Lennox 80MGF Series Manual page 30

80MGF WITH EGC−2 HEATING SEQUENCE OF OPERATION
NORMAL HEATING MODE
CONTROL MAIN POWER ON"
FLAME OFF?
YES
CONTROL SELF−CHECK OKAY?
YES
ROLL−OUT SWITCH CLOSED
YES
LED: SLOW FLASH RATE
THERMOSTAT CALLS FOR HEAT
LED: FAST FLASH RATE
COMB. AIR BLOWER PRESSURE SWITCH OPEN?
YES
COMBUSTION AIR BLOWER ON?
HTG ACC. TERM. ENERGIZED.
PRESSURE SWITCH CLOSED WITHIN 2.5 MIN.?
YES
COMB. AIR BLOWER PREPURGE (15 seconds)
IGNITION TRIAL (10 seconds) −− START IGNITION
SPARK, OPEN MAIN GAS VALVE.
HAS FLAME REGISTERED WITHIN 10 SECONDS
AFTER IGNITION TRIAL?
YES
IS FLAME SENSED AFTER 10 SECOND
FLAME RECTIFICATION PERIOD?
YES
INDOOR AIR BLOWER ON.
(Fixed 45−second delay)
PRIMARY/SECONDARY LIMITS MONITORED IN
HEAT CYCLE. ARE SWITCHES CLOSED?
YES
PRESSURE SWITCH CLOSED?
YES
THERMOSTAT OPENS
LED: SLOW FLASH RATE
COMB. AIR BLOWER OFF (5 sec. delay)
HTG ACC. TERM.DE−ENERGIZED.
INDOOR AIR BLOWER OFF (After selected 60, 90,
120, 180, or 240 delay)?
NO
NO
NO
NO
YES
NO
NO
NO
NO
NO
ABNORMAL HEATING MODE
GAS VALVE OFF. COMB. BLOWER ON. INDOOR
BLOWER ON HEAT SPEED. SEQUENCE HOLDS UNTIL
NO FLAME SENSED OR MAIN POWER IS INTERRUPTED
AND RESET. DIAG. CODE: 1− FLASHING; 2−OFF
(FLAME SENSED WITHOUT VALVE ENERGIZED)
GAS VALVE, COMB. BLOWER AND INDOOR BLOWER
(WITH DELAY) OFF. REMOVE POWER TO RESET
CONTROL. DIAG. CODE: BOTH ON (CONTROL
SELF−CHECK FAILURE OR INCORRECT WIRING)
GAS VALVE, COMB. BLOWER AND INDOOR BLOWER
(WITH DELAY) OFF. SEQUENCE HOLDS UNTIL
ROLL−OUT SWITCH IS MANUALLY CLOSED.
2−FLASHING (FLAME ROLL−OUT OPEN)
GAS VALVE, COMB. BLOWER AND INDOOR BLOWER
(WITH DELAY) OFF. SEQUENCE HOLDS UNTIL
PRESSURE SWITCH CLOSES OR THERMOSTAT
RESETS CONTROL. DIAG. CODE: 1−OFF;
2−FLASHING (C.A.B. PRESSURE SWITCH OPEN)
YES
PRESSURE SWITCH WATCHGUARD CONDITION:
GAS VALVE, COMB. BLOWER AND INDOOR BLOWER
(WITH DELAY) OFF. DIAG. CODE: 1−OFF /
2−FLASHING (C.A.B. PRESSURE SWITCH OPEN) IS 5
MINUTE RESET PERIOD COMPLETE?
GAS VALVE OFF. COMB. BLOWER ON. INDOOR
BLOWER (WITH 45 DELAY) ON. HAS CONTROL FAILED
FLAME SENSE 5 TIMES DURING ONE HEAT DEMAND?
IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD.
DIAG. CODE: 1−ALT. FLASHING / 2−ALT. FLASHING IF
NO, GO TO COMB. AIR BLOWER ON?"
HAS CONTROL RESET IGNITION SEQUENCE 5 TIMES
IF YES, SYSTEM GOES INTO 60 MIN. WATCHGUARD.
DIAG. CODE: 1−ALT. FLASHING / 2−ALT. FLASHING IF
NO, GO TO COMB. AIR BLOWER ON?"
GAS VALVE OFF. COMB. BLOWER OFF. INDOOR
BLOWER ON UNTIL LIMIT CLOSES. DIAG.
CODE: 1−FLASHING / 2−ON (LIMIT OPEN)
IS LIMIT NOW CLOSED?
HAS PRIMARY LIMIT OPENED 5 TIMES DURING
ONE UNSATISFIED HEAT DEMAND. IF YES,
SYSTEM GOES INTO 60 MIN.WATCHGUARD.
DIAG. CODE: 1−FLASHING / 2−ON
IF NO, GO TO COMB. AIR BLOWER ON?"
GAS VALVE, COMB. BLOWER AND INDOOR BLOWER
(WITH DELAY) OFF. DIAG. CODE: 1−OFF / 2−FLASHING
(C.A.B. PRESSURE SWITCH OPEN) HAS C.A.B.
PRESSURE SWITCH CLOSED IN 2.5 MINUTES?
Page 30
DIAG. CODE: 1−ON;
YES
YES
NO