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Troubleshooting: Heating Sequence of Operation (Continued)
2ND STAGE HEAT
RUN MODE:
1ST OR 2ND STAGE CALL FOR HEAT.
ALL INPUTS MONITORED (LIMIT, PRESSURE,
CALL FOR HEAT/COOL, FLAME LEVEL)
2ND STAGE
CALL FOR HEAT
SATISFIED?
NO
YES
DE−ENERGIZE 2ND STAGE
GAS VALVE
INDUCER SPEED SWITCHED
TO LOW SPEED
1
2 3
1ST STAGE HEAT
1ST STAGE
CALL FOR HEAT
SATISFIED?
NO
YES
GAS VALVE
DE−ENERGIZED
INDUCER OFF AFTER
5 SECOND POST PURGE
CALL FOR HEAT SATISFIED
FIRST−STAGE HEAT SECOND−STAGE HEAT
INDOOR BLOWER SWITCHED
TO LOW HEAT SPEED
INDOOR BLOWER OFF
AFTER FIELD SELECTABLE
OFF DELAY