ML193DF Gas Furnace Installation Manual - Lennox
ML193DF Gas Furnace Installation Manual - Lennox
ML193DF Gas Furnace Installation Manual - Lennox
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Troubleshooting: Heating Sequence of Operation<br />
HEATING SEQUENCE OF OPERATION<br />
NORMAL HEATING MODE<br />
ABNORMAL HEATING MODE<br />
POWER ON<br />
CONTROL SELF−CHECK OKAY?<br />
YES<br />
IS POLARITY CORRECT?<br />
YES<br />
IS THERE A PROPER GROUND?<br />
YES<br />
NO<br />
NO<br />
NO<br />
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.<br />
INDOOR BLOWER DELAY OFF.<br />
LED #1 ON<br />
LED #2 ON<br />
(RESET CONTROL BY TURNING MAIN POWER OFF.)<br />
POLARITY REVERSED.<br />
LED #1 −− FAST FLASH<br />
LED #2 −− SLOW FLASH<br />
IMPROPER GROUND.<br />
LED #1 −− ALTERNATING FAST FLASH<br />
LED #2 −− ALTERNATING FAST FLASH<br />
IS VOLTAGE<br />
ABOVE 90 VOLTS?<br />
NO<br />
LEDs SIGNAL FAST ALTERNATING FLASH.<br />
CONTROL WILL NOT RESPOND TO A CALL FOR<br />
HEATING UNTIL VOLTAGE RISES ABOVE 95 VOLTS.<br />
YES<br />
ROLLOUT SWITCH CLOSED?<br />
YES<br />
NO<br />
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.<br />
INDOOR BLOWER ON.<br />
LED #1 −− ON. LED #2 −− SLOW FLASH.<br />
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES<br />
AND POWER IS RESET OR T’STAT IS INTERRUPTED<br />
FOR MINIMUM OF 1 SECOND.<br />
BURNER OFF?<br />
(Flame sensed without gas valve energized)<br />
YES<br />
NO<br />
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.<br />
INDOOR BLOWER ON HEATING SPEED.<br />
LED #1 −− SLOW FLASH<br />
LED #2 −− OFF<br />
NO<br />
NORMAL OPERATION:<br />
LED #1 −− SLOW FLASH<br />
LED #2 −− SLOW FLASH<br />
YES<br />
THERMOSTAT CALLS FOR HEAT:<br />
LED #1 −− FAST FLASH<br />
LED #2 −− FAST FLASH<br />
YES<br />
NO<br />
COMBUSTION AIR INDUCER OFF.<br />
INDOOR BLOWER ON<br />
LED #1 SLOW FLASH RATE<br />
LED #2 −− ON<br />
PRIMARY LIMIT SWITCH. CLOSED?<br />
YES<br />
IS COMBUSTION AIR<br />
PRESSURE SWITCH OPEN?<br />
YES<br />
IS COMBUSTION AIR INDUCER<br />
ENERGIZED?<br />
NO<br />
GAS VALVE OFF.<br />
COMBUSTION AIR INDUCER OFF.<br />
INDOOR BLOWER OFF WITH DELAY.<br />
LED #1 OFF<br />
LED #2 SLOW FLASH<br />
(Sequence holds until pressure switch<br />
opens or thermostat resets control.)<br />
YES<br />
HAS COMBUSTION AIR PRESSURE<br />
SWITCH CLOSED IN 2.5 MINUTES?<br />
YES<br />
NO<br />
PRESSURE SWITCH IS IN WATCHGUARD MODE.<br />
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.<br />
INDOOR BLOWER OFF WITH DELAY.<br />
LED #1 −− OFF. LED #2 −− SLOW FLASH.<br />
IS 5-MINUTE RESET PERIOD COMPLETE?<br />
YES<br />
CONTINUED NEXT PAGE<br />
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