507868-02
Page 45 of 48
Issue 2128
Cleaning Heat Exchanger
If cleaning the heat exchanger becomes necessary,
follow the below procedures and refer to Figure 1 when
disassembling unit. Use papers or protective covering in
front of furnace while removing heat exchanger assembly.
1. Turn off electrical and gas supplies to the furnace.
2. Remove the furnace access panels.
3. Disconnect the 2 wires from the gas valve.
4. Remove gas supply line connected to gas valve.
Remove gas valve/manifold assembly.
5. Remove sensor wire from sensor. Disconnect 2 pin
plug from the ignitor.
6. Disconnect wires from flame rollout switches.
7. Loosen clamps at vent elbow. Disconnect condensate
drain tubing from flue collar and remove the vent
elbow.
8. Remove four burner box screws at the vestibule panel
and remove burner box. Set burner box assembly
aside.
NOTE:
If necessary, clean burners at this time. Follow
procedures outlined in Burner Cleaning section.
9. Mark and disconnect all combustion air pressure
tubing from cold end header collector box.
10. Mark and remove wires from pressure switches.
Remove pressure switches. Keep tubing attached to
pressure switches.
11. Disconnect the plug from the combustion air inducer.
Remove two screws which secure combustion air
inducer to collector box. Remove combustion air
inducer assembly. Remove ground wire from vest
panel.
12. Remove electrical junction box from the side of the
furnace.
13. 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.
14. Remove the primary limit from the vestibule panel.
15. Remove two screws from the front cabinet flange at
the blower deck. Spread cabinet sides slightly to allow
clearance for removal of heat exchanger.
16.
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.
17. Back wash heat exchanger with soapy water solution
or steam. If steam is used it must be below 275°F
(135°C).
18. Thoroughly rinse and drain the heat exchanger. Soap
solutions can be corrosive. Take care to rinse entire
assembly.
19. Reinstall heat exchanger into cabinet making sure
that the clamshells of the heat exchanger assembly
are resting on the support located at the rear of the
cabinet. Remove the indoor blower to view this area
through the blower opening.
20. Resecure the supporting screws along the vestibule
sides and bottom to the cabinet. Reinstall blower and
mounting screws.
21. Reinstall cabinet screws on front flange at blower
deck.
22. Reinstall the primary limit on the vestibule panel.
23. Route heating component wiring through hole in
blower deck and reinsert strain relief bushing.
24. Reinstall electrical junction box.
25. Reinstall the combustion air inducer. Reconnect the
combustion air inducer to the wire harness.
26. Reinstall pressure switches and reconnect pressure
switch wiring.
27. Carefully connect combustion air pressure switch
hosing from pressure switches to proper stubs on cold
end header collector box.
28. Reinstall condensate trap.
29. Reconnect exhaust piping and exhaust drain tubing.
30. Reinstall burner box assembly in vestibule area.
31. Reconnect flame rollout switch wires.
32.
Reconnect sensor wire and reconnect 2 pin plug from
ignitor.
33. Secure burner box assembly to vestibule panel using
four existing screws. Make sure burners line up in
center of burner ports.
34. Reinstall gas valve manifold assembly. Reconnect gas
supply line to gas valve.
35. Reconnect 2 wires to gas valve.
36. Replace the blower compartment access panel.
37.
Refer to instruction on verifying gas and electrical
connections when re-establishing supplies.
38. 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.
39. Replace heating compartment access panel.
