Troubleshooting: Heating Sequence of Operation (Continued)
CALL FOR HEAT SATISFIED
FIRST−STAGE HEAT SECOND−STAGE HEAT
23
RUN MODE:
1ST OR 2ND STAGE CALL FOR HEAT.
ALL INPUTS MONITORED (LIMIT, PRESSURE, CALL FOR HEAT/COOL, FLAME LEVEL)
2ND STAGE HEAT
NO
2ND STAGE
CALL FOR HEAT
SATISFIED?
YES
DE−ENERGIZE 2ND STAGE
GAS VALVE
INDUCER SPEED SWITCHED
TO LOW SPEED
INDOOR BLOWER SWITCHED
TO LOW HEAT SPEED
1ST STAGE HEAT
NO
1ST STAGE
CALL FOR HEAT
SATISFIED?
YES
GAS VALVE
DE−ENERGIZED
INDUCER OFF AFTER
5 SECOND POST PURGE
INDOOR BLOWER OFF
AFTER FIELD SELECTABLE
OFF DELAY
1
Page 70
