Cleaning the primary heat exchanger

What is going on

Clean the combustion chamber. Required after the first year, then at least yearly. Industrial sites may need more often.

Likely causes

• Deposits in the heat exchanger tubes
• Dirty heat exchanger causing the microfuse to open

Check in this order

1. Remove the heat demand, let post-purge finish, turn gas off and remove power.
2. Swing the control panel out. Disconnect the fan, gas valve, ignition and ionization electrode cabling.
3. Disconnect the stainless steel gas supply pipe at the gas valve inlet union. Discard the old fiber washers.
4. Once the chamber has cooled, remove the four nuts holding the burner assembly. Remove the assembly carefully so the refractory disc behind the burner door is not damaged. Replace refractory if damaged.
5. Check the ignition and ionization electrodes. Clean with a mild abrasive such as steel wool if needed.
6. Cover the refractory at the back of the chamber to keep it dry. Replace it after cleaning if damaged.
7. Vacuum loose debris with a high efficiency filter vacuum.
8. Remove the condensate trap and place a drain under the boiler condensate drain.
9. Wet the chamber with warm water only (no chemicals) using a trigger-nozzle hose to flush between the tubes until the water runs clean. Protect electrical components from water.
10. Clean the condensate trap, then reassemble and connect it (see condensate trap cleaning guide).
11. Reassemble in reverse order. Install new 1/2 in and 3/4 in fiber washers.
12. Check for gas leaks.

More boiler guides

• 0-10 VDC input to modulate firing rate (Mode 5)
• Annual maintenance and inspection
• Blank display
• Boiler pressure keeps dropping / FILL shows
• Boiler shows FILL and will not fire
• Cleaning the combustion side of the heat exchanger