Biasi
Kettling / Localised Boiling in Heat Exchanger
Boiler makes loud banging or knocking noises (kettling) during operation, especially on heating demand.
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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 at too low speed, Incorrect system balancing causing low flow
How to Fix / Troubleshooting
Safety: Allow the boiler to cool before touching any components. Noisy operation can indicate overheating.
- Check system pressure and flow: Ensure the pressure is around 1.0–1.5 bar cold and that all radiator valves are open to allow adequate circulation.
- Bleed radiators: Remove trapped air which can worsen kettling.
- Adjust pump speed: If your Biasi boiler has a multi-speed pump, set it to a higher speed to improve flow (refer to the manual).
- Engineer descaling: A technician may need to chemically descale the primary heat exchanger and flush the system to remove sludge and scale.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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