Heating Sequence Of Operation - Lennox F8AUH series Service Manual

NORMAL HEATING MODE
POWER ON
CONTROL SELF−CHECK OKAY?
YES
IS POLARITY REVERSED?
ROLLOUT SWITCH CLOSED?
YES
BURNER OFF?
(CONTINUOUS FLAME CHECK)
YES
NO
NORMAL OPERATION:
LED #1 −− SLOW FLASH
LED #2 −− SLOW FLASH
YES
THERMOSTAT CALLS FOR HEAT:
LED #1 −− FAST FLASH
LED #2 −− FAST FLASH
YES
PRIMARY AND SECONDARY LIMIT SWITCH.
CLOSED?
YES
IS COMBUSTION AIR
PRESSURE SWITCH OPEN?
YES
IS COMBUSTION AIR BLOWER
ENERGIZED?
YES
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
YES
CONTINUED NEXT PAGE

HEATING SEQUENCE OF OPERATION

NO
NO
NO
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ABNORMAL HEATING MODE
GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.
INDOOR BLOWER DELAY OFF.
NO
(RESET CONTROL BY TURNING MAIN POWER OFF.)
YES
POLARITY REVERSED.
LED #1 −− FAST FLASH
LED #2 −− SLOW FLASH
GAS VALVE OFF. COMBUSTION AIR BLOWER ON.
INDOOR BLOWER ON.
LED #1 −− ON. LED #2 −− SLOW FLASH.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.
GAS VALVE OFF. COMBUSTION AIR BLOWER ON.
INDOOR BLOWER ON HEATING SPEED.
LED #1 −− SLOW FLASH
LED #2 −− OFF
COMBUSTION AIR BLOWER OFF.
INDOOR BLOWER ON
LED #1 SLOW FLASH RATE
NO
COMBUSTION AIR BLOWER OFF.
NO
INDOOR BLOWER OFF WITH DELAY.
LED #2 SLOW FLASH
(Sequence holds until pressure switch
closes or thermostat resets control.)
PRESSURE SWITCH IS IN WATCHGUARD MODE.
NO
GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 −− OFF. LED #2 −− SLOW FLASH.
IS 5-MINUTE RESET PERIOD COMPLETE?
LED #1 ON
LED #2 ON
LED #2 −− ON
GAS VALVE OFF.
LED #1 OFF