Hoval Boiler Kettling / Localised Boiling

Boiler makes loud banging or knocking noises (kettling) during operation

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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 buildup in primary heat exchanger, Sludge in system restricting flow, Pump running too slowly, Air pockets in heat exchanger

How to Fix / Troubleshooting

Safety: Noisy boiling can precede overheating. Monitor temperature and pressure; switch off if pressure rises rapidly.

  • Bleed system: Bleed radiators and any high-point vents to remove trapped air. Check the boiler's automatic air vent is open and not leaking.
  • Increase pump speed: Set the circulation pump to a higher speed to improve flow through the heat exchanger.
  • System cleaning: Arrange for a professional chemical clean or power flush of the heating system, followed by fitting a magnetic filter on the return to the Hoval boiler.
  • Descale heat exchanger: In hard water areas, the primary heat exchanger may need to be chemically descaled or replaced by a technician.
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Repair Difficulty

Hard 4/5

Required Part

Primary Heat Exchanger
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