Fine Tuning Air Conditioning and Refrigeration Systems [illustrated] 088173358X, 9780881733587

Table of contents :
Why Fine Tune Equipment?..............3
Electric Heating..............7
Gas Heating Natural and LP..............17
Oil Burners..............29
Air Conditioning Systems and Heat Pumps Cooling Mode..............39
Heat Pumps Heating Mode..............53
Refrigeration..............61

Citation preview

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air c o ~ d i t i o ~ i nand g refrigeratio~systems/ 2. aintenance and repair. 3, in~--E~iciency. machinery” ting air. 4. Air condition in^" .R e f r i g e r a ~ oand ~ r e f r i g e r a ~ gmachinery--

Fine t ~ n i n gair ~onditioningand re~ige~ation s ~ s t e ~ s C. ~ i~l l~~ g l e ~ . 002 by The F ~ i r m o Press. ~ t All rights reserved. No part of this ~ublicationmay be itted in m y form or by any means, ~~ectronic or ~ ~ c h a ~ i cincludin al, or any i ~ f o ~ a t i storage on and retrieval system, without erm mission in w r i ~ from g the publis~er. Published by The Faimont Press, Inc. 700 Indian Trail Lilburn, GA 30047

Printed in the United States of America

While every effort is made to provide dependable information/the publisher, authors, and editors cannot be held responsible for any errors or omissions. Distributed by Prentice Hall PTR Prentice-Hall, Inc. A Simon & Schuster Company Upper Saddle River, NJ 07458 Prentice-Hall Inte~ational(UK)Limited, London Prentice-Hall of Australia Pty.Limited, Sydney Prentice-Hall Canada Inc., Toronto Prentice-Hall Hispanoamericana, S.A.,Mexico Prentice-Hall of India Private Limited, New Delhi Prentice-Hall of Japan, Inc., Tokyo Simon & Schuster Asia Pte. Ltd., Singapore Editora Prentice-Hall do Brasil, Ltda., Rio de Janeiro

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A ~ ~ eA~ ~ i x

ir ~on~itioning Formulas (Non-P§ychro~~tr~c) .................... 11 A p p e ~ ~Bi x

rksheets .......................................................................................

11

This manual was written to provide the service t e c ~ i c i a nwith the procedures necessary to bring heating, air condition~g,and ref~gerationsystems, including heat pumps, to full operating e~iciency.This manual was not intended to present "standard" service procedu~es butrather to provide advanced i n f o ~ a t i o nand procedures that, when followed, cause the e~uipmentto operate as it was designed by the manufac~rer. en used properly, the procedures presented in this manual will ensure ment operates more economically and to full capacity an has a longer life with a minimum amount of repairs.

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It would have beenim with this indusmanuf~cturersand friends who are conc a manual of this con~ibutionsover the past 35 years have le. They have been m e this text feasib those companies and individuals who value this dust^ as much as I do.

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ere are many reasons for fine~ i n heating, g air condi~oning/ and refrigeration equipment/ such as energy conservation, cost effectiveness, less need for new power plants, improvedp e r f o ~ a n c eand , equipment longevity. It is true it takes more time to fine tune equipment so that it operates at peak efficiency/ and this comes at a greater cost to the customer. Howenefits are properly explained, most are willing to pay the service fee, which is usually saved many times over through the more efonomical operation of the e~uipment.Also, thetechnician ility and desire to fine tune equipment can charge extra for ill always be in demand by the public.

' of oil, every possible step must cause of the constantly dec made to conserve use. its ating, air conditioning/ and reration e ui ment is a very good placeto start, because air conditioning est users of electricity in residential and many commercial heating, air conditioning/ and refrigeration units are operciency this percentage of power consumption is reduced much as 25%. Several tests have proven that nine out of eration units are operating at a reduced efficiency that is between 10% and 40% of their rating.

i t i o n ~ g and , refrigeration equipment is operating and the cost of operation is reduced. Thus, the

customer is savingmoney. When the technician finetunes the equipment so it operates more economically, the customer is more satisfied and is much more pleased with the serviceprovided. The service technician can usually charge more for providing this fine tuning service, because the customer is more willing to pay for d, thorough service that ensures the e~uipment isoperating as des cause of this, both tiesaresatisfiedandthe customer is more a mend the technic to others who may want this type of service.

When heating, air conditioning, and refrigerationequipment is working at peak efficiency, power generating plants cm be operated at less than h11 capacity. The power company not only saves onoperatin expenses, but the need to build new power plants to furnish power to inefficiently operating equipment is no longer a considera~on.Thus, the need for costly power plant construction and operation is eliminated.

Properly tuned heating, air conditioning,and refrigeration equipment performs better than equipment that is not properly adjusted. The customer will be more satisfied with theoperation of fine tuned equipment. In addition, the unit will keep the building more comfortable, the process refrigeration and heating equipment will satisfy the demands much more easily, and there will be less service and maintenance required.

Fine tuned equipment has the properamount of refrigerant and oil flowing through the system to maintain properly lubricated components at their desired operating temperatures. Properly lubricated equipment operating at the desired tem~eratureusually lasts much longer than equipment that does not have these characteristics.Thus, the customer is saved the costof having to replace the equipment,and major repairs are either eliminatedor postponed to a much later date.

A check of the operating refrigerant pressures and temperatures, along with determining the airflow through theunit and the temperature rise or drop

of the air, is usually all that is neededto determine the efficiencyof the unit, or more of these operating factors usually unit. Of course, the ductwork,, insulation, and thecondition of th rewilldetermine, to a greatextent,whether or notthesystemwillthedesiredconditionsinsidethebuilding. All of these factors must be considered when fine tuning equipment to ensure more complete customer satisfaction. member, the best equipment will not perfom if it is insta llation also is a part of fine ing a unit. The unit ma peak efficiency,, but if the conS not properly distributed, the oned air cannot reach t a thorough inspecresult will still be or ope ratio^. Give the ins~a~lation tion, and informcustomer of anything that can,,ormust,be done to obtain optimum efficiency an

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of the amount of heat input to veredbythe

hrnace.

in both residential and commercial applicaree-phase element designs. it is important that electric prevent drafty conditions.

units is probably the units available. The

e proper test hstr

ny rate, accurate test

inst~mentsmust be used for testing the efficiencyof electric heating units. The exact procedures for i n s t ~ m e nuse t are found in the manufacturer’s operating il~structions.The i n s t ~ m e n t smust be properly cared for an their accuracy maintained for optimum performmce. This chapter will discuss the specific procedures used to fine tune electric heating units, not specific inst~ments.The following is a list of the basic test inst~mentsrequired for testing and adjusting the efficiency of electric heating units: 1.

Dry bulb thermometer

3.

Voltmeter (a w a t ~ e t e rmay beusedin vol~eter)

.

eter er

lace of theammeterand

A dry bulb (db) thermometer is used for checkin 2-1. ~ e t e r ~ the ~ ntemperature g rise of the ai n process. g The dry heating unit is a very important step in the fine ~ bulb tempera~reis a measure of the heat absorbed from the heating elements by the air.The air temperature is measured in two locations: the return air stream and the discharge air stream, Figure 2-2. the tempera~rereadings after the mixing of m y air and within 6 ft of the air handling unit. The thermometers must be placed wherethe radiant heat from the elements cannot be measured by the thermometer. Radiant heat can cause a faulty tempera~rereading and an incorrect test. Two differentthermometersthathave been tested an found to produce exactly the same r e a d ~ g under s the same set of cir~mstancesshould be used. If two thermometers that read exactly the same tempera~resare not

ry bulb t~ermom~ters (Cou~esy, wyerInstruments,Inc.)

6 ft r n a % i ~ u ~

Do not rneasure

ir

in a I

air are ~ i % e d )

circulatin~air te~p~rature

available, then use one thermometer to measure both temperatures. An ~ o m e t e that r has se arate, properly adjusted leads also proired results. The best temperature rise of an electric S the blower to run longer, heating unit is about 40” to 50°F. the air more evenly thro~ghoutthe building.

e ammeter is used to determine the amount of electrical current used by -on type ammeter is the most popular, because the be measured without separating the wire. Thesei n s t ~ m e n t s ccurate when the wire being measured is in the center of the

The voltmeter is used to meas~rethe voltage in a wire, Figure 2-3. The -type meter is the most accurate when the indicator is in the center 1 be checked regularly to ensure they are in of the scale. The n the insulation becomes worn or cracked, firm, solid fit between the meter and the fitting lead can givean improper voltage

Figure 2-3. ~ i g i t amultimeters l (Courtesy, AM Sperry Instruments, Inc.)

e wattmeter is used to measure the voltage to the unit and the total wattage used by the unit. ese inst~mentsare usually more accurate than voltmeter and ammeter to determine the total wattage used by the unit. r the wever, w a t ~ e t e are ~ s more expensive.The analog-type w a ~ e t e is most accurate when the indicator is reading at the mid-scale point.

ending on the size and type of installation/ bo single- and three-phase heatingelementsareused.When d e t e ~ i n i n g lowatt input, be sure to measure the total voltage and amperage to the unit, including the fan motor, because it also adds heat to the air. en more than one heatin element is used, check the fan motor separately to prevent adding the motor amperage to each element. The meas~rementsshould be taken at a close d i s c o ~ e c tswitch or where the electrici~enters the unit, not at a distant point.

To d e t e ~ i n ethe c a p a c i ~of an electric heating unit, first d e t e ~ i n ethe tu input to the unit by p e r f o ~ i n gthe following steps: 1.

3,

easure the voltage and amperage to the fan motor and each heatin element. Add together the amperagedraw of each heating element and the fan motor. h et ermine the unit wattage by multiplying the voltageby the amperage. Use the following formula:

where:

4.

Determine the unit Btu output by multiplying the wattage by 3.413. Use the followin

tu = 5.

etermine the blower c h by dividing the tu by 1.08 x AT. Use the appropriate formula:

cfm = cfm = cfrn =

Make certain that all the return an rilles are open and unobstructed. If an air conditioning unit is included, make certainthat the coils and filters are clean.

6.

Determinethe AT by usingthefollowingsteps: a. Allow the unit to m continuously for about ten minutes. b. To avoid t h e ~ o m e t e rerror, U sure the return and supply air te c. Measure the temperatu~sat a point where the thermometer cannot "see" the heat source (see F cannot be measuredwhen radia eter. d. The air temperature measur~mentsmust be taken within 6 ft of the air handling unit. The return air temperature can be taken at the return air grille if it is located closeto the unit, as inFi 2. The air temperature taken at the supply air grille is not usually accurate enough for this purpose. e. M e n more than one discharge or return air uct is connected to theplenum,usetheaverage rature (AT).Forexample, 1 = 115"F, Duct 2 = llO°F/ Use the f o l l o w ~ g formula: AT = 7"-

Number of ducts

= 112"

f. 7.

Be sure to ta the temperature measurements after any source of mixed air, such as a fresh air intake. Check the manufac~rer'sspeci~cationsforthe par~cularunit to see if these conditions meet the design criteria.

en the cfm is too high, slow the blower. n the discharge cfmistoo low, speed up the blower. en a direct drive motor is used, the cfrn can be changed by moving the electric wireto a lower or higher speedt e ~ i n a l

en a direct drive motor c a ~ be~wire t to deliver the correct cfm/ use e the air inlet to the blower.Be sure to make otor to prevent overheatin cfmf and secure f sheet metal cut lower is used, the cfm can be c r shaft. To incre~sethe the pulley halves. t e ~ ~ e r a t ~ r e i r e ~~ air ~~tre ~~~s e r a t ~ r e . city b t is not heat

ure the cfm from each one, and total them.

insulation.

t

If the

en the duct system meets this criteria, the only other alternative is to more capacity. This c m be done by either adding more heat strips or installing some with higher capacity ratings. Table 2-1lists the tempera~re rise, the k W rating of the furnace, and thecorres~ondingcfm. This information can be used to reduce the time requiredto get a very close estimate of how efficient the unit is operating.

53

-

-

-

-

-

-

-

-

59

79

32

7

63

-

26

39

53

-

20

49

40

59

69

79

18

26 44

35

53

61

70

16

24

32

55 40

47

14

22

29

36

43

50

57

-

16

21

26

32

-

37

42

20 30

25

-

18

22

-

-

700 30

40 35 26

63

35 30

about insu~icientheat from an electric heating unit, th heating elements are delivering the amount of heat they at one or more of the heating elements is not operating properly. Thisis is easily pe~ormed. S

W

er, voltmeter, accurate thermometer, and tool kit. An accurate wa~metermay

rocedures: electricity to any other equipment that is used in conjunction with the electric

h

et the thermo~tatto d e ~ a n dheat. Allow the heater to operate for approximately 10 minutes so the tempe tures will st~bilize. easure the voltage an amperage of each heating element and record: Volts otor:

1.

eater: 1.

3.

Sum:

total wa~ageof the heat strips and record. Use the followin =Vxl _. _.

5.

ete ermine the

tu

=

U

outputoftheheatstripsandrecord.Usethefollowingformula:

Amps

etermine the cfm of the blower and record. Use the following instructions: *

Use the same thermometer, or two that measure exactly the some, to measure the return and supply air temperatures.

*

Do not measure the temperature in an area where the thermometer can sense the radiant heat from the heat strips (see Figure 2-2). True air temperature cannot be measured if the thermometer senses radiant heat.

5

Taketemperature the measurements within 6 ft of th return the and at n supply grilles that are at too great a distance from the unit are not usually accurate enough.

*

Use the average temperature when more than one duct is connected to the supply air plenum.

*

Besuretheairtemperaturehasstabilizedbeforetakingthetemperaturemeasurements.

5

Take the temperature measurements downstream from any source of mixed air. Use the following formula:

cfrn =

cfm

7.

Btu 1.Q8x AT

=

Is this whatthemanufacturerratesthe

e~uipment?

ultiple tear-out copies of this worksheet

Thepurpose ofadjustin the e ~ c i e n c yof anypiece of equipment is to deliver the most energy ossible to the conditioned space or process. The efficiency of a gas-fired furnaceor boiler is the difference between the input and the actual amount of heat produced by the unit. The efficiency adjustment must provi without ain producing undesirable conditions. In mathematical terns, efficiency is explained as:

Total energy The components must be clean and in good working condition, and clean air filters must be installed.

several are There the in close1 When an a d j uthe ctors, s ~ ~in t also affected. There is are as follows:

r or

a d j u s ~ p~ rn~t e s s . other factors a r to follow when making efficiency ral categories of these factors

ecomb~~o process n

rtant part in overall unit r are mixed in the proper

set this gas-air relations hi^, th tion. Therefore, the burner m

reareseveralfactorsthataff unit’s e~iciency,suchasthe gas and air.

r m ~ x of ~ the g

e proper test ~ s t ~ m e nare ts

of

efficiency

is chapter will discuss th not heating units, sp~cific list i the ~ s ~ r n ere~ t s

of test basic

6. 7.

e one ofthe first steps t, because if the heat is

eter used for checktempera~rerise of in. the unit is a very i m p o r t ~step t

heat from the elet heat can cause a Two different t h e ~ Q m e

available, then one use therm0 electronic t h e ~ o m e t ethat rhas

air are mixed)

tempera~resare not both temperatures. re An ly adjusted leads also prore rise of a as-fired ws the blower to run

measure the temperature of the flue gases in the vent system, or the stack tem~erature.The flue gas tem~eratureof a standard gas furnace or boiler should not be more than 480°F higher than the ambient or combustion air tempera~re.The m ~ i flue m gas ~ temperature on a standard gas furnace or boiler should be 350°F. If the flue gas temper the from b~rnin heat exchanger,e must be found

,not enough heat being is removed

tocirculating low dirty airflow, a unit beingover-fired.Thecauses

of theproblem

as tem~eratureof a high efficiency gas furnace will range from about 100" to 125°F. Chec the manufacturer's specifications for the specific e other combustion factors will remain the same. l

s an i n s t ~ m e n used t for measuring small pressures. It is

rate at which flue products are removed from the unit is taken on the chimney side of the draft

ve pressure reading indicates that there is sufficient air movement the combus~onzone to allow proper and complete combustion.If is past the halfway point on the negative side of the scale, there draft through the unit causing excess heat to be drawn out of the unit and inefficient operation. When the hand approaches zero or goes ositive side of the scale, there is too little draft through the unit and an insufficient amount of combustion air is being drawn into the combus-

Draft diverter

causing the products tobe re may be an obst~ctionin and corrected. ment, a blocked vent usually reso, the combustion blower may be ve combustion air to be delivered to the conditions must be found and corrected.

combustion e process.

A carbon mon~xide

er, sometimescalleda n into the draft

emsis to decreasethefiringrateand increase the ~ r ~ a air r yto the main b u ~ e r s . Insufficient secon ary air will also cause a hi carbon dioxide (C readin If the fla

no problems, check the secondary air.

in the heat exchanger and/or

ue outlet r e s ~ i c t i o ~ s .

co~bustionzone. It can

S

of combus~onefficiency.

S

the amount of exce

an increase in system, and the combusti~n ~fficiency decreases.

ration workf it is necessary that technicians airflow and what the readings indicate. Air ce air travels in a given period of time. It is usually fpm). When the air velocity is multi~lied by the cross section ct, the volume of air flowing past that point in theductcan be deThisvolume of airflow is usuallyexpressed in cubic feet per mi The velocity or air volume measureme~ts can be used to determine if the airflow system is operating properly, or if some repairs are needed. Some airflow inst~ments,su as the air velocity meter in Figure 3-$ have a direct read-out in cfm, while others require some ~alculationsto determine the cfm flowt ~ o u g h the system. Thisis one factor that must be taken

Figure 3-4.Air velocity m

wyer ~ n s ~ r ~ ~Inc.) en~s,

into account when purchasing the m er usually will inch in .Be sure follow to th

ins

.instrument The n the properofuse the

In use, the airflow i n s t ~ m e n is t held a ainst the air outlet reading is indicated on the meter scale Figure 3-5. Therea interpreted according to the instrument m rer’s i n s t ~ c ~ o nWhen s. the obtain gs istoused large grilles useare Use airflow. correct i n s t ~ c ~ o on n s how to take these readings.

theUse followtermine in^ thean steps efficiency of the heatin

combus~on

~ i s ~ a lcheck l y the entire u ~ i for t c l e a ~ i ~ ~and s s ensure , all componentsare in properworkingcondition.esuretheheatexchan passa~es venti theand of all o ~ s t ~ c t i o ~ s . local gas company or Start the heating unit, to bring e v e ~ t h i n gU

er cubicfoot. (Contact the

r l~strum~nts, Inc.)

and stop the fan at 100°F.

butisnoth

tin

total them. If the d 9, air is leaking f ently the leak must

o this,measure the

other a l t e ~ a ~ is v eto of the main burner e the recommended o so is very dangerous.

instrument test thed ructions m

to determin

manifold pressure

system for cleanliness, and ensu ger passages and the ventin

er cubic foot heating unit, and allow it to operate for about ten minut inches W.C. the type of flame and record.

7 . Adjust the burner if needed, and record the type of flam m~eraturerise of the circulatin

AT AT

=

= Discharge air temperat~re- ntering air tempe "F

. Determine the blower cfm and record. Use the followin

cfm tempe gas

flue

=

10. the Check

"F Oh

%

gases flue

the

of content

v3

any adjustments or repairs required to increase the combustion e~iciencyof the unit. Repeat Steps 3

n ~ f ~ c t u r rates e r the unit?

~ u l t i p l etear-out copies of this worksheet can be found in Appendix B.

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an oil burner, the main objective isto ensure the unit proossible with as little heat input as possible. The reatest heat gain without causing undesirable conditio^, h mathematical terms, efficiency may be explained

The components must be clean and in good working condition, and clean air filters must Le installed.

Thereareseveralcloselyfactorsinvolved in theadjustmentprocess. one of thesefactors,the other factorsare When an a d j ~ ~ e isn t also affected.

The proper test ins~umentsare needed to make accurate measurements of the product orprocessbein .Theoldprocedure of merelylooking at the e ~ ~ i p m eor n t feelin no longerindicateswhat is happening with the unit. There are many brands and models of test inst~mentsavailable. Which particular i ~ t r u m e n to t use is the user’s choice, but accurate test instmments must be used to roperly fine tune oil burners. The exact procedure for i ~ t ~ m e use n t can be found in the manufac~rer’soperating instructions. These i n s t ~ ~ e nmust t s be properly cared for and their accuracy maintained for o p ~ m u mperformance.

This chapter will discuss the S equipment, not S i n § ~ ~ e nrequ ts efficiency of an oil-fired unit:

bustion efficiency arious test results 5.

Dry bulb thermometer

useis This type of thermometer

er than normal tem-

h flue gas temperatur~sresult in excessive ssive oil c o n s ~ p t i o nand may

Lowflue gas t e m ~ e r a ~ r e s deterioration and sm of the gas t e m ~ e r a ~ r may e s also

r draft. flue Low

The flue gas tem~era about 12 ft from the before ing the

1/4 in. hole (behin~thermometer)

determines the amount of combustion air sLlpplied to the burner. An excessive amoLlntof draftcanreducethe eof CO, in thefluegasesand increase the tempera of instal~ationhas its own draft reqLlirements, Not enough draft can cause pressure in the CO bLlstion area, thus allowing smoke and odor toescape fromthe wit. of draftcanalso e itimpossibletoadjust emaximum r efficiency,becauseirnumefficiencyisdethe oil b ~ l ~ to pendent ~ p o ntheproper ~ i x t u r eof air andingburneroperation. Q

raft of at least0.0 develop and ~ a i n t a i npr below 0.02 inches w.c., S

The flue pipe

inches

W.C.

becheckedanjustedonoilburners:

inches W.C.is considered sLlfficie~tto hotlldtheover-firedraftfall r may be present in the burner onmaybe present when close are completed.

drafts must be a justed to prevent positive pressure in the flue passage requires a le flue passage requires or less require a flue pipe draft ntain an over-fire draft of 0.02 in the combLlstion zone,

The flue pipe draft is adjusted by changing the position of the draft re lator damper. Adjusting the co~terweightso the damper moves toward the closed position causes an increase in the draft. Adjusting the counterweight so the damper moves toward the open position causes a decrease in the draft through the combustion zone.

The smoke tester andthe smoke scale are used to d e t e r ~ i n ethe amoLlnt of containing an excessive amoLll~t smoke in the flue gases. Combustion gases of smoke indicate incomplete combustion and inefficient oil burner operation. An excessive amoLlnt of smoke allows soot formation on the heat exchanger surfaces. This soot slows down the heat transfer and clogs the flue passages, thus preventing proper draft through the combustion zone. A soot buildup of 1/8" can reduce heat transfer by LI The purpose of conducting the smoke test is to determine the amount of smoke the flue gases contain. The smoke test can then be used along with other tests to adjust the oil burner to obtain maximLlm efficiency. Thesmoke scale has 10 color-graded spots ranging from 0 to 9, where 0 is pure white and 9 is the darkest color on the scale. e smoke scale isalways used along withthesmoketesterforcompleteresults. Use the instrLlment manLlfactLlrer's inst~ctionswhen conducting the smoke test. Not all types of oil burners are affected the same way by the same amount of smoke in the flue ases. The type of comb~lstionzone const~lction,to a great extent, deter~ineshow fast soot accLlmLllates on the heat exchanger and other surfaces. Soot accumulates very rapidly on some types of construction when fired with a #3 smoke spot, whereas other units may accumulate soot at a much slower rate with the same smoke content. Table 41 shows the possible soot accL~mLllationrate for differentamoLlnts of smokc in the flue gases.

importal~tto oil Thecorrectpercentage of CO, in the fluegasesisry burner combLlstionefficiency testing.The desired C reading is between 9% and 10%. When the reading is below 9%, check for the following conditions: Air leakage Excess combustion air Worn, plugged, or incorrect nozzles High draft conditions Incorrect or defective combustion zone Poor atomization of the fuel oil Incorrect combustion air handlin Incorrectly set oil pressure Excessive combustion zone draft or air leaks Erratic draft regulator

Table 4-1. Smoke effect on burner performance

tin 1

2

accumulaExcellent light Reduced, very accumulation willSoot light, Good

accumulasoot 3 some be MayFair

4

5

some condition, Borderline Poor

Very accumulation Soot poorheavy very

oot a c c ~ m ~ l a t i o n

tion if at all not appreciably increase stack temperature tion, will seldom require cleaning more than annually units may require more than annual cleaning and rapid

Therearetwofactorsthatdeterminetheamount of heatlost in theflue gases. They are the flue gas tempera~reand the percentage of CO, in the flue gases. It is the flue as heat loss that determines the combustion efficiency of the oil burner. t isused to sampleflue gases to The CO2 analyzerisan i n s t ~ m e n that determine the CO, content. A low CO, reading indicates that not all of the fuel is burning completely, thus some adjustments are required. It is recommended that the CO, analyzer be used along with other testing devices. to determine One such deviceis the slide rule calculator, which can be used the unit efficiency and stack losses in oil burner installations by correlating the temperature of the flue gases and the CO, percentage. To properly use the CO2 analyzer, follow the instrument manufacturer’s instructions. When the CO, reading is above lo%, at least one of the following conditions must be corrected: InsLlfficient draft Oil pump not fLlnctioning properly Poor fuel supply Improper fuel/air ratio Rraft regulator improperly adjusted Improper combustion fan delivery Defective or incorrect nozzle type Wrong burner air handling parts Excessive air leaks in the combustion zone

A dry bulb (db) thermometer is used for measuring air temperatures (see Figure 2-1). r et er mining the temperature rise of the air as it passes through the heating unit is a very important step in the fine tuning process. The dry bulbtemperature is ameasL~re of the amount of heatabsorbedfromthe heat exchanger by the air. Theair tempera~reis measured in two locations: the return air stream and the discharge air stream, Figure 4-2. Be sure to take the temperatLlre readings after the mixing of any air. The thermometer must be placed where the radiant heat from the heat exchanger cannot be measured by the thermometer. Radiant heat can cause a faulty temperature reading and an incorrect test. Twodifferentthermometersthathavebeentestedandfound to produce exactly the same readin S under the same set of CircLlmstances should be used. If two thermometers that read exactly the same temperature are not available, thenuse one therm~meterto measLlreboth tem~eratLlres.An electronic thermometer that has separate, properly adjusted leads also produces the desired results. The best operating air temperature rise of an oilfired unit is between 60" and 80°F. This allows the blower to run longer, distribLlting the heat more evenly through the building.

6 ft maximum

Do not measure temperature in this area I

Fresh air entering in this area

T~ermometer

l

I "

Thermometer ocated after the resh and indoor air are mixed)

I'

Figure 4-2. ~ e a s u r i n t ~ ~ ~ e r a trise u r et h r ~ u ~a hfurna~e

"

Oil burner com~ustionefficiency is considered to be very good when a conversion oil burner talla at ion is operating with a flue gas temperature of between 600" a oil burner unit has agas flue bustion efficiency is also conr, these flue gas tempera~resmust be test rea~ings,including the following: ot, with a #3 spot being the m a x ~ u m 9% and 10%; and an over-fire draft of between 0.04 and 0.06 inches W.C. When any of these requirements are not met, some corrective measures must be taken to obtain maximum combustion efficiency.

Use the followin steps and the worksheet to determine the combustion efficiency of an oil burner: 1.

2. 3.

Visually check the entire unit for cleanliness, and ensure all components are in proper workin condition. Be sure the flue gas passages and the venting system are clear of all o b s ~ c t i o n s . Start the oil burner, and allow it to operate for at least 15 minutes. temperature, For conversion oil burner installamperature should be between 600" and 700°F.For as tem~eratureshould be between

4.

tent of the flue gases. Flue asesshould be between combustion efficienc~,Use the i n s t ~ m e n t

6.

7.

smoke spot. A #3 Check the over-fire

S

draft. I

e between 0.04 and 0.06 inches

W.C.

8.

it cfm, Use the following formula:

system. Find the leak and repair it. "he next step is to measLlretl-re duct heat loss. To do this, measure the discharge air tem~erature farthest located rille heating unit. the from "he temperatLlre the rat supply t air theand grille heatin irthe from unit should not exceed 3" to 5"E If the differe~ceis more than 5"F, the duct needs more insulatio~. When the heating system meets this criteria, the only other alternative is to either increase the firing rate of the oil burner or install a larger capacity burner that matches the furnace combLlstio~ re~Llirements.Check with various oil burner manufac~lrersfor the correct tnnit,

heat from an oil-fired unit, the techniciafl shou ~oufltof oil it was designed to Use the followi etermifle the combustion e~icieflcyof oil carbon dioxide analyzer e various test results to

"F YO

iciency is

YO

inches W.C.

10.

sur

ulti~letear-out copies af this worksheet can be found in

This Page Intentionally Left Blank

8

Air col~ditioning systems arethelargest users of electricity in boththe home and most smaller commercial buildings. The cooling process involves sensible and latent heat removal. The air is cooled to the dew point temperature,removingonlysensibleheat.Bothsensibleandlatentheatare removed below the dew point temperature. The removalof latent heat from the air requires a large part of the air condition in^ unit’s capacity. Therefore, fine tuning these systems results in lowering the consumption ofelectricity by as much as 25% in some cases. The percent by which the electrical consumption is lowered depends on the condition of the unit before it is fine tuned and the condition after the process is completed. There are several steps involved in the fine tuning process, and each step requires that all of the airc o ~ d i t i o n i n system ~ componentsbe clean and in good working condition and that clean air filters have been installed.

There are several closely related factors involvedin the adjustment process. W-ten an adjustment is made to one of these factors, the other factors are also affected.

The proper test instrL~ments are needed to make accurate measurements of the product or process being tested. The old procedure of merely looking at s o ~ e t or~ feeling ~ i ~ a~line to determinetheoperatingcharacteristics no

er indicates what is ha

accu- their and

There are many bran models of test ins nts available. Which particular i ~ t m m e n t the is user’s choic accurate test instmments must be used to procedure for instrum for instruc~ons. in These racy ma~tainedfor optimum p e r f o ~ ~ c e . This chapter will discuss the specific procedures used to fine tune air condi~oningunits, not specific ins ~ o l l o ~ i nisga list of the basic ustingtheefficiency of an air ents re~uiredfortesting an condition in^ system: 1.

.

3. 4. 5.

Wet bulb thermometer Dry bulb t h e ~ o m e t e r Totalheatchart (or a sychrome~cchart if t refer re Gauge mmifol ~elometer/ anemometer/or flowhood ( S ~esiredoravaila~le)

A wet bulb (wb) t h e ~ o m e ~ is e the r same as an ordinary dry bulb thermometer/ except that the bulb is covered with a wet cloth or gauze. Wet bulb thermometers of air. The same th bulb thermomet bulb t h e ~ o m e t e r fference b e ~ e e the n Eb ~ ~ r e sCalcula s ~ ~ ~ . ture in a room measures

60 is loo%, meaning the air

meter used to measure

measure of the amount of heat absorbed from the air by the cooling coil.

Dry bulb thermometer Wet bulb thermometer

32 90 79 82 91 36 40 92 84 44 93 85 48 93 87 52 94 88 56 94 88 60 94 89 95 64 90 68 95 90 72 95 91 76 96 91 80 96 91 84 96 92 88 96 92 92 96 92 96 93 100 96 93 104 97 93 108 97 93

69 60 50 41 31 22 13 4 73 65 56 48 6 14 23 31 39 23 31 38 46 76 68 61 53 16 51 44 37 31 24 18 125 78 71 64 57 80 73 67 60 54 48 42 36 34 25 19 14 8 58 52 46 41 36 30 25 20 15 81 75 69 63 82 77 71 66 6117 24 26 34 35 40 45 50 55 263 58 53 49 44 40 35 31 27 22 18 14 6 84 78 73 68 85 79 75 70 66 61 56 52 48 43 39 35 34 27 23 20 16 12 9 85 81 76 72 67 63 59 55 51 47 43 39 35 31 28 24 21 17 14 86 82 78 73 69 65 61 57 53 49 46 42 39 35 32 28 25 22 87 83 78 74 70 67 63 59 55 52 48 45 42 38 35 32 29 26 23 87 83 79 76 68 11 13 16 18 21 24 27 29 32 35 38 41 44 47 54 57 61 64 68 72 88 84 80 77 73 70 66 63 88 85 81 78 74 71 57 64 61 58 55 52 49 46 43 41 38 35 33 30 28 25 23 21 18 16 14 89 85 82 78 75 72 69 65 62 59 57 54 51 48 45 43 40 38 35 33 30 28 26 24 22 89 86 82 79 76 73 70 67 74 61 58 55 53 90 86 83 80 77 74 71 68 65 62 59 57 54 52 49 47 44 42 40 37 35 33 90 87 84 80 77 74 72 69 66 63 61 58 56 53 51 48 46 44 41 39 37 35 33 31 29 27 25 24 90 87 84 81 78 75 72 70 67 64 62 59 57 54 52 50 47 45 43 41 39 3'7 35 33 31 29 28 26

9

2

10

6 0 12 48

19

59 56 53 50 47 44 41 38 35 32 30 27 25 22 20 17 15 12 19

50

47 45 42 40 37 35 33

31

29 26 24 22 20 18 31 29 27 25 23 21

1 10 6 12 17 15

Do not ~ e a s u r e

6 ft ximu mum

Fresh air entering in

this area

Two different thermometers that have been tested and found to produce exactly the same readings under the same set of circumstances should be used. If two thermometers that read exactly the same temperat~reare not available, then use one thermometer to ~ e a s L ~both r e temperat~~res. It is best to measure the return air temperatLlre first, because it will not change as fast as the d' An electronic thermometer separate, prope rodLlces the desired results. bulb thermometers are also incorporated into sling psychrometers.

A total heat (H) chart, also known as an enthalpy chart, is used to deter~ The t y total heat chart in mine the total amount of heat in a ~ ~ ~ aofn air. Table 5-22 lists the wet bulb tem~eratures("F) in whole nLlmbers down the left-hand column. The degrees are broken down into one-tenth increments across the top of the table. Thea m o ~ ~ofn ttotal heat in the air is listed in the emeath to and the eratures.example, For if F, whatis the total heat in the air? the wet bulb tempera~lrerea Find50°Fin the left-h~ndcol lbw that line to the right until the 0.5 column is reacl~ed.The total heat content of the air at tu/lb of dry air.

ir with vapor to saturate it) Temp.

F'( wb)

.O

.l

50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88

20.31

20.36 20.86 21.49 22.06 22.68 23.28 23.90 24.53 25.18 25.85 26.53 27.21 27.92 5 29.38 30.13 30.92 31.70 32.51 33.34 34.17 35.04 35.92 36.83 37.76

90

55.93

21.43 22.00 2.62 23.22 23.80

27.15 27.84 29.30 30.01

34.09 34.96 35.83

40.58 41.58 2.63 43.70

46.99

50.66 51.93 53.22

40.68 41.69 42.73 43.81 44.89 46.02 47.16 49.56 50.79 52.06 53.35 54.70 56.07

.2 0.4 0.9 21.55 22.12 22.74 23. 23.96 24.59 25.25 25.91 26.60 27.28 28.00 28.72 29.45 30.21 31.00 31.77 32.59 33.42 34.26 35.13 36.01 36.92 37.85 38.80 39.77 40.78 41.79 42.83 43.91 45.00 46.13 47.28 48.4 49.6 50.91 52.1 9 53.48 54.83 56.20

.3

.4

.5

.6

20.47 20.98 21.60 22.19 22.80 23.40 24.03 24.66 25.32 25.99 26.67 27.35 28.07 28.79 29.53 30.29 31.07 31.85 32.67 33.50 34.34 35.22 36.10 37.02 37.94 38.90 39.87 40.88 41.89 42.94 44.02 45.11 46.24 47.40 48.58 49.80 51.04 52.32 53.62 54.97 56.34

20.53 21.04 21.66 22.24 22.86 23.46 24.09 24.72 25.38 26.06 26.74 27.42 28.14 28.86 29.60 30.37 31.15 31.93 32.76 33.59 34.43 35.31 36.19 37.11 38.04 38.99 39.97 40.98 42.00 43.05 44.1 3 45.23 46.35 47.52 48.70 49.92 51.16 52.45 53.75 55.10 56.48

20.58 21.09 21.72 22.30 22.92 23.52 24.15 24.79 25.45 26.12 26.81 27.48 28.21 28.94 29.68 30.45 31.23 32.01 32.84 33.67 34.51 35.40 36.27 37.21 38.14 39.09 40.07 41.08 42.10 43.15 44.24 45.34 46.47 47.63 48.82 50.05 51.29 52.58 53.89 55.24 56.62

20.64 21.21 21.78 22.36 23.98 23.58 24.21 24.85 25.51 26.19 26.88 27.55 28.29 29.01 29.76 30.52 31.31 32.09 32.92 33.75 34.60 35.48 36.37 37.30 38.23 39.18 40.17 41.18 42.20 43.26 44.36 45.45 46.58 47.75 48.94 50.17 51.42 52.71 54.02 55.38 56.76

.9 .7 20.70 21.26 21.83 22.43 23.04 23.64 24.28 24.92 25.58 26.26 26.94 27.62 28.36 29.08 29.93 30.60 31.39 32.17 33.01 33.84 34.69 35.57 36.46 37.39 38.33 39.28 40.27 41.28 42.31 43.37 44.46 45.57 46.69 47.87 49.06 50.29 51.55 52.84 54.15 55.52 56.91

.8 20.75 21.32 21.89 22.49 23.11 23.71 24.34 24.99 25.65 25.33 27.01 27.69 28.43 9.1 6 29.91 30.68 31.47 32.25 33.09 33.92 34.77 35.66 36.55 37.48 38.43 39.37 40.38 41.38 42.41 43.48 44.57 45.68 46.71 47.99 49.19 50.41 51.67 52.97 54.29 55.66 57.05

20.81 21.38 21.95 22.55 23.16 23.77 24.40 25.05 25.73 26.39 27.08 27.76 28.50 29.23 29.98 30.78 31,54 32.33 33.17 34.01 34.88 35.74 36.65 37.57 38.52 39.47 40.48 41.48 42.52 43.59 44.68 45.80 46.82 48.10 49.31 50.54 51.80 53.09 54.42 55.80 57.1 9

The gauge manifold is used to perform many procedures involving refrigerant, oil, and evacuation of the refrigeration system. ~ a u g manifolds e are made up of a pressure gauge, compound gauge/ valve manifold/ and hoses and connections. The operating refrigerant pressures can be directly related to tempera~rebytheuseof apressure-tturechart.Mostgauges cQrrespondin incorporate apressures fferent of various refrigerants. The manifol~has ports compound and pressure gauges. There are valves in the ma re operated by hand used to control the flow of fluids auge ports and the charging hose ports,

These very sensitive inst~mentsare used to measure the velocity of air past a given point. Figures5-3,5-4, and 5-5 show examples of these various airflow measurin~instruments. The air velocity readings measured by these inst~mentscan be converted into cfm by using the following formula: cfm = Area x Velocity

The area must be calculated according to the ~ s t ~ m e manufac~rer’s nt inst~ctionsor by multiply^ thelength of thecoilbywidthandthen checking the e~uipment manufac~rer’s SpecificatiQns for the free area of the coil. Thenumber of readings taken over thearea is usually recommended by the inst~ment manufac~rer. These reading are then averaged. The average is found by using the following formula:

igure 5-3.V e l ~ ~ e t ( er

Figure 5-5. Flowhoo(Courtesy,AirflowTechnicalProducts,Inc.)

At present, air-to-air heat pump units are the most popular types of heat pump systems. These units can provide both heating and cooling to the structure. Air-to-air heat pump units use air as the heat source during the heating phase andair for cooling the outdoor coil during the cooling phase,

The indoor unit, which is comprised of the evaporator and blower, is the component that delivers the cool airto the space being conditioned. Therefore, certain criteria must be met before the unit can operate as it was designed. Ensure that the following components are f~lnctioningproperly: ~efrigerantflow control Indoor blower Air delivery system (cleanliness)

rant flow control is usually either a capillary tube or thermostatic ).In most cases, there are no adjLtst~entspossible to only a d j ~ s ~ e for n t these devices refrigerantcharge;however, if thecapillarytubeisplu plLlgged, it should be replaced. When a TXV is used, the sLtperheat settin must be checked to ensure the correct amount for the specific application. Sinceair conditioning is considshould be set at ered to be a high temperature application, the s~tperl~eat about 8" to 10°F. This will sufficiently feed the coil with liquid refrigerant and provide ~aximLlmoperation.

The indoor blower and the air delivery part of the system also contribute to the system operating at peak efficiency. The indoor ir delivery system isdesigned to deliver about 400 cfm pertonofcoolinThiscanbemeasured with a velometer or flowhood. Also, the air flowing through the indoor coil should have a temperatLlre drop of about 18" to 22°F db. Most units are designed to have a 20°F drop across tile indoor coil.

The filter, blower, indoor coil, andductwor~must be clean enoughto allow the proper amount of air to flow through the system, Thismeans that each of these items must be checked and cleaned before any efficiency testing begins.

There are generally two major components located in the oLltdoor unit: the

compressorandthecondenser.Each of thesecomponentsplays a major part in theoperation of thecoolingsystem.Theheattaken fromthe air h the indoor coil is elivered by the cornpressor to the conere it is dissipated to the ambient air.

In effect, thecompressoristhecornponentthatcausestherefrigerant to circulate throLrgh the system, If the compressor is not fLrnctioning properly, the remainder of the system will not function as designed. Thecompressor shoe to pump a vacuumonitslowside of about 20 inches Hg. It s110 to holdthis vacLrum foratleastfiveminutes sstrre. If the compressor does not meet this against a normal d criteria, it will need to be replaced with one that does before full efficiency canbe realized. uringnormal operation, 01 er unitsshouldhaveanoperatingsuction pressure of about 70 psis when the indoor return air temperature is 80°F db. The high efficiency type units usually have a suction pressure of about 90 psig at this return air temperature. When servicing high efficiency units, it is best to use the unit manufacturer’s data sheet for that particular make andmodelin order determi~etheoperatinessures.Theproperpressure and its corresndingambient ternperewill be listed on the man~~factLlrer’s different aresheet. data from one another, and make tounit model el within the to same make.

The condenser is where the refrigerant is cooled to the condensing point.If there is a factor resent to preventthis condensation, theunitwill not operate s~tisfactoly. The condenser must be clean and free of all debris. ~ondensersare d e s i ~ e dto operate with an air temperature rise of about 25” to 35°F. Iftheteatureriseisout of this ‘range, thecausemustbe n rneasuringthe tempera~rein thecondenser,be foundandcorrected sure not to totlch the coil or any metal with the thermorneter or take the te~peratLrrein direct sLlnlight. TemperatLrres taken in stlchareas will notbe accLlrate because of theradiantheatfromthesun.ostcondensersare designed to have an airflow of about 1000 cfm per ton of cooling capacity.

.

es themuchneededsubcooling of theliquid model units, thedesiredliquidsubcoolingis about 10°F. The ency models sometimes require a different subcooling tempe ure to check the unit rnanLrfac~rrer’s specificationsfortheunitmakeandmodelbeingservicedforthemostaccurate information. The operating refri ressure LrsLrally corresponds to ration temperatLrre of about 30°F above the ambient temperature.

a satu-

umpunitsareoneversion

of thewater-to-aircoolin t soLlrce forthe

The indoor coil isanair-ov should be a temperatL~re dro cations for the exact readings.

The outdoor coil water as the heat each tlycycles. of the

Forother. of the a c o ~ ~ r e s s disor

charge pressure of about about 105°F. Duri set to maintain a suction pressL~re of a ~ o L70 ~ tpsig, or a sL~ction temperatL~re nt specifications for the exact of 40°F. Check the e ~ u i p ~ e man~lfac~lrer’s settings,

Thecompressorontheseunits lined sta~dards.

shod

e able to meetthe ~reviouslyout-

Use the following steps and the ~ o r ~ s h eto e t et ermine the cooling capacity of the cooling unit:

1. Visually check the entire unit for cle~liness,and ensure all compothe outdoor coils, the blower are cle about 15 ~ i n u t e st lize. eters that read exactly the same. 4. TakethewetbulbanddrybulbtemperatL~res of the air fromthe indoor coil, Use the same t h e ~ o m e t e rfor both readings or two

tl~ermometersthat read exactly the same. otal heat (enthalpy) output of the indoor coil. Use ychrome~icchart. e the total heat (enthalpy) of the outlet air. ethe total heat (enthalpy) difference.Usethefollowing

le, if the wet bulb temperatLrre of the inlet air is 60°F and trlb te~per~tLlre is 55”F/whatisthedifferencein the total heat (enthalpy) formula and Table 5-2:

easure the evaporator free area in square feet, easurethevelocity of theairflowithroughtheindoorcoil. oor coil cfm. Use following formula: cfm =

etermine the unit ca acity. Use the following formula:

al~ufac~lrer’s specifications/ the cause ump is operating at its peak effiperly, there are some other opgrilles, measure the cfm from ss than that determined in Step the leak and repair it. asuretheductheatgain. To do this,measurethe as it leavesthesupply air grille locatedfarthest he difference in the supply air temperat~reat the e supply air from the cooling unit nce is morethan 5*F, theduct needs more i ~ ~ ~ L ~ l ~ t i o n .

When the cooling system meets this criteria, the only other alternative isto increase the size of the coolin unit or the cooling capacity of the heat pump thedLrctworkwill handle the airflow required for the

Introduction: Use the

follow in^

procedures and the test instrument manufacturers' instructions

Tools ~eeded:wet ulb thermometer' dry bulb thermometer, total heat content of air (Table 5-2) chart, tool kit, and velomet

to determine the ca-

or psychrometric

1. Set the thermostat to dem

erate for about 15 minutes

to allow the pressures and temperatures

to stabilize.

3. Take thefollowintemperaturereadin

air Inlet

te~perature(db)

"F

"F

temperature ir (wb) Outlet temperature air (db)

"F

Outlet air

"F

tem~erature(wb)

temperature Inlet air (db) temperature utlet air (db)

"F

"F

4. Subtracttheoutletairtemperature(db)fromtheinletairtemperature(db)ontheindoorcoilandrecord. "F

erature (db) from the outlet air temperature (db) on the outdoor coil and record

~ychrometricchartorTable5-2,determinethe

total heat content

(enthal~y)of the inlet air and

a ~sychrometricchart or Table 5-2, determine the total heat content (enthalpy) record. Btullb ofairdry

. ete ermine the tot I heat (enthalpy) di~erenceand record. Use the

follow in^ formula:

of the outlet air and

2

cfrn =

tuh = rnan~facturer rates the equi~rnent?

This Page Intentionally Left Blank

umps in the heating mode is not difficult. In the heating mode,only sensible heat ised to the air as itpassesthroughtheunit. eref fore, drybulbtemperemeasLlrementsindicatethetotalperformance of the unit. owever, these units still must be thorou~hlychecked, and any reqL~ired adjLlstmel~ts to the indoor airflow or refrigerant charge must be made in order for the unit to operate as efficiently as possible.

The proper test instr~mentsare needed to make accurate measurements of e old proc~dLlre of merely looking at the eqLlipmentor feeling a line to d e t e r m ~ the e operating characteristics no er indicates what is happening with the unit. Therearemany rands anmodels of testinstrLlmentsavailable.Which particLllarinstrLlment to use is the user’s choice,butaccuratetestinstrzrments must be use to properly fine tune heat pumps in the heating mode. The exact procedu for i n s t ~ m e nuse t can be found in the manufacturer’s o p e r ~ tinst~lctions. i~~ ese i n s t ~ m e n t must s beproperlycaredforand their accLlracy maintai for optimLlm performance.

This chapter will discuss only those procedures used for efficiency testing heat pumps in the heat in^ mode, not specific inst~lments.The following is alist of thebasictest i n s t ~ m e n t sreuiredfortestingandadjustingthe efficiency of a heat pump o erating in the heating mode:

2.

. .

ry bulb thermometer Ve~ometer/ a~~emometer, or flowhood (as desired or available) ~mmeter Voltmeter

ese very s~n.sitivein.

Do not ~easure

6 ft ~ a x i m u ~

ent manufac~rer's the width and then for the free area of area is usually recomings are then averaged.

e, valve manifold, and the f ~ ~ e r apressures nt can be re-tempera~rechart. rature for the different ports for both the commanifold that are control the flow of fluids through the gauge

the a ~ o u of n ~electrical current usedby ar, because the pera age can s ~ e n t are s the most center of the tongs.

wire. The analog-type the center of the scale. re they are in good wor mes worn or cracked, the leads shoul meter and the leadmust be mainer voltage reading.

to the unit and ents are usuallymore accurate th e t e ~ i n the e total wattage use oreexpensive. The an

~ o n d i ~ oIfnnot, . any

ese units are U

e varies with theout~oor between usuallyis 90" an

m a n u f a ~ ~'sr e r

desired for that unit.

e o t h e ~ heat a ~ pump units are one versi they provide both heath the heat sour~efor the h e a o~p e~ ~ a ~are on provided with a water-sour~ecoil.

ach valve must be set independently of the other. For thevalveshould set to maintainacompressor dis22, or a condensing temperature of about 210 psig for about 105°F. During heating operation, the heating water valve should be set to m a i n t a ~a suction pressure of about 70 psig, or a suctiontempera~re fortheexact of 40°F. Check the equipment ~anLrfacturer’s speci~cations settings.

r on these units should be able to pump a vacuum of at least

hen subjected to a normal discharge pressure. It should be vacuum for about 5 minutes. If not, tile valves are leakin and either the compressor or the valves must be replaced.It is very critical that these compressors meet this requirement because of the very severe conditions in whichthey operate. Some e ~ u i p ~ e manufacturers nt may require a different efficiency test for their compressor. Be sure to check their re~uirements,

Use the followin the ity of a heat pump system:

works~eetto determine the heating capac-

1.

Visually check the entire system for cleanliness, and ensure all components are in roper working condition. e sure the indoor and otrtdoor or filter, and indoor blower are clean.

2.

Set the thermostat to demand heat pump heatingonly. It maybe necessary to disconnect the auxiliary heat strips so that only the heat can operate. Allow the unit to operate for about ten minutes to the system pressures and te~peraturesto stabilize.

3. 4.

the refrigera~tpressures on the operating system. heck both the indoor and the outdoor dry bulb

tempera~res.

5.

Comparethetemperatureandpressurereadingstothe ~anLrfactLrrer’sspecificatio~s.

eqLripment

6.

easure the entering and leavingair dry bulb t e ~ p e r a ~ r racross es the indoor unit.

7.

etermine the indoor unitc h . Use either an airflow measLrring meter as described above, or disable the heat pump unit and set the thermoon the auxiliary heat strips. If the auxiliary heat strip d i s c o ~ e cwas t turned off, be sure that it is turned back on. Then use themethoddescribedin Chapter 2 todeterminetheairflow, After

determining the indoorcfm, turn off the auxiliary heat strips and turn on the heat pump unit. e t e ~ i n the e heating capacity ( hr output) of the unit. Use the folHeating capacity = c h 9.

X

1.08 X AT

~ e t e ~ i the n esystemcoefficient of performance (COP) bymeasuring thewattsusedbytheunit,includintheindoorfanmotor.Usethe following formula:

or:

For example, if a eat pump has a measured heatin capacity of 40,000 Bhrh and the measured watta e is 4.380 kW, what is the C ~ ~ ? .380 kW to watts:

Then use the formula outlined earlier:

W e n the heat pump unit is operatingat its peak efficiency but is not heatingthestructureproperly,therearesome other options available. First, open all of the supply air grilles, measure the cfm from each one, and-total them. If the cfm is 10% less than that deter~inedin Step 8, air is leakin from the duct system. Find the leak and repair it. Thenext step is to measuretheductheat loss. To do this,measurethe supply air temperatureas it leavesthesupply air rillelocatedfarthest from the indoor unit. The difference in the supply air temperature at the supply air grille and the temperahrre of the supply air from the indoor unit shouldnotexceed 3" to 5°F. If thedifferenceismorethan 5OF, theduct needs more insulation. When the heat p~rmpsystem meets this criteria, the only other alternative is to increase the sizeof the heat pump unitor increase the heating capacity of the auxiliary heat strips. Be aware that the electric bill will increase with an increase in heat strip capacity. ake sure the ductwork will handle the required airflow.

met~r,and tool kit.

t th

1.

sure t

oor coil. True air tem~eratu

the s u ~ ~and l y retur~

c.

th

ir t

tur

T

cfm =

ies

S of food stores, restaurants, procause of this expense, the owners and operators of interested in having the equipment e, Tec~icianswho are capable of fine in these applications will always be eir services. There are several steps tion systems. All of these steps rean and in good working condition

There are several closely related factors involved inthe adjustment process. ent is made to one of these factors, the other factors are

The proper test instruments are needed to make accurate measureme~tsof e old procedure of looking at equiprating characteristics no longer

models of test i n s t ~ ~ ~ eavailable. nts Which is the user's choice, but accurate test instmrly finetune commercial refrigerationsystems. ment use can be found in the manufac~rer 's inst~mentsmust be properly cared for and optimum performance.

'This chapter will iscuss only those procedures used for efficiency testing refrigeration systems,not specific ~struments.The basic test inst~ment§required for testing and adju

1.

Dry bulb t h e ~ o m e t e r

3. 4. 5.

Voltmeter Ammeter Velometer, anemo~eter,orflowhood (as desired or available)

is an ordinary thermometer used to measure air temperature (see Figure2-1). ~ e t e ~ i n i the n g temperature drop of air as it passes through the evaporator or the temperatLlre rise as it passes over the condenser is very important when fine ~ l n i n grefri~erationsystems. ry bulb temperat~~re is a measLlre of the heat given up to the air or in by the coil from the air. The air tempera~lresare measured in two locations: the return air stream and the discharge air s t r e a ~Fi , Two dif~erent drybulb thermometers that have been tested and found to produce exactly the same readings under the same set of CircLl~stances should be used. If two thermometers that read exactly the same temperature are not available, then use one thermometer to ~ e a s u r both e temperat is best to measure the return air tempera~lrefirst, because it will not change as fast as the discharge air temperatLlre. An electronict h e ~ o m eter with two separate, properly adjusted leads also produces the desire results.

L-

-

" -

? ) L

Leaving airflow

Leaving airflow

""C

" " )

"

"

Thermometers

ir t e m ~ e r ~ t in ~ roe refri

for the di~erent for both the comontrol the flow of fluids through the gauge

arly to ensure they are in

ents are the most

esevery

sensitive ~ t ~ e n are t us s

e area must becalculated

m e a s ~ the r ~velocityof air is read^^ can then

accord^ to the ~ s t ~ e mna nt u ~ a c ~ r e r ’ s the lengthof the coil by the width and chec r’s s~ecifica~ons for the free area of ver the area isus~ally recom~ende

Refrigeration systems are classified as either low temperature, medium temperature, or high tempera~re.Low temperature systems usually operate with a refrigerant evaporating temperature of 0°F or below. M e ~ i u m tempera~resystems operate with a refrigerant evapora 0" to 35°F. High temperat~~re systems operate with a refr tempera~reof 30" to 50°F. These systems are designed to operate with a temperature drop across the evaporator of 10°F db. Some special applications may require a different temperature drop.

The most popular refrigerant flow control device used on commercial refrigeration systems is the thermostatic expansion valve (TXV). The TXV is usually set to maintain superheat settings of 8" to 12°F on high temperat~lre "F on m e d i ~ ~temperature m systems, and 2" to 5°F on low temperature systems.

ere are generall~WO major com~onentslocated in the condensing unit: e compressor an the condenser. Each of these components important part in the opera~ionof the refrigeration system. The h from the air flowin through the evaporator coil is delivered by the compressor to the condensing coil, where itis dissipated to the coolin

ompressor is the component that causes the refrigerant to circulate through the system. If the compressor is not ~~nctioning properly, the remainder of the system will not fLlnction as desi e compressor should be able to pumpa vacuum on its low side of about inches Hg. It should be capable of holding this v a c u L ~for ~ at least 5 m ~ L ~ tagainst es a normal discha pressure with the compressor not running. If the com~ressordoes not meet this criteria, it will need to be replaced with one that does before full efficiency can be realized. The suction pressure on commercial refrigeration varies according to the application and the temperature of the air flowing over the evaporator. To determine the correct suction pressure, refer to the man~~fact~~rer's specifications for the application being tested.

heat from the sun.

ondenser, do not touch the coil or ake the t e ~ ~ e r ain ~ direct r e sunli be urate because of the rad

where:

r

X

X

where:

e t e ~ i n ethe effec

lowing f o ~ ~ l a s :

+

specifications, the cause

ensure all compo-

.Allow the unitto operate S

on container.

have stabilized.

r water t e ~ ~ e r a t ~ ~ r e s . e conde~ser.This can be it takes to fill a one fications, the cause must

1. Visually check the entiresystem for cleanliness, and

unit and allow it to ope rat^ until the sys pe of s y s t e ~is this (high, m e manifold, and record the ~ r e ~ s u r e s . ~uction

sig condenser leaving air tem~er~ture (d ntering air temper at^

rmine the te~peraturerise of the conden~erair. Use th

AT = Leaving air t AT =

0

the condenser cfm. Use the followin cfm = Area x Velocity cfm = cted by the condenser. Use the f o i ~ o ~ i ~

= cfm x CHR

=

1.08 x AT x 0.30

tu h

0

0

ment?

th

ensure all are componentsworkin in proper

1.

"F

"F m nser. Use the followin

e ~ u i ~ m ~Use n t .the follo~in

_.

10. Is this wh

nts are in proper

ork kin^

~ondition.

lete, plus an additional hour.

record. and plates

"F

.

7.

Weigh the

total ice haweste for

one hour and record.

~ e t e r ~ i nthe eunitefficiency.Usethe

foilo~ing for~ula:

nterin~water t e ~ ~ e r a t u -r e

Y* 8.

Is thiswhatthe

~anufactu

I

e. This is not to say that kits or mois~lreindicators, egohmmeters are es ecially useful in a reventive maintenance program, egohmmeters are also very use eration systems before signing a maintenance contrac

aken with a m~gohmm

istance is norma11 crossthe w ~ d i n

eadings should be ta e basic con~itionsand with virtual various reasons, the To meas~~re the resistance, turn off all e

movetheelectricalwiresfromthe me~ohmm~ter will mea sur^ all electrical measure attache left wiring ill resisthe the isen oftance the complete cir~uit round in the circuit,

lowest resistanc~to

henusing a megohmmet anufacturer’s inst~ctionsto use an ohmmeter on a motor instrument test leads are in p re-

be should tes be ent should in willrecord .This

system. of the

S

tami~ation.

that have less

of a s ~ s t e mwith vary in^ degrees of con-

of 100 megohms ssor motor terminal block. You may want to

t are ~ r e f e r r ~for d

30%

35%

xarnple of a rne~oh~rneter check i

ate

m is that it cannot

r, just learning the

.Each one has its

S

is to study water,

except similar,

a that at

water boils at

as the number of

When the water reaches its s a ~ r a t i o npoint of sure, boiling will start at a c ~ n ~ t a tern nt remains cons tan^. water absorbs app ~ k~~~t of ~~v a p o~r a t ~~o ~ . This is called the l

*P t i

I

more heat is added to the vapor, rises above the saturation tempera~~re of 212°F. sensible heat is again experid is in thesuperheatedstate. es thevapor tempera~reis pressure. If the temperature of then the amount of superheat the saturation temperatureof 212°F. Note the tremendo~~s amoL~ntof heat required to oil a fluid or cause it to e of state (latent heatof evaporation) when compared to it takes to simply change its tempera~re.For this reabe kept as full of liq d refrigerant as possible the compressor in o r to getthemaximum amount of heat transfer. ot indicate what

the temperat~reat that point is

zones:saturated,subcooled,and anttravelsaroundthesystem, it exists in one of the three zones indicated on the diagram. The refrigerant is always changing ~onditionsand never exists in any two zones at the same a ~ r a t e dsubcooled, , or super~eate~. If technicians an U these basic ~rinciples,they will never do not have eration systems operate,

to a vapor (~oiling),and in the con~enser,where the refri state from a vapor to a liquid (condens reviously noted, the temperatures and pressures shown on the erature chart are all in the s a ~ r a t e dstate.

To the right of the 100% satur

where the refrigerant is above

ture of the vapor minus the

S

The critical point on the Pcurve and the saturated vap this point, the refri rant may exist i

re at a given pressure.

this use.

ake this onv version ~essuresto absolute for

lines of c o n ~ t ~tern nt ,hori~ontallyin the tu,% per degree of lines of constant entro~yextend

ure 9-4. Enth~ipy~ i a ~ r a (r n

ure 9-5. ons st ant ternpe

to the right from the sat~~rated vapor line,re calculatio~s.Themai refrigerant is comp constant entropy,

9-6. Entropy is us em of theservicete

The lines of ~ 0 ~0~~~~ ~ extend s out ~from the ~ saturated ~ vapor ~ line into the superheated zone, Figure 9-7. These values indicate how much space (cu ft) is taken up by each poun

~ s ~ a l lthe y / ref ration c cle is shown as an i ~ ecycle. ~ l "his is ~enerally an i l l u ~ t r a ~o o ~ S not show superheat in^ in evapothe r~tor,suction line, va~or-coole~ c ~ ~ ~ r e s Also, setc. or~/ sure losses are not shown. /

nt to the service t e c ~ i c i ~ n ,

The four fmcti function§.

shows the c o d e

enser must- reto c).

tion lin

~ o ~ ~ e ~ starts s ~ t i o ~ ( ~ o ic)~ into t the sa

t h ~ as t the refr

which the pressure is re~sL~re within the e x ~ a n s i o ~

-12.The ideal cycl

re

refrig

(and device is no external transfer of heat into or therefore, the refri (line e to d). Since it the sat~ratedzone, to the latent heat of a vapor. 'The refri~erantis now ready to enter the eva~orator(point d).

alistic cycle will be disr.

tain ~uantitiesof the cycle may be S should use the variis made up from the simpler to use the

enser, Figure 9-13. If the at content) entering the ing the condenser of38 e condenser. Note that evaporator plus t added to the ref following f o ~ ~to~ l a t Ull

orator, as indicated by h2

and h1 in Figure 9-14. Since the total heat content is38 Btu/lb enterin 10’7 Btu/lb leaving, then the heat picked up in the evaporator is: tullb =

t Ull

If the refrigerating capacity is known, we can then determine the total circ ~ l a t i orate ~ in lb/min by dividing the ca tu/min by the refrigerating effect of 69 €3tu/lb.

Figure 9-13. Heat of r e j ~ ~ t i o n

Figure 9-14. Refrigeratjn~effect

e c o ~ ~ ~~~~~o ~ sis the s ~absolute o ~ discharge pressure divided by the ab-

Also, the lower the discharge pressure the lower the compression ratio. ~ h i l maintaining e operating t e ~ p e r a ~ r to e s satisfy the product requireion ratio as low as possible. The lower the compression ratiovolumetric t efficiency. The higher the volurant pumped by the cornompressor the greater the ime is required. The less r ~ i n time g

asit mayseem,keee ering the compress

suction pressure up has a greater ratio than lowering the discharge presefit of a lower compressionratio is turn result in less refrigerant-oil ~reakdownand less contamin~tsformed by high operating temperatures.

ember that the ideal cycle discussed earlier in the chapter did not have sure drops, subcoolin ,or evaporator superheat, Such a system does

""C""*

orator superheat in the refrigeration the compressor; withoutpressure is cycleideal

an excelle

to L~derstandthe

To begin, consider a sim le system with the following basic components: evaporator,compressor,andexpansiondevice.eothercomponentscan beaddedlater.Thissectionwill ill~Istratesome of the horrors that can in the field and show how your h to provide a sol~tionto these pr

Certain assumption§ have to be made to illustrate the difference between the ideal cycle and the actual cycle. Let’s Notice that it is no longer called the eva volves more than just the evaporator. The SLI evaporator tubes and suction line, andadditional§uperheatoccursinction Line. Also, assumethatthis semi-hermetic, a is vapor-coole ssor. There also additional is superheat in the c o ~ ~ r e s sbo r ure 9-16, there is quite perature between the two discharge tempera~reat t at the discharge icate that this temperatu the tempera~remeasured

ure 9-16. ~ ~ othe~ actual i n refri ~

charge service valve. ConseqL~ently,if the oi~-refrigerantmixture starts to breakdown at about 300°F, then the temperature of the discharge vapor should be limited to about 225°F. By observing the di ram, it is evident that moving the point where compression starts tow the left decreases the chances of running excessively high discharge temperatures, which result in refrigerant-oil breakdown. The following are some ideas to reduce the discharge tempera~re: 1. 2. 3. 4.

Check to see if the evaporator superheat istoohigh. Re-route the suction line if possible to a cooler location. Check to see if a liquid-suction heat exchanger is used u~ecessarily. Inject liquid into the suction line (consult the V manufacturer).

The idea behind all of these steps is to move the compression line further to the left by decreasing the superheat and the discharge gas temperature. Also, if the superheat in the evaporator is too high, lowering it to the reco m ~ e n d e damount increases the evaporator capacity, because it contains more refri~erant.This also raises the suction pressure, which results in a lower compression ratio, which in turn increases system capacity. ith liquid refrigerant

.Admittedly, there CO uid present when frost is present, but not always. It depends on the operating pressures and tempera~resof the system. Suppose we had an ice cream case operatin at a -40°F evaporator saturation temperature, an we adjusted to a frost line at the SLZC valve. This meansthe temperature at the service valve would be about 32°F. Since superheat is defined as the vapor temperature minus the evaporator saturation temperature, would result in a 72°F superheat at the suction servicevalve (32°F -42 72°F). Thisisexcessive.Generally,casemanufacturers recommend superheat in the evaporator. With the valve adjusted properly and ing a 20°F risein the suction line, the temperature at the suction se vewouldbe -13°F. Therewouldcertainlybe frost at this tempera wever, there would be no liquid refrigerant present. This type of a d j u s ~ e nalso t makes quite a difference in the operating efficiency of the system.

The high pressure line consists of the discharge line, condenser, receiver(if used), and the liquid line, Since the refrigerant is still superheated when it enters the condenser and is subcooled when it leaves the condenser, the condenser is the only co~ponentin which all three states (sL~perheat,saturation, and subcooling) exist simult~eously.There are some systems that have the liquid line subcooled below the evaporator saturation temperahrre. This would roduce all three states in the evaporator, but these systems are the exception rather than the rule.

tion gas t e m ~ ~ r a ~ r e sults in a h i g h ~ rdis-

t of lift. Add to the ac~essori~s.

lower before thee x p ~ s i o nline c that not only is s ~ s t capaci e ~ y, a eat content, or e ~ t h a ~ pbut

W

l

3:

a

R P 0

\

I

. . *

.

l-

. I

I

r'

A

-1-

I

N

+ - A

T-

W

W

N

. i

L

This Page Intentionally Left Blank

hour

r

wh

-

Step 6 ~ a l c ~ l atht ~

n.

where, d~ustmentFactor from e Annual Fuel CO

lculate the Estimated Annual lectrical Usage,

EAEU, for your specific ins

EAEU = AF x Eae where,

kW- h rs

tep 8

- Calculate th

inst specific your C, for

!l.

where,

per gallon for Heating Oil.

Electrical Cost = Cost of electrici~in your area in !$ per kW-hr.

This procedure can be repeated for other models of essentially the same size with different efficiencies to compare their Estimated Annual~ p e r ~ t i Costs. ng Models with higher efficiency (AFUE) ratings will consume less fuel and cost less to operate, but generally have a higher purchase price and may have a higher installation cost. Therefore, is a period there of time, referredto as a “Payback Period,” before the savings that result from the lower opera tin^ costs of a more efficient model makes up the difference in price of that furnace or boiler as compared to a less efficient model. EXAMP~E: Assumeyouareintenditobuyanewgasfurnaceandhave c~lculatedtheEstimatedAnnual the procedure outlined above for two m,odels of essentially the same size ~uirementsbut with different efficiency (AFUE) ratin

Price of

s t i ~ a t e dAnnual AFUE

78% Q1O h

The additional cost of more e~icientmodel (Model 6) is: $775 The e s t i ~ a t e d ~ n n uSavings al in per~tingCostsforModel

- 600 =

-

$425 365 = $60 lower operating cost per year.

-

51000 101000 l1 Iooo 1~Iooo 1 71000 251000 2 ~ 1 0 0 0421000

-

-

~ 0 , 0 0 0 761000

1 oIooo

20,000

3olooo

-

7 ~ 1 0 0 0~31000 ~41000110,000 111 1000-1 ~ 7 1 0 0 0 1 281000-144,000 1ooIooo 110,000 1~0,000

Alaska

-3500 HLH

I1

This Page Intentionally Left Blank

1. Latent heat removed =

er hour (gph) x ixed air t e m ~ e r a ~ (db) re =

turn air x Returnairtern Total airternperat~re

3. Mixed air t e m ~ ~ (wb) r a =~ ~

utdoor heat content+ eturn airx Heat content Total air

. Sensible heat

5. Sensible heat removed of db t e ~ p e r a t ~ r e

where:

at of air con~tant( 6. Totalheatremoved

=

x Change of enthal

where:

7. 0.24 Btu requiredtoraiseone

8. 1060 Btu removetocondenseonepound

of water

9. 7000 grains of watervaporperpound

10. 0.68 = Btu r e ~ ~ i to r eremove ~ onein of air:

33 lb

= one gallon of water

of water fromone cu ft

This Page Intentionally Left Blank

d in co~junction~ i t the h ter to o~eratefor a ~ ~ r o x i m

sure the volta

record. Use the follo~in

tu =

cfm of the blower and record. Use the following instructions: Use the same thermometer, or two that measure exactly th temperatures. temperature in an area where the thermometer can sen e the radiant heat from the re 2-2). True air temperature cannot be measured if the thermometer sens

Take the temperature measurements within 6 ft of the air handler. easurements taken at the return rilles that ares at too great a distance from the unit are not usu e temperature when more than on Be sure the air temperature has stabilized before taking the tempe Take the temperature measurementsowns stream from any source of m i x e ~air. Use th cfm =

cfm 7.

Btu

l .08x AT

=

Is this whatthemanufacturerratesthe

e~uipment?

YO

This Page Intentionally Left Blank

This Page Intentionally Left Blank

st instrument manufact~rers'instr~ctionsto determine the

uib thermometer, total heat content of air (Table

5-2)or psychromet~c

min~testo allow the pressures win

"F 0

) from the inlet air temperature (db) on the i n ~ o o coil r and recor~. ) from the outlet air tem~erature( ) on the o ~ t ~ ocoil o r and record.

rmine the total heat cont

of y)

etermine the total heat content (enthal~y)o

the inlet air an

AH AH 9.

= Inlet H, -Outlet H, air Btullb dry of

2:

Measure the evaporator free area

in square feet and record.

ft2

IO. Measuretheairvelocitythroughtheindoorcoilandrecord. 11.

ete ermine theindoorcoilcfmandrecord.Usethe

follo~ingformula:

cfm = Area x Velocity cfm 12.

=

ete ermine theunitcapacityandrecord.Usethefollowingformula:

Btuh

= cfm X 4.5

X

AH

Btuh = 13.

Is this ~

h the~manufacturer t ratesthe

equipm~nt?

~anifoid, volt~eter, wa~rneter,and tool kit.

1.

h the indoor unit. Use the f o l l o ~ i ~

th "in view" of the indoor coil. True air tern

c.

of the i n ~ o o r ~ n j t .

th

AT

=

tu output. Use the f o l ~ o ~ formula: in~ tu

= cfm X

1.08 X AT

w~ere:

1.08x AT

= specific heat of air constant ly air temperatur~minus return air temperature Is thiswhatthmanufacturerratestheequipment?

cy test should be performd annually on every commercialref~geration unit. Ifthis procedure tter, use less electricity, and lost longer. The technician who can perform demand. Use the fol~owing procedure long with the proper i n s t ~ ~ e n t s auge ~anifo~d, voltmeter, ammeter, velometer, and too] kit. rocedures: ir-cooled condensers: system for cl~anliness, nd ensure all components are in prop

1.

e until the system pressures and temperatures have stabili~ed.

2.

4.

"F

5.

"F rise of the condenser air. Use the following formula:

7.

AT

=

"F r cfm. Use the fo~iowin~ formula:

cfm = ected by the con~enser.Use the follow in^ formula:

WR =

tuh

rge

10.

Is this whatthemanufacturerratestheequpiment?

Use the following procedure for water-cooled condensers: 1.

Visually check the entire system for cleanliness, and ensure all components are

2.

Start the unit and allow it to operate until the system pressures and temperatures have stabilized.

3.

What type of system

4.

Install the gauge manifold, read the pressures, and record. Suction

5.

Measure leaving the condenser water temperature and record.

6.

Measure entering the condenser water temperature and record.

?.

Measure the water flow through the condenser and record. gpm

8.

Calculate the heat rejected by the condenser. Use the following formula:

psig,

in proper working condition.

is this (high, medium, or low temperature)?

"F "F

CHR = gpm x 500 x AT CMR 9.

=

h

Btu

Determine the effective refrigerating capacity of the equipment. Use the

follow in^

formula:

ER="----CHR

15,000

ER = 10.

Btuh

Is this what the manufacturer rates the equpiment?

Use the following procedure for ice makers: 1.

Visuallychecktheentiresystemforcleanliness,andensureallcomponentsare

2.

Starttheunitandallowittooperateuntilthefirstharvestcycleiscomplete,plusanadditionalhour.

3.

Removethefirstharvestofice.

in properworkingcondition.

5.

Measure the

tem~erature the harvested of ice and record.

6.

Weigh the total ice harvested for one hour and record.

7.

Reterminetheunit

"F Ib

e~iciency.Usethe follow~n~ formula:

= [(Entering water tem ...32OF)I + 144 + l(32OF - Ice tem

HR fficiency = 8.

YQ

Is this what themanufacturerrotesthe

e~ui~ment?