Defro Water Hammer / Boiling in Heat Exchanger

Furnace makes loud banging or knocking noises in the pipes when heating

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.

Possible Causes

Flow rate too low through boiler, Air pockets in system, Overheated boiler due to pump failure, Incorrectly set thermostatic valves

Safety: If you suspect boiling, switch off the burner but leave the circulation pump running to dissipate heat.

Bleed air from radiators and high points in the system.
Ensure all thermostatic radiator valves are not fully closed when the boiler is firing.
Check that the circulation pump is running and set to an adequate speed.
Verify that bypass valves or differential pressure valves are correctly adjusted.

Persistent banging may indicate system design issues; consult a heating engineer.

Medium 3/5

Circulation Pump

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