Lennox EL297UH045XV36B Unit Information page 85

17 - Remove electrical junction box from the side of the
furnace.
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
assembly to cabinet. Remove two screws from
blower rail which secure bottom heat exchanger
flange. Remove 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 engaged 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
blower 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
exhaust drain tubing.
36 - Replace flexible exhaust adapter on combustion air
inducer and flue collar. Secure using two existing
hose clamps.
37 - Reinstall burner box assembly in vestibule area.
Secure 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 furnace 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
after 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.
Remove gas valve/manifold assembly.
5 - Mark and disconnect sensor wire from the sensor.
Disconnect wires from flame rollout switches.
6 - Disconnect combustion air intake pipe. It may be
necessary to cut the existing pipe to remove burner
box assembly.
7 - Remove four screws which secure burner box
assembly 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 blockage 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 burner box cover.
12 - Reconnect wires to gas valve.
13 - Replace the blower compartment access panel.
14 - Refer to instruction on verifying gas and electrical
connections when re-establishing supplies.
15 - Follow lighting instructions to light and operate
furnace 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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CAUTION