Cleaning The Burner Assembly - Lennox ML296UHV(X) Series Manual

17 - Remove electrical junction box from the side of the fur­
nace.
18 - 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.
19 - Remove the primary limit from the vestibule panel.
20 - Remove two screws from the front cabinet flange at
the blower deck. Spread cabinet sides slightly to allow
clearance for removal of heat exchanger.
21 - 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.
22 - Back wash heat exchanger with soapy water solution
or steam. If steam is used it must be below 275°F
(135°C) .
23 - Thoroughly rinse and drain the heat exchanger. Soap
solutions can be corrosive. Take care to rinse entire
assembly.
24 - Reinstall heat exchanger into cabinet making sure that
the clamshells of the heat exchanger assembly is en­
gaged properly into the support bracket on the blower
deck. Remove the indoor blower to view this area
through the blower opening.
25 - Re‐secure the supporting screws along the vestibule
sides and bottom to the cabinet.
26 - Reinstall cabinet screws on front flange at blower
deck.
27 - Reinstall the primary limit on the vestibule panel.
28 - Route heating component wiring through hole in blow­
er deck and reinsert strain relief bushing.
29 - Reinstall electrical junction box.
30 - Reinstall the cold end header box.
31 - Reinstall the combustion air inducer. Reconnect the
plug to the wire harness.
32 - Reinstall pressure switches and reconnect pressure
switch wiring.
33 - Carefully connect combustion air pressure switch
tubing from pressure switches to proper ports on
cold end header collector box.
34 - Reconnect condensate drain line to the cold end
header box.
35 - Use securing screws to reinstall flue collar to the top
cap on the furnace. Reconnect exhaust piping and ex­
haust drain tubing.
36 - Replace flexible exhaust adapter on combustion air in­
ducer and flue collar. Secure using two existing hose
clamps.
37 - Reinstall burner box assembly in vestibule area. Se­
cure burner box assembly to vestibule panel using
four existing screws. Make sure burners line up in
center of burner ports
38 - Reconnect flame roll-out switch wires.
39 - Reconnect sensor wire and reconnect 2-pin plug from
ignitor.
40 - Reinstall gas valve manifold assembly. Reconnect
gas supply line to gas valve.
41 - Reconnect the combustion air intake pipe.
42 - Reinstall burner box cover.
43 - Reconnect wires to gas valve.
44 - Replace the blower compartment access panel.
45 - Reconnect gas supply piping. Turn on power and gas
supply to unit.
46- Follow lighting instructions on unit nameplate to light
and operate furnace for 5 minutes to ensure the fur­
nace is operating properly.
47- Check all piping connections, factory and field, for gas
leaks. Use a leak detecting solution or other preferred
means.
48- Replace heating compartment access panel.
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.
Cleaning the Burner Assembly (if needed)
1 - Turn off electrical and gas power supplies to furnace.
Remove upper and lower furnace access panels.
2 - Disconnect the wires from the gas valve.
3 - Remove the burner box cover (if equipped).
4 - Disconnect the gas supply line from the gas valve. Re­
move gas valve/manifold assembly.
5 - Mark and disconnect sensor wire from the sensor. Dis­
connect wires from flame rollout switches.
6 - Disconnect combustion air intake pipe. It may be nec­
essary to cut the existing pipe to remove burner box
assembly.
7 - Remove four screws which secure burner box assem­
bly to vest panel. Remove burner box from the unit.
8 - 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.
9 - Reinstall the burner box assembly using the existing
four screws. Make sure that the burners line up in the
center of the burner ports.
10 - Reconnect the sensor wire and reconnect the 2-pin
plug to the ignitor wiring harness. Reconnect wires to
flame rollout switches.
11 - Reinstall the gas valve manifold assembly. Reconnect
the gas supply line to the gas valve. Reinstall the burn­
er box cover.
12 - Reconnect wires to gas valve.
13 - Replace the blower compartment access panel.
14 - Refer to instruction on verifying gas and electrical con­
nections when re-establishing supplies.
15 - 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.
16 - Replace heating compartment access panel.
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