BoilerFaultCodesYour boiler is heating up too quickly and has shut down to prevent damage, usually because water isn't flowing through the system fast enough.
Book a Gas Safe engineer within 24–48 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 this 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.
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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A boiler cover plan would cover faults like 2966 B — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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