Lennox G43UF SERIES Unit Information page 47

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 VALVE OPENS. IGNITOR ENERGIZED FOR
UP TO 3 SECONDS.
YES
FLAME STABILIZATION PERIOD.
4 SECONDS
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
(0.5 microamps)
YES
FLAME PRESENT?
YES
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
INDOOR BLOWER ON
AFTER 45−SECOND DELAY
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
Ignition Control 78M47 / 100973−01
NO
IS VOLTAGE ABOVE 90 VOLTS?
YES
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
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER DE−ENERGIZED.
INDOOR BLOWER ON UNTIL SWITCH CLOSES.
NO
LED #1 −− SLOW FLASH. LED #2 −− ON.
HAS PRIMARY / SECONDARY
EXCEEDED 3 MINUTES?
NO
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
NO
THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF WITH DELAY
LED #1 −− OFF. LED #2 −− SLOW FLASH.
HAS CAB SWITCH CLOSED IN 2.5 MINUTES?
Page 47
ABNORMAL HEATING MODE
INDOOR BLOWER OFF.
HEAT DEMAND?
COMBUSTION AIR INDUCER OFF.
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
MODE. GAS VALVE, COMB. AIR
INDUCER AND INDOOR BLOW-
IS LIMIT SWITCH CLOSED?
YES
LIMIT RESET TIME
GAS VALVE POWER OFF.
COMBUSTION AIR INDUCER POWER ON.
INDOOR BLOWER ON
LED #1 −− ON. LED #2 −− SLOW FLASH.
AND MAIN POWER IS INTERRUPTED OR
NO
5-MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
LEDS SIGNAL
ALTERNATING
NO
FAST FLASH UNTIL
VOLTAGE IS ABOVE
95 VOLTS, THEN
RESTARTS HEATING
SEQUENCE.
NO
YES
YES
YES
NO
LIMIT SWITCH WATCHGUARD
ER OFF. LEDs SIGNAL LIMIT
SWITCH OPEN UNTIL MAIN
POWER IS
INTERRUPTED OR
T'STAT IS CYCLED
OFF/ON FOR 1
SEC. MINIMUM.
60−MINUTE WATCH-
GUARD PERIOD
STARTS AT TIME
LIMIT CLOSES.
YES
IS 60−MIN. PERIOD
COMPLETE?
NO
YES