Worcester Bosch Kettling / Localised Boiling in Heat Exchanger

Boiler makes loud banging or kettling noises when heating is on.

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 restricting flow, Pump running too slowly, Air in primary circuit

Safety first: Noisy boilers can indicate overheating. Do not ignore persistent banging or kettling.

Bleed system: Remove air from radiators and high points. Top up pressure afterwards.
Check pump setting: Ensure the pump is set to an appropriate speed (engineer may need to adjust).
Engineer treatment: A professional should chemically clean or powerflush the system, descale the heat exchanger if necessary, and add inhibitor to protect against future scale and sludge.

Hard 4/5

Primary Heat Exchanger

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