heat-timer EPU-D User Manual

4EPU‐DInstallationandOperationManual
059840‐00Rev.A Heat‐TimerCorp.
DetailedOperation
Overview
TheEPU‐Disamicroprocessor‐basedcontroldesignedtomanagealow‐pressuresteamheatingsystem.The
controlcanoperateasteamboileroratwo‐waysteamvalveusinga“cycle”concepttoprovidethedesired
amountofheattothebuilding.
The“Cycle”Concept
The“cycle”conceptwascreatedbyHeat‐Timerspecificallytoallowsteamheatingsystemstoovercomethe
inabilitiesofstandardthermostaticcontrolstocopewiththeuniquechallengesoflow‐pressuresteamheating.
Unlikewaterandairsystems,steamsystemstaketimetobuildupa“headofsteam”.Moreover,afterthe
systemstartsheatingup,ithasmomentumthattakestimetodissipate.Thismakesitdifficulttocontrolits
temperature.
CycleLengthBasedonOutdoorTemperature
Bymonitoringtheoutdoortemperature,theEPU‐Disabletoanticipatethebuildingheatingneeds.Eachcycle
period(usually60minuteslong,butadjustabledependingonthetypeofradiationunits)consistsofaCycle‐ON
segmentandaCycle‐OFFsegment.ThelengthoftheCycle‐ONsegmentwillvarywiththeoutdoor
temperature.Thecolderitisoutdoor,thelongertheCycle‐ONsegment.
Figure2: Example60MinuteCycle
TheEPU‐Dconstantlycheckstheoutdoortemperaturebymeansofasolid‐statesensorlocatedontheexterior
ofthebuilding.Atthesametime,itmonitorstheheatingsystemofthebuildingbymeansofeitheraheating
systemsensororreverse‐actingpressuretrol.Thesesensorstellthecontrolwhensteamhasreachedthe
furthestlocationinthebuilding(orthehardesttoheatarea,see“PipingDiagrams”onpage 38).Basedonthis
combineddata,theEPU‐Dsendsinstructionstotheheatingplanttocontroltheheatlevelinthebuilding.
TheEPU‐Dalsoprovidestwoadjustableoutdoortemperaturecutoffsettings,onefordaytimeoperationand
onefornighttimeoperation.Whentheoutdoortemperaturerisesaboveoneofthecutoffsettings,theEPU‐D
willnotcallforanyheat.

heat-timer EPU-D Specifications

General

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