How much does it cost to fix Keston error code B 24?

Typical repair cost for the Keston B 24 fault is £120-250 including labour.

B 24 High

Keston B 24 Fault Code

Q: What does the Keston B 24 fault code mean?

Your boiler has detected that hot water is moving in the wrong direction or the sensors are misreading the temperature, causing the system to stop working to protect itself.

Also written as B24 — same fault.

The Keston B 24 fault code means: your boiler has detected that hot water is moving in the wrong direction or the sensors are misreading the temperature, causing the system to stop working to protect itself.. It appears on 3 Keston models in our database.

Technical description: Return temperature exceeded flow temperature. Check pump direction on boiler and any external pumps. Check wires on flow and return thermistors are not crossed.

Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Keston models that show the B 24 fault code

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

Source

Keston B 24 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

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