Lennox G50UHi Unit Information page 21

Cleaning the Heat Exchanger and Burners
WARNING
Safety glasses should be worn when cleaning heat
exchanger
NOTE − Use papers or protective covering in front of the fur-
nace during cleaning.
Cleaning the heat exchanger requires a steel spring
snake," a reversible drill and a vacuum cleaner. The steel
spring snake may be constructed by purchasing a 4 ft. long
by 1/4 inch diameter steel wire cable and a 1/4 inch diame-
ter wire brush. These items are available at a hardware
store. Insert wire end of brush into the open end of the
spring cable. Crimp the cable around the brush so that the
brush is secured and will not come off during cleaning. At-
tach the other end of the cable to the reversible drill to com-
plete the tool for cleaning the heat exchanger.
1 − Turn off both electrical and gas power supplies to fur-
nace.
2 − Remove flue pipe and top cap from the unit. Label the
pressure switch wires, then disconnect them.
3 − Remove the four screws that secure the combustion air
inducer. Carefully remove the combustion air inducer to
avoid damaging blower gasket. If gasket is damaged, it
must be replaced to prevent leakage.
G50UHi BURNER & HEAT
EXCHANGER REMOVAL
HEAT EXCHANGER
BURNER BOX ASSEMBLY
FIGURE 23
4 − Remove the collector box located behind the combus-
tion air inducer. Be careful with the collector box gas-
ket. If the gasket is damaged, it must be replaced to
prevent leakage.
5 − Label the wires from gas valve and rollout switches,
then disconnect them.
6 − Disconnect gas supply piping. Remove four screws se-
curing the burner manifold assembly to the vestibule
panel and remove the assembly from the unit.
7 − Insert the brush end of cable snake into the top of one
of the heat exchanger openings. Do not force the
cable into the heat exchanger. Insert the cable and
operate the drill on slow speed. Move the cable in and
out of the heat exchanger section three or four times or
until sufficient cleaning is accomplished. Reverse drill
and slowly work the cable out of opening.
8− Repeat procedure for each heat exchanger section.
9− After each of the top heat exchanger sections has been
cleaned, insert the brush end of the cable snake into
the bottom openings of each of the heat exchanger
sections and clean as described in step 8.
10− Remove the cable from the heat exchanger. Use a vac-
uum cleaner to remove debris knocked loose during
cleaning.
11− Attach the exhaust end (positive pressure) of the vacu-
um cleaner to the top of the heat exchanger section.
Any loose debris will be forced to the bottom of the heat
exchanger section. Vacuum debris from bottom open-
ings.
NOTE − Take care not to inhale loose debris. Surgical
mask should be worn when using vacuum cleaner.
12− Replace collector box and combustion air inducer.
Check gaskets for damage. Damaged gaskets must be
replaced to avoid heat exchanger leaks. Replace all
screws to the collector box and combustion air inducer.
Failure to replace all screws may cause leaks.
13− 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.
14− Replace burner/manifold assembly onto the vestibule
panel.
15− Reconnect wires to pressure switch, roll−out switches,
gas valve and combustion air inducer. Refer to unit wir-
ing diagram.
16− Reconnect vent pipe to combustion air inducer outlet.
17− Reconnect gas supply piping.
18− Turn on power and gas supply to unit.
19− Set thermostat and check for proper operation.
20− 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.
21− If a leak is detected, shut gas and electricity off and
repair leak.
22− Repeat steps 23 and 24 until no leaks are detected.
23− Replace front access panel.
Page 21
CAUTION