Vaillant
Kettling / Localised Boiling in Heat Exchanger
Boiler making loud banging or kettling noises when 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 reducing flow, Pump running too slow, Incorrect system balancing
How to Fix / Troubleshooting
Safety: Noisy kettling can precede overheating. Monitor pressure and temperature; switch off if boiler overheats.
- Check system pressure and bleed: Ensure correct pressure and remove air from radiators and high points.
- Clean system filter: If a magnetic filter is fitted, isolate and clean it to improve flow.
- Adjust pump speed: On models with adjustable pumps, set to a higher speed or auto mode as per manual.
- Engineer descaling: In hard water areas, the primary heat exchanger may need chemical descaling or replacement. A powerflush of the heating system may also be recommended.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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