BoilerFaultCodesYour boiler has detected that the water is heating up too quickly or isn't circulating properly, causing it to shut down to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Temperature differential exceeded
What causes this 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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A boiler cover plan would cover faults like b30 — no call-out fees, no surprises.
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