Troubleshooting: Heating Sequence of Operation
HEATING SEQUENCE OF OPERATION
NORMAL AND ABNORMAL HEATING MODE
POWER ON
CONTROL SELF−CHECK OKAY?
POLARITY OKAY?
YES
IS THERE A
PROPER GROUND?
YES
| NO | GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. |
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| INDOOR BLOWER OFF. (RESET CONTROL BY |
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| TURNING MAIN POWER OFF.) |
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| NO | POLARITY REVERSED. |
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| STATUS ERROR CODE 5 + 4. |
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| NO |
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| SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. | ||
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| STATUS ERROR CODE 5 + 3. | |
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NO
A
NORMAL OPERATION:
STATUS LED −− PULSE
B
THERMOSTAT CALLS FOR HEAT:
STATUS LED −− HEARTBEAT
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
ROLLOUT SWITCH CLOSED?
YES
FIRST (LOW) STAGE PRESSURE SWITCH
CONTACTS OPEN?
YES
SECOND (HIGH) STAGE PRESSURE SWITCH
CONTACTS OPEN?
YES
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON. HAS PRIMARY OR
SECONDARY LIMIT RESET WITHIN 3 MINUTES?
STATUS ERROR CODE 3 + 1.
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| NO |
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NO |
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| 60−MINUTE LIMIT WATCHGUARD MODE. | ||
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| GAS VALVE OFF, COMBUSTION AIR INDUCER | ||
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| OFF, INDOOR BLOWER OFF WITH DELAY. | ||
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| STATUS ERROR CODE 4 + 5. | ||
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NO | GAS VALVE OFF. COMBUSTION AIR INDUCER ON. | |||
| INDOOR BLOWER ON. | |||
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| STATUS ERROR CODE 5 + 1. | ||
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| SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS | ||
NO |
| RESET AND MAIN POWER IS INTERRUPTED OR | ||
T’STAT IS CYCLED OFF/ON FOR 3 SEC. MINIMUM. | ||||
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GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF. CONTROL REMAINS UNTIL PRESSURE SWITCH IS DETECTED OPEN. STATUS ERROR CODE 2 + 4
NO
YES |
NO |
YES |
TWO−STAGE OR SINGLE−STAGE THERMOSTAT
CALL FOR HEAT
COMBUSTION AIR INDUCER ON LOW SPEED.
1STATUS LED −− HEARTBEAT
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF.
CONTROL WILL NOT ATTEMPT SECOND−STAGE
OPERATION DURING THIS HEAT DEMAND.
FIRST−STAGE OPERATION WILL BE ATTEMPTED.
STATUS ERROR CODE 2 + 6.
CONTINUED ON NEXT PAGE
1If the furnace is operating on continuous fan mode (terminals
air inducer will energize on high speed, the gas valve will energize on second−stage heat and the furnace
will operate on high fire. Furnace will stay on high fire 60 seconds then switch to low fire.
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