508031-02Issue 2135Page 22 of 29
Cleaning the Heat Exchanger and Burners
NOTE: Use papers or protective covering in front of the
furnace during cleaning.
1. Turn o both electrical and gas power supplies to
furnace.
2. Remove 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 intake 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
ve screws from the left side or right side of cabinet.
See Figure 23.
8. Back wash using steam. Begin from the burner
opening on each tube. Steam must not exceed 275°F.
9. To clean burner, remove from the air gas plenum and
run a vacuum cleaner over the face of burner. Visually
inspect inside the burner for any blockage caused
by foreign matter. Remove any blockage. Figure 22
shows burner detail. Replace gasket between burner
plate and air fuel plenum then re-install burner plate.
10. To clean the combustion air inducer visually inspect
and using a wire brush clean where necessary. Use
compressed air to clean o debris and any rust.
11. Reinstall heat exchanger in vestibule. (Replace the
ve screws in the cabinet from step 10 if removed).
12. Reinstall the air fuel plenum and air intake assembly.
Re-install the combustion air inducer assembly. Make
note to re-install all screws. Failure to replace all
screws may cause leaks.
13. 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 eld, 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 after
leak test has been completed. Do not use matches,
candles, ame or other sources of ignition to check for
gas leaks.
CAUTION
19. If a leak is detected, shut gas and electricity o and
repair leak.
20. Repeat steps 24 and 26 until no leaks are detected.
21. Replace access panel.
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