Cleaning The Burner Assembly - Lennox G43UF SERIES Unit Information

16 − Mark and disconnect any remaining wiring to heating
compartment components. Disengage strain relief
bushing and pull wiring and bushing through the hole in
the blower deck.
17 − Remove the primary limit from the vestibule panel.
18 − Remove two screws from the front cabinet flange at
the blower deck. Spread cabinet sides slightly to allow
clearance for removal of heat exchanger.
19 − Remove screws along vestibule sides and bottom
which secure vestibule panel and heat exchanger as-
sembly to cabinet. Remove two screws from blower
rail which secure bottom heat exchanger flange. Re-
move heat exchanger from furnace cabinet. Do not
remove turbulators or baffles from secondary
heat exchanger.
20 − Back wash heat exchanger with soapy water solution
or steam. If steam is used it must be below 275°F
(135°C) .
21 − Thoroughly rinse and drain the heat exchanger. Soap
solutions can be corrosive. Take care to rinse entire
assembly.
22 − Reinstall heat exchanger into cabinet making sure that
the clamshells of the heat exchanger assembly are
resting on the support located at the rear of the cabi-
net. Remove the indoor blower to view this area
through the blower opening.
23 − Re-secure the supporting screws along the vestibule
sides and bottom to the cabinet.
24 − Reinstall cabinet screws on front flange at blower
deck.
25 − Reinstall the primary limit on the vestibule panel.
26 − Route heating component wiring through hole in blow-
er deck and reinsert strain relief bushing.
27 − Reinstall pressure swtich and reconnect pressure
switch wiring.
28 − Carefully connect combustion air prove switch hos-
ing from prove switch to proper stubs on cold end
header box.
29 − Reinstall condensate collars on each side of the fur-
nace. Reconnect drain tubing to collector box.
30 − Reinstall condensate trap on same side as exhaust
pipe. Reconnect condensate drain line to the conden-
sate trap.
31 − Reinstall electrical junction box.
32 − Reinstall the combustion air inducer. Reconnect the
2−pin plug to the wire harness. Reconnect the two
wires to the secondary limit, if applicable.
33 − Use securing screws to reinstall flue collars to either
side of the furnace. Reconnect exhaust piping and ex-
haust drain tubing.
34 − Replace flexible exhaust tee on combustion air induc-
er and flue collars. Secure using three existing hose
clamps.
35 − Reinstall burner box assembly in vestibule area.
36 − Reconnect flame roll−out switch wires.
37 − Reconnect sensor wire and reconnect 2−pin plug from
ignitor.
38 − Secure burner box assembly to vestibule panel using
four existing screws. Make sure burners line up in
center of burner ports.
39 − Reinstall gas valve manifold assembly. Reconnect
gas supply line to gas valve.
40 − Reinstall burner box cover.
41 − Reconnect wires to gas valve.
42 − Replace the blower compartment access panel.
43 − Refer to instruction on verifying gas and electrical con-
nections when re−establishing supplies.
44 − Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
45 − Replace heating compartment access panel.

Cleaning the Burner Assembly

1 − Turn off electrical and gas power supplies to furnace.
Remove upper and lower furnace access panels.
2 − Mark all gas valve wires and disconnect them from the
valve.
3 − Disconnect the gas supply line from the gas valve. Re-
move gas valve/manifold assembly.
4 − Mark and disconnect sensor wire from the sensor. Dis-
connect 2-pin plug from the ignitor at the burner box.
5 − Remove burner box front cover and remove screws
which secure burner box assembly to vest panel. Re-
move burner box from the unit.
6 − Use the soft brush attachment on a vacuum cleaner to
gently clean the face of the burners. Visually inspect
the inside of the burners and crossovers for any block-
age caused by foreign matter. Remove any blockage.
7 − Reconnect the sensor wire and reconnect the 2−pin
plug to the ignitor wiring harness.
8 − Reinstall the burner box assembly using the existing
four screws. Make sure that the burners line up in the
center of the burner ports.
9 − Reinstall the gas valve manifold assembly. Reconnect
the gas supply line to the gas valve. Reinstall burner
box cover.
10 − Reconnect the gas valve wires to the gas valve.
11 − Replace the blower compartment access panel.
12 − Refer to instruction on verifying gas and electrical con-
nections when re−establishing supplies.
13 − Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
14 − Replace heating compartment access panel.
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