The boiler is noisy with kettling sounds, exhibits poor heat transfer, and experiences frequent overheat trips, but the burner appears to run.

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

Limescale build-up in waterways, sludge accumulation from a dirty system, inadequate inhibitor levels, long-term operation without flushing.

Safety: Allow boiler to cool and isolate power and water before disconnecting any pipework.

Engineer actions:

Assess the primary heat exchanger on the Grant boiler for signs of restriction or hot spots.
Powerflush the heating system with appropriate chemicals to remove sludge and scale.
In severe cases, remove and chemically descale or replace the primary heat exchanger following Grant procedures.
Refill the system with fresh water and a suitable corrosion inhibitor to prevent recurrence.

This is not a DIY repair; specialist equipment is required.

Professional Required 5/5

Primary heat exchanger

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