Troubleshooting: Heating Sequence of Operation (Continued)
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE | ABNORMAL HEATING MODE |
INITIATED BY CLOSED PRESSURE SWITCH.
YES
IGNITOR
YES
GAS VALVE OPENS. IGNITOR ENERGIZED FOR
FIRST 3 SECONDS OF THE TRIAL.
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| LEDS SIGNAL |
NO |
| NO | ALTERNATING | |||
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| IS VOLTAGE ABOVE 90 VOLTS? | FAST FLASH UNTIL | ||
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| VOLTAGE IS ABOVE |
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| YES |
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| 95 VOLTS, THEN |
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| RESTARTS HEATING |
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| SEQUENCE. |
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YES
FLAME STABILIZATION PERIOD.
4 SECONDS
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN 4 SECONDS AFTER GAS VALVE OPENS?
(0.5 microamps)
YES
FLAME PRESENT?
NO
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF.
HAS CONTROL FAILED TO SENSE FLAME FOR FIVE CONSECUTIVE TRIES DURING A SINGLE HEAT DEMAND?
WATCHGUARD MODE. GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY
LEDs SIGNAL WATCHGUARD FAILURE CODE.
IS
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
NO
YES
YES
NO
YES
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
INDOOR BLOWER ON
AFTER 30−SECOND DELAY
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
ROLLOUT SWITCH CLOSED?
YES
COMBUSTION AIR PRESSURE
SWITCH CLOSED?
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| YES | |
NO | LOW FLAME SIGNAL | LIMIT SWITCH WATCHGUARD | |||
(Does not affect operation of control) | MODE. GAS VALVE, COMB. AIR | ||||
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| LED #1 −− SLOW FLASH | INDUCER AND INDOOR BLOW- | ||
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| LED #2 −− FAST FLASH | ER OFF. LEDs SIGNAL LIMIT | ||
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| SWITCH OPEN UNTIL MAIN | ||
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| POWER IS | |
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| GAS VALVE DE−ENERGIZED. |
| INTERRUPTED OR | |
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| T’STAT IS CYCLED | ||
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| COMBUSTION AIR INDUCER DE−ENERGIZED. | |||
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| OFF/ON FOR 1 SEC. | |||
NO | INDOOR BLOWER ON UNTIL SWITCH CLOSES. | ||||
MINIMUM. 60−MINUTE | |||||
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| LED #1 −− SLOW FLASH. LED #2 −− ON. | |||
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| WATCHGUARD PE- | |||
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| IS LIMIT SWITCH CLOSED? |
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| RIOD STARTS AT | ||
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| YES |
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| TIME LIMIT CLOSES. | ||
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| HAS PRIMARY / SECONDARY | YES | IS 60−MIN. PERIOD | |
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| COMPLETE? | ||
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| LIMIT RESET TIME |
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| EXCEEDED 3 MINUTES? |
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| NO | |
NO | GAS VALVE POWER OFF. | |||
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| COMBUSTION AIR INDUCER POWER ON. | |
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| INDOOR BLOWER ON | |
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| LED #1 −− ON. LED #2 −− SLOW FLASH. | |
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| SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET | |
NO | AND MAIN POWER IS INTERRUPTED OR | |||
THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM. | ||||
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YES
THERMOSTAT DEMAND SATISFIED.
YES
LED #1 & #2 SIMULTANEOUS SLOW FLASHES.
YES
COMB. AIR INDUCER CONTINUES
POST PURGE AFTER T’STAT DEMAND IS SATISFIED. INDOOR AIR BLOWER COMPLETES SELECTED
DELAY BEFORE SHUTTING OFF.
HAS PRESSURE SWITCH OPENED 5
TIMES IN THE SAME HEAT DEMAND?
NO | YES |
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF WITH DELAY LED #1 −− OFF. LED #2 −− SLOW FLASH. HAS CAB SWITCH CLOSED IN 2.5 MINUTES?
NO 
WATCHGUARD MODE.
1HR
PRESSURE
SWITCH
WATCHGUARD
MODE
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