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HEATING SEQUENCE OF OPERATION
FIRST−STAGE (LOW FIRE) PRESSURE
SWITCH CLOSED WITHIN 2.5 MINUTES?
GAS VALVE OFF. COMBUSTION AIR INDUCER
OFF. INDOOR BLOWER OFF. UNIT WILL RETRY
AFTER 5−MINUTE WAIT PERIOD.
DS1 OFF, DS2 SLOW FLASH.
YES
NO
15−SECOND COMBUSTION AIR INDUCER
PRE−PURGE INITIATED BY CLOSED FIRST−STAGE
PRESSURE SWITCH (or 15 SECOND
INTER−PURGE PERIOD.)
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
IGNITOR WARM−UP
(20 SECONDS)
DS1 AND DS2 SIMULTANEOUS FAST FLASH
IS VOLTAGE ABOVE 75 VOLTS?
NO
COMBUSTION AIR INDUCER OFF, IGNITER OFF.
SIGNAL HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS.
DS1 AND DS2 ALTERNATING FAST FLASH.
YES
IS THERE A PROPER GROUND?
NO
COMBUSTION AIR INDUCER OFF, IGNITER OFF.
SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED.
DS1 AND DS2 ALTERNATING FAST FLASH.
NO
COMBUSTION AIR INDUCER OFF, IGNITOR OFF.
SIGNAL HOLDS UNTIL IGNITOR IS REPLACED
OR RECONNECTED.
DS1 AND DS2 ALTERNATING FAST FLASH.
YES
AT END OF IGNITOR 20 SECOND WARM UP
PERIOD, 4−SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS, IGNITOR ENERGIZED DURING
4−SECOND TRIAL UNTIL FLAME SENSED.
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
YES
4−SECOND FLAME STABILIZATION PERIOD.
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
FLAME RECTIFICATION CURRENT CHECK
CAN FLAME BE PROVEN WITHIN 4
SECONDS AFTER GAS VALVE OPENS?
(
u
0.16 microamps)
NO
GAS VALVE OFF. COMBUSTION AIR
INDUCER ON. INDOOR BLOWER OFF.
DS1 SLOW FLASH, DS2 FAST FLASHN.
HAS CONTROL FAILED TO SENSE
FLAME FOR FIVE CONSECUTIVE TRIES
DURING A SINGLE HEAT DEMAND?
YES
THERMOSTAT CALLS FOR HEAT
DS1 AND DS2 SIMULTANEOUS FAST FLASH
(Refer to box A on previous page)
YES
FLAME PRESENT?
NO
HAS CONTROL RESET IGNITION SEQUENCE
FOUR (4) TIMES?
DS1 SLOW FLASH, DS2 FAST FLASH.
YES
CONTINUED ON NEXT PAGE
YES
NO
NO
CONTINUED
IS IGNITOR INTACT AND CONNECTED?
WATCHGUARD MODE. GAS VALVE OFF,
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF.
DS1 AND DS2 ALTERNATING SLOW FLASH.
IS 60−MINUTE RESET PERIOD COMPLETE?
