Roca
Kettling / Water Hammer in Heat Exchanger
Furnace makes loud banging or knocking noises when starting or stopping
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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 Roca heat exchanger, Incorrect pump speed, Air pockets in system, Rapid temperature rise due to low flow
How to Fix / Troubleshooting
Safety first: Turn off power and allow the system to cool before touching pipes or the boiler casing.
- Bleed system: Remove air from radiators and any high-point vents. Refill and pressurize the system correctly.
- Adjust pump speed: Increase pump speed to improve flow through the heat exchanger, reducing rapid boiling.
- Check valves: Ensure all radiator and isolation valves are open and that no bypass valve is incorrectly set.
- Descale (professional): If noises persist, the primary heat exchanger may need chemical descaling or replacement by a technician.
Warning: Severe kettling can damage the heat exchanger. Do not ignore persistent banging noises.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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