Lennox G61MPV Service Manual page 106

PROBLEM 7: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
Flash Code
LED X + Y
7.3
Combustion air inducer energizes
with a heating demand.
Burners light.
Roll−out switch trips during the
heating demand.
Diagnostic lights flash roll−out switch
failure.
LED 5 + 1
7.4
Combustion air inducer energizes
with a heating demand.
Burners light roughly and the unit
fails to stay lit.
Diagnostic lights flash watchguard
flame failure.
LED 4 + 3
PREMATURELY (CONT.)
Possible Cause
7.3.1
Unit is firing above 100% of the
nameplate input.
7.3.2
Gas orifices leak at the manifold con-
nection.
7.3.3
Insufficient flow through the heat ex-
changer caused by a sooted or re-
stricted heat exchanger.
7.3.4
Burners are not properly located in
the burner box.
7.3.5
Poor Venting
7.3.6
Improper burner cross−overs
7.4.1
Poor Venting
7.4.2
Improper burner cross−overs
7.4.3
Burrs in gas orifices
Page 106
Corrective Action/Comments
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 the input rate to verify rate
matches value listed on nameplate.
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).
ACTION 1 − Check for sooting deposits or other
restrictions in the heat exchanger assembly.
Clean assembly as outlined in instruction manu-
al.
ACTION 2 − Check for proper combustion.
See IV−Heating System Service Checks
section G−.
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.
ACTION 1 −Check vent pipe and remove any ob-
structions
ACTION 2 − Check for correct exhaust vent
installation. See instructions
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.
ACTION 1 −Check vent pipe and remove any ob-
structions
ACTION 2 − Check for correct exhaust vent
installation. See instructions
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.
ACTION 1 − Remove gas orifices and inspect.
Remove any burrs that are present or replace ori-
fice.