EnclosureThermalManagementProductTypesandSelectionOverview

ReasonstoControlEnclosureClimate

Industrial facilities have lots of enclosures housingautomation and electrical/electronic components, many ofwhich need cooling and/or heating.

When fluctuating temperatures exist, heating and coolingare required to maintain optimal operating temperaturesthat keep components from overheating or condensationfrom forming.

HeatTransfer

Controlling an enclosure’s climate is done by transferring heat into orout of the enclosure. There are three basic heat transfer mechanisms:

1. Convection: The movement of heat through a moving fluid (a gasor a liquid) or from a moving fluid to the surface of a solid.

2. Conduction: The flow of heat through solid material or betweentwo solids.

3. Radiation: The transfer of thermal energy via conversion to andfrom electro-magnetic energy (light).

Convection is the primary mechanism used to control the climate insidean enclosure because the air inside the enclosure is the most effectivemeans to transmit heat between the enclosure components and theheating and/or cooling devices.

ConvectionOne of the factors that affects the rate of heat transfer inside an enclosure is themovement of the air inside the enclosure. The faster the airmoves inside the enclosure,the faster the heat transfer occurs. This results in twobasic types of convection:

• Natural Convection: Air expands (becomes less dense) as it warms and contracts(more dense) when it cools. So whenever the air meets a heat source inside anenclosure, that air expands and rises. The space that air occupied is then replaced bycooler air, which is heated, expands, rises and gets replaced. This continuous cyclecauses air to circulate inside the enclosure.

• Forced Convection:Airmovement created by an artificialmeans, typically a fan.

Within the context of enclosure climate control, forced convection is utilized whenhigher heat transfer rates (more heating or cooling) is needed. But don’t discount thepowerofnaturalconvection– naturalconvectioncancreateahurricane;there’snofanbigenoughforthat!

ReasonsforEnclosureHeating• Enclosure heating is NOT for keeping internal components warm.Electric and electronic components typically perform better at coldertemperatures.

• As temperature drops, the capacity for air to hold water vapor isreduced, so the relative humidity of the air increases (even if theamount of water vapor remains constant).

• Moisture and corrosion become a problem when relative air humidity isabove 65%. So the goal of enclosure heating is to keep the relativehumidity inside the enclosure below 65%.

• Temperature must be consistent to guarantee optimal operatingconditions and prevent condensation.

EnclosureHeatingConsiderations

• In some applications, an enclosure may need to be cooled during dayand heated at night.

• Heater placement is important. Ideally, optimal performance is achievedby placing heater near the enclosure bottom to allow natural convectionto distribute the heat. Review specific heater recommendations.

• Larger enclosures often require fan heaters to distribute the heatthroughout the enclosure. Generally, heaters over 150 Watts will includean axial fan to move the heat throughout the enclosure.

SelectinganEnclosureHeater

This answer is provided using the calculations foundon the next few slides.

What size heater do I need?

These calculations will find PH(Heating Power) required in Wattsto efficiently heat your enclosure.

SelectinganEnclosureHeater1. DeterminetheEnclosureSurfaceArea(A)exposedtoopenair• Height (feet or meters) • Width (feet or meters) • Depth (feet or meters)(Choose one mounting option representation from the graphics shown on this slide or the next threeslides, then use the formula below the picture to calculate Surface Area A):

1. Free-Standing

A= _____ft2 orm2

Area(A)=1.8(HxW)+1.8(HxD)+1.8(WxD)

Area(A)=1.8(HxW)+1.4(HxD)+1.8(WxD)

Area(A)=1.8(HxW)+(HxD)+1.8(WxD)

SelectinganEnclosureHeater(continued)(Choose one mounting option representation from the graphics shown on this slide, previous slide, or thenext two slides, then use the formula below the picture to calculate Surface Area A):

2. Wall-Mounted

A= _____ft2 orm2

Area(A)=1.4(HxW)+1.8(HxD)+1.8(WxD)

Area(A)=1.4(HxW)+1.4(HxD)+1.8(WxD)

Area(A)=1.4(HxW)+(HxD)+1.8(WxD)

SelectinganEnclosureHeater(continued)(Choose one mounting option representation from the graphics shown on this slide, previous two slides, orthe next slide, then use the formula below the picture to calculate Surface Area A):

3. Ground

A= _____ft2 orm2

Area(A)=1.8(HxW)+1.8(HxD)+1.4(WxD)

Area(A)=1.8(HxW)+1.4(HxD)+1.4(WxD)

Area(A)=1.8(HxW)+(HxD)+1.4(WxD)

SelectinganEnclosureHeater(continued)(Choose one mounting option representation from the graphics shown on this slide or previous threeslides, then use the formula below the picture to calculate Surface Area A):

4. Ground and Wall

A= _____ft2 orm2

Area(A)=1.4(HxW)+1.8(HxD)+1.4(WxD)

Area(A)=1.4(HxW)+1.4(HxD)+1.4(WxD)

Area(A)=1.4(HxW)+(HxD)+1.4(WxD)

2. ChooseaHeatTransmissionCoefficients(k)value(imperialormetric)fromthetablebelowbasedontheenclosureconstructionmaterial:

SelectinganEnclosureHeater(continued)

EnclosureMaterial Coefficient(W/(ft2•K) CoefficientW/(m2•K)PaintedSteel 0.511 5.5StainlessSteel 0.344 3.7Aluminum 1.115 12

PlasticorInsulatedStainlessSteel 0.325 3.5

Coefficient(k)Valueselected=(Imperial)____W/(ft2•K)or(metric)_____W/(m2•K)

4. DetermineComponentHeatingPower(PV),ifany(heatgeneratedbyinternalcomponents,i.e.transformer)

PV =_____Watts(totalofalldevices)

SelectinganEnclosureHeater(continued)

3. DeterminetheTemperatureDifferential(ΔT)a. Decide the desired enclosure interior temperature = ___°F or ___°Cb. Ascertain the lowest ambient (outside) temperature = ___°F or ___°C

Subtractbfroma=TemperatureDifferential(ΔT)(°For°C)(ΔT)mustbeindegreesKelvin(°K).IfFahrenheitwasusedforthiscalculation,thendivideΔT(°F)by1.8.IfCelsiuswasused,noconversionisneeded.

ΔT(°K)=_____ΔT(°C)orΔT(°K) =_____ΔT(°F)/1.8

5. CalculatetherequiredHeatingPower(PH)foryourenclosurebasedonthepreviousvalues• If enclosure is located inside:

PH =(AxkxΔT)– PV (Watts)• If enclosure is located outside:

PH =2x(AxkxΔT)– PV (Watts)

SelectinganEnclosureHeater(continued)

Where:PH =HeatingPower(fromthisStep#5)A =EnclosureSurfaceArea(fromStep#1)k =HeatTransmissionCoefficient(fromStep#2)ΔT=TemperatureDifferential(fromStep#3)PV =HeatingPowerinWatts(fromStep#4)

SelectinganEnclosureHeater(continued)Otherthingstoconsider• Fan or No Fan: In most cases, this is determined by the heater capacity. However, there are

somesizeswhere auserhas to choosebetweenaheaterwith a fanandonewithout.• Operating Voltage: Heaters are available in a variety of operating voltages. Choose one

compatiblewith available power inside theenclosure.• Control:Heaters should always be controlled with a thermostat or a hygrostat to turn themOFF

when the enclosure internal temperature and/or relative humidity is sufficient to preventcondensation. Controls may be adjustable or preset to fixed ON/OFF setpoints. Control devicesmaybe integrated into theheater, ormaybean independentdevice.

• Element type: Cartridge heaters are a common type of heating element in industrialapplications; they typically include a nickel-chromium (Nichrome) resistor at their core. PositiveTemperature Coefficient (PTC) heaters use a ceramic or polymer resistor whose electricalresistance increases with temperature. This makes them self-limiting in the temperature thatthey canachieve.

SelectinganEnclosureHeater(continued)Otherthingstoconsider(continued)

• Touch Safe Heater: Heaters, by definition, get hot. Touch-safe heatershave a shroud covering the heating element to protect againstinadvertent contact by persons working inside the enclosure.

• Protection Rating: Since heaters are inside the enclosure, in most casesprotection rating is not a concern. However, in hazardous locations anexplosion-proof heater may be required.

• Heater Mounting: Most heaters can be DIN rail mounted or panelmounted. Some are foot mounted, allowing them to be mounteddirectly to the floor of the enclosure.

• Space Available: Heaters are available in various shapes and sizes toallow for appropriate fit in the enclosure.

WaystoHeatEnclosures

Stego heaters offered by AutomationDirect:

• PTCheaters,5W– 13W, forheatingsmall enclosures,panel mount.

• Touch-SafePTCheaters,10W– 150W,35mmDINrailmount, optionalintegralfixed-rangethermostat.

• Explosion-proof(IP6X)heaters,50W&100W,high-performancecartridge,35mmDINrailmount.

WaystoHeatEnclosures

Stego heatersofferedbyAutomationDirect:

• Touch-safePTCheaters,150W– 400W,axialfan,35mm DIN or panelmount.

• Touch-safePTCheaters,250W– 400W,axialfan,integral fixed-rangethermostat,35mmDINrailorpanelmount.

• High-performancecartridgeheater,500W– 700W, axial fan,35mmDINrailorpanelmount,compact designideal forlimitedspaces.

WaystoHeatEnclosures

Stego heatersofferedbyAutomationDirect:

• PTCheaters,550– 650W,axialfan,integraladjustablethermostat,35mmDINrailmount.

• High-performancecartridgeheaters,950W,axialfan,optionalfixedhygrostatoradjustablethermostat,35mmDINrail,panelorfootmount.

WaystoHeatEnclosures

Stego heatersofferedbyAutomationDirect:

• PTCheater,1000W,axialfan,35mmDINrailorpanelmount,optionalfixed-rangethermostat,compactdesignidealfortightspaces.

• PTCheater,1200W,axialfan,optionaladjustablethermostat,35mmDINrail,panelorfootmount.

ReasonstoControlEnclosureClimate

Reasons for Enclosure Cooling

• Heat may be added to enclosure from both internalcomponents (drives, power supplies, etc.) or externalsources (furnaces, foundry equipment, ovens, etc.).

• Heat decreases life expectancy of components such asPLCs, HMIs, AC drives, etc.

• Heat may cause electrical/electronic component faults(i.e., overload tripping, change in performance ofcircuit breakers and fuses, power failures, and more).

WaystoKeepEnclosuresCoolSelecting a cooling method depends on several factors:• How much heat must be removed? The cooling capacity of themethod selected needs to be greater than the combined internaland external heat load.

• The desired internal enclosure temperature and the ambienttemperature around the enclosure: Heat will naturally flow fromhigher temperatures to lower temperatures. The higher the ambienttemperature relative to the enclosure temperature, the harder it isto move heat from the enclosure to the atmosphere.

• The protection rating of the enclosure: Some NEMA enclosureratings preclude allowing outside air to enter the enclosure as partof the cooling system, since other outside contaminants (water,dust, oil, etc.) could enter via the same path.

WaystoKeepEnclosuresCoolHow can you keep an enclosure’s interior air temperature cool?Heat can be generated to raise the temperature of an enclosure butcold cannot be generated. Cooling an enclosure is accomplished byremoving heat from the enclosure to the surrounding atmosphere.There are several types of cooling methods, all of which will bedescribed in greater detail:• Natural Convection: Typically for small heat loads. The ambient

temperaturemust be lower than thedesired temperature insideenclosure.• Forced Convection: The ambient temperature must be lower than

the desired temperature inside the enclosure.• Closed Loop Cooling: Used when the ambient temperature is as

high or higher than the desired internal temperature. This methodis also used for areas with harsh environments.

NaturalConvectionCooling

• Usewhenoutsideisclean,dry,andcoolerthanenclosure interior.• Heatistransferredtotheenclosuresurface,andthendissipatesto atmosphere.• Louversorgrilleswithfilterscanbeusedtodissipateheatmorequicklybyallowingwarmairtoescapeenclosureandbereplacedbycoolerairfromsurroundingatmosphere.

NaturalConvectionCooling

• STEGOEnclosureExhaustGrilleswithFilters:Availableforno-screwinstallationwithoptionalmountingscrewsforadditionalsupportandindoororoutdoorinstallationoptions.

• Hubbell-WiegmannEnclosureExhaustGrillesandFilters:Polycarbonate,fire-retardantplasticgrilleswithdurablereusablefiltermat.

• Hubbell-WiegmannVents,LouverPlatesandFilters:Openlouversandventsforbothmetalandfiberglassenclosures.

• IntegraLabyrinthVent:ForIntegrapolycarbonateenclosures.

Natural Convection Cooling Devices offered by AutomationDirect:

ForcedConvectionCooling

• Usewhencleanandcooloutsideairisavailable.• Usefilterfanandgrilletoforcecoolambientairintoenclosure.• Useexhaustgrilletoallowhotairinenclosuretoexhaustascoolairisforcedin.

ForcedConvectionCooling

• STEGOEnclosureFilterFans:Createconstantairflowthroughtheenclosuretopreventlocalizedheatpocketsandprotectcomponentsfromoverheating.

• Hubbell-Weigmann EnclosureFans:Coolingfansandexhaustgrillesthatprovidehighqualitycooling.

Enclosure fans provide optimum climate in enclosures channeling cooler filtered outside air into the enclosure and expelling hot internal air. The following forced convection fans are offered by AutomationDirect:

ForcedConvectionCoolingSometimestheenclosurecoolingsystemhasthecapacitytodissipatethetotalheatloadinanenclosure,butifahighheatloadfromoneormorecomponentsora“hotspot”developsbecausethearrangementofthecomponents,thisrestrictsairmovementinonearea.Thesesituationscancreatea“bottleneck”intheflowofheatfromtheenclosuretotheoutside.

Insuchcases,STEGOStegoJet CompactFans fromAutomationDirect canprovidespotcoolingbycreatingafocusedstreamofairinsidetheenclosuretomovetheheatawayfromthehotspotorhighheatloadcomponent,allowingtheenclosurecoolingsystemtomovetheheattotheoutside.

ClosedLoopCoolingClosed loop cooling devices are used when there is a need to maintain temperatureinside an enclosure at or below safe levels for the equipment/components withoutintroducing outside air into the enclosure.

Closedloopcoolingistypicallyusedin:• Harshenvironments• Areaswherewashdown isrequired• Areaswithheavydustanddebris• Areaswherechemicalsareairborne

ClosedloopcoolingoptionsofferedbyAutomationDirect:• EnclosureHeatExchangers• EnclosureAirConditioners

ClosedLoopCooling

Howclosedloopcoolingsystemswork:• Theheartofthesystemisarefrigerantthecirculatesthroughasealedsystemthatpassesfromanevaporatorcoilinsidetheenclosuretoacondensercoilontheoutsideandback.• Astherefrigerantcirculates,itactsasaconveyorbeltforheat,pickingupheatfrominsidetheenclosureattheevaporatoranddroppingitofftotheoutsideairatthecondenser.

ClosedLoopCoolingHowclosedloopcoolingsystemswork(continued):

• Afancirculatesairfrominsidetheenclosureacrosstheevaporatorcoil.Sincetherefrigerantintheevaporatoriscolderthantheairintheenclosure,itabsorbsheatfromairandcoolsit.• Asecondfancirculatesambientairacrossthecondensercoil.Sincetherefrigerantinthecondenserishotterthantheambientair,heatfromtherefrigerantisrejectedtotheatmosphere.

ClosedLoopCooling

ClosedloopcoolingoptionsofferedbyAutomationDirect:

• StratusEnclosureAir-to-AirHeatExchangers• StratusEnclosureAirConditionersTheprimarydifferencesbetweentheoperationofanenclosureheatexchangerandanenclosureairconditioneristherefrigerantandhowitiscirculatedthroughtheevaporatorandthecondenser.

ClosedLoopCoolingEnclosureHeatExchangers: Air-to-AirHeatExchangersusetheheatpipeprincipletoexchangeheatinsideanelectricalenclosuretothe outside:• A liquid refrigerantissealedinabundleofcoppertubesunderapartialvacuum.Thepartialvacuumlowerstheboilingpointoftherefrigerant.• Thetubebundleismounteddiagonally,withthetopsectionformingthecondenserandthebottomendformingtheevaporator.• Thecondenserandevaporatorsectionsareseparatedbyapermanentbaffle.• Sincetherefrigerantisunderapartialvacuum,theheatabsorbedintheevaporatorboilstherefrigerant(changesitfromliquidtovapor).

ClosedLoopCoolingEnclosureHeatExchangers (continued)

• Therefrigerantvaporislighterthantheliquidrefrigerant,sotheheatedrefrigerantrisestothecondensersectionatthetopofthetube.• Thecoolerambientairpassingoverthecondensersectioncoolstherefrigerantvaporuntilitcondenses(returnstoliquidphase).• Liquidrefrigerantfallstotheevaporator,replacingtherefrigerantvaporthatisrising.• Thecyclerepeatsendlesslyaslongasambientairiscoolerthantheairinsidetheenclosure.Iftheambienttemperatureequalsorexceedstheenclosuretemperature,theflowofrefrigerantstops.

ClosedLoopCoolingEnclosureHeatExchangers (continued)• Heatexchangerstypicallyaffordsimilarcoolingasfilterfans:thecoolertheambientairisrelativetotheenclosureairthefastertheenclosureairiscooled.• Likefilterfans,heatexchangersarenoteffectivewhenambienttemperaturescanexceedthedesiredenclosuretemperature.Enclosureslocatedinambienttemperaturesmayrequireanairconditionerorvortexcooler.• Thoughthecoolingcapabilitiesaresimilartofilterfans,heatexchangerscanmaintainhigherNEMAratingsthanfilterfans.

ClosedLoopCoolingEnclosureHeatExchangers (continued)• TheStratusheatexchangerdesignhasatop-to-bottomenclosureairflowpatternwithmaximumseparationoftheinletandoutlet.• Theunitsusealuminumendplatesandbaffleswhichimproveconductionandreducecorrosionforlongerlife.• Thecenteraluminumbaffle,whichisswagedintotheheatpipecoil,providesanairtightsealbetweenthetwoairsystems.

ClosedLoopCoolingEnclosureAirConditioners workessentiallythesamewayasheatexchangers,exceptthattherefrigerationsystemismorecomplex.• Theevaporatorandcondenserarestillinseparatecompartments,butareseparatecoilsconnectedbyaloopofpiping.• Upstreamofthecondensercoilisacompressor,whichactslikeapumptoforcetherefrigerantthroughthesystem.Thecompressionoftherefrigerantvaporalsomakesitveryhot,sowhenitentersthecompressoritishotterthantheambientair(evenonahotday)enablingittorejectheattotheatmosphere.• Thecompressedrefrigerantcondensesatamuchhighertemperaturethanitdoesuncompressed.Soeventhoughitishotterthantheoutsideairitstillchangestoliquidformwhenitpassesthroughthecondenser.

ClosedLoopCoolingEnclosureAirConditioners (continued)• Justupstreamoftheevaporator,thehot,pressurizedrefrigerantpassesthroughanexpansionvalve,whichcausesalargedropintherefrigerantpressure.• Justascompressioncausedtherefrigerantvaportogetveryhot,thesuddenreductionofpressurecausestherefrigerantliquidtogetverycoldasitenterstheevaporator.Thecoldliquidisveryeffectiveatabsorbingheatfromtheenclosureairthatisbeingblownacrosstheevaporatorcoils.• Thelowpressurerefrigerantevaporatesbackintovaporform.Itsexpansionpushesthevaportothesuctionsideofthecompressor,wherethecyclestartsagain.

ClosedLoopCoolingEnclosureAirConditioners (continued)• Thecompressionandexpansionoftherefrigerant(andtheaccompanyingtemperatureextremestheyproduce)meansthatanairconditionercanmaintainenclosuretemperaturesthatarelowerthanambienttemperatures.Thismakesairconditionersusefulinenvironmentsthathavehighambienttemperatures,wherefansorheatexchangerswouldbeineffective.• Theeffectivenessoftheairconditionerdoescomeataprice.Thecompressorusesmuchmoreelectricalpowerthanafilterfanoraheatexchanger.

ClosedLoopCoolingEnclosureAirConditioners (continued) Stratusairconditionersfeature

• Highlyenergy-efficientcompressors• Aprogrammabletemperaturecontrollerwithvisiblealarmfeatures• ProtectivecoatingsonthecondensercoilsofNEMA4andNEMA4Xmodelsforcorrosionresistance• Activecondensateevaporationsystemwithsafetyoverflow(foreliminationofwatervaporthatmayformontheoutsideoftheevaporatorcoilswhentheenclosureairiscooled)• Antishort-cyclecompressionprotection

ClosedLoopCoolingStratusRefrigerant-freeVortexCoolers(Technically, vortex coolers aren’t closed loop, they are actually displacing hot air inside the enclosure withcold air from the outside. However, since the cold air comes from a filtered compressed air system, theystillmaintain highNEMAenclosure ratings like air conditioners andheat exchangers.)

• The vortex generator inside the cooler creates a vortexthat rotates the compressed air supply at speeds up to1,000,000 rpm.• The rotation air separates the air into hot and cold airstreams.• The hot air stream is vented to the atmosphere, whilethe super-cooled air is forced through the center of theincoming air stream, through the cold air exhaust port,and into the enclosure.• Hot air from the enclosure is forced out through a vent.

Vortexcoolersgenerateastreamofcoldairusingnothingexceptcompressedair– nofans,nomovingparts,noelectricityrequired.

ClosedLoopCoolingStratusRefrigerant-freeVortexCoolers (continued)• Stratus vortex coolers are useful when air conditioner or heatexchanger cooling is not possible. (i.e., small to medium sizeenclosures, non-metallic enclosures, areas where the size ofcooling devices is restricted, areas where access to electricalpower is limited but compressed air is available).• Vortex coolers are very inexpensive up front and require nomaintenance. But they do consume a lot of compressed air,which must be accounted for in their operating cost.• Like an air conditioner, a vortex cooler is effective even in highambient temperatures.• Unlike competing brands, the cooling capacity of a Stratusvortex cooler can be changed by simply replacing the vortexgenerator. The vortex generator costs less than $10, and can bechanged in less than five minutes with common hand tools.

SizingofCoolingDevicesAfter choosing the most appropriate cooling method (natural convection,forced convection, or closed-loop), calculations are needed to determinethe size/capacity of the cooling components.

SizinganEnclosureFanToselectthepropersize(CFM)fan,determinetheamountofheattoberemovedandthemaximumtemperaturedifferentialthatneedstobeaccommodated.

CubicFeetperMinute(CFM)calculation

CFM=(3.17xPwatts)/ΔT°F

Where:P=PowertobedissipatedinwattsΔT =(max.allowableinternalenclosuretemperature°F)–

(max.outsideambienttemperature°F)

FanSizingExample

A NEMA 12 Hubbell Wiegmann N12302412 enclosure (30ʺ high x 24ʺ wide x 12ʺ deep) contains a GS3-2020 AC drive (20 HP 230 volt) that has a maximum allowable operating temperature of 104°F and is located in a warehouse with a maximum outside ambient air temperature of 95°F.

Power to be dissipated is stated in the specifications of the GS3-2020 and is found to be 750 watts, so P = 750 watts.

ΔT =104°F(max.operatingtemperaturefortheGS3-2020)– 95°F(max.ambientairtemperature)=9°F

SizinganEnclosureFan(continued)

CFM=(3.17x750watts)/9°F=264

Informative video for AutomationDirect’s STEGO line of enclosure filter fans andexhaust grilles.

SizinganEnclosureFan

SizinganAirConditionerorVortexCoolerToselectthepropersizeunit,considertheworst-case conditions,butdonotoversize.Twomainfactorswhenchoosingforanindooruninsulatedmetal NEMAratedenclosure:

• Internalheatload:Theheatgeneratedbycomponents insidetheenclosure.Thepreferredmethodtodeterminethisistoaddthemaximumheat outputspecificationsthatthemanufacturerslistforalltheequipmentinstalledinthecabinet.LoadisneededinBTU,butthevaluesaretypicallygiveninWatts,so usethefollowingconversion:

BTUperHour=Wattsx3.413

Example:TheWatt-losschartfortheAutomationDirectGS3Drivesshowsthata GS3-2020ACdrivehasaWatt-lossof750watts.

BTUperHour=750wattsx3.413=2559

SizinganAirConditioner(continued)

Note:1.25isanindustrystandardconstantformetalenclosures;forplasticenclosuresuse0.62.

• HeatLoadTransfer: Theheatlost(negativeheatloadtransfer)or gained(positiveheatloadtransfer)throughtheenclosurewalls withthesurroundingambientair. Calculateusingthe followingformula:

Heatloadtransfer(BTU/H)=1.25xsurfacearea(sq.ft.)x(max.outsideambientair(°F)–

max.allowableinternalenclosuretemperatureair(°F)) SurfaceArea(sq.ft.)=2[(HxW)+(HxD)+(WxD)]/144sq.inches

Coolingcapacity(BTU/H)=InternalHeatLoad± HeatLoadTransfer

OnceyoudeterminetheInternalHeatLoadandthe HeatLoadTransfer,youcanchoosethepropersizeunitby calculatingtheneededcoolingcapacity.

BTUperHour=1290wattsx3.413BTUperHour=4403BTU/H

Heatloadtransfer:Heatloadtransfer(BTU/H)=1.25x19sq.ft.x(115°F– 104°F)

Heatloadtransfer(BTU/H)=261BTU/H

SizinganAirConditioner(continued)AirConditionerSizingExampleA NEMA 12 Hubbell Wiegmann N12302412 enclosure (30ʺ high x 24ʺ wide x 12ʺ deep) contains a GS3-4030 AC drive (30 HP 460 volt) that has a maximum allowable operating temperature of 104°F and is located in a warehouse that has a maximum outside ambient air temperature of 115°F. Power to be dissipated is stated in the specifications of the GS3-4030 and is found to be 1290 watts.InternalHeatLoad:

AirConditionerSizingExample(continued)CoolingCapacity:• Coolingcapacity(BTU/H)=4403BTU/H+261BTU/H=4664BTU/H

Now review the cooling capacity charts for Stratus air conditioners on the AutomationDirect website for an air conditioner that can provide at least 4664 BTU/hour at 115 at an operating temperature of 104°F and a 115°F ambient temperature.

SizinganAirConditioner(continued)

Select a TA10-060-46-12 Stratus air conditioner

Informative video about AutomationDirect’s Stratus™ enclosure 480V airconditioner models.

SizinganAirConditioner(continued)

SizingaHeatExchangerTo select the proper size unit, consider theworst-case conditions. For a heat exchangerto work, ambient air temperature must be lower than the desired internal enclosureair temperature. There are three main factors in choosing a heat exchanger for anuninsulatedmetal NEMA rated enclosure located indoors:• Internalheatload:Theheatgeneratedbycomponents insidetheenclosure.Thepreferredmethodtodeterminethisistoaddthemaximumheat outputspecificationsthatthemanufacturerslistforalltheequipmentinstalledinthecabinet.ThisistypicallygiveninWatts.

• DeltaT(ΔT):ΔT=(max.allowableinternalenclosuretemperature)–

(max.outsideambientairtemperature°F)Example:TheWatt-losschartfortheAutomationDirect GS3Drivesshowsthata GS3-2020ACdrivehasaWatt-lossof750watts.

BTUperHour=750wattsx3.413=2559

SizingaHeatExchanger(continued)

Note:Onlyincludeexposedsurfaces.HeatLoadTransfer(W/°F)=0.22W/°Fsq.Ft.xSurfaceAreaNote:Use0.22Watts/°Fsq.ft.forpaintedstainlessandnon-metallicenclosures.Use0.10Watts/°Fsq.ft.forstainlesssteelandbarealuminumenclosures.OnceyoudeterminetheInternalHeatLoadandtheHeatLoadTransferandtheDeltaT,youcanchoosethepropersizeunitby calculatingtheneededcoolingcapacity.

• HeatLoadTransfer: Theheatlost(negativeheatloadtransfer)or gained(positiveheatloadtransfer)throughtheenclosurewalls withthesurroundingambientair. Calculateusingthe followingformula:SurfaceArea(sq.ft.)= 2[(HxW)+(HxD)+(WxD)]/144sq.inches

Coolingcapacity(W/°F)=InternalHeatLoad/ΔT - HeatLoadTransfer

SurfaceArea(ft.2)=2[(30x24)+(30x12)+(24x12)]/144sq.inches=19ft.2

Heatloadtransfer=0.22x19ft.2=4.2Watts/°F

SelectingaHeatExchanger(continued)

HeatExchangerSelectionExampleA NEMA 12 Hubbell Wiegmann N12302412 enclosure (30ʺ high x 24ʺ wide x 12ʺ deep) contains a GS3-4010 AC drive (10 HP 460 volt) that has a maximum allowable operating temperature of 104°F and is located in a warehouse that has a maximum outside ambient air temperature of 90°F. Power to be dissipated is stated in the specifications of the GS3-4010 and is found to be 345 Watts.InternalHeatLoad=345WattsDeltaT(ΔT)=104°F– 90°F=14°FHeatloadtransfer:

HeatExchangerSizingExample(continued)CoolingCapacity=345Watts/°F– 4.2Watts/°F=20.4Watts/°F

Inthisexample,wecandeterminethataStratusheatexchanger,withacapacityofatleast20.4Watts/°Fisneeded,suchasaTE30-030-17-04.

SizingaHeatExchanger(continued)

Note:Thisselectionprocedureappliestometalandnon-metal,uninsulated,sealedenclosuresinindoorlocations.Thisselectionproceduregivestheminimumrequiredsize;becarefulnottoundersizewhenpurchasing.

SizingaHeatExchanger(continued)Informational video of AutomationDirect’s Stratus™ line of air-to-air heatexchangers in 120VAC and 24VDC models.

EnclosureThermalManagementControls

Enclosure heaters controlled with thermostats,humidistats (hygrostats) and hygrotherms provide themost consistent temperature and humidity control

• Many enclosure heaters include integratedthermostats or other controls

• Certain heaters may allow for or requireexternal controls

EnclosureThermalManagementControls

The need for control of cooling devices depends on the type of device:

• Filter fans and Stratus heat exchangers do not require a thermostat since theyconsume very little power. However if they do not need to operatecontinuously, a control device will prolong the life of their filters.

• Stratus air conditioners have an integral thermostat, so an external controldevice is never needed.

• Stratus vortex coolers should ALWAYS be controlled by a thermostat tominimize compressed air consumption (and in some cases, to preventfreezing of components inside the enclosure).

EnclosureThermalManagementControlsClimatecontrolcomponentsofferedbyAutomationDirect:• Tamperproof Thermostats (DIN Rail-mounted): Tamperproof (pre-set) NC (normally closed) thermostat opens on temperature rise above fixed setpoint. Tamperproof NO (normally open) thermostat closes on temperature rise.

• Adjustable Thermostats (DIN Rail-mounted): NC adjustable thermostat opens on temperature rise above setpoint. NO adjustable thermostat closes on temperature rise.

• Adjustable Dual Setpoint Thermostats for Enclosure Heaters (DIN Rail-mounted): Houses two separate thermostats, allowing independent control of heating, cooling or other equipment. The NC thermostat (red dial) opens on temperature rise above set point. The NO thermostat (blue dial) closes on temperature rise.

NOTE:Red(NC)thermostatscontrolheating;blue(NO)thermostatscontrolcooling.

EnclosureHeatingControlsHygrostats/Hygrotherms fromAutomationDirect:• ElectronicHygrostatsforEnclosures(DINRailMounted):Electronic hygrostats(humidistats)senserelativehumidityinanenclosureand turnonaheateratthesetpoint.Thishelpspreventenclosure condensationformation.

• ElectronicHygrothermsforEnclosures(DINRailMounted):Electronic hygrotherms senseambienttemperatureandrelativeairhumidity.

Dependingontheselectedcontactcombination,thehygrotherm willturnaconnecteddeviceONorOFFifeitherthetemperatureisbelowthesetpoint,orthehumidityisabovethesetpoint.TypicallyusedtocontrolPTCheaters,fanheaters,condensationheaters,orotherclimatecontroldevices.

EnclosureThermalManagementControlsInstructionalvideoforAutomationDirect’s thermostatsandhygrostats.

Weather keepingyourenclosurecool,orsafeanddry,wehavetheclimatecontrolsolutionatpricesthatwon’tmakeyousweat!