2966 B High

Worcester Bosch 2966 B Fault Code

Also written as 2966B — same fault.

The Worcester Bosch 2966 B fault code means: your boiler is heating up too quickly and has shut down to prevent damage, usually because water isn't flowing through the system fast enough.. It appears on 5 Worcester Bosch models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Flow temperature rise in heat exchanger too rapid

What causes the Worcester Bosch 2966 B fault?

This fault occurs when the water inside the boiler heats up much faster than the system can carry it away, causing the internal safety sensors to shut the unit down. The most common reason is a blockage or a failing pump preventing the hot water from circulating through your radiators. It can also be triggered if your radiator valves are all closed or if there is excessive air trapped in the pipework.

This fault is more frequent in autumn when heating systems are switched back on after a long summer break, as internal pump components can seize during periods of inactivity.

Typical repair cost £120-£350 (including labour)

DIY fix possible

Check that your radiator valves (TRVs) are fully open and not stuck.Ensure the blue filling loop handle is closed and the system pressure is between 1 and 1.5 bar.Restart the boiler using the reset button on the display panel.

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Worcester Bosch models that show the 2966 B fault code

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

Source

Worcester Bosch 2966 B fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026