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Heat Exchanger and Burners Figure 21
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 flue 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
five screws from the left side or right side of cabinet.
See Figure 20.
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 21
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 off debris and any rust.
11. Reinstall heat exchanger in vestibule. (Replace the
five 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 21. 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.
31-5000734 Rev. 0
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 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 after
leak test has been completed. Do not use matches,
candles, flame 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.
Remove 5 screws if necessary
(cabinet for reference only)
Page 33
CAUTION
1
2
3
4
5
Figure 20.
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