Lennox SL280UHNV Series

Page 35
10 - To clean the combustion air inducer visually inspect
and using a wire brush clean where necessary. Use
compressed air to clean off debris and any rust.
11 - Reinstall heat exchanger in vestibule. (Replace the
fi ve screws in the cabinet from step 7 if removed).
12 - Reinstall the air fuel plenum and air intake
assembly. Make note of the numbered sequence
when re-installing the air fuel plenum. Follow the
sequence as shown in Figure 20. Torque screws to
a maximum of 100 + 5 in - lbs. and a minimum 60
in - lbs.
13 - Re-install the combustion air inducer assembly.
Make note to re-install all screws. Failure to replace
all screws may cause leaks. Reconnect all wires.
14 - Reconnect top cap and vent pipe to combustion air
inducer outlet.
15 - Reconnect gas supply piping.
16 - Turn on power and gas supply to unit.
17 - Set thermostat and check for proper operation.
18 - Check all piping connections, factory and fi eld, for
gas leaks. Use a leak detecting solution or other
preferred means.
CAUTION
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, fl ame or other sources of ignition to check for
gas leaks.
19 - If a leak is detected, shut gas and electricity off and
repair leak.
20 - Repeat steps 18 and 19 until no leaks are detected.
21 - Replace access panel
A-Heat Exchanger and Burners Figure 20
Cleaning the Heat Exchanger and Burners
NOTE - Use papers or protective covering in front of the
furnace during cleaning.
1 - Turn off both electrical and gas power supplies to
furnace.
2 - Remove fl ue pipe and top cap (some applications
top cap can remain) from the unit.
3 - Label the wires from gas valve, thermal switch,
primary limit switch and make-up box then
disconnect them.
4 - Remove the screws that secure the combustion air
inducer to the collector box.
5 - Disconnect gas supply piping. Remove the screw
securing the air fuel plenum and remove along with
the air inake assembly as one component.
6 - Remove screws from both sides, top and bottom of
vestibule panel.
7 - Remove heat exchanger. It may be necessary
to spread cabinet side to allow more room. If so,
remove fi ve screws from the left side or right side of
cabinet. See Figure 21.
8 - Back wash using steam. Begin from the burner
opening on each tube. Steam must not exceed
275°F.
9 - To clean burner and intake debris screen, run a
vacuum cleaner over the face of burners. Visually
inspect inside the burner. Remove any blockage.
Figure 20 shows burner detail. Replace gasket
between burner plate and air fuel plenum then re-
install burner plate.