Engineered air EngA W-TRAC User Manual

A W-TRAC


IOM‐49 9of12 Mar99R4



Whentheoutdoorambienttemperatureisbelow15°F(‐10°C)thespeedoftheheatwheelwillbereduced
tomaintaintheleavingexhaustairhumiditybetween80–90%.Thisapplicationrequireshighaccuracy
humiditysensors.

RETURNAIRRH%SENSOR

ThismethodoffrostcontrolrequiresaRHsensorinstalledintheequipmentreturnairsection,justbefore
theheatwheel,wiredintoterminalsRMHandC2.DIP3mustbeON,DIP1and2mustbeOFF.

UsingthevaluesoftheRHandambient(outsideair)sensor,theW‐TRACcalculatestheminimum
allowableexhaustairtemperaturethatwillkeepfrostfromformingonthewheel.

BDRHPREDICTEDRETURNAIRRELATIVEHU MIDITY

RH%sensingisnotusedinthismethodoffrostcontrol.DIP1and3mustbeON,whileDIP2isOFF.

TheW‐TRACmayoperatewithouttheuseofhumiditysensinginsituationswheretheRH%valuesare
expectedtobereasonablyconstant.Inthesecases,theW‐TRACoperatesbysensibletemperatureonly.

Whenenabled,theBDRHpot(BuildingDesignRelativeHumidity)issetaccordingtotheexpecteddesign
returnairconditions.RefertothetablebelowtosettheexpectedvaluesbasedontemperatureandRH%.
Table1
BDRHsetting
ReturnAirConditions
70°F(21°C) 75°F(24°C) 80°F(27°C)
1 <25% <21% <18%
2 26–32% 22–27% 19–23%
3 33–39% 28–33% 24–27%
4 40–49% 34–42% 28–35%

Tousethistable,firstselectthereturnairtemperature,thenselecttheRH%rangeinthecolumnbelow,
thenselecttheBDRHsettingtotheleft.

WIRING

TheW‐TRACterminalsHandNrequireaminimum24VAC,40VAclass2powersupplythatdoesnotneed
tobeisolatedfromtherestofthesystemscomponents.

TerminalNshouldbewiredtothecommonofthesamesourcesupplyingpowertoterminalsE,A,andK.
Allremotewiringshouldbeinstalledinaclean(noelectricalnoise)environment.Wiresizeshouldbea
minimumof24ga.twistedpairtoreduceelectricalnoise(shieldedwireisrecommended).Forlongerruns

Engineered air EngA W-TRAC Specifications

General

Brand	Engineered air
Model	EngA W-TRAC
Category	Controller
Language	English