Page 59
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE ABNORMAL HEATING MODE
INDOOR BLOWER SWITCHES TO HEATING SPEED.
CFM" LED−DS4 BLINKS ONCE FOR EVERY 100 CFM.
W2 TIMED MODE
SINGLE STAGE T’STAT
PROVE SWITCH CLOSED?
TWO−STAGE MODE
CALL FOR 1st STAGE HEAT
CALL FOR 2nd STAGE
HEAT (HIGH HEAT)
FROM THERMOSTAT
2nd STAGE ON DELAY
ON CONTROL BOARD
COMPLETE
(8, 12 OR 15 MIN.)
W2 TIMED MODE
SINGLE STAGE T’STAT
SINGLE−STAGE MODE
HIGH HEAT ONLY
TWO−STAGE MODE
CALL FOR 1st STAGE HEAT
CONTROL CHECKS: FLAME PRESENCE, CLOSED
PRIMARY LIMIT, CLOSED PROVE SWITCHES,
CONTINUOUSLY CLOSED ROLLOUT SWITCH (during
heating cycle).
SEE PREVIOUS SEQUENCES FOR FAILURE MODES.
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER POST−PURGE 5
SECONDS. HTG ACC. TERM. DE−ENERGIZED
INDOOR BLOWER
SELECTED TIME OFF DELAY.
YES
HIGH HEAT PROVE SWITCH CLOSED?
HIGH HEAT GAS VALVE OPEN? (8 SEC. DELAY)
GAS VALVE DE−ENERGIZED.
INDOOR BLOWER DE−ENERGIZED.
COMBUSTION AIR INDUCER ON FOR 2.5 MINUTES.
NO
PROVE SWITCH
CLOSED?
PROVE SWITCH WATCHGUARD
COMBUSTION AIR INDUCER
DE−ENERGIZED.
5−MINUTE DELAY
COMBUSTION AIR
INDUCER ON.
PREPURGE
(See top of previous page.)
DEMAND FOR HEAT SATISFIED.
THERMOSTAT OPENS.
DIAGNOSTIC CODES
LED #1 LED #2 DESCRIPTION
SLOW FLASH
SLOW FLASH
SLOW FLASH
SLOW FLASH
FAST FLASH
FAST FLASH
ON
ON
OFF
ON
OFF
ON
SLOW FLASH
SLOW FLASH
SLOW FLASH
SLOW FLASH
FAST FLASH
FAST FLASH
ALTERNATING SLOW FLASH
Primary or secondary limit open
Rollout switch open
Flame sensed without gas valve energized
PROVE switch open
Power on
Heating demand
Polarity reversed
Low flame signal
Circuit board failure
Watchguard −− burners failed to ignite
¦ 2.5
MINUTES
YES YES
COMBUSTION AIR INDUCER SWITCHES TO
HIGH SPEED?
NO
ALTERNATING FAST FLASH
Watchguard −− low voltage, below 75V or
improper main ground.
YES
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