Heat exchanger removal, cleaning and reinstallation

What is going on

Clean the heat exchanger when it is fouled. Remove it from the cabinet, wash it, rinse it fully and put it back in the same position. Steps 1 to 20 are not on these pages.

Check in this order

1. Remove the heat exchanger from the cabinet after removing the blower, primary limit, wiring, pressure switch and burner parts as the earlier steps direct.
2. Back wash the heat exchanger with soapy water or steam. If steam is used, keep it below 275°F (135°C).
3. Rinse and drain the heat exchanger thoroughly, rinsing the whole assembly because soap solutions are corrosive.
4. Reinstall the heat exchanger, making sure the rear baffle sits under the support at the back of the cabinet. Check this through the blower opening.
5. Re-secure the vestibule side screws, the blower rail screws, the blower deck flange screws and the top cap screws.
6. Reinstall the primary limit, wiring, strain relief bushing, pressure switch and its hose to the cold end header collector box.
7. Reinstall the 1/2 inch NPT fitting if removed, reconnect drain tubing, condensate trap and junction box.
8. Reinstall the combustion air inducer with its flexible connector, reconnect its 2 pin plug, and reconnect the drain tubes between the flue collar and cold end header box.
9. Secure the burner assembly to the vestibule with the four existing screws, reconnect gas line, rollout switch, sensor, ignitor and gas valve wires.
10. Replace the blower and heating compartment access panels.
11. Verify gas and electrical connections before restoring supplies, then light the furnace and run it for 5 minutes to confirm the heat exchanger is clean, dry and operating properly.

More furnace guides

• Annual planned service inspection
• Annual service checklist
• Blower access panel and carbon monoxide hazard
• Burner assembly cleaning
• Change blower speed tap
• Check temperature rise and adjust blower speed