Lennox G50UHi Unit Information page 25

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 DURING TRIAL UNTIL FLAME
SENSED.
YES
FLAME STABILIZATION PERIOD.
4 SECONDS
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
See table 19
YES
FLAME PRESENT?
YES
FLAME SIGNAL NORMAL?
See table 19
YES
INDOOR BLOWER ON DELAY BEGINS
(45 seconds.)
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
ROLLOUT SWITCH CLOSED?
YES
COMBUSTION AIR PROVE
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.
HEAT SPEED, ACCESSORY AND EAC. TERMINAL OFF.
ABNORMAL HEATING MODE
IS VOLTAGE ABOVE 75 VOLTS?
NO
YES
IS THERE A PROPER GROUND?
YES
YES
IS IGNITOR INTACT AND CONNECTED?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF.
HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
NO
NO
IGNITION WATCHGUARD MODE. GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY
LED 1 ALT. SLOW FLASH LED 2 ALT SLOW FLASH
IS 60-MINUTE RESET PERIOD COMPLETE?
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
NO
LOW FLAME SIGNAL
(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
NO
ON UNTIL SWITCH CLOSES.LED #1
−− SLOW FLASH. LED #2 −− ON.
IS LIMIT SWITCH CLOSED?
HAS PRIMARY/SECONDARY LIMIT
RESET (CLOSED) WITHIN 3
MINUTES?
NO
COMBUSTION AIR INDUCER POWER OFF.
INDOOR BLOWER OFF WITH DELAY
LED #1 −− ON. LED #2 −− SLOW FLASH.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
NO
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?
5-MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
Page 25
NO
NO
NO
HEAT DEMAND?
LIMIT SWITCH WATCH GUARD
MODE. GAS VALVE OFF.
COMB. AIR INDUCER OFF. IN-
DOOR BLOWER OFF WITH
DELAY. LED#1−SLOW FLASH
LED#2− ON. IS 60MINUTE RE-
SET PERIOD COMPLETE.?
YES
NO
YES
GAS VALVE POWER OFF.
NO
LEDS SIGNAL
ALTERNATING
FAST FLASH
NO
YES
YES
NO
YES
YES
YES