Page 58
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE ABNORMAL HEATING MODE
IGNITION SEQUENCE BEGINS
(Ignition trial counter initiated.)
FLAME RECTIFICATION CURRENT CHECK
(u0.20 microamps)
W2 TIMED MODE
SINGLE STAGE T’STAT
SINGLE−STAGE MODE
HIGH HEAT ONLY
CFM" LED−DS4 BLINKS ONCE
FOR EVERY 100CFM. INDOOR
BLOWER ON LOW SPEED
PREPURGE
15 SECONDS
CFM" LED−DS4 BLINKS ONCE FOR
EVERY 100CFM. INDOOR BLOWER
ON HIGH HEATING SPEED
GAS VALVE
DE−ENERGIZED
NO
IGNITOR WARM−UP
(20 SECONDS)
TWO−STAGE MODE
CALL FOR 1st STAGE HEAT
GAS VALVE OPEN
HIGH AND LOW HEAT
MAIN GAS VALVE OPEN
LOW HEAT ONLY
MAIN GAS VALVE OPEN
LOW HEAT ONLY
SECOND STAGE
TIME ON BEGINS
4 SECONDS
FLAME PRESENT?
(Response time −− 2 seconds maximum.)
"HEAT" LED−DS2 LIT INDOOR BLOWER ON DELAY BEGINS
(45 seconds.)
W2 TIMED MODE
SINGLE STAGE T’STAT
SINGLE−STAGE MODE
HIGH HEAT ONLY
TWO−STAGE MODE
CALL FOR 1st STAGE HEAT
FLAME PRESENT?
(Continuous flame check)
FLAME SIGNAL
(u0.61 microamps)
PRIMARY LIMIT SWITCH CLOSED?
ROLLOUT SWITCH CLOSED?
PROVE SWITCH CLOSED?
(CONTINUED ON NEXT PAGE)
CONTROL CHECKS RETRY
FOR IGNITION COUNT.
HAVE FOUR RE-TRIES
BEEN COMPLETED?
WATCHGUARD −− FLAME FAILURE.
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF.
LED #1 & LED #2 ALTERNATE FLASH.
NO YES
LOW FLAME SIGNAL
LED #1 −− SLOW FLASH
LED #2 −− FAST FLASH
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER DE−ENERGIZED.
INDOOR BLOWER ON.
LED #1 − SLOW FLASH; LED #2 − ON.
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER DE−ENERGIZED.
INDOOR BLOWER OFF DELAY (Selected time)
LED #1 −− ON
LED #2 −− SLOW FLASH
WATCHGUARD 60-MINUTE DELAY
(SIGNAL LIMIT OR IGNITION FAILURE)
GAS VALVE OFF. COMBUSTION AIR
AND INDOOR BLOWER OFF.
LED #1 AND LED #2
ALTERNATING SLOW FLASHES
NO
NO
NO
NO
HAS LIMIT RESET?
(See table 8 DIAGNOSTIC CODES for limit reset operation)
YES
NO
CONTINUED ON NEXT PAGE
WATCHGUARD 60-MINUTE DELAY
LIMIT SWITCH. GAS VALVE OFF.
COMBUSTION AIR AND INDOOR
BLOWER OFF. LED #1 SLOW FLASH
AND LED #2 ON. IS 60 MINUTE RESET
PERIOD COMPLETE?
YES
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