14− To clean the burner, run a vacuum cleaner with a soft
brush attachment over the face of burners. Visually in-
spect inside the burners and crossovers for any blockage
caused by foreign matter. Remove any blockage.
15− NOx Units − Reattach the NOx inserts to the corbels
at the entrance to each heat exchanger opening. See
figure 32.
16− Replace burner/manifold assembly onto the vestibule
panel.
17− Reconnect wires to pressure switch, roll−out switches,
gas valve and combustion air inducer. Refer to unit wir-
ing diagram.
18− Reconnect vent pipe to combustion air inducer outlet.
19− Reconnect gas supply piping.
20− Turn on power and gas supply to unit.
Repair Parts List
The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model
number listed on the CSA nameplate −− Example: G40UH(X)−24A−045−1.
Cabinet Parts
Upper access panel
Blower panel
Top cap
Control Panel Parts
Transformer
Integrated ignition control board
Door interlock switch
Circuit breaker
Blower Parts
Blower wheel
Motor
Motor mounting frame
Motor capacitor
Blower housing cutoff plate
21− Set thermostat and check for proper operation.
22− Check all piping connections, factory and field, for gas
leaks. Use a leak detecting solution or other preferred
means.
Some soaps used for leak detection are corrosive to
certain metals. Carefully rinse piping thoroughly af-
ter leak test has been completed. Do not use
matches, candles, flame or other sources of ignition
to check for gas leaks.
23− If a leak is detected, shut gas and electricity off and
repair leak.
24− Repeat steps 23 and 24 until no leaks are detected.
25− Replace front access panel.
Heating Parts
Flame sensor
Heat exchanger assembly
Gas manifold
Combustion air inducer
Gas valve
Main burner cluster
Main burner orifices
Pressure switch
Igniter
Primary limit control
Flame rollout switch
Secondary limit (not used on 24A−45−1)
Page 30
CAUTION
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