Lochinvar Kettling / Boiling in Heat Exchanger

Heater makes loud banging or knocking noises during operation.

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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

Heavy scale buildup inside heat exchanger, Low water flow, Air pockets in heat exchanger, Incorrect bypass setting

How to Fix / Troubleshooting

Safety: Turn off power and allow the heater to cool before inspection.

Steps:

  • Check water flow: Ensure the pump is running at adequate speed and that the filter is clean. Verify valves are fully open.
  • Inspect bypass: If a bypass is installed, adjust it to increase flow through the heater. Too little flow can cause localized boiling.
  • Bleed air: If the system was recently opened, bleed air from high points and ensure the pump is fully primed.
  • Consider descaling: Persistent banging often indicates scale. A professional can chemically descale the heat exchanger using a circulation pump and approved cleaner.

Do not ignore kettling; it can damage the heat exchanger over time.

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Repair Difficulty

Hard 4/5

Required Part

Heat Exchanger
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