BoilerFaultCodesYour boiler has switched itself off to prevent damage because the internal water temperature has become too hot.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Overheat fault
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature limit, triggering a safety shutdown. The most common reasons are a failed pump that isn't moving water around the system or a build-up of sludge and debris that has blocked the flow within the narrow pipes of the heat exchanger.
This issue is more frequent in autumn or winter when the heating is first turned on after a long summer break, as internal pump parts can seize from inactivity.
DIY fix possible
Check that all radiator valves are fully open to allow water to circulateEnsure the boiler pressure is between 1 and 1.5 bar on the digital displayWait for the boiler to cool down and press the 'Reset' button (flame symbol)
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like F20 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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