BoilerFaultCodesVokera b 30 Fault Code
Also written as B30 — same fault.
The Vokera b 30 fault code means: your boiler has detected that the water is not circulating properly, meaning it is getting too hot inside the unit compared to the temperature of the water being sent out to your radiators.. It appears on 1 Vokera model in our database.
Technical description: Temperature differential exceeded
What causes the Vokera b 30 fault?
This fault occurs when the boiler's internal sensors detect that the water temperature is rising too fast or there is too much of a difference between the flow and return pipes. The most common reason is a blockage in the system or a failing pump that prevents the hot water from moving away from the heat exchanger quickly enough. It can also be caused by air trapped in the boiler or sensors that have become faulty and are giving incorrect readings.
This issue often appears when the heating is first turned on after summer, as the pump can seize or debris can settle in the pipes during the months of inactivity.
DIY fix possible
Check that your radiator valves are open to allow water flowCheck the boiler pressure gauge and top up to 1.5 bar if it is lowBleed your radiators to remove any trapped air pocketsReset the boiler using the control dial
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Gas Safe Register →Vokera models that show the b 30 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera b 30 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