Lennox G27M Series Unit Information

Page 20
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE ABNORMAL HEATING MODE
IGNITION SEQUENCE BEGINS
(Ignition trial counter initiated.)
FLAME RECTIFICATION CURRENT
CHECK
(0.15 microamps)
W2 TIMED MODE
SINGLE STAGE T'STAT
SINGLE-STAGE MODE
HIGH HEAT ONLY
CFM" LED-DS4 BLINKS ONCE
FOR EVERY 100CFM. INDOOR
BLOWER ON LOW SPEED
PREPURGE
15 SECONDS
CFM" LED-DS4 BLINKS ONCE FOR
EVERY 100CFM. INDOOR BLOWER
ON HIGH HEATING SPEED
GAS VALVE
DE-ENERGIZED
NO
IGNITOR WARM-UP
(20 SECONDS)
TWO-STAGE MODE
CALL FOR 1st STAGE HEAT
GAS VALVE OPEN
HIGH AND LOW HEAT
(Ignitor remains energized
for another 1 second.)
MAIN GAS VALVE OPEN
LOW HEAT ONLY
(Ignitor remains energized
for another 1 second.)
MAIN GAS VALVE OPEN
LOW HEAT ONLY
(Ignitor remains energized
for another 1 second.)
SECOND STAGE
TIME ON BEGINS
4 SECONDS
FLAME PRESENT?
(Response time -- 2 seconds maximum.)
"HEAT" LED-DS2 LIT INDOOR BLOWER ON DELAY BEGINS
(45 seconds.)
W2 TIMED MODE
SINGLE STAGE T'STAT
SINGLE-STAGE MODE
HIGH HEAT ONLY
TWO-STAGE MODE
CALL FOR 1st STAGE HEAT
FLAME PRESENT?
(Continuous flame check)
FLAME SIGNAL
(0.7 microamps)
PRIMARY LIMIT SWITCH CLOSED?
ROLLOUT SWITCH CLOSED?
PRESSURE SWITCH CLOSED?
(CONTINUED ON NEXT PAGE)
CONTROL CHECKS RETRY
FOR IGNITION COUNT.
HAVE FOUR RETRIES
BEEN COMPLETED?
WATCHGUARD -- FLAME FAILURE.
GAS VALVE OFF.
COMBUSTION AIR BLOWER OFF.
INDOOR BLOWER OFF.
LED #1 & LED #2 ALTERNATE FLASH.
NO YES
LOW FLAME SIGNAL
LED #1 -- SLOW FLASH
LED #2 -- FAST FLASH
GAS VALVE DE-ENERGIZED.
COMBUSTION AIR BLOWER DE-ENERGIZED.
INDOOR BLOWER ON.
LED #1 - SLOW FLASH; LED #2 - ON.
GAS VALVE DE-ENERGIZED.
COMBUSTION AIR BLOWER DE-ENERGIZED.
INDOOR BLOWER OFF DELAY (Selected time)
LED #1 -- ON
LED #2 -- SLOW FLASH
WATCHGUARD 60MINUTE DELAY
(SIGNAL LIMIT OR IGNITION FAILURE)
GAS VALVE OFF. COMBUSTION AIR
AND INDOOR BLOWER OFF.
LED #1 AND LED #2
ALTERNATING SLOW FLASHES
NO
NO
NO
NO
HAS LIMIT RESET?
(See table 1 DIAGNOSTIC CODES for limit reset operation)
YES
NO
CONTINUED ON NEXT PAGE
WATCHGUARD 60MINUTE DELAY
LIMIT SWITCH. GAS VALVE OFF.
COMBUSTION AIR AND INDOOR
BLOWER OFF. LED #1 SLOW FLASH
AND LED #2 ON. IS 60 MINUTE RESET
PERIOD COMPLETE?
YES

Lennox G27M Series Specifications

General

Brand	Lennox
Model	G27M Series
Category	Furnace
Language	English