BoilerFaultCodesVokera b24 Fault Code
Also written as B24 — same fault.
The Vokera b24 fault code means: your boiler has detected that the water temperatures are the wrong way around, usually because the water is not flowing through the pipes correctly.. It appears on 1 Vokera model in our database.
Technical description: Temperature differential inverted
What causes the Vokera b24 fault?
This fault occurs when the boiler's sensors detect that the return pipe is hotter than the flow pipe, which is the opposite of how it should function. The most common reasons are a pump failure that prevents water from circulating or a blockage in the heat exchanger that forces the heat to back up. It can also be caused by temperature sensors that have become faulty and are sending incorrect readings to the control board.
This issue often appears when the heating is first turned on after summer, as circulation pumps can seize up during long periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Vokera models that show the b24 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera b24 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