Lennox G43UF SERIES Unit Information page 42

NORMAL HEATING MODE
15-SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
YES
IGNITOR WARM-UP −− 20 SECONDS.
YES
4-SECOND TRIAL FOR IGNITION. GAS VAVLE OPENS.
IGNITOR ENERGIZED FOR UP TO 4 SECONDS.
YES
FLAME STABILIZATION PERIOD.
4 SECONDS
FLAME RECTIFICATION CURRENT CHECK. CAN FLAME BE
PROVEN WITHIN 4 SECONDS AFTER GAS VALVE OPENS?
FLAME SIGNAL u0.15 microamps
YES
FLAME PRESENT?
YES
FLAME SIGNAL
0.18 MICROAMPS OR GREATER
YES
INDOOR BLOWER ON DELAY BEGINS
(45 seconds.)
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
ROLLOUT SWITCH CLOSED?
YES
COMBUSTION AIR PRESSURE
SWITCH CLOSED?
YES
THERMOSTAT DEMAND SATISFIED.
YES
LED #1 & #2 SIMULTANEOUS SLOW FLASHES.
YES
COMB. AIR INDUCER CONTINUES 5-SECOND
POST PURGE AFTER T'STAT DEMAND IS SATISFIED.
INDOOR AIR BLOWER COMPLETES SELECTED
OFF" DELAY BEFORE SHUTTING OFF.
HEATING SEQUENCE CONTINUED
SureLight Control Board 32M88
ABNORMAL HEATING MODE
IS VOLTAGE ABOVE 75 VOLTS?
NO
IS THERE A PROPER GROUND?
YES
IS IGNITOR INTACT AND CONNECTED?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
NO
HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
WATCHGUARD MODE. GAS VALVE OFF.
INDOOR BLOWER OFF WITH DELAY
LEDs SIGNAL WATCHGUARD FAILURE CODE.
IS 60-MINUTE RESET PERIOD COMPLETE?
NO
LOW FLAME SIGNAL
NO
(Does not affect operation of control)
LED #1 −− SLOW FLASH
LED #2 −− FAST FLASH
COMBUSTION AIR INDUCER DE−ENERGIZED.
INDOOR BLOWER ON UNTIL SWITCH CLOSES.
NO
LED #1 −− SLOW FLASH. LED #2 −− ON.
NO
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
NO
THERMOSTAT IS CYCLED OFF/ON FOR 1 TO 20 SEC.
COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF WITH DELAY
LED #1 −− OFF. LED #2 −− SLOW FLASH.
HAS CAB SWITCH CLOSED IN 2.5 MINUTES?
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YES
YES
INDOOR BLOWER OFF.
HEAT DEMAND?
COMBUSTION AIR INDUCER OFF.
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
GAS VALVE DE−ENERGIZED.
IS LIMIT SWITCH CLOSED?
YES
HAS PRIMARY SECONDARY
LIMIT RESET (CLOSED)
WITHIN 3 MINUTES?
GAS VALVE POWER OFF.
COMBUSTION AIR INDUCER POWER ON.
INDOOR BLOWER ON
LED #1 −− ON. LED #2 −− SLOW FLASH.
AND MAIN POWER IS INTERUPTED OR
GAS VALVE DE−ENERGIZED.
NO
5-MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
NO
LEDS SIGNAL
NO
ALTERNATING
FAST FLASH
NO
NO
YES
YES
NO
YES
LIMIT SWITCH
WATCHGUARD
MODE. GAS VALVE
OFF. COMB. AIR
INDUCER OFF.
INDOOR BLOWER
OFF WITH DELAY.
LED#1−SLOW
FLASH LED#2− ON.
IS 60−MINUTE
RESET PERIOD
COMPLETE?
NO
YES
YES