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Troubleshooting: Heating Sequence of Operation
HIGH
LIMIT SWITCH
CLOSED?
LOW
PRESSURE
SWITCH
OPEN?
INDUCER ON
PRE−PURGE
(15 SECONDS)
1ST STAGE GAS
VALVE ENERGIZED
FLAME
SENSED WITHIN
4 SECONDS?
(LOW HEAT SPEED)
HEAT FAN OFF DELAY
(LOW HEAT SPEED)
AFTER HEAT FAN
OFF DELAY (LOW
HEAT SPEED)
YES
YES
YES
YES
ERROR
CODE
FLASHES
ON(LOW HEAT
SPEED)
NO
NO
NO
NO
CALL
FOR HEAT
ENDS?
ERROR CODE
FLASHES (AFTER
5 SECONDS)
5TH
UNSUCCESSFUL
TRIAL?
POSTPURGE
(5 SECONDS)
INDUCER
OFF
NO
YES
NO
NO
ROLLOUT
CIRCUITS
CLOSED?
DE−ENERGIZE
GAS VALVE
ERROR
CODE
FLASHES
INDOOR BLOWER
ON (LOW HEAT
SPEED)
INDUCER ON
(HIGH SPEED)
LIMIT
SWITCH
CLOSED WITHIN 3
MINUTES?
CALL FOR
1ST STAGE HEAT
(LOW FIRE)
NO
GAS VALVE
DE−ENERGIZED
H.S.I. OFF
H.S.I. ON
(20 SECONDS)
WATCHGUARD −
ERROR CODE
FLASHES
CALL FOR HEAT SATISFIED
IGNITION TRIAL
BEGINS (H.S.I. ON)
HEAT FAN ON DELAY
TIMER STARTED
INTERPURGE
(15 SECONDS)
H.S.I. OFF
NO
INDUCER OFF
AFTER POST
PURGE
HARD LOCKOUT −
ERROR CODE
FLASHES
YES
YES
YES
1
2
1
LOW PRESSURE
SWITCH OPENS
1
2
HARD LOCKOUT REQUIRES THERMOSTAT RESET OR CYCLING OF POWER TO RESET THE LOCKOUT.
3
IN CASE HIGH SPEED INDUCER IS RUNNING AT THE TIME THE GAS VALVE GETS ENERGIZED,
2ND STAGE GAS VALVE IS ENERGIZED INSTEAD OF 1ST STAGE. 20 SECONDS AFTER FLAME
IS SENSED, INDUCER SWITCHES TO LOW SPEED, AND GAS VALVE SWITCHES TO 1ST STAGE.
1
2
1
NO
LOW
PRESSURE SWITCH
CLOSED WITHIN 120
SECONDS?
LOW & HIGH
PRESSURE SWITCH
CLOSED WITHIN 30
SECONDS?
HIGH
PRESSURE
SWITCH
OPEN
BEFORE
INDUCER WAS
TURNED ON?
INDUCER TO
HIGH SPEED−
ERROR CODE
FLASHES
NO
INDUCER OFF−
WAIT
5 MINUTES
ERROR CODE
FLASHES
YES
YES
YES
YES
NO
3
INDOOR BLOWER OFF AFTER
INDOOR
BLOWER OFF
INDOOR
BLOWER
ROLLOUT
CIRCUIT
CLOSES
(MANUAL
RE−SET)
NO
LOW SPEED
INDOOR BLOWER
OFF AFTER HEAT
OFF DELAY
YES
INDOOR
BLOWER
ON?
WATCHGUARD −
ERROR CODE
FLASHES
INDOOR
BLOWER
ON?
INDOOR
BLOWER ON 30 SEC.
WATCHGUARD LOCKOUT AUTOMATICALLY RESETS AFTER ONE HOUR
CALL FOR FIRST−STAGE HEAT
INDOOR
BLOWER
OFF AFTER
HEAT FAN
OFF DELAY