Lennox EL280UH110P60C Unit Information page 31

Troubleshooting: Heating Sequence of Operation (Continued)
CONTINUED
FIRST−STAGE (LOW FIRE) PRESSURE
1
SWITCH CLOSED WITHIN 2.5 MINUTES?
YES
15−SECOND COMBUSTION AIR INDUCER
PRE−PURGE INITIATED BY CLOSED FIRST−STAGE
PRESSURE SWITCH (or 15 SECOND
INTER−PURGE PERIOD.)
1
STATUS LED −− HEARTBEAT.
IGNITOR WARM−UP (20 SECONDS)
STATUS LED −− HEARTBEAT.
YES
IS IGNITOR INTACT AND CONNECTED?
YES
2
AT END OF IGNITOR 20 SECOND WARM UP
PERIOD, 4−SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS, IGNITOR ENERGIZED DURING
4−SECOND TRIAL UNTIL FLAME SENSED.
YES
4−SECOND FLAME STABILIZATION PERIOD.
FLAME RECTIFICATION CURRENT CHECK
CAN FLAME BE PROVEN WITHIN 4
SECONDS AFTER GAS VALVE OPENS?
(u0.19 microamps)
FLAME PRESENT?
YES
CONTINUED ON NEXT PAGE
If the furnace is operating on continuous fan mode (terminals R" and G" are energized), the combustion
1
air inducer will energize on high speed, the gas valve will energize on second−stage heat and the furnace
will operate on high fire. Furnace will stay on high fire 60 seconds then switch to low fire.
If combustion air inducer is operating on high speed and gas valve is energized on second−
2
stage heat, 20 seconds after flame is sensed furnace will switch to low fire.
HEATING SEQUENCE OF OPERATION
OFF. INDOOR BLOWER OFF. UNIT WILL RETRY
NO
COMBUSTION AIR INDUCER
ENERGIZED ON HIGH SPEED
NO
COMBUSTION AIR INDUCER OFF, IGNITOR OFF.
SIGNAL HOLDS UNTIL VOLTAGE RISES ABOVE 95
NO
FLAME FOR FIVE CONSECUTIVE TRIES
WATCHGUARD MODE. GAS VALVE OFF,
IS 60−MINUTE RESET PERIOD COMPLETE?
NO
HAS CONTROL RESET IGNITION SEQUENCE
Page 31
THERMOSTAT CALLS FOR HEAT
STATUS LED − HEARTBEAT.
(Refer to box A on previous page)
GAS VALVE OFF. COMBUSTION AIR INDUCER
AFTER 5−MINUTE WAIT PERIOD.
STATUS ERROR CODE 2 + 3.
PRESSURE SWITCH
CLOSED WITHIN 30
COMBUSTION AIR INDUCER OFF, IGNITOR OFF.
SIGNAL HOLDS UNTIL IGNITOR IS REPLACED
OR RECONNECTED.
STATUS ERROR CODE 4 + 7.
IS VOLTAGE ABOVE 90 VOLTS?
NO
VOLTS. STATUS ERROR CODE 4 + 8.
GAS VALVE OFF. COMBUSTION AIR
INDUCER ON. INDOOR BLOWER OFF.
STATUS LED −− HEARTBEAT.
HAS CONTROL FAILED TO SENSE
DURING A SINGLE HEAT DEMAND?
YES
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF.
STATUS ERROR CODE 4 + 1.
YES
FOUR (4) TIMES?
WATCHGUARD MODE.
STATUS ERROR CODE 4 + 3.
LOW AND HIGH
NO
YES
SECONDS
YES
NO
YES
NO