Troubleshooting: Heating Sequence of Operation

NO

HEATING SEQUENCE OF OPERATION

NORMAL HEATING MODE

 

 

ABNORMAL HEATING MODE

 

 

 

 

 

 

 

 

 

 

 

 

 

POWER ON

 

 

 

 

 

 

 

 

 

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

INDOOR BLOWER DELAY OFF.

 

CONTROL SELF−CHECK OKAY?

 

 

LED #1 ON

 

 

 

 

 

 

 

 

 

LED #2 ON

 

 

 

 

 

 

 

 

 

(RESET CONTROL BY TURNING MAIN POWER OFF.)

 

 

 

YES

 

 

 

NO

 

 

 

 

 

 

 

POLARITY REVERSED.

 

 

 

 

 

 

 

 

 

 

IS POLARITY CORRECT?

 

 

LED #1 −− FAST FLASH

 

 

 

 

 

 

 

 

 

LED #2 −− SLOW FLASH

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

IMPROPER GROUND.

 

IS THERE A PROPER GROUND?

 

 

LED #1 −− ALTERNATING FAST FLASH

 

 

 

YES

 

 

 

 

 

LED #2 −− ALTERNATING FAST FLASH

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LEDs SIGNAL FAST ALTERNATING FLASH.

 

 

 

IS VOLTAGE

 

 

 

 

 

 

 

 

 

 

 

CONTROL WILL NOT RESPOND TO A CALL FOR

 

 

 

ABOVE 90 VOLTS?

 

 

 

 

 

 

 

 

 

 

HEATING UNTIL VOLTAGE RISES ABOVE 95 VOLTS.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

NO

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

 

 

 

 

 

INDOOR BLOWER ON.

 

ROLLOUT SWITCH CLOSED?

 

 

LED #1 −− ON. LED #2 −− SLOW FLASH.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES

 

 

 

YES

 

 

 

 

AND POWER IS RESET OR T’STAT IS INTERRUPTED

 

 

 

 

 

 

 

 

 

FOR MINIMUM OF 1 SECOND.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

 

 

 

BURNER OFF?

 

INDOOR BLOWER ON HEATING SPEED.

 

 

 

 

 

 

(Flame sensed without gas valve energized)

 

 

LED #1 −− SLOW FLASH

 

 

 

 

 

 

YES

 

 

 

 

 

LED #2 −− OFF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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 INDUCER

ENERGIZED?

NO

NO

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER ON

LED #1 SLOW FLASH RATE

LED #2 −− ON

GAS VALVE OFF.

COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 OFF

LED #2 SLOW FLASH

(Sequence holds until pressure switch opens or thermostat resets control.)

YES

HAS COMBUSTION AIR PRESSURE SWITCH CLOSED IN 2.5 MINUTES?

YES

CONTINUED NEXT PAGE

PRESSURE SWITCH IS IN WATCHGUARD MODE. NO GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF WITH DELAY.

LED #1 −− OFF. LED #2 −− SLOW FLASH.

IS 5-MINUTE RESET PERIOD COMPLETE?

YES

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Lennox International Inc Merit Series Gas Furnace installation instructions Troubleshooting Heating Sequence of Operation

Merit Series Gas Furnace specifications

Lennox International Inc. is a leading name in the heating and cooling industry, and their Merit Series Gas Furnace embodies the commitment to quality and efficiency that the company is known for. The Merit Series is designed to provide reliable heating in a sustainable manner, making it an excellent choice for homeowners seeking comfort without excessive energy bills.

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