Lennox G50UHi Series, Unit Information

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PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR INDUCER DOES
NOT ENERGIZE (CONT.).
Condition Possible Cause Corrective Action/Comments
3.3
− Unit operates with a cooling and con-
tinuous fan demand.
− Combustion air inducer will not start
with a Heating demand.
− Diagnostic lights flash the pressure
switch failure code 2.5 minutes after
3.3.1
Miswiring of furnace or improper
connections to combustion air induc-
er.
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
switch failure code 2.5 minutes after
heating demand.
LED#1−Off,
LED#2−Slow Flash
3.3.2
Combustion air inducer failure.
ACTION 1 − If there is 120V to combustion air in-
ducer and it does not operate, replace combus-
tion air inducer.
PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER
ENERGIZES, IGNITOR IS NOT ENERGIZED.
Condition Possible Cause Corrective Action/Comments
4.1
− Unit operates with a cooling and
continuous fan demand.
− Combustion air inducer energizes
with a heating demand
4.1.1
Prove switch does not close due to
incorrect routing of the pressure
switch lines.
ACTION 1 − Check that the prove switch lines are
correctly routed. Correctly route pressure switch
lines.
with a heating demand.
− Diagnostic lights flash the pressure
switch failure code 2.5 minutes after
heating demand.
4.1.2
Prove switch does not close due to
obstructions in the pressure lines.
ACTION 1 − Remove any obstructions from the
the prove lines and/or taps.
g
LED#1−Off
4.1.3
Prove switch lines damaged
ACTION 1 − Check prove switch lines for leaks.
Replace any broken lines.
LED#1 Off
LED#2−Slow Flash
4.1.4
Condensate in prove switch line.
ACTION 1 − Check prove switch lines for conden-
sate. Remove condensate from lines.
4.1.5
Prove switch does not close due to a
low differential pressure across the
prove switch.
ACTION 1 − Check the differential pressure
across the prove switch. This pressure should
exceed the set point listed on the switch.
ACTION 2 − Check for restricted inlet vent. Re-
move all blockage.
ACTION 3 − Check for proper vent sizing and
run length. See installation instructions.
4.1.6
Wrong prove switch installed in the
unit, or prove switch is out of
calibration.
ACTION 1 − Check that the proper prove switch
is installed in the unit. Replace prove switch if
necessary.
4.1.7
Miswiring of furnace or improper
connections at prove switch.
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
4.1.8
Prove switch failure.
ACTION 1 − If all the above modes of failure have
been checked, the prove switch may have failed.
Replace prove switch and determine if unit will
operate.