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CALL FOR HEAT SATISFIED
1st Stage Heat
2nd Stage Heat
2nd Stage
Call for Heat
satisfied?
NO
1st Stage
Call for Heat
satisfied?
Gas valve
De
−
Energized
YES
NO
Wait for Call
−
2
−
StageThermostat
Wait for Call
−
Single StageThermostat
1
4
3A
3B
YES
OR
Combustion Air Inducer
switched to 70% rate speed
Adjust Indoor Blower
to appropiate speed
Combustion Air Inducer OFF
after 20
−
Second Post Purge
Indoor Blower OFF
after OFF Delay
RUN MODE (2 STAGE THEREMOSTAT)
1ST OR 2ND STAGE CALL FOR HEAT ALL
INPUTS MONITORED (LIMIT, PRESSURE,
CALL FOR HEAT / COOL, FLAME LEVEL)
RUN MODE (SINGLE STAGE THERMOSTAT)
ALL INPUTS MONITORED (LIMIT, PRESSURE,
CALL FOR HEAT / COOL, FLAME LEVEL)