Worcester Bosch
Primary Heat Exchanger Scaled or Sludged
Boiler makes loud banging or kettling noises when heating water.
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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 heating circuit, Insufficient flow rate through boiler
How to Fix / Troubleshooting
Safety first: Noisy boilers may be overheating; do not ignore. Turn off power if noise is severe and call an engineer.
User checks:
- Ensure all radiator valves are open and that system pressure is correct.
Engineer actions:
- Assess the primary heat exchanger for signs of overheating and restriction.
- Powerflush the heating system with an approved chemical cleaner to remove sludge.
- Descale the primary heat exchanger where appropriate or replace if heavily scaled.
- Verify pump performance and correct bypass setting to maintain adequate flow.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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