING SlJKVEY .\ND LO>\11 ESlIM.\IE 1-3

ljacity, pressure, maximum temperature.7. SLetlm .semice - Location, size, capacity, tern-

perature, pressure, type of return system.8. I

l-4 l.\Rl I . LO,\11 I:SII,\I.\~IIN(~

HAP

=tEF

3&4

5

8

TABLE REFERENCESI

ITEM AREA OR S U N G A I N O RCluANTlrv ! /TEMP DIFF. FACTOR

SOLAR GAIN-GLASSG L A S S Wlill S O FT U T0~56&7 6 2 TBL 1 6 . 1 7

9.lORll 1G L A S S ~ S T O R A G E SQ FT X, wL9-3++ PP 5 2 . 5 4 !

SOFTX, 1:GLASS--1

G L A S SWITHOUT

-1 S T O R A G ES o F T k

TEL 15 id--;

roi 15 CORR I

S K Y L I G H T !: -- PP 44-49 ,

CHAPTER I. I1UILDINC; SlJKVliY .\NI> LO,\D ESIIM;\TE 1-s

4. The clir 71~ipr)~ ~MS~~W - i\ Iiighcr wpoipressure surrounding contlitionctl space ca~scswater v a p o r t o liow tilt-u the l)uilding niate-rials. This load is signilicant only in low dcw-1)oint al~l~lications. Tile data required t o esti-nlate this load is containccl in Table JO, p(/geSf. In comlort applications, this load is neg-lected.

5 . The wield blorui,lg trgtrilrst ~1 side of tlte I~rliltl-irjg-1Vintl c;iuscs the outdoor air that is higlicrin tempcraturc ant1 moisture content to infil-trate thru the cracks around the doors andwindows, resulting in locali~ctl scnsiblc ant1latent heat gains. All or part of this infiltrationmay be ofFset by air being introduced thru theapparatus for ventilation purposes. Cl/npler hcontains the estimating data.Ozltdoor niy usunlly wquired /(II. ueiltilntiotlpz+oses - Outdoor air is usually necessary toflush out the space and keep the odor leveldown. This ventilation air imposes a coolingand dehumidifying load on the apparatus be-cause the heat and/or moisture must beremoved. i\Iost air conditioning equipmentpermits some outdoor air to bypass the coolingsurface (see Chapter 8). This bypassed outdoorair becomes a load within the conditionedspace, similar to infiltration; instead of comingthru a crack around the window, it enters theroom thru the supply air duct. The amountof bypassed outdoor air depends on the typeof equipment used as outlined in Chnptey 8.Table $5, page 97, provides the data from whichthe ventilation requirements for most comfortapplications can be estimated.

ie foregoing is that portion of the load on thea; .anditioning equipment that originates outsidethe space and is common to all applications.

INTERNAL LOADSChapter 7 contains the data required to estimate

the heat gain from most items that generate heatwithin the conditioned space. The internal load, orheat generated within the space, depends on thecharacter of the application. Proper diversity andusage factor should be applied to all internal loads.AS with the solar heat gain, some of the internalgains consist of radiant heat which is partially stored(as described in Chnpter 3), thus reducing the loadto be impressed on the air conditioning equipment.

Generally, internal heat gains consist of some orall of the following items:

1. People - The human body thru metabolismc

VI

generates heat within itself ant1 rcleascs it byradiation, convection, and evaporat ion Iromthe su~l;~cc, mtl by coI1vection arid evaporationin the respiratory tract. The amount of heatgenerated 2nd rcleasetl depends on surrountl-ing tcniperaturc and on the activity level ol theperson, as listed in Ttrble fS, f-1ge 100.

2. Liglct.9 - Illi~niinaiits convert electrical powerinto light ant1 licat (refer to Cllclptel- 7). Someof the heat is radiant and is partially stored(see C/upter 3).

3 . Appliuuces - Rcstaiirants, hospitals, labora-tories, and some specialty shops (beauty shops)have electrical, gas, or steam appliances whichrelease heat into the space. Tables 50 th?-u 52,pnges 101-103, list the recommendecl heat gainvalues for most appliances when not hooded. Ifa positive exhaust hood is used with the ap-pliances, the heat gain is reduced.

4. Electric calcfilnting machines - Kefer to manu-facturers data to evaluate the heat gain fromelectric calculating machines. Normally, notall of the machines would be in use simulta-neously, and, therefore, a usage or diversityfactor should be applied to the full load heatgain. The machines may also be hooded, orpartially cooled internally, to reduce the loadon the air conditioning system.

5. Electric motors - Electric motors are a signifi-cant load in industrial applications and shouldbe thoroughly analyzed with respect to operat-ing time and capacity before estimating theload (see Item 13 under Space Character-istics and Heat Load Sozlrces). It is frequentlypossible to actually measure this load in exist-ing applications, and should be so done wherepossible. Table 53, page 105, provides data forestimating the heat gain from electric motors.

6. Hot pipes and tanks - Steam or hot waterpipes running thru the air conditioned space,or hot water tanks in the space, add heat. Inmany industrial applications, tanks are opento the air, causing water to evaporate into thespace. Tables 54 thou 58, pages 107-109 pro-vide data for estimating the heat gain fromthese sources.

7. Miscellaneous sowces - There may be othersources of heat and moisture gain within aspace, such as escaping steam (industrial clean-ing devices, pressing machines, etc.), absorptionoE water by hygroscopic materials (paper, tex-tiles, etc.); see Chapter 7.

In addition to the heat gains from the indoorand outdoor sources, the air conditioning equip-ment and duct system gain or lose hcnt.. The fansand pumps requirctl to distribute the air or waterthru the system add heat; heat is also added tosupply and return air ducts running thru warmeror hot spaces; cold air may leak out of the supplyduct and hot air may leak into the return duct. Theprocedure for estimating the heat gains from thesesources in percentage of room sensible load, roomlatent load, and grand total heat load is containedin Clmrt 3, ;b~ge I IO, and Tables 59 rind 60, pa.ges111-113.

HEATING LOAD ESTIMATEThe heating load evaluation is the foundation for

selecting the heating equipment. Normally, theating load is estimated for the winter design

temperatures (Chnpter 2) usually occurring at night;therefore, no credit is taken for the heat given offby internal sources (people, lights, etc.). This esti-mate must take into account the heat loss thru thebuilding structure surrounding the spaces and theheat required to offset the outdoor air which mayinfiltrate and/or may be required for ventilation.Chnpter 5 contains the transmission coefficients andprocedures for determining heat loss. Chapter 6 con-tains the data for estimating the infiltration airquantities. Fig. 2 illustrates a heating estimate formfor calculating the heat loss in a building structure.

Another factor that may be considered in theevaluation of the heating load is temperature swing.Capacity requirements may be reduced when thetemperature within the space is allowed to drop afew degrees during periods of design load. This, of-ourse, applies to continuous operation only. Table

pnge 20, provides recommended inside designconditions for various applications, and Table 13,page 37, contains the data for estimating the pos-sible capacity reduction when operating in thismanner.

The practice of drastically lowering the tempera-ture to 50 F db or 55 F db when the building isunoccupied precludes the selection of equipmentbased on such capacity reduction. Although this typeof operation may be effective in realizing fuel econ-omy, additional equipment capacity is required for

pickup. In fact, it may be desirable to provide theadditional capacity, even if continuous operation iscontcmplatctl, because of pickup required afterforcctl shutdown. It is, thcrclore, evident that theuse of storage in reducing the heating load for thepurpose of equipment selection should be appliedwith care.

HIGH ALTITUDE LOAD CALCULATIONSSince air conditioning load calculations are based

on pounds of air necessary to handle a load, adecrease in density means an increase in cfm re-quired to satisfy the given sensible load. The weiglitof air required to meet the latent load is decreasedbecause of the higher latent load capacity of theair at higher altitudes (greater gr per lb per degree .tlitference in dewpoint temperature). For the samedry-bulb and percent relative humidity, the wct-bulb temperature decreases (except at saturation)as the elevation above sea level increases.

The following adjustments are required for highaltitude load calculations (see Chapter 8, Table 66,page 148):

Design room air moisture content must beadjusted to the required elevation. .Standard load estimating methods and formsare used for load calculations, except that thefactors affecting the calculations of volumeand sensible and latent heat of air must bemultiplied by the relative density at the partic-ular elevation.Because of the increased moisture content ofthe air, the effective sensible heat factor mustbe corrected.

EQUIPMENT SELECTIONAfter the load is evaluated, the equipment must

be selected with capacity sufficient to offset this load.The air supplied to the space must be of the properconditions to satisfy both the sensible and latentloads estimated. Chapter S, Applied Psychromet-Tics , provides procedures and examples for deter-mining the criteria From which the air conditioningequipment is selected (air quantity, apparatus dew-point, etc.).

(:II.\ITTR I. I:1711.1>1NC; SllRVIO.\D ESTIM,\'II~ l-7

HEATING CONDITIONS TEMPERATURE OF AIR ENTERING UNIT

TOTAL TRANSMISSION LOSS

FORM El0

F1c.2 - HEATING LOAD ESTIMATE

l - 9

CHAPTER 2. DESIGN CONDITIONS

This chapter presents the data from which theoutdoor design conditions are established for variouslocalities and inside design conditions for variousapplications. The design conditions established de-termine the heat content of the air, both outdoorand inside. They directly affect the load on theair conditioning equipment by influencing thetransmission of heat across the exterior structureand the difference in heat content between the out-door and inside air. For further details, refer to

OUTDOOR DESIGN CONDITIONS - SUMMERAND WINTER

The outdoor design conditions listed in Table 1are the industry accepted design conditions as pub-lished in AR1 Std. 530-56 and the 1958 ASHAEG :. The conditions, as listed, permit a choice ofouLdoor dry-bulb and wet-bulb temperatures for dif-ferent types of applications as outlined below.

B.NORMAL DESIGN CONDITIONS - SUMMERNormal design conditions are recommended for

use with comfort and industrial cooling applicationswhere it is occasionally permissible to exceed thedesign room conditions. These outdoor design con-ditions are the simultaneously occurring dry-bulband wet-bulb temperatures and moisture content,which can be expected to be exceeded a few timesa year for short periods. The dry-bulb is exceededmore frequently than the wet-bulb temperature, andusually when the wet-bulb is lower than design.

When cooling and dehumidification (dehydra-tion) are performed separately with these types ofapplications, use the normal design dry-bulb tem-

perature for selecting the sensible cooling appara-tus; use a moisture content corresponding to thenormal design wet-bulb temperature and 80% rhfor selecting the dehumidifier (dehydrator).

Daily range is the average difference between the high and low dry-bulb temperatures for a 24-hrperiod on a design day. This range varies with localclimate conditions.

A, MAXIMUM DESIGN CONDITIONS-SUMMERMaximum summer design conditions are recom-

mended for laboratories and industrial applicationswhere exceeding the room design conditions foreven short periods of time can be detrimental to aproduct or process.

The maximum design dry-bulb and wet-bulbtemperatures are simultaneous peaks (not individualpeaks). The moisture content is an individual peak,and is listed only for use in the selection of sep-arate cooling and dehumidifying systems for closelycontrolled spaces. Each of these conditions can beexpected to be exceeded no more than 3 hours ina normal summer.

NORMAL DESIGN CONDITIONS - WINTERNormal winter design conditions are recommended

for use with all comfort and industrial heating ap-plications. The outdoor dry-bulb temperature canbe expected to go below the listed temperatures afew times a year, normally during the early morn-ing hours. The annual degree days listed are thesum of all the days in the year on which the dailymean temperature falls below 65 F db, times thenumber of degrees between 65 F db and the dailymean temperature.

l-10 PART I. LO/\D ES?IM,\?ING

TABLE l-OUTDOOR DESIGN CONDITIONS-SUMMER AND WINTER

mti-udadeg)

MAXIMUM DESIGN N O R M A LC O N D . - S U M M E R DESIGN COND.

July at 3:00 PM WINTER WIND DATA ilava-than

4boveSe0

Level(ft)

STATEANDCITY I

I

A L A B A M AAnnistonBirminghamMobileMontgomery

ARIZONAFlagstaffPhoenix

T l J C S O l lWinslowYuma

ARKANSASFort Smithlittle Rock

CAL IFORNIABakersfieldEl CentroEurekaFresll0

Laguno BeachLong BeachLos AngelesOakland

MontaguePasadenaRed BluffSacramento

San BernadineSan DiegoSon Francisco

San JoseWilliams

COLORADODenverDurango

Fort CollinsGrand JunctionPueblo

_CONNECTICUT

BridgeportHartfordNew HavenWaterbury

D E L A W A R EWilmington

DIST. OF COLUMBIAWashington

F L O R I D AApalachicolaJacksonvilleKey WestMiami

PensacolaTampaTallahorsee

Correspondr to dry-bulb and

--Dry-Bu lb iVI

I 1

lolrture Avg. Velocity andontentt Dry- Annual Prevailing DirectionDry-

Bulb(F)

95959595

90105

105100110

9595

105110

90105

909085

9 5100100

I058585

91

9595

9595

959395

95

95

95959891

9595

wet-l

8 2

Vet-iulbIF)-

19I912I5

6576

727078-

8194

778593

2630

30

30

7678-

104.5 I6117.5 I6

70 5478 9465 5274 76

25

707065

787860

707072 I8 30

726865

706273

657560

76.5

IO17

7040

-

64 6065 70

2.5

6565-

6263

2425

757575

9910299

I41614

78 117.5

78 117.5

80 I3178 117.578 I 12.579 I31

7878

-

117.5117.5

Dry-Bulb

(F)~ (pr/lb o f I Bu lb I Degree I

I cr

i,; a i r ) 1 IFI 1 Doyr S u m m e rI

Winter

2806261 I1566207 I

8 .0 N9.9 N7.5 NW

733694

IO293

34343132

72421441 5 . 0 w

6,8941,108

5 . 0 w

1036

7 .7 SW5.4 E

5 .2 NW

6.7 N

2,3764,853

I46

323533

3226 7.0 E 8.3 E 4483009 6.0 NW 8.3 NW 324

4758 7 . 0 N 7.32403 8.0 NW 5.4 NW

49943

132287

1391 6.0 SW 6.4 NE

1047

261I7

34343438

2.635 ,

2680 7.2 SE305I16

42344039

15963137

2823

7 . 0 w2 . 0 w

6.3 NW 267 . 5 N I7

343338

10086

3739

7.0 s 7 .5 s 5.22 I6 ,558

4037

56135558

6.0 SE 4.4 NW7.9 NW

4,5874,770

413938

6113 7.0 s 8 .7 NW5880 7.0 s 9.4 N

95823

41424142

IO.0 S W N W 134 40

5.0 s 7.8 NW 72 39

1252II85

59I85

- -1281571

1463

5.0 SW, 8.4 23 308.0 SW 9.0 NE I8 309.0 SE 10.6 NE 23 257.0 SE 10.1 E II 26

6.0 NE10.9 N 408 31

8.6 NE 25 28N 68 30

155.6 1

90II3

103103

110

78 126.9-10

25

25-10

30-

83-

75

70

145.5

95.9

25

3025

82

9494 68

103.0

99.33530

0

88 74 78.4 3535

25110

99

80-

68

102

9495

68

-

82

74.4

89.4

86.2

000

- 1 5

99 84 155.6 0

99 82

92 81

150.5

150.5

25254535

95203025

-3 temperatures listed, and is corrected for altitude of city.

tcorrespondr to peek dewpoint temperature, corrected for altitude.

(:I I.\III~:I< 11. I>I

l-12 IAKT I . LO:\11 IiSIlhl,\llNG

TABLE l-OUTDOOR DESIGN CONDITIONS-SUMMER AND WINTER (CONT.)

l-STATEANDCITY

MAXIMUM DESIGNCOND.-SUMMER

July at 3:00 PM

NORMALXSIGN COND.

WINTER EleVa-W I N D D A T A

78 117.5 18

tionAbove

Sea Lati-Level tude

(ft) kg)

rDry-Bulb

(F)

Dry-Bulb

(F)

05

- 5- 5

10

AntWaDegreeDays

Avg. Velocity andPrevailing Direction

MoistureNet- contenttBulb (gr/lb o f(F) dry air)

Dry- Wet-Bulb Bulb

(F) (F) S u m m e r / W i n t e r

6.0 SW 1 8.2 NWI NW

L

4487

-.--.

14 39MARYLAND

BaltimoreCambridgeCumberland_ _ .--FrederickFrostburgSalirbury

95

95 753939-__.-~404040

L

WNW

.

4242

199 42625 42

MASSACHUSETTSAmherstBostonFall River

-__FitchburgLowellNantucket

.ew Bedford/lymouthSpringfieldWorcester

- 1 00

- 1 0

- 1 0- 1 5

0

0- 5

-IO0

- 1 0-I5-IO-I5

- 1 0- 1 0

- 5-IO

- 1 0- 1 0

- 2 0

104 1 3

-/-02 17

z+-

96 5936

6743

8278

65608777

6702

7149

74588745

9307

c

101

c

W9.0 SW102 / 17

102 I 1793 7593 75

i cI

95 75 99I111.0 SW

MICHIGANAlpenoBig RapidsDetroitEscano ba

FlintGrand RapidsKalamazooLansing

LudingtonMarquetteSaginawSoult Ste Marie

615 45

69 j ;aNW

10.0 SW 12.0 SW95 75 19

+

2099

11

20

j 20

79 135.9

-I9> 759.5 75 / 9 . 5 N WWI wc t_-95 I 75

/9395

7375

93 7395 75~__

95 1 75

95 7995 78

100 78100 76

95 / 78

c90 66

-- L

98

96

8.0 w / 12. Lzw, 9.8 SW

1 . 9 w, 10.6 NW/

L c90 20

99 I 8.9 SE

5.0 SW 7.7 SE4.0 SW 6.3 N6.0 SW 8.3

MINNESOTAAlexandriaDuluthMinneapolis

St. CloudSt. Paul

-2.5- 2 5- 2 0

- 2 5- 2 0

151010

- 1 0-IO

97237966

+79 131.1

96 19103 I 17

1,128 47

*

102

tc

103

96

10908

108

98

7975t

23302069

5070 8.9 SW4962 9.0 s 10.3 NW

- -459655964569

SW 19.0s 111.8s

9.3 NW8.0 S 0.9 SE

tMlSSlSSlPPlJackson

teridianucksburg

I83 / 55.6 36 32

410 32226 32

MISSOURIColumbiaKansas CityKirksville

St. LouisSt. JosephSpringfield

0-IO- 1 018

MONTANABillingsButteGreat FallsHovre

HelenaKalispellMiles CityMisroula

70 20

82__-71 Gc56

95 / 66 I- 49 20

104

97 170 77.4- 2 5- 2 0- 2 0- 3 0

- 2 0- 2 0- 3 5- 2 0

*Corresponds to dry-bulb and wet-bulb temperatures listed, and is corrected for altitude of city.

tCorresponds to peak dewpoint temperature, corrected for altitude.

7213 j 12.4 W

846

7930803275917604

t

5.6 SEi

( : I l.\l1l~:I~ 2. I)lL5l(;N C:ONI)I~IIONS 1-13

TABLE 1 -OUTDOOR DESIGN CONDITIONS-SUMMER AND WINTER (CONT.)

STATE

NORMAL DESIGN A V G . M A X I M U M D E S I G N N O R M A LC O N D . - S U M M E R DAILY CON&-SUMMER DESIGN COND.

July at 3:00 PM RANGE July at 3:00 PM WINTER W I N D D A T A Eleva-

Lati-tudkg)

NEBRASKAGrand Island

North PlatteOmahaValentineYork

414142414143

N E V A D Atar VegasRetlOTonopah%memucca

115 75 4095 65 41 102

95 65 40

36403042

20 s 1,88266 66.9 - 5 562 I 7.0 S W 6.0 W 4,493

5 5812 9.9 SE 5.42 1- 1 5 6357 7.0 S W 8.1 NE 4,293

h HAMPSHIRE IBerlinC o n c o r d I I i90 73 95 j 14

4543434343I I I I / I 17

5 5015 13.0 S W 15.8 N W125

82 145.5 0 10.0 S W 30173

0 N W81 140.6 0 5500 13.0 S W 17.1 N W 10

13.0 S W 1016.1

9.0 S W 10.9 N W 56

I

394140414141

414140

CamdenEast Oronae

+

Jersey Cit;NewarkPatersonSandy HookT r e n t o n

95 75 99 a95 75 99 14 9995 75 99 14 95

95 78 117.5 14 96

353236

434243434343424244- -4145

i 43

4343434344

3635373634

77 126.9 - 5 6925 12.0 S W 1 17.1 w 604- 2 5 8305 8.0 10.5 458- 1 0 N W- 1 5 W_ lens F a l l s

IthacaJamestown I I I I 1Lake Placid

+

Roche&r I 95 I 75 I 102 I 18 I 95Schenectady 1 93 / 75Syracuse I 93 I 75

Corresponds to dry-bulb and wet-bulb temperatures listed, and is corrected for altitude of city.tcorresponds to peak dewpoint temperature, corrected for altitude.

TABLE 1 -OUTDOOR DESIGN CONDITIONS-SUMMER AND WINTER (CONT.)

i

NORMAL DESIGN A V G . MAXIMUM DESIGN NORMALCOND.-SUMMER DAILY COND.-SUMMER DESIGN COND.

STATEANDCITY

NORTH DAKOTABirmarckDevils Lake

FargoGrand ForksWilliston

c

OHIOAkronCincinnatiClevelandColumbusDaytonLima

SanduskyToledoYoungstown

95 75 99 1995 78 117.5 22 10695 75 99 19 101

95 76 104.5 23 9595 78 123 23 99

95 75 9995 75 99 19 9995 75 99 19

101 77 108 21 104101 77 101.5 I 106

- 5 104 4181 145.5 0 4990 7.0 SW 8.5 SW 553 3979 135.9 0 6144 11.0 s 14.7 SW 651 42

-10 5506 9.0 SW 11.6 SW 724- 40 ,0 5412 8.0 SW 11.1 SW 900 40

- 5 41

0 6095 II.0 608 42-IO 6269 10.0 SW 12.1 SW 589 42

1,186 41

I iOKLAHOMAArdmoreBartlesvilleOklahoma CityTulsa 79

t1 / -5 / 7197 (

OREGONBakerEugeneMedfordPendletonPortlandRoseburgWamic

I -15 I I I 1 366 / 44

PENNSYLVANIAAltoonoBethlehemErieHarrisburg

New CastleOil CityPhiladelphiaPittsburgh

ReadingScrantonWarren

~ Williamsport

95 75 9995 78 117.595 75 105

95 75 9995 75 99

181414

14

9798

95

95 75 9993 75 102 1493 75 102 / 14

420 4739 10.0 SW 11.0 NW 26 40

79 126.9 0 5430 9.OSW 11.6 W 1,248 40

0 5232 9.0 311 40- 5 6218 6.0 SW 7.6 SW 746 41

- 1 5 NW 41- 5 NW 525 42

RHODE ISLANDBlock IslandPawtucketProvidence

SOUTH CAROLINACharlestonColumbiaGreenville

95 78 117.5 17 98 a2 155.6 15 1066 10.0 SW 10.5 SW 9 3395 75 99 17 IO 2488 8.0 SW 401 3495 76 104.5 17 10 3059 7.0 N E 8.4 902 35

SOUTH DAKOTAHuronRapid CitySioux Falls

7671

95 75 106 19 I0695 70 05 22 10395 75 99 20

*Corresponds to dry-bulb ond wet-bulb temperatures listed, and is corrected for altitude of city.

tcorrespondr to peak dewpoint temperature, corrected for altitude.

,- _ ----_-.., _.

(:f I \ll~I~:l< 2. I)LSI~;N (:ONl)I-IIoNS l-15

TABLE l-OUTDOOR DESIGN CONDITIONS-SUMMER AND WINTER (CONT.)

MAXIMUM DESIGN NORMALCOND.-SUMMER D E S I G N C O N D .

Ju ly at 3100 PM W I N T E R ElSVo-tlon

Avg. Velocity and AboveS e a

LevelS u m m e r (ft)

STATEANDC I T Y

loirtura-I--ontent* Dry-gr/lb of B u l bdry a i r ) VI Dry- Wet-B u l b B u l b(F) (F)98

10010398

7983

-

101

96

105 80

101 72

100 81

102 83

97

102 68-

91

-

999590

86 70106 68

I05

102

98

tI

-.-

Dry- Net.Bulb Bulb(F) WI

Vloisturehtentt:gr/lb ofdry a i r )

AnnualD e g r e e

D a y s

Loti-tude

(deeI

T E N N E S S E EChattanoogaJohnson CiLy

-Knoxv i l l e

104.5 I8

---i--

103.5 I7117.5 18117.5 17

I7.7 NW / 68995

959595

76

757878

3536- -363536

6.0 S W

6.0 S W7.0 S W8.0 w

9.0 s11.0 s

9.0 SE13.0 SE8.0 s

10.0 SE9.0 E

10.09.0 s8.0 s

MemphisNashville

93TEXAS

AbileneAmarilloAustinBrownsvilleCorpus ChrirtiDallasDel RioEl PosoFort WorthGalvestonHoustonP a l e s t i n ePort ArthurSan Antonio

100 74100 72100 7895 8095 80

100 78100 78100 69100 78

95 8095 80

100 7895 79

100 78

323531262833293233

257341961679

628965

2367150125322355II741315206815321435

I

293032302 1

124109.5 I9

UTAHModemLoganOgdenSa l t t ake C i ty

95..

95

65

65

38424141

66 25

61 25S 4,446

7.8 SE 4,222

8.0 s 11.6 S 308

11.0 s6 .0 SW

VERMONTBenningtonBurlingtonRutland

9090

7373

VIRGINIACape HenryLynchburgNorfolkRichmondRoancke

95 7895 7595 7895 7895 76

3737373838

vVASHINGTONNorth HeadSeattleSpokaneTacomaTatoosh IslandWalla WalloWenatcheeYakima

536785 6585 6593 6585 64

95 6590 6595 65

16.19.8 SE6.2 S W8.0

18.95.4 s

7 . 0 N7 .0 SW

48484748464847

WEST VIRGINIABluefieldCharlestonElkinrHuntingtonMartinsburgPorkersburgWheeling

76

37383938393940

W 603

4928 4.0 SE

*Corresponds to dry-bulb and wet-bulb temperatures listed, and is corrected for altitude of city.tcorrerponds to peak dewpoint temperature, corrected for altitude.

,TABLE l-OUTDOOR DESIGN CONDITIONS-SUMMER AND WINTER (CONT.)

STATEA N DCITY

W I S C O N S I NAshlandEau ClaireGreen BayL o CrosreMadisonMilwaukee

WYOMINGCarperCheyenneLanderSheridan

CANADA

P R O V I N C EANDC I T Y

A L B E R T ACa lgaryEdmontonG r a n d P r a i r i e

LethbridgeMCMUrKlyMedicine Hat

BRITISH COLUMBIAEstevon PointFort NelsonPentictonPrince GeorgePrince RupertVClllCOtJVC3~Victoria

MANITOBABrandonChurchillThe PasWinnipeg

N E W B R U N S W I C KCampbelltonFreder ic tonMonctonSaint John

NEWFOUNDLANDCorner BrookGanderGoose BaySaint Johns

N O R T H W E S TT E R R I T O R I E S

AklovikFort NormanF r o b i r h e rResoluteYellowknife

NORMAL DESIGN AVG. MAXIMUM DESIGN NORMALCOND.-SUMMER DAILY COND.-SUMMER D E S I G N C O N D .

July at 3 :00 PM R A N G E July at 3 :00 PM W I N T E R WIND DATA Eleva-t i o n

Moisture Moisturevi.,- contentt

Avg. Velocity and AboveDry- Wet- content* Dry- Dry- Dry- Annual Prevailing Direction S e a Lati-Bulb Bulb (gr/lb of B u l b B u l b Bulb (gr/lb of B u l b D e g r e e Level t u d e(F) (F) dry air) (F) IF) (F) dry air) (F) Days S u m m e r Winter (ft) be)

- 20 S W 42- 2 0 N W 885 45

95 75 99 14 / 99 79 131.1 - 2 0 7931 8.0 S 10.5 S W 589 4595 75 99 -r 17 100 83 161.2 - 2 5 742 I 6.0 S 9.3 s I 673 4495 75 103.5 18 96 , -I5 7405 8.0 S W 10.1 N W 938 4395 75 99 14 99 - 1 5 7079 9.0 S W 12.1 w 619 43

- 20 S W 5,321 4395 65 68.5 28 -15 7536 9.0 s 13.3 N W 6,139 4295 65 66 28 -18 8243 5.0 S W 3.9 5,448 44

102 - 3 0 7239 5.0 N W 4.9 N W 3,773 45

.

I I

90 66 71 - 2 9 9520 9.7 10.1 3,540 5190 68 77 - 3 3 10320 8.9 7 .6 2,219 54

- 3 9 7 .9 2 ,190 55- -- 3 2 8650 15.0 3,018 50- 4 2 1,216 57

90 65 - 3 5 8650 9.1 9.0 2,365 50

i .l7 9.9 20 49

- 3 8 3.7 1,230 59- 6 1,121 50

- 3 2 9500 7.2 2,218 548 6910 8.0 170 54

80 67 78 11 5230 7.7 22 4915 5410 12.3 228 48

- 3 2 10930 1,200 50- 4 2 16810 14.7 115 59- 3 9 6.4 894 54

90 71 83.5 - 2 9 10630 11.5 12.0 786 50

- 1 1 42 4890 75 I 107

/

- 6 8830 9.2 164 46

-8 -3 8700 8380 7.9 13.8 14.9 248 119 46 45

-I 9210 40 49- 3 9440 17.2 482 49

- 2 6 12140 10.3 144 53I 1 8780 19.3 463 , 48

30 69300 65

689.2 56

682 62

*Corresponds to dry-bulb and wet-bulb temperatures listed, and is corrected for altitude of city.tcorrerponds to peak dewpoint temperature, corrected for altitude.

(:fl.\lll-I< II. I)ICSI(iN (:ONI)IIIONS 1-17

TABLE 1 -OUTDOOR DESIGN CONDITIONS-SUMMER AND WINTER (CONT.)

COND.-SUMMER ------IW I N D D A T A Eleva-tionAvg. Velocity and AboveNORMAL DESIGNCOND.-SUMMERJuly at 3:00 PM NORMALDESIGN COND.WINTERCANADAPROVINCEANDCITY

Dry-BulbVI

Direction----I SWLevelWinter (ft) Lati-tudeidee)9.6 83 45

13.1 197 4613.5 136 44

AnnualDegreeDay5

757082207520

f

T

reVallill

Summer

6.6

9.9

Dry-BulbVI

NOVA SCOTIA

Halifax

Sydney

Yarmouth

90 75 107

ONTARIO

Fort William

Hamilton

KapuskodngKingstonKitchener&donNorth BoyOttOWClPeterboroughSouix LookoutSudburyTimminrT o r o n t oWindsorSoult Ste. Marie

- 2 40

- 3 0-11

- 3-I

- 2 0-IS- 1 1- 3 3- 1 7- 2 6

03

103506890

11790

7810- -7380

8830

8.4 4843494443434645445047

,48434247

9.6 644303

10.0 752Ia90 75 107- 11.9 91211.3 1,2109.68.97020 8.1

=---I+

+--I93 75 102.93 75 102 +PRINCE EDWARDISLAND

Charlottetown - 3 8380 a.7 11.3 74 46

, H QUEBEC - ~__90

75 107 190 75 107

- ~__90 75 107

90 75 107

90 7190 71 92.592.590 70 8190 70 81

,:,.-

/ArvidoKnob LakeMont JoliMontrealPort HarrisonQuebec CitySeven IslandsSherbrookeThree Rivers

- 1 9- 4 0-II

- 9- 3 9- 1 2- 2 0- 1 2- 1 3

8.2 37510440

-I 81309070

8610

- 4 1 11430- 3 4 10770- 3 7 10960- 3 3 9660

5548465847504546

4.9 1,414 5312.1 1,884 509.7 1,645 52

14.6 2 ,677 50

9.9

9.0

12.410.7

tSASKATCHEWANPrince AlbertReginaSoskatoonSwift Current

.

YUKON TERRITORYDaV4?.0n

Whitehorse15040 1,062 64

8.7 2,289 61

1*Corresponds to dry-bulb and wet-bulb temperatures listed, and is corrected for altitude of city.tcorrespondr to peak dewpaint temperature, corrected for altitude.

1-18 I.IlR-I I. LOAD ESTIhI.\?ING

CORRECTIONS TO OUTDOOR DESIGN CONDITIONSFOR TIME OF DAY AND TIME OF YEAR

The normal design conditions for summer, listedin Table 1, are applicable to the month of July atabout 3:00 P.M. Frequently, the design conditionsat other times of the day and other months of theyear must be known.

Table 2 lists the approximate corrections on thedry-bulb and wet-bulb temperatures from 8 a.m. to12 p.m. based on the average daily raqge. The dry-bulb corrections are based on analysis of weatherdata, and the wet-bulb corrections assume a rela-t i v e l y c o n s t a n t dewpoint t h r o u g h o u t t h e 24-hrperiod.

Ta6le 3 , l ists the approximate corrections of thedry-bulb and wet-bulb temperatures from March toNovember, based on the yearly range in dry-bulbI 3erature (summer normal design dry-bulb minusw,,lter nprmal design dry-bulb temperature). Thesecorrections are based on analysis of weather dataand are applicable only to the cooling load estimate.

Example J - Corrections to Design ConditionsGiven:

A comfort application in New York City.Find:

The approximate dry-bull, and wet-bulb temperatures at12:00 noon in October.

Solution:Normal design conditions for New York in July at 3:00p.m. are 95 F db, 75 F wb (Table I).

Daily range in New York City is 14 F db.Yearly range in New York City = 95 - 0 = 95 F db.Correction for time of day (12 noon) from Table 2: I

Dry-bulb = -5 FWet-bulb = -1 F

Correction for time of year (October) from Table 3:Dry4,ulb = -16 F

Wet-bulb = - 8 F

Design conditions at 12 noon in October (approximate) :Dry-bulb = 95 - 5 - 16 = 74 FWet-bulb = 75 - 1 - 8 = 66 F

INSIDE COMFORT DESIGN CONDITIONS -SUMMER

The inside design conditions listed in Table 4 arerecommended for types of applications listed. Theseconditions are based on experience gathered frommany applications, substantiated by ASHAE tests.

The optimum or deluxe conditions are chosenwhere costs are not of prime importance and forcomfort applications in localities having summeroutdoor design dry-bulb temperatures of 90 F or less.Since all of the loads (sun, lights, people, outdoorair, etc.) do not peak simultaneously for any pro-longed periods, it may be uneconomical to designfor the optimum conditions.

TABLE 2-CORRECTIONS IN OUTDOOR DESIGN TEMPERATURES FOR TIME OF DAY

(For Cooling Load Estimptes)

DAILY / .YGE OF DRY-

.,, _ /,;UN TIME- -.

.-MPERA- O R AM P MTURE* WET-

(F) B U L B B 10 12 , . . . . + : - 3 -A 4 6 8 1 0 - 1 21 0 Dry-Bulb - 9 / - 7 I -5- -I I 0 I -1 I - 2 I -5 I - a I - 9

W & - B u l b - 2 - 2 - 1 0 0 0 - 1 - 1 - 2 - 215 Dry-Bulb - 1 2 - 9 -5, - 1 0

0- 1 - 2 -6 -10 -14

Wet&lb - 3 - 2 ->1 \ 0 0 -1 - 1 - 3 - 4my D r y - B u l b - 1 4 - 1 0 - 5 - 1 -11 - 1 6i../ W e t - B u l b - 4 - 3 - 1 0

0 0 - 1 0 - 3 - 1 -7 -2- 3 - 4

2 5 Dry-Bulbs -I6 -IO - 5 - 1 0 -1 - 3 -8 - 1 3 - 1 8Wet-Bulb - 4 - 3 -1 0 0 0 - 1 - 2 - 3 - 5

3 0 D r y - B u l b - 1 8 - 1 2 - 6 - 1 0 -I - 4 -1Q - 1 5 - 2 1W e t - B u l b - 5 - 3 - 1 0 9 0 - 1 - 3 - 4 - 6I

3 5 Dry-Bulb - 2 1 - 1 4 - 7 - 1 d - 1 - 6 - 1 2 -18 - 2 4W e t - B u l b - 6 - 4 - 2 0 1) 0 - 1 - 3 - 5 - 7

40 Dry-Bulb - 2 4 - 1 6 -8 - 1 0 -1 - 7 - 1 4 - 2 1 - 2 0W e t - B u l b - 7 - 4 - 2 0 0 0 - 2 - 4 - 6 - 9

4 5 D r y - B u l b - 2 6 - 1 7 - a - 2 0 - 2 -8 - 1 6 - 2 4 - 3 1W e t - B u l b . - 7 - 5 - 2 0 0 -I - 2 - 4 - 0 - 1 0

* T h e d a i l y range o f d r y - b u l b t e m p e r a t u r e i s t h e d i f f e r e n c e b e t w e e n t h e h i g h e s t a n d l o w e s t d r y - b u l b t e m p e r a t u r e d u r i n g o 24-hour pe r iod on a t yp ica ld e s i g n day. (See Tab le I fo r the va lue o f da i l y range fo r a pa r t i cu la r c i t y ) .

E q u a t i o n : O u t d o o r d e s i g n t e m p e r a t u r e a t o n y t i m e = O u t d o o r d e s i g n t e m p e r a t u r e f r o m Table I + C o r r e c t i o n f r o m a b o v e t a b l e .

(:fI.\IIb:I~ 2. I)l3I(;N (:oKl)I~lI

iPAR-l- I . LO,\D E!xIhI,\-rIKGl -20

TABLE 44tECOMMENDED INSIDE DESIGN CONDITIONS*-SUMMER AND WINTER

TYPE OFAPPLICATION

GENERAL COMFORTApt., House, Hotel, OfficeHospital, School, etc.

R E T A I L S H O P S(Short term occupancy)

Bank, Barber or BeautyShop, Dept. Store,Supermarket, etc.

L O W S E N S I B L E H E A TFACTOR APPLICATIONS( H i g h L a t e n t l o a d )

Auditorium, Church, Bar,Restaurant, Kitchen, etc.

FACTORY COMFORTAssembly Areas ,Machinina Rooms. etc. I I I I I ,

* he room design dry-bulb temperature should be reduced when hot radiant panels ore adjacent to the occupant and increased when cold Panels are~di,,en+ to compensate for the increase or decrease in radiant heat exchange from the body. A hot IX Cold Panel mJY be unshaded glass or 9lssblock wjidows (hot in summer, cold in winter) and thin partitions with hot or cold spaces adjacent. An unheated slab floor on the ground or walls belowthe ground level are cold panels during the winter and frequently during the summf~ ~Iso. Hot tanks, fUrnoceS Or machines are hot Panels.

TTemperoture swing ir above the thermostat setting at peak summer load conditions-

JTemperature swing is below the thermostat setting at peak winter load conditions (no lights, People Or solar heat gain).

**Winter humidification in retail clothing shops is recommended to maintain the quality texture of goods-

SUMMER W I N T E R

Commercial Prodice W i t h H u m i d i f i c a t i o n W i t h o u t H u m i d i f i c a t i o n

INSIDE INDUSTRIAL DESIGN CONDITIONSTable 5 lists typical temperatures and relative

humidities used in preparing, processing, and manu-facturing various products, and for storing both rawand finished goods. These conditions are only typicalof what has been used, and may vary with appli-cations. They may also vary as changes occur inprocesses, products, and knowledge of the effect oftemperature and humidity. In all cases, the tem-perature and humidity conditions and the permis-sible limits of variations on these conditions shouldbe established by common agreement with the cus-tomer.

Some of the conditions listed have no effect on theproduct or process other than to increase the effi-ciency oE the employee by maintaining comfortconditions. This normally improves workmanshipand uniformity, thus reducing rejects and produc-tion cost. In some cases, it may be advisable tocompromise between the required conditions andcomfort conditions to maintain high quality com-mensurate with low production cost.

Generally, specific inside design conditions arerequired in industrial applications for one or moreof the following reasons:

1. A constant temperature level is required forclose tolerance measuring, gaging, machin-ing, or grinding operations, to prevent expan-sion and contraction of the machine parts,machined products and measuring devices.Normally, a constant temperature is more im-;portant than the temperature level. A constant:relative humidity is secondary in nature but,should not go over 457, to minimize formationof heavier surface moisture film.Non-hygroscopic materials such as metals, glass,plastics, etc., have a property of capturingwater molecules within the microscopic surfacecrevices, forming an invisible, non-continuoussurface film. The density of this film increaseswhen relative humidity increases. Hence, thisfilm must, in many instances, be held below acritical point at which metals may etch, or theelectric resistance of insulating materials is sig-nificantly decreased.

2. Where highly polished surfaces are manufac--tured or stored, a constant relative humidityand temperature is maintained, to minimizeincrease in surface moisture film. The tem-perature and humidity should be at, or a little

(:F1.\lllCK 2. I)ESI(;N (:ONI)IIIONS l-21

below, the comfort conditions to minimizeperspiration of the operator. Constant tem-perature ant1 humidity may also be r~quirctlin machine rooms to prevent etching or cor-rosion of the parts of the machines. Withapplications of this type, if the conditions arenot maintained 24 hours a day, the starting ofair conditioning after any prolonged shutdownshoultl bc tlonc carefully: (1) During the sum-mer, the moisture accumulation in the spaceshould be reduced before the temperature isreduced; (2) During the winter, the moistureshould not be introduced before the materialshave a chance to warm up if they are cooledduring shutdown pcriotls.

3. Control of relative humidity is required tomaintain the strength, pliability, and regain ofhydroscopic materials, sucll as textiles andpAper. The humidity must also be controlledin some applications to reduce the effect ofstatic electricity. Development of static electriccharges is minimized at relative humidities of55% or higher.

4. The temperature and relative humidity con-trol are required to regulate the rate of chemi-cal or biochemical reactions, such as drying of

varnishes or sugar coatings, preparation ofsynthetic fibers or chemical compounds, fer-mentation of yeast, etc. Generally, high tem-peratures with low humidities increase dryingrates; high temperatures increase the rate ofchemical reaction, and high temperatures andrelative humidities increase such processes asyeast fermentations.

5. Laboratories require precise control of bothtemperature and relative humidity or either.Roth testing and quality control laboratoriesare frequently designed to maintain the ASTMStandard Conditions of 73.4 F db and 50%rh.

6. With some industrial applications where theload is excessive and the machines or materialsdo not benefit from controlled conditions, itmay be advisable to apply spot cooling for therelief of the workers. Generally, the conditionsto be maintained by this means will be abovenormal comfort.

*Published in ASTM pamphlet dated 9-29-48. These condi-tions have also been approved by the Technical Committeeon Standard Temperature and Relative Humidity Conditionsof the FSB (Federal Specifications Board) with one varia-tion: FSB permits 24%/,, whereas ASTM requires *2710 per-missable humidity tolerance.

l-24 I,\RT I. LOAD ESTIMATING

TABLE S-TYPICAL INSIDE DESIGN dONDlTlONS-INDUSTRIAL(Listed conditions are only typical; final design conditions are established by customer requirements)

r DRY-BULB(F) DRY-BULB(Fl110-150

8060-80___75-80

75-80

INDUSTRY PROCESS INDUSTRY PROCESS

rtanufacture 45-50 CERAMICS efroctory\olding Rm.lay storage

lecol 8 Decorating

ABRASIVE 75-80

75-80 40-5075-82 70-7592-96 80-8570-80 80-8540.45 -78-82 65-7095-105 -60-65 5060-65 60-65

BAKERY )ough Mixer:ermen~ingroof Boxbread CoolerZold Room&cake-up Rm.Zake Mixinglrackerr & BiscuihNrappingjtoroge-

CEREAL ackoging

Ifa.COSMETICS 65-70

-_60--__

32-3460-75~-65-72

DISTILLING w a g e -Grain

Liquid YeastM f g .- ~~~~~___Aging

45-6050-60

50-5540-4560-63

50

5050

65-7020-40

30-60

Dried Ingred. 70 55-65

Fresh Ingred. 30-45-.70-75

80-85 ELECTRICALPRODUCTS

7268

70

76

7672

74-76

lectronic & X - r a yCoils & Trans.Winding

ube Arrem.lectrical Inst.

Mfg . 8. t a b .hermortot Assem. &

Calib.humidistat Assem.

6. &lib.3o.w Tol. Assem.Aeter Asrem. Testiwi~chgear-

Fuse 8. Cut-OutAssem.

CCID. W i n d i n aPaper storage

Conductor Wrapping.ightning ArrestorCircuit Brkr.

Assem. & Test?ectifiers-

Process Selenium& Copper Oxid SYSIICRI FJ1:.\1 C..\IN l -109

TABLE 57-HEAT TRANSMJSSION COEFFICIENTS FOR UNINSULATED TANKS

SENSIBLE HEAT GAIN*

Btu/(hr) (sq ft) (deg F diff between liquid and room)

METAL W O O D CONCRETE2 % in. Thick 6 in. Thick

C O N S T R U C T I O NPainted Bright (Nickel) Painted or Bare Painted or Bore

Vertical(Sider)TOPl3attmn

Temp Diff Temp Diff Temp Diff Tamp Diff

50 F 100 F 150 F

1.8 2.0 2.32.1 2.4 2.71.5 1.7 2.0

*To estimate latent heat load if water is being evaporated, see Table 58

TABLE 58-EVAPORATION FROM A FREE WATER SURFACE-LATENT HEAT GAINS T I L L A I R , R O O M A T 7 5 F d b . 50% RH

WATER TEMP i 75 F 1 100 F 1 125 F 1 150 F 1 175 F 1 200 F

Btu/(hr)(sq f t ) 42 I 140 / 330 ) 680 ( 1260 ) 2190

SYSTEM HEAT GAINThe system heat gain is considered as the heat

added to or lost by the system components, such asthe ducts, piping, air conditioning fan, and pump,etc. This heat gain must be estimated and includedin the load estimate but can be accurately evaluatedonly after the system has been designed.

SUPPLY AIR DUCT HEAT GAIN

The supply duct normally has 50 F db to 60 Fdl r flowing through it. The duct may passthrough an unconditioned space having a tempera-ture of, say, 90 F db and up. This results in a heatgain to the duct before it reaches the space to beconditioned. This, in effect, reduces the coolingcapacity of the conditioned air. To compensate forit, the cooling capacity of the air quantity must beincreased. It is recommended that long runs of ductsin unconditioned spaces be insulated to minimizeheat gain.

Basis or Chart 3- Percent Room Sensible Heat to be Added for Heat

Gain to Supply Duct

Chart 3 is based on a difference of 30 F db be-tween supply air and unconditioned space, a supplyduct velocity of 1800 fpm in a square duct, still airon the outside of the duct and a supply air rise of 17

F db. Correction factors for different room tempera-tures, duct velocities and temperature differences areincluded below Chnrt 3. Values are plotted for usewith uninsulated, furred and insulated ducts.

Use of Chart 3- Percent Room Sensible Heat to be Added for Heat

Gain to Supply Duct

To use this chart, evaluate the length of ductrunning thru the unconditioned space, the tempera-ture of unconditioned space, the duct velocity, thesuppIy air temperature, and room sensible heat sub-total.

Example 5 - Heat Gain to Supply Duct

Given:20 ft of uninsulated duct in unconditioned space at 100 F dhDuct velocity - 2000 fpmSupply air temperature - 60 F dbRoom sensible heat gain - 100,000 Btu/hr

Find:Percent addition to room sensible heat

Solution:The supply air to unconditioned space temperature differ-ence = 100 - GO = 40 F db

From Chart 3, percent addition = 4.5%Correction for 40 F db temperature difference and2000 fpm duct velocity = 1.26Actual percent addition = 4.5 X 1.26 = 5.7%

l-110 I.\K-r I. I.O.\I) I:SIlhI.\~IING

CHART 3-HEAT GAIN TO SUPPLY DUCT

Percent of Room Sensible Heat

00 1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0

D U C T V E L O C I T Y (FPMI

.

MULTIPLYING FACTORS FOROTHER ROOM TEMPERATURES

Room Temp Multiplying Factor

7 5 1.10 .

7 6 1.067 7 1 .oo7 8 0.977 9 0.9480 0.92

Q = UPI X(2.162;6x5 /r&A: UPI (3--11)

where:

Q = duct heat gain (Btu/hr)

U = duct heat transmission factor (Btu/hr-sq ft-F)

P = rectangular duct perimeter (ft)

I = duct length (ft)

A = duct area (sq ft)

V = duct velocity (fpm)

tl = temperature of supply air entering duct (F)

t 3 = temperature of surrounding air (F)

Based on formulas in ASHRAE Guide 1963, p. 184, 185.

SUPPLY AIR DUCT LEAKAGE LOSS

Air leakage from the supply duct may be a seriousloss of cooling effect, except when it leaks into theconditioned space. This loss of cooling effect mustbe added to the room sensible and latent heat load.

Experience indicates that the average air leakagefrom the entire length of supply ducts, whether largeor small systems, averages around lo

(;H,\I~1~:11 7 . INIEIIN,\I, :\NI) SYSIEM HE,\1 C;,\IN 1-111

TABLE 59-HEAT GAIN FROM AIR CONDITIONING FAN HORSEPOWER, DRAW-THRU SYSTEMIf

CENTRAL STATION SYSTEMS$ APPLIED OR UNITARY SYSTEM**

Temp Diff Temp DiffR o o m t o S u p p l y A i r Room to Supply Air

10 F 15 F 2 0 F 25 F 3 0 F 10 F 15 F 20 F 25 F 30 F

PERCENT OF ROOM SENSIBLE HEAT*

Fan Motor1.25 3.9

N o t i n 1 4.6soC o n d i t i o n e d

S p a c e

L - - - - l - 1 . 7 5 5 . 4

2.00 6.2o r

Air Stream3.004.00

5.00 19.26.00 24.48.00 38.0

10.415.3

0.50L0.751 .oo

1.62.63.6

Fan Motortt 1.25 5.0i n 1 so 6.0

C o n d i t i o n e d

s p a c eor

Air Stream

I 1.75 7.0

2.00 8.03.00 13.24.00 19.0

12.8 9.6 7.7 6.416.3 12.2 9.9 0.225.4 19.0 15.2 12.7

1.1 0.8 0.6 0.5 2.7 1.81.8 1.3 1.1 0.9 4.2 2.82.4 1.8 1.5 1.2 5.8 3.8

3.4 2.5 2.0 1.7 7.6 5.14.0 3.0 2.4 2.0 9.2 6.14.7 3.5 2.8 2.4 10.7 7.2

I

1.4 1.1 0.92.1 I 1.7 I 1.42.9 2.3 1.9

*Excludes from heat gain, typical values for bearing losses, etc. which are dissipated in apparatus room.

tFon Total Pressure equals fan static pressure plus velocity pressure at fan discharge. Below 1200 fpm the fan total pressuce is approximately equal tothe fan static. Above 1200 fpm the total pressure should be figured.

$7Oyo fan efficiency assumed.

**5Oyo fan efficiency assumed.

tt8Oyo motor and drive efficiency assumed.

$$For draw-thru systems, this heat is on addition to the supply air heat gain and is added to the room sensible heat. For blow-thru systems this fan heatis added to the grand total heat; use the RSH times the percent listed and add to the GTH.

3. All ducts outside the conditioned space -assume 10% leakage. This leakage is a totalloss and the full amount must be included.When only part of the supply duct is outsidethe conditioned space, include that fraction of10% as the leakage. (Fraction is ratio of lengthoutside of conditioned space to total length ofsupply duct.)

HEAT GAIN FROM AIR CONDITIONINGFAN HORSEPOWER

The inefficiency of the air conditioning equip=ment fan and the heat of compression adds heatto the system as described under Electric Motors.In the case of draw-through systems, this heat is anaddition to the supply air heat gain and should beadded to the room sensible heat. With blow-throughsystems (fan blowing air through the coil, etc.) thefan heat added is a load on the dehumidifier and,

therefore, should be added to the grand total heat(see Percent Addition to Grand Total Heat).

Basis of Table 59- Heat Gain from Air Conditioning Fan Horsepower

The air conditioning fan adds heat to the systemin the following manner:

1. Immediate temperature rise in the air due tothe inefficiency of the fan.

2. Energy gain in the air as a pressure and/orvelocity rise.

3. With the motor and drive in the air stream orconditioned space, the heat generated by theinefficiency of the motor and drive is also animmediate heat gain.

The fan efficiencies are about 707, for centralstation type fans and about 50% for packagedequipment fans.

1-112 PAKT I. LOAD ESTIMATING

Use of Table 59- Heat Gain from Air Conditioning Fan Horsepower

The approximate system pressure loss and de-humidified air rise (room minus supply air tempera-ture) differential must be estimated from the systemcharacteristics and type of application. These shouldbe checked from the final system design.

The normal comfort application has a dehumidi-fied air rise of between 15 F db and 25 F db and thefan total pressure depends on the amount of duct-work involved, the number of fittings (elbows, etc.)in the ductwork and the type of air distributionsystem used. Normally, the fan total pressure can beapproximated as follows:

1. No ductwork (packaged equipment) - 0.5 to1.00 inches of water.

2. Moderate amount of ductwork, low velocitysystems - 0.75 to 1.50 inches of water.

3. Considerable ductwork, low velocity system -1.25 to 2.00 inches of water.

4. Moderate amount of ductwork, high pressuresystem - 2.00 to 4.00 inches of water.

5. Considerable ductwork, high pressure system- 3.00 to 6.00 inches of water.

Example 6 -Heat Gain from Air Conditioning FanHorsepower

Given:Same data as Example 580 ft of supply duct in conditioned space

Find:Percent addition to room sensible heat.

Solution:Assume 1.50 inches of water, fan total pressure, and20 F db dehumidifier rise. Refer to Table 59.Heat gain from fan horsepower = 2.3%

SAFETY FACTOR AND PERCENT ADDITIONS TO ROOMSENSIBLE AND LATENT HEAT

A safety factor to be added to the room sensibleheat sub-total should be considered as strictly afactor of probable error in the survey or estimate,and should usually be between 0% and 5yo.

The total room sensible heat is the sub-total pluspercentage additions to allow for (1) supply ductheat gain, (2) supply duct leakage losses, (3) fanhorsepower and (4) safety factor, as explained in thepreceding paragraph.

Example 7 - Percent Addition to Room Sensible Heat

Given:Same data as Examples 5 and 6

Find:Percent addition to room sensible heat gain sub-total

.

Solution:Supply duct heat gain = 5.7%Supply duct leakage (20 ft duct of total 100 ft) = 2.07,Fan horsepower = 2.37Safety factor = 0.07,

Total percent addition to RSH = 10.0%

The percent additions to room latent heat forsupply duct leakage loss and safety factor should bethe same as the corresponding percent additions toroom sensible heat.

RETURN AIR DUCT HEAT AND LEAKAGE GAIN

The evaluation of heat and leakage effects onreturn air ducts is made in the same manner as forsupply air ducts, except that the process is reversed;there is inward gain of hot moist air instead ofloss of cooling effect. .

Chart 3 can be used to approximate heat gain tothe return duct system in terms of percent of RSH,using the following procedure:

1. Using RSH and the length of return air duct,use Chart 3 to establish the percent heat gain.

2. Use the multiplying factor from table belowChart 3 to adjust the percent heat gam foractual temperature difference between the airsurrounding the return air duct and the air in-side the duct, and also for the actual velocity.

3. Multiply the resulting percentage of heat gainby the ratio of RSH to GTH.

4. Apply the resulting heat gain percentage toGTH.

To determine the return air duct leakage, applythe following reasoning:

1. Bare duct within conditioned space - no in-leakage.

2. Furred duct within conditioned space or furredspace used for return air - a matter of judg-ment, depending on whether the furred spacemay connect to unconditioned space.

3. Ducts outside conditioned space - assume upto 37, inleakage, depending on the length ofduct. If there is only a short connection be-tween conditioned space and apparatus, in-leakage may be disreg?rded. If there is a longrun of duct, then apply judgment as to theamount of inleakage.

HEAT GAIN FROM DEHUMIDIFIER PUMP HORSEPOWER

With dehumidifier systems, the horsepower re-quired to pump the water adds heat to the system asoutlined under Electric Motors. This heat willbe an addition to the grand total heat.

1-113

TABLE 60-HEAT GAIN FROM DEHUMIDIFIER PUMP HORSEPOWER

PUMP HEAD(ftl

357 0

100

5 F

2.03.55.0

SMALL PUMPS* O-100 GPM LARGE PUMPS+ 100 GPM AND LARGER

CHILLED WATER TEMP RISE CHILLED WATER TEMP RISE

7 F 10 F 12 F 15 F 5 F 7 F 10 F 12 F 15 P

PERCENT OF GRAND T O T A L H E A T

1.5 1 . o I .o 0.5 1.5 1 . o 0.5 0.5 0.52.5 2.0 1.5 1 . o 2.5 2.0 1.5 I .o I .o4.0 2.5 2.0 1.5 4.0 ! 3.0 2.0 I .5 I .o

*Efficiency 50% tEfficiency 70%

Basis of Table 60- Heat Gain from Dehumidifier Pump Horsepower

Table 60 is based on pump efficiencies of 50% forsmall pumps and 70% Eor large pumps. Smallpumps are considered to have a capacity of less than100 gallons; large pumps, more than 100 gallons.

u. I Table 60- Heat Gain from Dehumidifier Pump Horsepower

The chilled water temperature rise in the dehu-midifier and the pump head must be approximatedto use Table 60.

1. Large systems with considerable piping andfittings may require up to 100 ft pump head;normally, 70 ft head is the average.

2. The normal water temperature rise in the de-humidifier is between 7 F and 12 F. Applica-tions using large amounts of water have a lowerrise; those using small amounts of water havea higher rise.

PERCENT ADDITION TO GRAND TOTAL HEAT

The percent additions to the grand total heatto compensate for various external losses consist ofheat and leakage gain to return air ducts, heat gainfrom the dehumidifier pump horsepower, and theheat gain to the dehumidifier and piping system.

These heat gains can be estirpated as follows:1. Heat and leakage gain to return air ducts, see

a b o v e .2. Heat gain from dehumidifier pump horse-

power, Table 60.3. Dehumidifier and piping losses:

a. Very little external piping - 1% of GTH.b. Average external piping - 2% of GTH.c. Extensive external piping - 4% of GTH.

4. Blow-through fan system - add percent roomsensible heat from Table 59 to GTH.

5. Dehumidifier in conditioned apparatus room -reduce the above percentages by one half.

I

1-115

CHAPTER 8. APPLIED PSYCHROMETRICS

The lxccccling chapters contztin the prncticnl clatato lxol)erly evnlu:tte the he:tting ant1 cooling loacls.They also reconlnlcnd ottt(loor air quantities forventilzttion l>url~oses i n :tre;ts where state, c i ty orlocnl cocks tlo not exist.

T h i s challter tlcscrilxx lxxtical lxychrometricsas al~l~lietl to ~tl~lxttxttts selection. It is tlivitlctl intothree parts:

1. Descliplior7 of mwrs, p7wesses and factors - asencoitnterec! in nortnztl air contlitioning appli-cntions.

rv.bulb Temperature -The temperature of air as registered by.n orditiazy thermometer.

Wet-bulb Temperature -The temperature registered by a ther-mometer whose bulb is covered by a wetted wick and exposedto a current of rapidly moving air.

Dewpoint Temperature-The temperature at which condensa-tion of moisture begins when the air is cooled.

Relative Humidity - Ratio of the actual water vapor pressure ofthe air to the saturated water vqpor pressure of the air at thes a m e t e m p e r a t u r e .

Specific Humidity or Moisture Content-The weight of water vaporin grains or pounds of moisture per pound of dry air.

Enthalpy - A thermal property indicating the quantity of heatin the air above an arbitrary datum, in Btu per pound of dryair. The datum for dry air is 0F and, for the moisture con-tent, 32 F water.Entholpy Deviation - Enthalpy indicated above, for any givencondition, is the enthalpy of saturation. It should be cor-rected by the enthalpy deviation due to the air notbeing in the saturated state. Enthalpy deviation is inBtu per pound of dry air. Enthalpy deviation is

qplied where extreme accuracy is required; how-er, on normal air conditioning estimates.

it is omitted.

2 . Air u~rttli~ionir~~ :~)+wmtus - ktctors Afcctingcot~t~non lxocesses xntl the clfcct oC these lactorson selection of xir contlitionitig ccluilxncrtt.

3. P.ryrl~7~omeI~ic.r II/ pa7~tinl lorrtl co77 trd - t h eclfect ol lxtrtial lo;~ct on ecluilxncnt s e l e c t i o nand on the cotntnon lxocesses.

70 hells rccognizc ternis, lactors z~ntl lxocessesdcscrilxxl in this chapter, a brief tlefinition of lxy-chronletrics is offeretl at this point, along with anillusttxtion aticl tlcfinition 0E terms nl>l>earing on ;1stanclartl lxychrotnetric chart (Fig. 32).

Specific Volume -The cubic feet of the mixture per pound ofd r y a i r .

Sensible Heat Factor-The ratio of sensible to total heat.

Alignment Circle - Located at 80 F db and 50% rh and used inconjunction with the sensible heat factor to plot the variousair conditioning process lines.

Pounds of Dry Air-The basis for all psychrometric calculations.Remains constant during all psychrometric processes.

The dry-bulb, wet-bulb, and clewpoint temperatures and therelative humidity are so related that, if two properties areknown, all other properties shown may then be determined.When air is saturated, dry-bulb, wet-bulb, and dewpoint tem-peratures are all equal.

Dry-Bulb Temperature

FIG. 32 -SKELETON PSYCHROMETRIC CHART

PSYCHROMETRIC CHARTNormal Temperatures

AIR CONDITIONING PROCESS

I. RETURN AIR FROM THE ROOM @ IS MIXED WITHOUTDOOR AIR @ REOUIRED FOR VENTILATION.

2 THIS M,XTRE OF OUTDOOR AND RETURN AIR

E N T E R S T H E A P P A R A T U S @ W H E R E I T I S

CONDITIONED TO @ AND SUPPLIED TO THE SPACE 0.

3. T,,EN THE A,R CYCLE IS REPEATED AGAIN.

Flc. 33 - TYI~ICAL AIR CONDITIONING PROCESS TRACED ON A STANDARD PSYCHROMETRIC CHART

.

CH,\I-IEK 8 . ,\IILIED ISYC:HKO~ll:.~TliI(:S l-117

DEFINITIONPsychrometrics is the science involving thermo-

dynamic properties of moist air and the effect ofatmospheric moisture on materials and human com-lort. it applies to this chapter, the definition mustbe broadened to include the method ol controllingthe thermal properties of moist air.

AIR CONDITIONING PROCESSESFig. 33 shows a typical air conditioning process

traced on a psychrometric chart. Outdoor air (2)* ismixed with return air from the room (I) and entersthe apparatus (3). Air flows through the condition-ing apparatus (3 - 4) and is supplied to the space (4).The air supplied to the space moves along line (4 - 1)as it picks up the room Ioads, and the cycle is re-

peated. Normally most o[ the air supplied to thespace by the air conditioning system is returnedto the conditioning apparatus. There, i t is lnixetlwith outdoor air required Lor ventilation. The mix-ture then passes tliru tile apparatus where heat andmoisture are added or removed, as required, tomaintain the desired conditions.

The selection of proper equipment to accomplishthis conclitioning and to control the thcrmotlynanlicpropert ies ot the air depends upon a variety of-elements. However, only those which affect the psy-chromctric properties of air will bc discussed in thischapter. These elements are: room sensible heatfactor (RSHFj)t , grand sensible heat factor (GSHF),effective surface temperature (tCJ, bypass factor (UF),and effective sensible heat factor (UHF).

DESCRIPTION OF TERMS, PROCESSES AND FACTORS

SENSIBLE HEAT FACTOR

The thermal properties of air can be separatedinto latent and sensible heat. The term sensibleheat factor is the ratio of sensible to total heat, wheretotal heat is the sum of sensible and latent heat.This ratio may be expressed as:

SHF= SH =-SH

SHfLH T Hwhere: SHF = sensible heat factor

SH = sensible heatLH = latent heatT H = total heat

R M SENSIBLE HEAT FACTOR (RSHF)The room sensible heat factor is the ratio of room

sensible heat to the summation of room sensible androom latent heat. This ratio is expressed in the fol-lowing formula:

RSHF = R S H R S HRSH+RLH=-R T H

The supply air to a conditioned space must havethe capacity to offset simultaneously both the roomsensible and room latent heat loads. The roomand the supply air conditions to the space may beplotted on the standard psychrometric chart andthese points connected with a straight line (1 - 2),

*One italic numljer in parentheses represents a point, and twoitalic numl,ers in parentheses represent a line, plotted on theaccompanying psychrometric chart examples.

Fig. 34. This line represents the psychrometric proc-ess of the supply air within the conditioned spaceand is called the room sensible heat factor line.

The slope of the RSHF line illustrates the ratioof sensible to latent loads within the space and isillustrated in Fig. 34 by ~h,~ (sensible heat) and AA,(latent heat). Thus, if adequate air is supplied tooffset these room loads, the room requirements will

,

DRY-BULB TEMPERATURE/ :$

FIG. M - RSHF LINE PLOTTED BETWEEN ROOM ANDSUPPLY AIR CONDITIONS

tRefer to page 119 for a tlescription of all al)lneviations ant1:yml>ols tlsecl in this chapter.

l-118, l.\l

CHAPTEK 8 . ,\IIt,IEI> ISY(:HIIOIVIEII~I(:S l-119

BOFDRY-BULB TEMPERATURE

r IG. 37 - GSHF LINE PLOTTED ON SKELETONPSYCHROMETRIC CHART

OUTDOOR

ROOM AND AIRLEAVING APPARATUS

IDRY-BULB TEMPERATURE

FIG. 38 - RSHF AND GSHF LINES PLOTTED ONSKELETON PSYCHROMETRIC CHART

the space. It is also the condition of the air leavingthe apparatus.

This neglects fan and duct heat gain, duct leakagelosses, etc. In actual practice, these heat gains andlosses are taken into account in estimating the cool-ing load. Chapter 7 gives the necessary data for eval-uating these supplementary loads. Therefore, thetemperature of the air leaving the apparatus is notnecessarily equal to the temperature of the air sup-plied to the space as indicated in Fig. 38.

Fig. 39 illustrates what actually happens when

these supplementary loads are considered in plottingthe RSHF and GSHF lines.

Point (I) is the condition of air lcaving the ap-paratus and point (2) is the condition of supply airto the space. Line (1 - 2) represents the temperaturerise of the air stream resulting from fan horsepowerand heat gain to the duct.

/

OUTDOOROUTDOORDESIGN

I

MIXTURE /MIXTURE /CONDITION TOCONDITION TO

APPARATUSt, I cisI1

288

CONDlTlON OF AIR LEAVING APPARATUSt f/&,1 %A-1CONDlTlON OF AIR LEAVING APPARATUSt f/&,1 %

IDRY-BULB TEMPERATURE

1 *

FIG. 39 - RSHF AND GSHF LINES PLOTTEDWITH SUPPLEMENTARY LOAD LINE

The air quantity required to satisfy the room loadmay be calculated from the following equation:

cfm,, =RSH

1.08 (Ln - LJ

The air quantity required thru the conditioningapparatus to satisfy the total air conditioning load(including the supplementary loads) is calculatedfrom the following equation:

Cfmda =T S H

1.08 (L - trd

The required air quantity supplied to the spaceis equal to the air quantity required thru the ap-paratus, neglecting leakage losses. The above equa-tion contains the term t,,, which is the mixturecondition of air entering the apparatus. With theexception of an all outdoor air application, theterm t, can only be determined by trial and error.

One possible procedure to determine the mixturetemperature and the air quantities is outlined below.This procedure illustrates one method of apparatusselection and is presented to show how cumbersomeand time consuming it may be.

A

l-120 I:\RT I . LOAD ESIIMATING

1. Assume a rise (trm - t,,J in the supply air to theSpaCC, and calculate the supply air quantity(cfm,,) to the space.

2. Use this air quantity to calculate the mixturecondition of the air (t,,,) to the space, (Equation1, p~lge 150).

3. Substitute this supply air quantity and mixturecondition of the air in the formula for airquantity thru the apparatus (cfm,,) and deter-mine the leaving condition of the air from theconditioning apparatus (t,,,).

4. The rise between the leaving condition fromthe apparatus and supply air condition to thespace (L - tl,,) must be able to handle thesupplementary loads (duct heat gain and fanheat). These temperatures (t,,,, t,,) may beplotted on their respective GSHF and RSHFlines (Fig. 39) to determine if these conditionscan handle the supplementary loads. If theycannot, a new rise in supply air is assumed andthe trial-and-error procedure repeated.

In a normal, well designed, tight system this dif-ference in supply air temperature and the conditionof the air leaving the apparatus (t,, - t,& isusually not more than a few degrees. To simplifythe discussion on the interrelationship of RSHF andGSHF, the supplementary loads have been neglectedin the various discussions, formulas and problemsin the remainder of this chapter. It can not be over-emphasized, however, that these supplementaryloads must be recognized when estimating the cool-ing and heating loads. These loads are taken intoaccount on the air conditioning load estimate inChapter 1, and are evaluated in Chapter 7.

The RSHF ratio will be constant (at full load)under a specified set of conditions; however, theGSHF ratio may increase or decrease as the outdoorair quantity and mixture conditions are varied fordesign purposes. As the GSHF ratio changes, thesupply air condition to the space varies along theRSHF line (Fig. 38).

The difference in temperature between the roomand the air supply to the room determines the airquantity required to satisfy the room sensible androom latent loads. As this temperature differenceincreases (surlplying colder air, since the room con-ditions are fixed), the required air quantity to thespace decreases. This temperature difference canincrease up to a limit where the RSHF line crossesthe saturation line on the psychrometric chart, Fig.38; assuming, of course, that the available condition-ing equipment is able to take the air to 100%

saturation. Since this is impossible, the condition ofthe air normally falls on the RSHF line close tothe saturation line. How close to the saturation linedepends on the physical operating characteristicsand the efficiency of the conditioning equipment.

In determining the required air quantity, whenneglecting the supplementary loads, the supply airtemperature is assumed to equal the condition of theair leaving the apparatus (tY,l - tldb). This is illus-trated in Fig. 38. The calculation for the requiredair quantity still remains a trial-and-error pro-cedure, since the mixture temperature of the air(t,,,) entering the apparatus is dependent on therequired air quantity. The same procedure previ-ously described for determining the air quantity isused. Assume a supply air rise and calculate thesupply air quantity and the mixture temperature tothe conditioning apparatus. Substitute the supply lair quantity and mixture temperature in the equa-tion for determining the air quantity thru theapparatus, and calculate the leaving condition ofthe air frbm the apparatus. This temperature mustequal the supply air temperature; if it does not, anew supply air rise is assumed and the procedurer e p e a t e d .

Determining the required air quantity by eithermethod previously described is a tedioui process,since it involves a trial-and-error procedure, plottingthe RSHI; and GSHF ratios on a pspchrometricchart, and in actual practice accounting for thesupplementary loads in determining the supply air,mixture and leaving air temperatures.

This procedure has been simplified, however, byrelating all the conditioning loads to the physicalperformance of the conditioning equipment, andthen including this equipment performance in theactual calculation of the load.

This relationship is generally recognized as apsychrometric correlation of loads to equipment per-formance. The corrtilation is accomplished by cal-culating the effective surface temperature, bypassfactor and effective sensible heat factor. Thesealone will permit the simplified calculation of stiip-ply air quantity.

EFFECTIVE SURFACE TEMPERATURE (fJThe surface temperature of the conditioning

equipment varies throughout the surface of the ap-paratus as the air comes in contact with it. However,the effective surface temperature can be consideredto be the uniform surface temperature which wouldproduce the same leaving air conditions as the non-uniform surface temperature that actually occurs

when the apparatus is in operation. This is moreclearly understood by illustrating the heat transfereffect between the air and the cooling (or heating)medium. Fig. 40 illustrates this process and is appli-cable to a chilled water cooling medium with thesupply air counterflow in relation to the chilled

FIG. 40 - RELATIONSHIP OF EFFECTIVE SURFACE TEMP

SURFACE AREA

TO SUPPLY AIR AND CHILLED WATER

The relationship shown in Fig. 40 may also beillustrated for heating, direct. expansion cooling andfor air *flowing parallel to the cooling or heatingmedium. The direction, slope and position of th,elines change, but the theory is identical.

Since conditioning the air thru the apparatus re-duces to the basic principle of heat transfer betweenthe heating or cooling media of the conditioningapparatus and the air thru that apparatus, theremust be a common referen$e point. This point isthe effective surface temperature of the apparatus.The two heat traiisfers are relatively independent ofe2-h other, but are quantitatively equal when re-1 . d to the effective surface temperature.

Therefore, to obtain the most economical appara-tus selection,