Page 55
PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
PREMATURELY (CONT.)
Condition
Possible Cause
Corrective Action/Comments
6.3
− Combustion air blower energizes
with a heating demand.
− Burners light.
− Roll−out switch trips during the
heating demand.
− Diagnostic lights flash roll−out fail
ure.
6.3.1
Unit is firing above 100% of the
nameplate input.
ACTION 1 −
Check that the manifold pressure
matches value listed on nameplate. See installa
tion instructions for proper procedure.
ACTION 2 −
Verify that the installed orifice size
match the size listed on the nameplate or installa
tion instructions.
ACTION 3 −
Check gas valve sensing hose to in
sure no leaks are present.
ACTION 4 −
Check the input rate to verify rate
matches value listed on nameplate.
ure.
G32−1 through −3 Units Only
LED#1−On
LED#2−Slow Flash
6.3.2
Gas orifices leak at the manifold con
nection.
ACTION 1 −
Tighten orifice until leak is sealed.
NOTE:
Be careful not to strip orifice threads.
ACTION 2 −
Check for gas leakage at the
threaded orifice connection. Use approved meth
od for leak detection (see unit instructions).
LED#2−Slow Flash
G32−5 Units
LED#1−Slow Flash
LED#2−On
6.3.3
Air leakage at the connections be
tween the primary heat exchanger,
secondary heat exchanger, and com
bustion air blower.
ACTION 1 −
Check for air leakage at all joints in
the heat exchanger assembly. Condition may
cause high CO2 with high CO.
ACTION 2 −
Seal leakage if possible (high tem
perature silicon is recommended), replace heat
exchanger if necessary, tag and return heat ex
changer to proper Lennox personnel.
6.3.4
Insufficient flow through the heat ex
changer caused by a sooted or re
stricted heat exchanger.
ACTION 1 −
Check for sooting deposits or other
restrictions in the heat exchanger assembly.
Clean assembly as outlined in instruction manu
al.
ACTION 2 −
For G32V gas furnaces, check for
proper combustion and flow. CO2 should mea
sure between 7.9% and 8.5% for high fire and be
tween 5.5% and 6.3% for low fire. CO should
measure below .04% (400PPM) in an air−free
sample of flue gases.
6.3.5
Burners are not properly located in
the burner box.
ACTION 1 −
Check that the burners are firing into
the center of the heat exchanger openings. Cor
rect the location of the burners if necessary.
6.4
−
Combustion air blower energizes
with a heating demand.
− Burners light roughly and the unit
fails to stay lit.
− Diagnostic lights flash Watchguard
flame failure.
6.4.1
Recirculation of flue gases. This con
dition causes rough ignitions and op
eration. Problem is characterized by
nuisance flame failures.
ACTION 1 −
Check for proper flow of exhaust
gases away from intake vent. Remove any ob
stacles in front of the intake and exhaust vent
which would cause recirculation.
ACTION 2 −
Check for correct intake and exhaust
vent installation.
flame failure.
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
6.4.2
Improper burner cross−overs
ACTION 1 −
Remove burner and inspect the
cross−overs for burrs, or any restriction or if
crossover is warped. Remove restriction or re
place burners.