Ferroli Kettling / Localised Boiling in Heat Exchanger

Boiler makes loud banging or knocking noises (kettling) during operation, especially when heating is on, with no error code.

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.

Possible Causes

Limescale build-up in primary heat exchanger, Sludge in system restricting flow, Pump running at too low speed, Air trapped in heat exchanger

Safety first: Noisy boiling can indicate overheating. Do not ignore persistent loud noises.

Check system pressure: Ensure pressure is correct (1.0–1.5 bar cold). Low pressure can worsen kettling.
Bleed radiators: Remove air from the system to improve circulation.
Engineer actions:
- Assess the primary heat exchanger for scale and perform a chemical descaling if appropriate.
- Powerflush the heating system to remove sludge and restore flow.
- Adjust pump speed or replace the pump if weak.
- Add inhibitor to prevent future scale and corrosion.

Hard 4/5

Primary Heat Exchanger

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