F24 High

Saunier Duval F24 Fault Code

The Saunier Duval F24 fault code means: your boiler has stopped working because the water returning from your radiators has become too hot, which usually means the water isn't circulating properly through the system.. It appears on 1 Saunier Duval model in our database.

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Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Central heating return temperature is greater than90°C

What causes the Saunier Duval F24 fault?

This fault occurs when the water returning to the boiler is too hot, which happens when heat cannot be transferred away into your radiators effectively. The most common reasons are a pump failure that has stopped water from moving, or a blockage caused by a build-up of sludge and debris in the pipework.

This fault often appears during the first cold spell of autumn when the heating is turned back on after being idle all summer, which can cause internal pump components to seize.

Typical repair cost £120-350 (including labour)

DIY fix possible

Check that all radiator valves (TRVs) are fully openEnsure the boiler pressure is between 1.0 and 1.5 barCheck if any bypass valves in your pipework are accidentally closed

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Saunier Duval models that show the F24 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Saunier Duval F24 fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026