Heating Sequence Of Operation - Lennox ML180DF045P24A Unit Information

Troubleshooting: Heating Sequence of Operation
NORMAL HEATING MODE
CONTROL SELF-CHECK OKAY?
IS POLARITY CORRECT?
IS THERE A PROPER GROUND?
ROLLOUT SWITCH CLOSED?
(Contiuous Flame Check)
NO
NORMAL OPERATION:
THERMOSTAT CALLS FOR HEAT:
PRIMARY AND SECONDARY LIMIT SWITCH.
PRESSURE SWITCH OPEN?
IS COMBUSTION AIR INDUCER
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
CONTINUED NEXT PAGE

HEATING SEQUENCE OF OPERATION

POWER ON
YES
YES
YES
NO
IS VOLTAGE
ABOVE 90 VOLTS?
YES
YES
BURNER OFF?
YES
LED: STEADY ON
YES
LED: STEADY ON
YES
CLOSED?
YES
IS COMBUSTION AIR
YES
ENERGIZED?
YES
YES
ABNORMAL HEATING MODE
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
NO
INDOOR BLOWER DELAY OFF.
NO
NO
CONTROL WILL NOT RESPOND TO CALL FOR HEAT
IGNITOR WILL GLOW DIMLY BUT WILL NOT LIGHT
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
NO
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND POWER IS RESET OR T'STAT IS INTERRUPTED
FOR MINIMUM OF 1 SECOND.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
NO
INDOOR BLOWER ON HEATING SPEED.
COMBUSTION AIR INDUCER OFF.
NO
COMBUSTION AIR INDUCER OFF.
NO
INDOOR BLOWER OFF WITH DELAY.
(Sequence holds until pressure switch
opens or thermostat resets control.)
PRESSURE SWITCH IS IN WATCHGUARD MODE.
NO GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
IS 5‐MINUTE RESET PERIOD COMPLETE?
Page 23
LED: OFF
POLARITY REVERSED.
LED: 9 FLASHES
IMPROPER GROUND.
LED: OFF
UNTIL PROPER GROUND.
LED: ON STEADY
INDOOR BLOWER ON.
LED: 5 FLASHES
LED: 1 FLASH
INDOOR BLOWER ON
LED: 4 FLASHES
GAS VALVE OFF.
LED: 2 FLASHES
LED: 3 FLASHES
YES