Clean the heat exchanger combustion chamber

What is going on

Remove the combustion assembly, clean the heat exchanger tubes, then reassemble with new seals. Use a nylon brush and an FDA approved lime scale remover. Do not use solvents. Protect the back wall insulation from water. Wear N95 respirator, gloves and eye protection, and wet the chamber lining to limit dust.

Check in this order

1. Power off and close the gas supply before starting.
2. Remove the silencer.
3. Remove the gas diaphragm if one is fitted.
4. Disconnect the electrode, igniter and blower electrical connections.
5. Unscrew the two nuts and remove the gas pipe.
6. Unscrew the four nuts on the burner door and remove it.
7. Disconnect the condensate hose and siphon cap from the boiler, taking care as condensate may escape.
8. Remove the blower and electrodes.
9. Remove the combustion assembly.
10. Check the back wall insulation and replace it if needed.
11. Spray water or approved solution into the combustion assembly and watch each tube. Liquid must flow freely; if a tube is blocked, increase flow on that tube to force the blockage out.
12. Check the burner for damage and replace it if needed. Replace the burner gasket whenever the burner is replaced.
13. Replace any damaged or deteriorating gaskets.
14. Check the combustion assembly sealing ring and replace it if damaged.
15. Reassemble the combustion assembly and reinstall the electrodes and screws.
16. Reconnect the gas line with a new sealing ring and reconnect the electrode wiring.
17. Reinstall the silencer.
18. Restore power and gas, restart the boiler, check the combustion system for gas leaks and observe for 5 to 10 minutes. Confirm condensate flows normally.

More boiler guides

• Access the low voltage wiring connections
• Blocking errors versus lockout errors
• Blower not running
• Blower runs at high speed with burner off
• Boiler bangs or hisses; Lockout 81 delta T
• Burner not running on a call for heat