EngA DJM3

A DJM3
IOM-17 12 of 27 Mar 99 R3
BMSRESET(continuousbloweroperationonly)
DIPswitchonemustbeontoactivateBMSreset.Thisoptionrequiresananalogvoltageorcurrent
signaltobewiredtotheopticallyisolated+and‐terminals.Theanaloginputsignalproportionally
increasesthecalculateddischargeairset‐point.Thecalculateddischargeset‐pointequalsthedial
dischargeset‐pointplustheinputsignalmultipliedbyaresetratiofactor.
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Themaximumamountofresetisadjustablefrom15°F(8°C)to60°F(33°C).Themaximumdischarge
temperature(dialset‐pointplusreset)islimitedto120°F(49°C).TheBMSresetoptionisactivatedby
DIPswitch1.
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Note: Asstandard,theDJM3isdesignedtooperatewith4‐20mAor2‐10Vdcintoa500‐ohminput
impedance.SomeBMSdevicesmaynothaveenoughpower(Volt‐Amps)toprovideafull10
VDCwhenconnectedtoa500‐ohmload.Theinputresistanceforthisoperationcanbe
increasedto1500ohmsbycuttingresistorR43.Tocutthisresistoryoumustturntheboard
over.Itislocatedonthebackofthelargerboard,justbelowtheDIPswitchblockandbeside
PotResetRatio.Thisisa1‐watt,680‐ohmresistorcoloursblue,grey,brown,gold.
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BMSresetisnottrulylinear.Resetwillusuallybeginatabout4volts.Following,isanexampleofreset
fromoneapplicationthatgivesa13°Cor24°Freset.
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CALCULATEDSETPOINTFROMBMSRESETAPPLIEDTO+AND–
TABLE10
Current
Reset
Voltage
Reset
CalculatedSetpoint
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mA Vdc °C
°F
‐ 0 13 55
3 3 13.5 56
5 4 14.5 58
12 6 16 61
‐ 7 18 65
16 8 20 68
‐ 9 23 75
20 10 26 79
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AMBIENTRESET
(continuousbloweroperationonly)
ThisoptionrequiresDIPswitch2tobeonandanambientsensor(JohnsonControlsTE6000‐960)
wiredtoterminalsXandZ.Thedischargeairset‐pointwillberesetupwardsbasedontheambient
temperature.Ambienttemperaturesbelow70°F(21°C)willgraduallyincreasethecalculateddischarge
airset‐point.Themaximumincreaseinthedischargetemperaturewillbereachedwhentheambient
fallsto20°F(‐7°C).TheamountofresetisdependentonthepositionofResetRatioPotandthe
dischargeset‐pointassetonthedial.
(Thedischargeset‐pointwillberesetbelowmasterset‐pointifambientisabove70°F(21°C).Inmost
caseswhentheoutsideambientisabove70°F(21°C),theheatwillbeoff.)
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