Troubleshooting: Cooling Sequence of Operation

COOLING SEQUENCE OF OPERATION

NORMAL COOLING MODE

 

 

ABNORMAL COOLING MODE

 

 

 

 

 

 

 

 

 

 

 

 

POWER ON

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IGNITION CONTROL MAIN POWER ON.

 

 

 

 

 

 

 

 

 

 

NO

 

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

 

CONTROL SELF DIAGNOSTIC CHECK.

 

INDOOR BLOWER OFF WITH NORMAL DELAY.

 

IS CONTROL OPERATING NORMALLY?

 

 

SIGNAL CIRCUIT BOARD FAILURE AT LED.

 

 

 

YES

 

 

 

 

INTERRUPT MAIN POWER TO RESET CONTROL.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SIGNAL IMPROPER GROUND AT LED.

 

IS THERE A PROPER GROUND?

 

 

CONTROL WILL CONTINUE TO CALL FOR COOLING

 

 

 

YES

 

 

 

 

IN THIS CONDITION.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

SIGNAL POLARITY REVERSED AT LED. CONTROL

 

 

 

 

 

 

 

 

 

IS POLARITY CORRECT?

 

 

WILL CONTINUE TO CALL FOR COOLING IN THIS

 

 

 

 

 

 

 

 

CONDITION.

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

 

 

 

 

 

 

IS VOLTAGE

 

 

 

LED SIGNALS LOW VOLTAGE. CONTROL WILL

 

 

 

 

 

 

 

 

 

ABOVE 90 VOLTS?

 

 

 

CONTINUE TO CALL FOR COOLING

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

IN THIS CONDITION.

 

 

 

 

 

 

 

 

 

 

 

 

 

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

 

 

 

 

 

 

 

 

 

 

 

 

NO

 

INDOOR BLOWER ON.

ROLLOUT SWITCH MONITORED CONTINUOUSLY.

 

 

SIGNAL ROLL-OUT SWITCH OPEN AT LED.

IS ROLLOUT SWITCH CLOSED?

 

 

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES

 

 

 

 

 

 

 

AND MAIN POWER IS INTERRUPTED OR THERMOSTAT

 

 

YES

 

 

 

 

IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LED: SLOW FLASH RATE REMAINS UNCHANGED

THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

COMPRESSOR CONTACTOR AND SYSTEM FAN

ENERGIZED WITH 2-SECOND DELAY

(COOLING SPEED). EAC TERM. ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND EAC TERM. OFF

WITH 45-SECOND DELAY.

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

Merit Series Gas Furnace specifications

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