Accurex XDG Installation, Operation And Maintenance Manual
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Contents
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Direct Gas Make-Up Air40OPTIONAL EXHAUSTExhaust Fan Contact (S1) Closed (optional)• Power passes to normally closed exhaust overloadcontact (ST2 OL).• Power passes to exhaust starter(s) ST2.• Normally open exhaust starters are energized andclosed.• Power passes to exhaust fans.• Exhaust fan(s) (M2) start.SUPPLY FANSupply Fan Contact (S2) Closed• Power passes through normally closed field-supplied fire system contact (FSC).• Power passes through normally open exhaust fancontact (ST2), which is closed when the exhaustrelay (ST2) is activated (optional).• Power passes to normally closed supply overloadcontact (ST1 OL or VFD).• Power passes through normally closed contacton optional freeze protection timer (RT4) whichremains closed if the temperature has remainedabove the set point.• Power passes to optional inlet damper whichopens.• When damper is fully opened, optional normallyopen damper limit switch (DL1) closes.• Power passes to and energizes supply starter relay(RF).• Power passes to normally open fan contact (RF),which is energized and closed.• Supply starter (ST1) or variable frequency drive(VFD) is energized.• Supply starter contact (ST1) closes or VFD isenergized and power reaches and energizessupply fan.• Supply fan (M1) starts.HEATINGHeat Contact (S4) Closed• Power passes to normally open fan relay (RF orST1) which is energized and closed.• Power passes to optional inlet air sensor contact(TS4) which is closed if the inlet air temperature isbelow the set point.• Power passes to and energizes the heat relay (RH).• Normally open heat relay contact (RH) closes.Commercial Flame Safeguard Ignition Sequence• Power passes to normally closed high limit controlcontact (HLC1) which is closed if temperature hasremained below set point.• Power passes to optional normally open andnormally closed high and low gas pressurecontacts (PS4 and PS3), which are both closed ifgas pressure is within the set range.• Power passes to normally open and normallyclosed airflow switches (PS2) which are closed ifthere is proper airflow across the burner.• Power passes to terminal TH on the flamesafeguard (FSG).• Flame safeguard checks for proper airflow andcompletes verification of no flame present atburner.• A 15 second prepurge is initiated.• Power is passed to normally closed gas valve(V2) which opens and the spark generator (SG) isenergized.• The trial for ignition will last for up to 30 seconds oruntil flame is confirmed.• Spark generator (SG) is de-energized.• The flame and airflow are continuously monitored.Industrial Flame Safeguard Ignition Sequence• Power passes to and energizes terminal 5 of theflame safeguard (FSG). Power light on FSG is on.• Power passes to normally closed high limit controlcontact (HLC1) which is closed if temperature hasremained below set point.• Power passes to optional normally open andnormally closed high and low gas pressurecontacts (PS4 and PS3), which are both closed ifgas pressure is within the set range.• Power passes to terminal 6 of the flame safeguard(FSG).• Flame safeguard checks for proper airflow andcompletes verification of no flame present atburner.• A 10 second prepurge is initiated.• Power is passed to normally closed pilot gas valve(V1) which opens and the spark generator (SG) isenergized.• The trial for ignition will last for up to 10 seconds oruntil flame is confirmed.• After flame is confirmed, power is passed to thenormally closed main gas valves (V2) which open.• Spark generator (SG) is de-energized.• The flame and airflow are continuously monitored.• A self-diagnostic check is performed every fiveseconds.Sequence of OperationIf the unit has a microprocessor, reference thesupplemental Microprocessor Controller for Make-UpAir Reference Guide for more information. |
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