heat-timer EPU-D User Manual

DetailedOperation7
059840‐00Rev.AHeat‐TimerCorp.
AvailableHeatLevels
TheEPU‐Disabletomaintaintwodifferentheatlevels:
• Dayheatlevelprovidescomfortabletemperatureswhenthebuildingtenantsareactiveduringtheday.
Thisrequiresahigherlevelofheat.
• Nightheatlevelprovideslowerheatandconservesenergywhenthebuildingisemptyorwhentenantsare
asleep.Bothheatlevelsrelyontheidenticalcycleconcept,butthelowerNightsettingsprovidelessheat
giventhesameoutdoortemperature.
SequenceofOperation
ThissectiondescribesthetypicalsequenceofoperationfortheEPU‐D.
1. TheEPU‐Dactivatesthesteamsourcewhentheoutdoortemperaturefallsbelowtheoutdoorsensor
cutoff.Thecutoffisfactorysetat55°F(13°C)forDayorNight,butisfullyadjustable.
2. TheEPU‐Dcontinuestocallforheat,keepingthesteamsourceactive,untiltheheatingsystemsensor
reachesitsadjustableSetPoint.Thisindicatesthatsteamhasgottenentirelythroughthesystem,orthat
"heatisestablished".
3. After"heatisestablished",theCycle‐ONsegmentofthecyclebegins.
4. DuringtheCycle‐ONsegment,theEPU‐Dkeepsthesteamsourceactivated.ThelengthoftheCycle‐ON
segmentisdependentontheoutdoortemperature,theDay/Nightsetting,andseveraluser‐selectable
adjustmentsthatcanbetunedtothespecificheatlosscharacteristicsofthebuilding.
5. AftertheCycle‐ONsegmenthasended,theCycle‐OFFsegmentofthecyclebegins.TheEPU‐Dturnsoff
theboilerorclosesthesteamvalvefortheremainderofthissegment.
6. AftertheCycle‐OFFsegmenthasended,theEPU‐Donceagainactivatesthesteamsourceunlesseither
theoutdoortemperaturehasrisenabovethecutofforthethermallockoutisactive.
Withthethermallockout,theheatingsystemsensortemperaturemustfallbelowtheSetPointminusa
25°Fdifferentialbeforetheheatingsourcecanbereactivated.Thisallowsresidualheatinthepipesto
continuetoheatthebuilding.Afterthepipeshavecooledsufficiently,anewcyclecanbegin.

heat-timer EPU-D Specifications

General

Brand	heat-timer
Model	EPU-D
Category	Control Panel
Language	English