BoilerFaultCodesVokera b30 Fault Code
Also written as B30 — same fault.
The Vokera b30 fault code means: your boiler has detected that water is heating up too quickly or not circulating properly through the system, causing it to shut down for safety.. It appears on 1 Vokera model in our database.
Technical description: Temperature differential exceeded
What causes the Vokera b30 fault?
This fault occurs when the water inside the boiler heats up much faster than the system can carry it away, suggesting a major flow restriction. The most common reasons are a failed pump that isn't pushing the water around or a blockage caused by a buildup of sludge and debris in the main heat exchanger. In some cases, air trapped in the system or closed valves can also prevent the necessary circulation.
This issue is more common in autumn when heating systems are switched back on after being idle all summer, which can cause internal pump components to seize.
DIY fix possible
Check that all radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barBleed all radiators to remove trapped air pockets
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Vokera models that show the b30 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera b30 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