Lennox G50UHi Unit Information page 24

NORMAL HEATING MODE
CONTROL SELF−CHECK OKAY?
COMBUSTION AIR INDUCER ON FOR 1 SECOND.
TURN INDUCER ON FOR 1 SECOND.
IS POLARITY REVERSED? (Control board 9748)
LED#1 AND LED#2
ALTERNATING FAST
FLASH. SIGNAL
NO
HOLDS UNTIL UNIT IS
PROPERLY GROUND.
ROLLOUT SWITCH CLOSED?
(CONTINUOUS FLAME CHECK)
THERMOSTAT CALLS FOR HEAT:
IS COMBUSTION AIR INDUCER ENERGIZED?
(ACCESSORY TERMINAL IS ENERGIZED WITH C.A.I.)
HAS COMBUSTION AIR PROVE SWITCH
CLOSED IN 2.5 MINUTES?
15-SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PROVE SWITCH.
CONTINUED NEXT PAGE
SURELIGHT CONTROL
HEATING SEQUENCE OF OPERATION
Control board 69M15 LED #1 = DS1, LED #2 = DS2
Control board 97L48 LED #1 = DIAG1 LED #2 = DIAG2
POWER ON
(Control board 9748)
NO
IS THERE
YES
PROPER GROUND?
YES
YES
BURNER OFF?
YES
NORMAL OPERATION:
LED #1 −− SLOW FLASH
LED #2 −− SLOW FLASH
LED #1 −− FAST FLASH
LED #2 −− FAST FLASH
YES
IS COMBUSTION AIR
PROVE SWITCH OPEN?
YES
YES
YES
YES
SureLight Control Board
ABNORMAL HEATING MODE
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
LED #1 ALTERNATING FAST FLASH
NO
CHECK FOR BROKEN IGNITOR OR
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
YES
(RESET CONTROL BY TURNING MAIN POWER OFF.)
NO
IS VOLTAGE
ABOVE 75 VOLTS?
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 −− ON. LED #2 −− SLOW FLASH.
NO
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
NO
INDOOR BLOWER OFF WITH DELAY.
PROVE SWITCH IS IN WATCHGUARD MODE.
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 −− OFF. LED #2 −− SLOW FLASH.
IS 5-MINUTE RESET PERIOD COMPLETE?
FLAME SENSE SIGNAL
97L48
69M15
Page 24
INDOOR BLOWER ON.
LED#2 ALTERNATING FAST FLASH
OPEN IGNITOR CIRCUIT
INDOOR BLOWER DELAY OFF.
LED #1 ON
LED #2 ON
POLARITY REVERSED.
LED #1 −− FAST FLASH
LED #2 −− SLOW FLASH
LED#1 AND LED#2 ALTERNATING FAST
FLASH. SIGNAL HOLDS UNTIL VOLTAGE
RISES ABOVE 75 VOLTS.
LED #1 −− SLOW FLASH
LED #2 −− OFF
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
LED #1 OFF
LED #2 SLOW FLASH
(Sequence holds until PROVE switch
closes or thermostat resets control.)
TABLE 19
Low
Normal
0.61
0.21 − 0.60
0.31
0.25 − 0.30
Drop Out
0.20
0.24