Lennox 80UHG3-60 - Burners Light Prematurely Shut Down (Cont.)

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PROBLEM 5: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
PREMATURELY (CONT.)
Condition Possible Cause Corrective Action/Comments
5.3
- Combustion air inducer energizes
with a heating demand.
- Burners light.
- Roll-out switch trips during the
heating demand.
Diagnostic lights flash roll out fail
5.3.1
Unit is firing above 100% of the
nameplate input.
ACTION 1 - Check that the manifold pressure
matches value listed on nameplate. See installaĆ
tion instructions for proper procedure.
ACTION 2 - Verify that the installed orifice size
match the size listed on the nameplate or instalĆ
lation instructions.
ACTION 3 - Check the input rate to verify rate
matches value listed on nameplate.
- Diagnostic lights flash roll-out failĆ
ure.
LED#1-On
5.3.2
Gas orifices leak at the manifold conĆ
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
method for leak detection (see unit instructions).
LED#1 On
LED#2-Slow Flash
5.3.3
Insufficient flow through the heat exĆ
changer caused by a sooted or reĆ
stricted heat exchanger.
ACTION 1 - Check for sooting deposits or other
restrictions in the heat exchanger assembly.
Clean assembly as outlined in instruction manuĆ
al.
ACTION 2 - Check for proper combustion. See
NO TAG Heating System Service Checks secĆ
tion NO TAG.
5.3.4
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. CorĆ
rect the location of the burners if necessary.
5.4
- Combustion air inducer energizes
with a heating demand.
- Burners light roughly and the unit
5.4.1
Poor Venting
ACTION 1 -Check vent pipe and remove any obĆ
structions
ACTION 2 - Check for correct exhaust vent
installation. See instructions
Burners
light
roughly
and
the
unit
fails to stay lit.
- Diagnostic lights flash watchguard
flame failure.
5.4.2
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 reĆ
place burners.
LED#1-Alternating Slow Flash
LED#2-Alternating Slow Flash
5.4.3
Burrs in gas orifices
ACTION 1 - Remove gas orifices and inspect.
Remove any burrs that are present or replace
orifice.
5.5
- Combustion air inducer energizes
with a heating demand.
- Burners light.
- Diagnostic lights flash watch guard
flame failure.
- NOTE" Unit might go into 60 minĆ
ute Watchguard mode depending on
5.5.1
Loose sensor wire connection
causes intermittent loss of flame sigĆ
nal.
ACTION 1 - Check that the sensor is properly loĆ
cated.
ACTION 2 - Check that the sense wire is properĆ
ly attached to both the sensor and the control.
Pay extra attention to the pin connectors.
ute Watchguard mode depending on
intermittent nature of sensor signal.
LED#1-Alternating Slow Flash
LED#2-Alternating Slow Flash
5.5.2
Poor ground to burner box
ACTION 1 - Check for proper ground and repair
as necessary.