Fondital
Kettling / Thermal Shock in Heat Exchanger
Boiler makes loud banging or knocking noises when starting or stopping heating
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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 Fondital primary heat exchanger, Poor water circulation due to sludge, Incorrect pump speed setting, Air trapped in heat exchanger
How to Fix / Troubleshooting
Safety: No immediate danger in most cases, but turn down the flow temperature to reduce stress until serviced.
User checks:
- Bleed radiators: Remove air from all radiators to improve circulation.
- System pressure: Maintain 1.0–1.5 bar cold.
- Temperature setting: Reduce the heating flow temperature on the Fondital control panel to 60–65°C to lessen noise.
Technician actions:
- Power flush the heating system and clean filters to remove sludge.
- Descale or replace the primary heat exchanger if heavily scaled.
- Check pump speed and operation; adjust or replace the pump if needed.
- Ensure proper venting via the automatic air vent and manual vents.
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Repair Difficulty
Medium
3/5
Required Part
Primary Heat Exchanger
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