Vokera
Kettling / Localised Boiling in Heat Exchanger
Boiler makes loud banging or kettling noises during operation, especially on heating
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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, Poor circulation due to partially blocked pipes, Pump running at incorrect speed
How to Fix / Troubleshooting
Safety first: No immediate danger in most cases, but persistent kettling can damage the boiler. Do not remove covers while the boiler is hot.
- Check system pressure: Ensure it is within the recommended range.
- Bleed radiators: Remove trapped air which can worsen noise.
- Engineer tasks:
- Assess water quality and check for sludge.
- Powerflush the system and add inhibitor.
- Descale or replace the primary heat exchanger if heavily scaled.
- Adjust pump speed and check bypass operation.
Kettling is common in hard water areas and should be addressed to prevent premature failure.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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