Buderus Kettling / Boiling in Heat Exchanger

The water heater makes loud banging or knocking noises during operation.

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

Heavy scale buildup in the heat exchanger, insufficient water flow, air trapped in the system, incorrect pump speed setting

Safety: Turn off power and gas. Allow the unit to cool before touching the piping.

Bleed air: Open air vents or bleed valves on the heater and system to remove trapped air.
Check the pump and valves: Ensure the circulation pump is running and that all isolation valves are fully open.
Descale the heat exchanger: Connect a flushing pump and circulate an approved descaling solution through the heat exchanger until noise is reduced.
Adjust the pump speed: If the pump has adjustable speeds, set it according to Buderus recommendations to ensure adequate flow.
Test operation: Restore power and gas, then run the heater and listen for reduction in noise.

Hard 4/5

Primary Heat Exchanger / Circulation Pump

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