System Installation Guide
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69-2490 —03
Backup heat differential and upstage timerBasic and Advanced Temperature Control Options (ISU 3010)
Abackupheatdifferentialandbackupheatupstagetimercanbeset onany
systemthathasmorethanonetypeofheatingequipment.See installersetup
options(ISU3070-3110).
Normal operation
WhentheBackup Heat DifferentialissettoComfort,thethermostatuses backup
heatasneededtokeeptheindoortemperaturewithin1°F (0.5°C)oftheset-
point.IftheBackup Heat Upstage Timerisused,thethermostatdelaystheback-
upheatfromturningonuntilthetimerexpires.
WhentheBackup Heat Differentialissetto2°Forhigher,backupheatisnot
used unless the indoor temperature drops to the Backup Heat Differentialsetting
or the Backup Heat Upstage Timerexpires.Theupstagetimerstartswhenthe
higheststageofthepreviousequipmenttypeturnson.
Manual temperature change
WhentheBackup Heat DifferentialissettoComfort,thethermostatuses backup
heatasneededtokeeptheindoortemperaturewithin1°F (0.5°C)oftheset-
point.
WhentheBackup Heat Differentialissetto2°Forhigher,iftheprimaryheat is
makingprogressasexpected,backupheatwillnotbeusedtoreach thenew
setpoint.Settoahighernumbertouselessbackup heat(agreaterdifference
betweenthecurrentindoortemperatureandthenewsetpointisrequiredtotur n
onbackupheat).Seenotebelow.
Programmed recovery
Iftheprimaryheatismakingprogressasexpected,backupheatwill notbeused
toreachthesetpointofthenextprogramperiod.Backupheatis always restrict-
edduringaprogrammedrecoverywhentheAdaptiveIntelligentRecoveryfeature
isused.SettheBackup Heat Differentialtoahighernumberto uselessbackup
heat.Seenotebelow.
Basic Options:TheInstallerSetupdisplaysbasictemperaturecontroloptions
whichincludeBackupHeatDifferential,BackupHeatUpstageTimerandOutdoor
TemperatureLockouts.Note:OutdoorTemperatureLockoutsonlyapplytoHeat
Pumpapplications.
Advanced Options:TheInstallerSetupdisplaysbothBasicandAdvanced
Options.AdvancedtemperaturecontroloptionsincludeFinishWithHighCool
Stage,FinishWithHighHeatStage,TemperatureDifferentialsettingsperstage
andCycleRatesettingsperstage.
During a programmed recovery (or when the temperature setpoint is changed by the user), the thermostat waits to turn on the
backup heat depending on system performance, load conditions and how many degrees the temperature setpoint is changed.
Backup heat will be used ONLY when the temperature is not rising quickly enough to reach the setpoint in a reasonable time.
Finish With High Heat or Cool Stage - When a multi-stage heating or cooling system is used, this feature keeps the high stage
of the heating or cooling equipment running until the desired setpoint is reached. Recommended setting for Geothermal Heat
Pumps to allow the loop to rest.
69-2490_B.indd 20 7/13/2011 1:42:00 PM