Lennox 80MGF Series User Manual

Page 30
80MGF WITH EGC−2 HEATING SEQUENCE OF OPERATION
NORMAL HEATING MODE
ABNORMAL HEATING MODE
LED: SLOW FLASH RATE
THERMOSTAT CALLS FOR HEAT
LED: FAST FLASH RATE
FLAME OFF?
CONTROL SELF−CHECK OKAY?
COMB. AIR BLOWER PRESSURE SWITCH OPEN?
PRESSURE SWITCH CLOSED WITHIN 2.5 MIN.?
COMB. AIR BLOWER PREPURGE (15 seconds)
HAS FLAME REGISTERED WITHIN 10 SECONDS
AFTER IGNITION TRIAL?
YES
YES
YES
YES
NO
CONTROL MAIN POWER ON"
ROLL−OUT SWITCH CLOSED
YES
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.
DIAG. CODE: 1−ON;
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)
COMBUSTION AIR BLOWER ON?
HTG ACC. TERM. ENERGIZED.
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?
INDOOR AIR BLOWER ON.
(Fixed 45−second delay)
PRIMARY/SECONDARY LIMITS MONITORED IN
HEAT CYCLE. ARE SWITCHES CLOSED?
YES
NO
GAS VALVE OFF. COMB. BLOWER OFF. INDOOR
BLOWER ON UNTIL LIMIT CLOSES. DIAG.
CODE: 1−FLASHING / 2−ON (LIMIT OPEN)
IS LIMIT NOW CLOSED?
PRESSURE SWITCH CLOSED?
YES
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?"
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)?
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?
NO
NO
NO
NO
NO
YES
NO
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?"
IS FLAME SENSED AFTER 10 SECOND
FLAME RECTIFICATION PERIOD?
NO
NO
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?"
YES
YES
YES
YES
IGNITION TRIAL (10 seconds) −− START IGNITION
SPARK, OPEN MAIN GAS VALVE.
YES

Lennox 80MGF Series Specifications

General

Brand	Lennox
Model	80MGF Series
Category	Furnace
Language	English