Grant
Kettling Due to Scale or Sludge
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 on heat exchanger surfaces, Sludge in primary circuit, Poor water circulation, Incorrect system design flow rate
How to Fix / Troubleshooting
Safety: No immediate danger in most cases, but turn down the boiler thermostat slightly to reduce stress until serviced.
User actions:
- Reduce the boiler flow temperature setting slightly to lessen noise.
- Ensure all radiator valves are open to improve circulation.
Engineer actions:
- Assess the level of sludge and scale in the system; consider a powerflush.
- Apply a chemical descaler to the Grant boiler’s primary circuit if recommended by the manufacturer.
- Install or clean a magnetic filter on the return to the boiler.
- Balance the system and verify correct pump speed.
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Repair Difficulty
Medium
3/5
Required Part
Primary heat exchanger
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