(3) central a c plants
TRANSCRIPT
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CentralAirConditioningPlants
Inourdepartment,theseplants(Aircooledorwatercooled)arecommonlyavailableabove10TR
upto100TR.ThesetypesofplantsaremoresuitableforlargeinstallationssuchasAIRRadioStudio/TV
StudioBuildingsandHighPowerTransmitterBuildings. Inwatercooledplants,externalcoolingtowers/
waterspraypondswithwatersofteningplantsare thecommon features.Theseare invariablyprovided
withAHU
(Air
Handling
Unit)
and
supply
&
return
ducts
for
carrying
air.
Thecentralairconditioningplantsorthesystemsareusedwhenlargebuildings,hotels,theaters,airports,
shoppingmallsetcaretobeairconditionedcompletely.Thewindowandsplitairconditionersareusedfor
singleroomsorsmallofficespaces.Ifthewholebuildingistobecooleditisnoteconomicallyviabletoput
windowor splitair conditioner ineachandevery room.Further, these smallunits cannot satisfactorily
coolthelargehalls,auditoriums,receptionsareasetc.
In the central air conditioning systems there is a plant room where large compressor, condenser,
thermostaticexpansionvalveandtheevaporatorarekept inthe largeplantroom.Theyperformallthe
functions
as
usual
similar
to
a
typical
refrigeration
system.
However,
all
these
parts
are
larger
in
size
and
havehighercapacities.Thecompressorisofopenreciprocatingtypewithmultiplecylindersandiscooled
by thewaterjust like theautomobileengine.Thecompressorand thecondenserareof shelland tube
type.Whileinthesmallairconditioningsystemcapillaryisusedastheexpansionvalve,inthecentralair
conditioningsystemsthermostaticexpansionvalveisused.
Thechilledispassedviatheductstoalltherooms,hallsandotherspacesthataretobeairconditioned.
Thusinalltheroomsthereisonlytheductpassingthechilledairandtherearenoindividualcoolingcoils,
andotherpartsoftherefrigerationsystemintherooms.Whatiswegetineachroomisthecompletely
silent andhighlyeffective air conditions system in the room. Further, the amountof chilledair that is
neededintheroomcanbecontrolledbytheopeningsdependingonthetotalheatloadinsidetheroom.
Thecentralairconditioningsystemsarehighlysophisticatedapplicationsoftheairconditioningsystems
andmanyatimestheytendtobecomplicated.Itisduetothisreasonthatthereareveryfewcompanies
intheworldthatspecializeinthesesystems.Inthemoderneraofcomputerizationanumberofadditional
electronicutilitieshavebeenaddedtothecentralconditioningsystems.
Therearetwotypesofcentralairconditioningplantsorsystems:
1)DirectexpansionorDXcentralairconditioningplant:
In
this
system
the
huge
compressor,
and
the
condenser
are
housed
in
the
plant
room,
while
the
expansion
valveandtheevaporatororthecoolingcoilandtheairhandlingunitarehousedinseparateroom.The
coolingcoilisfixedintheairhandlingunit,whichalsohaslargeblowerhousedinit.Theblowersucksthe
hotreturnairfromtheroomviaductsandblowsitoverthecoolingcoil.Thecooledairisthensupplied
throughvariousductsandintothespaceswhicharetobecooled.Thistypeofsystemisusefulforsmall
buildings.
2)Chilledwatercentralairconditioningplant:
http://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50160.aspxhttp://www.brighthub.com/engineering/mechanical/articles/50158.aspx -
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Thistypeofsystemismoreusefulforlargebuildingscomprisingofanumberoffloors.Ithasthe
plantroomwherealltheimportantunitslikethecompressor,condenser,throttlingvalveandthe
evaporatorarehoused.Theevaporatorisashellandtube.OnthetubesidetheFreonfluidpassesat
extremelylowtemperature,whileontheshellsidethebrinesolutionispassed.Afterpassingthroughthe
evaporator,thebrinesolutiongetschilledandispumpedtothevariousairhandlingunitsinstalledat
differentfloorsofthebuilding.Theairhandlingunitscomprisethecoolingcoilthroughwhichthechilled
brineflows,andtheblower.
Theblowersuckshotreturnairfromtheroomviaductsandblowsitoverthecoolingcoil.Thecool
airisthensuppliedtothespacetobecooledthroughtheducts.Thebrinesolutionwhichhasabsorbed
theroomheatcomesbacktotheevaporator,getschilledandisagainpumpedbacktotheairhandling
unit.Tooperateandmaintaincentralairconditioningsystemsweneedtohavegoodoperators,
techniciansandengineers.Properpreventativeandbreakdownmaintenanceoftheseplantsisvital.
Figure5,showingcontrolpanel,compressor,condenserandaccessories
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Figure6,ShowingviewofAirConditioningPlantRoom
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Figure7,ShowingoveralllayoutofAirConditioningSysteminamultistorybuilding
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Aircycle
Figure8,ShowingoveralllayoutofAirConditioningDuctSysteminamultistorybuilding
Indoorairmaybetoocold,toohot,toodry,toowet,toodraftyortoostill.Theseconditionsare
changedbyrotatingtheairandthesetreatmentsareprovidedintheairconditioningaircycle.
Airdistribution systemdirects the treated air from the air conditioning equipment to the space tobe
conditionedandthenbacktotheequipment.Themaincomponentsintheaircycleare
(i)Fan (ii)Supplyduct
(iii)SupplyOutlets (iv)Returnoutlets
(v)Returnduct (vi)Filter
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(vii)Coolingcoil(orheatingcoilforlowtemperatureareas).
Thetotalresistanceofthesecomponentstotheflowoftheairplusthefrictionresistancecaused
bytheairpassingthroughtheductrunaremajorfactorsindeterminingthesizeofthefanandfanmotor
andtheamountofairpressurethatisrequired.
ForaBroadcastStudiosetupthisresistanceisoftheorderof25mmto50mmofwatergauge.
Centrifugalfanismostcommonlyusedincommercialandresidentialinstallations.Itconsistsofascroll,a
shaftandawheel.Thescrollisactuallyahousingfortheshaftandwheelandtheshaftservesasanaxle
forthewheel.Thewheel iscylindrical inshapeandhasmanyblades.Centrifugalfansareavailablewith
forwardorbackwardcurvedblades.Aforwardcurvedfancandeliverarequiredquantityofairatlowfan
speed.Theairvelocityandspeedofthefanwheel(tipspeed)notonlyplayalargepartindeterminingthe
efficiencyofthefanbutalsoaffectthelevelofnoisegeneratedbythefan.Hightipspeedandhighvelocity
usuallyresultinmorenoise.
Remotelocationofthefanreducesthenoisebutthesystembecomemoreexpensive.Ductsmay
becircular,rectangularorsquareinshape.Fromtheappearanceandpracticalpointofview,rectangular
ductsare
generally
adopted.
Ducts
are
fabricated
from
awide
variety
of
materials.
Ducts
made
of
sheet
metalareverycommon.Theductsare linedwithglasswoolormineralwoolslabsof25mm thickness
wrappedincoppernaphthanatetreatedcloth.
Outletsareanothermajorpartoftheairdistributionsystem.Theyareimportantfromthepointof
viewofappearance,functionsandperformance.Theprimaryfunctionoftheoutletsistoprovideproperly
controlleddistributionofairtotheroomandremovingtheairfromtheroom.
Ceilingdiffusers,grillesandregistersareusedassupplyoutletandgrillesareusedasreturnoutlets.
Operation
Beforestartingtheplant,ensurethatproperfunctioningofsafetycontrolsincludinginterlockcircuithave
beencheckedandcorrectlyset,andthatallmotorsaremeggertested,directionofrotationverified,all
bearingslubricatedandrefrigerationsystemfullycharged.Thecrankcaseheatermustbeenergisedwell
inadvance.
Proceedstepbystepforoperatingthesystemasfollows:
Starttheairhandlingunit,ensuringthatdampersinthesupplyductarefullyopen.
Openallwatervalvesandstartthewaterpump.Observepressuresatcondenserinletandoutlet.
Open hotgas valve on the condenser and the discharge service valve on the compressor.Open
discharge
gauge
valve
to
read
the
pressure.
Followthesameprocedureandreadthesuctionpressure.
Openliquidlinevalve.Observestandingpressureonthegauges.Thisshouldbeapproximately7.03
kg/cm2
(100psi)forR12and10.5kg/cm2
(150psi)forR22toindicatethatthesystemistightwith
noleakage.
Open suction service valve and start the compressor.Observe the refrigerant and oil pressures.
Checkthecurrentdrawnbythecompressormotor,observetheoil level inthecompressorsight
glass.Oilshouldbeclearwithoutfoamafteroperationhasstabilised.
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CompressorPumpDown
It isessential tocollect the refrigerant in thecondenserwith isolation toprevent its lossbefore
opening the compressoror anyotherpartof the system.This is calledpumpdown and theoperation
involvesthefollowingprocedure:
Shortthe lowpressureswitchwithatemporaryjumperwiresothatthecompressordoesnotstop
beforethe
refrigerant
from
it
is
emptied.
Slowlyclosethesuctionvalvewiththecompressorrunning.
Whenthesuctionpressuredropstoabout0.15kg/cm2
(2psi),stopthecompressor.
Neverpumpthecompressorbelow0.15kg/cm2
topreventinfiltrationofmoistureanddirtintothe
crankcase.
Afterafewminutes,thedissolvedrefrigerantwillleavethecrankcaseraisingthesuctionpressure.
Thisadditionalrefrigerantcanbepumpedtothecondenserbyoperatingthecompressoragainfor
ashortwhile.
Repeattheaboveproceduretillthesuctionpressuredoesnotriseabove0.15kg/cm2
afterclosing
theservice
valves.
RemovingRefrigerantfromtheSystem
Itmaybenecessarytoremovetherefrigerantfromthesystemintoacylinderifthereisanexcesscharge
orthereisaleakinthecondenser.Takethefollowingstepsforthisoperation:
(a) Connect a suitable line between the angle valve provided for charging and an empty refrigerant
cylinder.
(b)Purgetheairfromtheconnectionline.
(c)Keep
the
cylinder
cold
by
immersing
it
in
ice
cold
water
to
ensure
afaster
refrigerant
flow
from
the
system.
(d) Start the compressor and open the liquid line charging valve, allowing the liquid into the empty
cylinder. If excess refrigerant is to be removed, hold the charging valve open only until the
dischargepressurereachesthenormalreading.Afterthisoperation,removethecharginglineand
closethechargingvalve.
Donotoverchargethecylinderasexcessivepressureisdangerous.
PurgingNonCondensibleGases
Presenceofnoncondensiblesgasessuchasaircauseshighdischargepressure,resulting inreductionof
capacityandhighpowerconsumption.Incasesuchsymptomsarepresent,thefollowingcheckshouldbe
done:
Shutdownthesystemovernight,longenoughforthetemperatureofallcomponentstoleveloff.
Readthestandingpressureandcompareitwiththerefrigerantsaturationpressurecorrespondingto
the temperatureofthesystem. Ifthestandingpressureexceedsthesaturationpressureby0.75
kg/cm2
(10psi)ormore,thenoncondensiblesareexcessiveandmustberemoved.
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Forexample, ifR22 isusedandthesystemtemperature is85o
F(29.4o
C)andstandingpressure is12.8
kg/cm2
(175psi),thenthereisexcessofnoncondensibles.SaturationpressureforR22correspondingtoa
temperature85o
Fis11kg/cm2
.Thedifferenceis1.05kg/cm2
morethan0.75kg/cm2
,indicatingcorrective
purging.Forpurging,takethefollowingsteps:
Pumpdownthesystemasdescribedearlier.
Immediately
after
stopping
the
compressor,
close
the
compressor
discharge
valve.
Runthewaterthroughthecondensorforcondensationofrefrigerantvapour.
Crackopenthepurgevalveonthetopofthecondensorforaninstant,shutitagain.
Allow the system to stabilize for a fewminutes before reopening and closing the purge valve.
Repeatedpurgingandclosingoperationshouldclearthesystemofnoncondensible.
Restorenormalsystemoperation,checkthe improvement indischargepressure.Checkrefrigerant
chargeandcompressoroilpressure.
RefrigerantCharging
Acorrect
operating
charge
of
refrigerant
in
the
system
is
essential.
Loss
due
to
leakage
in
the
systemhas tobemadeup. Itmaybenecessary to replace theentirecharge.Anovercharge results in
undulyhigh temperatures,pressuresandoperatingcostsandmaydamage thesystemcomponents.An
undercharged system leads to insufficient cooling, high operating cost, and, in hermetic system, the
compressormotormayfail.
Refrigerantmaybeaddedtothesystemeitherasavapourorliquiddependinguponthelocation
of charging point and quantity required. Generally, for adding makeup refrigerant, vapour charging
method ismoreconvenient.Fortotalsystemcharge, liquidchargingatthehighsidefollowedbyvapour
chargingatcompressorlowsidewillbequicker.
Under no circumstances should liquid refrigerant be allowed to enter the compressor to avoid
damagetothecompressor.Theprocedureforvapourchargemethodisdescribedbelow:
Openthesuctionanddischargeshutoffvalvesofthecompressor. Installagauge inthedischarge
gaugeportandopenthegaugelineifagaugeporthasnotbeenprovided.
Connecta refrigerant cylinderand theconnectionwitha compoundgauge, to the chargingvalve
providedoncompressorsuctionline.Purgetheairfromthelinesandtightentheconnections.
Admit the refrigerant by slowly opening the refrigerant cylinder. The cylinder should be kept in
uprightpositiontopreventtherefrigerantfromenteringthecompressorinliquidstate.
Start
the
compressor.
Asthecylindergetsemptied, itspressurewilldropto thesame levelasthesuctionpressure.The
remaining refrigerant canbedrawn from the cylinderby closing the suction shutoff valve and
pullingavacuumonthecylinderwiththecompressorrunning.
Checkthequantityofrefrigerantchargebynotingthedifference intheweightofthecylinderand
observingthepressure.
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WaterTreatment
Algae/slime scale and corrosionon thewater sideof theheat transfer equipment retardsheat
transfer causing general loss of efficiency and breakdowns. Oxygen, Carbon Dioxide, Sulphur Dioxide
absorbed from theairanddissolved inwatercausecorrosion,reducing thecapacityof lines, increasing
frictionallossesandpumpingcost.Hardwatercausesscalingproblem.Whenheated,themineralsareleft
behind,whichformadepositontheheatexchangersurface.Theheattransferratingofthescaleisvery
much lower thanmetal.Retardedheat transfer results in increased dischargepressure causing loss in
capacityandincreasedpowerconsumption.
Scalingofthecondensortubesinarecirculatedwatersystemisunavoidable.Descalinghastobe
carriedoutasapreventivemaintenanceonceevery12monthsorearlierdependingonthehardnessof
thewater.Descalingcanbecarriedoutquiteconvenientlybycirculatingmildinhibitedacidsolutionwith
thehelpofasmallpumpconnectedacrossthecondensorinletandthewatervalvesareclosedtoconfine
thecirculationtothecondenseronly.
Chemical compounds are available which suspend minerals of dissolved scale. Algae attach
themselvesto
the
surfaces,
and
since
they
are
living
plants,
they
grow
until
they
clog
the
passages
of
the
system. Bacteria forms slime and close the system in much the same way as algae. Algae/Slime is
controlledbyuseoftoxic.Aspecialistshouldbeconsultedtodeterminethealgae/slime.
Thetroubleshouldbediagnosedasaccuratelyaspossiblebeforeanyrepairisattempted.Definite
symptomswillaccompanyafaultyoperationinthesystem.Thefollowingtroubleshootingchartwillhelp
infaultlocationandpromptcorrection:
********
TONNAGE MEASUREMENT OF AC PLANTS
(I) By air-flow method
Tonnage of refrigeration (TR) = A x V x (H1 - H2) {FPS units}S 200
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Where
A = Cross sectional area of duct through which air is passing in sq. ft.V = Air velocity per minute, in Ft. per minute, measured by anemometer in
ft./minS = Specific volume of (return) airH1 = Enthalpy for return air, in Btu/lb
H2 = Enthalpy for supply air, in Btu/lb
Note:Both H1 andH2 are determined from the psychometric chart with help of Dry bulbtemperature (Tdb in deg F.) and Wet bulb temperature (Twb in deg F.) SimilarlySpecific volume (S) is determined from the psychometric chart
Example 1:
Calculate Tonnage of AC Plant having the following measurement figures:A = 30.25 sq. ft.
V = 293 Ft. per minuteS = Specific volume of return air = 13.7 cubic Ft./ Lb.
For Return duct,Tdb = 73
0F and Twb = 670 F. ------------- (X)
For Supply duct,Tdb = 53
0F and Twb = 490 F. ------------- (Y)
Calculations:
H1 = Enthalpy for return air, in Btu/ Lb, determined from psychometric chart in r/o(X)
= 31.8 Btu/Lb.H2 = Enthalpy for supply air, in Btu/ Lb, determined from psychometric chart in r/o(Y)
= 19.8 Btu/Lb.S = Specific volume of return air = 13.7 cubic Ft./ Lb.
Therefore Tonnage = Tonnage of refrigeration = A x V x (H1 -H2)TRS 200
= Tonnage of refrigeration = 30.25x293 x (31.8 19.8) TR13.7 200
= 38.8 TR (Answer)
(II) By Water-flow method
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Points to be remembered:
1Watt = 0.86 k Cal / Hr** (unit of power i.e. rate of energy)
1 Watt = 3.412 Btu / Hr* or [1 Btu = 1 3.412 Watts]
1 k Watt = 3412 Btu / Hr or [1 Btu = 1 3412 k Watts] #
1 Btu = 0.252 k Cal
1 Ton = 12000 Btu / Hr
= 200 Btu / Min
= 50 k Cal / Min [200 Btu x 0.252 k Cal]
= 3024 k Cal / Hr [200 Btu x 0.252 k Cal x 60 Min]
= 3.561 kW # [12000 3412 = 3.561]
Heat gained by water = { Q x Sp. Heat x (Th Tc) x 60} Btu/Hr ---- (A)= heat rejected by the refrigerant in the condenser
Heat developed due to work done by compressor ={ 3 V x I x Cos }Watts= { 3 V x I x Cos x 3.412}*Btu/Hr ----- (B)Or= { 3 V x I x Cos x 0.86} ** k Cal /Hr
Refrigeration capacity in TR =[Heat gained by water in Btu/Hr] [Heat developed due to work done by compressor in Btu/Hr]
12000= (A) - (B)
12000
= { Q x Sp. Heat x (Th Tc) x 60} { 3 V x I x Cos x 3.412}12000
Where Q = Quantity of water flowing through the water cooled condenser in Ltr/ Min
Th = Temperature after condenser in0
FTc = Temperature before condenser in 0 F
Sample measurements
Q = Quantity of water flowing through the water cooled condenser = 620 Ltr/ MinTh = Temperature at condenser outlet = 990 F
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Tc = Temperature at condenser inlet = 92 FV = compressor Voltage = 390 VoltsI = compressor Current = 60 AmpCos = Power Factor = 0.85
Calculations:(A) = Heat rejected by the refrigerant in the condenser
= Q x Sp. Heat x (Th Tc) x 60 Btu/Hr= 620 x 2.204 x (99 92) x 60 = 57,3922 Btu/Hr
(B) = Heat developed due to work done by compressor
= { 3 V x I x Cos x 3.412} Btu / Hr= { 3 x 390 x 60 x .85 x 3.412} Btu / Hr = 11, 7476 Btu / Hr
Refrigeration capacity in TR = (A) - (B) = (57,3922) - (11,7476) = 38 TR, ANSWER 12000 12000
***********
HVAC AirConditioningTroubleshootingandRepair
ThefollowingisangeneralA/Csystemtroubleshootingguide.Realizethatitisgenericandmanyofthe
thingslisted
here
may
not
apply
to
the
944.
Symptom/PossibleCause Solutions
LowCompressorDischargePressure
1.Leakinsystem
2.Defectiveexpansionvalve
3.Suctionvalveclosed
4.Freonshortage
5.Pluggedreceiverdrier
Repair
1.Repairleakinsystem
2.Replacevalve
3.Openvalve
4.Addfreon
5.Replacedrier
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6.Compressorsuctionvalveleaking
7.Badreedvalvesincompressor
6.Replacevalve
7.Replacereedvalves
HighCompressorDischargePressure
1.Airinsystem
2.Cloggedcondenser
3.Dischargevalveclosed
4.Overcharged
system
5.Insufficientcondenserair
6.Loosefanbelt
7.Condensernotcenteredonfanortoofarfrom
radiator
Repair
1.Rechargesystem
2.Cleancondenser
3.Open
valve
4.Removesomerefrigerant
5.Installlargefan
6.Tightenfanbelt
7.Centerandcheckdistance
LowSuctionPressure
1.Refrigerantshortage
2.Worncompressorpiston
3.Compressorheadgasketleaking
4.Kinkedorflattenedhose
5.Compressorsuctionvalveleaking6.Moistureinsystem
7.Trashinexpansionvalveorscreen
Repair
1.Addrefrigerant
2.Replacecompressor
3.Replaceheadgasket
4.Replacehose
5.Changevalveplate6.Replacedrier
7.Replacedrier
HighSuctionPressure
1.Looseexpansionvalve
2.Overchargedsystem
3.Expansionvalvestuckopen
4.Compressorreedvalves
5.Leakingheadgasketoncompressor
Repair
1.Tightenvalve
2.Removesomerefrigerant
3.Replaceexpansionvalve
4.Replacereedvalves
5.Replaceheadgasket
CompressorNot
Working
1.Brokenbelt
2.Brokenclutchwireorno12vpower
3.Brokencompressorpiston
4.Badthermostat
5.Badclutchcoil
6.LowRefrigerant lowpressureswitchhascut
offclutchpower
Repair
1.Replacebelt
2.Repairwireorcheckforpower
3.Replacecompressor
4.Replacethermostat
5.Replaceclutchcoil
6.Addrefrigerant
EvaporatorNotCooling
1.Frozencoil,switchsettoohigh
2.Drive
belt
slipping
3.Hotairleaksintocar
4.Pluggedreceiverdrier
5.Capillarytubebroken
6.Shortageofrefrigerant
7.Highheadpressure
8.Lowsuctionpressure
9.Highsuctionpressure
Repair
1.Turnthermostatswitchback
2.Tighten
belt
3.Checkforholesoropenvents
4.Replacedrier
5.Replaceexpansionvalve
6.Addrefrigerant
7.Seeproblem#2
8.Seeproblem#3
9.Seeproblem#4
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10.Defectiveexpansionvalve
11.Frozenexpansionvalve
10.Replaceexpansionvalve
11.Evacuateandreplacedrier
FrozenEvaporatorCoil
1.Faultythermostat
2.Thermostatnotsetproperly
3.Insufficient
evaporator
air
Repair
1.Replacethermostat
2.Settodrivingcondition
3.Checkforexcessiveducthoselength,
kinkor
bend.
ACSystemGaugeReadings
ThefollowingtableisageneralguidelineforA/Csystempressuresandtemperaturesbasedonambient
outsidetemperature.Rememberthattheseareaguidelineandyouractualtemperaturesandpressures
willvarydependingonhumidityintheairandtheconditionofyoursystem.
A/CSystemPressureReadings
AmbientTemperature
Low
Side
Pressure
High
Side
Pressure
Center
Vent
Temperature
60F 2838psi 130190psi 4446F
70F 3040psi 190220psi 4448F
80F 3040psi 190220psi 4348F
90F 3540psi 190225psi 4450F
100F 4050psi 200250psi 5260F
110F 5060psi 250300psi 6874F
120F 5565psi 320350psi 7075F
*********