Intergas
Kettling / Localised Boiling in Heat Exchanger
Boiler makes loud banging or knocking noises (kettling) during operation
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Limescale build-up in primary heat exchanger, Sludge in system reducing flow, Incorrect pump speed, Air in heat exchanger
How to Fix / Troubleshooting
Warning: Kettling indicates overheating in the heat exchanger. Prolonged operation can damage the boiler.
- Check system pressure: Ensure pressure is 1.0–1.5 bar. Low pressure can worsen kettling.
- Bleed radiators: Remove air from the system to improve circulation.
- Reduce flow temperature: Temporarily lower the CH flow temperature on the boiler controls to reduce stress on the heat exchanger.
- Water quality treatment: Arrange for a heating engineer to powerflush the system, add inhibitor, and, if necessary, perform a chemical descaling of the primary heat exchanger.
- Engineer tasks: The engineer will assess the level of scale/sludge, clean or replace the primary heat exchanger, and verify correct pump operation.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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