Page 44
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE
ABNORMAL HEATING MODE
FLAME RECTIFICATION CURRENT CHECK
CAN FLAME BE PROVEN WITHIN 4
SECONDS AFTER GAS VALVE OPENS?
(
>
0.15 microamps)
NO
FLAME PRESENT?
INDOOR BLOWER ON DELAY BEGINS. AFTER 45
SECOND DELAY, ACB HEAT SPEED TERMINAL IS
ENERGIZED. ACC. TERMINAL IS ENERGIZED.
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 BLOWER 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 BLOWER 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 BLOWER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
YES
IGNITOR WARM-UP -- 20 SECONDS.
YES
4-SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS. BOARD 24L85, 56L83, 63K8901:
IGNITOR ENERGIZED FOR 1 SECOND AFTER VALVE
OPENS. BOARD 97L48: IGNITOR ENERGIZES
THROUGH OUT 4 SECOND TRIAL.
YES
FLAME STABILIZATION PERIOD.
GAS VALVE OFF. COMBUSTION AIR BLOWER ON.
INDOOR BLOWER OFF.
HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
HEAT DEMAND?
NO
WATCHGUARD MODE. GAS VALVE OFF.
COMBUSTION AIR BLOWER OFF.
INDOOR BLOWER OFF WITH DELAY
LEDs SIGNAL WATCHGUARD FAILURE CODE.
IS 60-MINUTE RESET PERIOD COMPLETE?
YES
YES
NO
4 SECONDS
YES
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
YES
NO
FLAME SIGNAL ABOVE 0.7 MICROAMPS?
NO
YES
YES
HAS PRIMARY LIMIT RESET?
(See table 6 DIAGNOSTIC CODES for limit reset operation).
NO
YES
NO
YES
ROLLOUT SWITCH CLOSED?
GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 -- ON. LED #2 -- SLOW FLASH.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.
NO
YES
YES
NO
THERMOSTAT DEMAND SATISFIED.
LED #1 & #2 SIMULTANEOUS SLOW FLASHES.
COMB. AIR BLOWER CONTINUES 5-SECOND
POST PURGE AFTER T’STAT DEMAND IS SATISFIED.
HTG ACC. TERM. IS DE-ENERGIZED. INDOOR AIR
BLOWER COMPLETES SELECTED “OFF” DELAY BE-
FORE SHUTTING OFF. ACC. TERM. DE-ENERGIZED.
YES
YES
YES
NO
5-MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
YES