Clean the heat exchanger and combustion chamber

What is going on

Cleaning requires a nylon brush and an FDA-approved liquid lime scale remover. Insulation contains ceramic fiber. Wear a NIOSH-certified N95 respirator, gloves and eye protection, and dampen the lining to limit dust.

Likely causes

• Scale or dirt in the combustion chamber

Check in this order

1. Make sure power and gas are off, and let the boiler cool before draining water.
2. Remove the silencer.
3. Disconnect the gas pipe by unscrewing its two nuts. Remove the gas pipe.
4. Remove the gas diaphragm if one is fitted.
5. Disconnect the electrical connections to the electrodes, igniter and blower.
6. Unscrew the four nuts on the burner door and remove the door.
7. Check the back wall insulation and replace it if needed.
8. Disconnect the condensate hose and siphon cap from the boiler.
9. Clean the heat exchanger with the nylon brush and lime scale remover, then rinse.

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