BuildingManagementSignal/0-10VDCor4-20mASignalConditioner/Blower-HeatRelays

DescriptionofTemperatureControl

• Signalconditionerfortemperaturecontrol• Conditioneraccepts0-10VDCor4-20mAsignalfromBASSystem• DischargeSensorMountedinBlower• Allnecessarysafetiesprovidedintegraltotheunit

ApplicationsWheretemperedmake-upairisrequiredforabuildingwithaBuildingAutomationSystemandthecontrollerisprovidedbyothers.

HeaterType100%OutsideAirSingleSpeedorVariableAirVolume(VAV)IndustrialUnit

SequenceofOperationsWiththedisconnectinONpositionandcontactclosurefromanexternalsourcetothebloweron-offrelay(RE-55),powerissuppliedtothedampermotor(MT-02),ifequipped.

WhenthedampermotorapproachestheOPENposition(approximately70%),thedamper-endswitch(SW-07)closesenergizingtheblowermotorstartercontactor(ST-01)andpoweringtheblowermotor(MT-01).Theblowermotorcanalsobeenergizedfromtheserviceswitch(SW-05).

Iftheunitisequippedwiththelow-temperaturelimitcontrol(TS-07),aftertenminutes,thelow-temperaturelimitcontrolshutsdowntheunitifthedischargetemperaturedoesnotreachtheminimumset-pointonthelow-temperaturelimitcontrol.

Iftheunitisequippedwithasmokedetector(AL-02),thesmokedetectorwillshutdowntheunitifsmokeisdetected.

Ifanexhaustfanstartercoilistiedintotheexhaustfaninterlock(C1-01),theexhaustfanwillturnon.

Iftheunitisequippedwithafirestat(TS-22),theunitwillshutdownifthetemperatureexceedsthecontrol’ssetting.

Iftheunitisequippedwithacloggedfilterswitch(PS-02),thepressuredropacrossthefilterswillbemonitored.

Whenthelowairflowswitch(PS-01)isproven,thehightemperaturelimitcontrol(TS-04)isenergized.Thehightemperaturelimitcontrolwillmonitortheairtemperatureandshutdowntheburnerifthetemperaturesetpointisexceeded.Thehightemperaturelimitwillrequireamanualreset.

Ifequipped,theoptionallowandhighgaspressureswitches(PS-03&PS-04)willbeenergized.Ifthegaspressureisnotbetweentheset-pointstheburnerwillturnoffandrequireamanualreset.

Theburneron-offrelay(RE-56)mustbeenergizedfromacontactclosureandtheburnerON/OFFintakeairstat(TS-06)mustcallforheatfortheflamesafetycontroller(RE-07)tobeenergized.Thepilotvalve(VA-03)opens,andtheignitiontransformer(TR-03)energizes,providingasignaltosparkthesparkrod.

Aftertheflamerod(SN-02)provesflame,themainvalves(VA-01&VA-02)open,andtheignitiontransformerde-energizes.Theburnercanalsobeenergizedfromtheserviceswitch(SW-06).Iftheflameroddoesnotproveafter3ignitioncycles,theburnerwillshutoff.Thepilotvalve(VA-03)staysenergized.

Iftheunitisequippedwithdualflamerods(SN-03),timer(T1-11)isenergized.Afterthetimer’ssetpointisexceeded,theflamesensingisswitchedfromSN-02toSN-03(SN-03islocatedattheoppositeendoftheburner)forcontinualflamemonitoringduringunitoperation.

Thetemperaturecontrolsystem’samplifier(AM-01)receivestwosignals;onefromthedischargesensorandonefromanexternal0-10VDCor4-20mAsignalfromtheBuildingAutomationSystem.TheamplifiercontinuallycomparesthesesignalsandwhenheatisrequiredtheamplifierwillsendaDCvoltagetothemodulatingvalve(VA-05).AstheDCvoltagefromtheamplifierincreasesthemodulatingvalvewillopen,allowingmoregastoflow.Bycomparingthetwosignalstheamplifierwillmaintainthedischargetemperaturebysendingasignaltothemodulatinggasvalve.

AdditionalSequenceofOperationforVAVunits

VAVwithStaticPressureControl

TheVFDwillbeenergizedinplaceoftheblowermotorstartercontactor(ST-01)listedabove.

Thephotohelic,usedtomonitortheindoorairpressure,sendsasignaltotheVFDprovingthattheindoorpressureiseithersatisfied,positive,ornegative.Basedonthissignal,theVFDalterstheHZtotheblowerandsendsanoutputsignaltotheVAVdampermotor(MT-08),whichisusedtocontrolthepressuredropacrosstheburnerfortheentireairflowrange.Dependingonthesignalfromthephotohelic,theVFDwilldothefollowing:

• Ifthespaceissatisfied,theVFDwillmaintaincurrentoperation• Ifthespaceisnegative,theVFDwillrampuptorebuildthepressureinthespace• Ifthespaceispositive,theVFDwillmodulatedowntoreducethepressureinthespace

Thehighairflowswitch(PS-10)isenergizedatthesametimethelowairflowswitch(PS-01)isenergizedabove.Thehighairflowswitchwillensurethatthepressuredropacrosstheburnerdoesnotexceed0.65”w.c.

Theflamelimitingpotentiometer(PO-02)isenergizedwiththemodulatinggasvalve(VA-05)listedinthesequenceabove.Theflamelimitingpotentiometerlimitsthevoltagetothemodulatinggasvalvetopreventover-firinginlowspeed.

VAVwithManualPotentiometer

TheVFDwillbeenergizedinplaceoftheblowermotorstartercontactor(ST-01)listedabove.

ThemanualpotentiometeraltersthespeedoftheVFD.TheVFDcontrolstheHZtotheblowerandsendsanoutputsignaltotheVAVdampermotor(MT-08),whichisusedtocontrolthepressuredropacrosstheburnerfortheentireairflowrange.

Thehighairflowswitch(PS-10)isenergizedatthesametimethelowairflowswitch(PS-01)isenergizedabove.Thehighairflowswitchwillensurethatthepressuredropacrosstheburnerdoesnotexceed0.65”w.c.

Theflamelimitingpotentiometer(PO-02)isenergizedwiththemodulatinggasvalve(VA-05)listedinthesequenceabove.Theflamelimitingpotentiometerlimitsthevoltagetothemodulatinggasvalvetopreventover-firinginlowspeed.

VAVwithConstantSpeedControlorAnalogInputControl

TheVFDwillbeenergizedinplaceoftheblowermotorstartercontactor(ST-01)listedabove.

TheVFDcanoperatebyeitherananaloginputorpresetspeeds.

Ifanaloginputisrequired,ananaloginputsignalissenttotheVFDbyanexternalsource,whichwilldirectlycontrolthesignaltotheblowerandVAVdampermotor(MT-08).TheVAVdampermotorisusedtocontrolthepressuredropacrosstheburnerfortheentireairflowrange.

Ifpresetspeedsarerequired,anexternalswitchcanbeusedtomanuallyadjustbetweenprogrammedspeedsintheVFD.TheVFDwillsendasignaltotheblowerandVAVdampermotor(MT-08)basedontheselectedspeed.TheVAVdampermotorisusedtocontrolthepressuredropacrosstheburnerfortheentireairflowrange.

Thehighairflowswitch(PS-10)isenergizedatthesametimethelowairflowswitch(PS-01)isenergizedabove.Thehighairflowswitchwillensurethatthepressuredropacrosstheburnerdoesnotexceed0.65”w.c.

Theflamelimitingpotentiometer(PO-02)isenergizedwiththemodulatinggasvalve(VA-05)listedinthesequenceabove.Theflamelimitingpotentiometerlimitsthevoltagetothemodulatinggasvalvetopreventover-firinginlowspeed.