How much does it cost to fix Vokera error code b 25?

Typical repair cost for the Vokera b 25 fault is £150-300 including labour.

b 25 High

Vokera b 25 Fault Code

Q: What does the Vokera b 25 fault code mean?

Your boiler is overheating because it cannot circulate heat away from the burner fast enough, so it has safely shut itself down to prevent damage.

Also written as B25 — same fault.

The Vokera b 25 fault code means: your boiler is overheating because it cannot circulate heat away from the burner fast enough, so it has safely shut itself down to prevent damage.. It appears on 1 Vokera model in our database.

Technical description: Excessive temperature rise

What causes the Vokera b 25 fault?

This fault occurs when the water inside the boiler heats up at an unnaturally fast rate, causing the sensors to trigger a safety shutdown before the unit overheats. The most common reason is a lack of water flow, often caused by a failing internal pump or a blockage in the system that prevents heat from being moved away from the burner quickly enough.

This issue often appears when the heating is first turned on after summer, as the circulation pump can seize up after long periods of inactivity.

Typical repair cost £150-300 (including labour)

DIY fix possible

Check that all radiator valves are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barPress the reset button once the boiler has cooled down

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Vokera models that show the b 25 fault code

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

Hydra Repair: £150-300

Source

Vokera b 25 fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.

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