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Troubleshooting: Heating Sequence of Operation (Continued)
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE ABNORMAL HEATING MODE
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
(0.5 microamps)
FLAME PRESENT?
INDOOR BLOWER ON
AFTER 30−SECOND DELAY
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
COMBUSTION AIR PRESSURE
SWITCH CLOSED?
LOW FLAME SIGNAL
(Does not affect operation of control)
LED #1 −− SLOW FLASH
LED #2 −− FAST FLASH
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER DE−ENERGIZED.
INDOOR BLOWER ON UNTIL SWITCH CLOSES.
LED #1 −− SLOW FLASH. LED #2 −− ON.
IS LIMIT SWITCH CLOSED?
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?
15-SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
YES
IGNITOR WARM-UP −− 20 SECONDS.
YES
YES
FLAME STABILIZATION PERIOD.
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 60-MINUTE RESET PERIOD COMPLETE?
YES
4 SECONDS
YES
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
YES
YES
ROLLOUT SWITCH CLOSED?
GAS VALVE POWER OFF.
COMBUSTION AIR INDUCER POWER ON.
INDOOR BLOWER ON
LED #1 −− ON. LED #2 −− SLOW FLASH.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
AND MAIN POWER IS INTERRUPTED OR
THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
YES
THERMOSTAT DEMAND SATISFIED.
LED #1 & #2 SIMULTANEOUS SLOW FLASHES.
COMB. AIR INDUCER CONTINUES 5-SECOND
POST PURGE AFTER T’STAT DEMAND IS SATISFIED.
INDOOR AIR BLOWER COMPLETES SELECTED OFF"
DELAY BEFORE SHUTTING OFF.
YES
NO
5-MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
YES
IS VOLTAGE ABOVE 90 VOLTS?
LEDS SIGNAL
ALTERNATING
FAST FLASH UNTIL
VOLTAGE IS ABOVE
95 VOLTS, THEN
RESTARTS HEATING
SEQUENCE.
NO
YES
YES
YES
NO
NO
NO
NO
NO
NO
YES
YES
NO
NO
NO
YES
YES
HAS PRIMARY / SECONDARY
LIMIT RESET TIME
EXCEEDED 3 MINUTES?
LIMIT SWITCH WATCHGUARD
MODE. GAS VALVE, COMB. AIR
INDUCER AND INDOOR BLOW-
ER OFF. LEDs SIGNAL LIMIT
SWITCH OPEN UNTIL MAIN
POWER IS
INTERRUPTED OR
T’STAT IS CYCLED
OFF/ON FOR 1 SEC.
MINIMUM. 60−MINUTE
WATCHGUARD PE-
RIOD STARTS AT
TIME LIMIT CLOSES.
IS 60−MIN. PERIOD
COMPLETE?
NO
YES
4-SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS. IGNITOR ENERGIZED FOR
FIRST 3 SECONDS OF THE TRIAL.
HAS PRESSURE SWITCH OPENED 5
TIMES IN THE SAME HEAT DEMAND?
NO
1 HR
PRESSURE
SWITCH
WATCHGUARD
MODE