BoilerFaultCodesYour boiler has switched itself off because it has reached an unsafe temperature and needs to cool down before it can restart.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Over heat cut off activated | Cause: Maximum temperature exceeded
What causes this fault?
This fault occurs when the water inside the boiler gets too hot, triggering a safety switch to prevent damage. The most common reason is that the water isn't moving through the system quickly enough, often due to a pump failure or a blockage in the pipework. It can also happen if the sensors that monitor temperature become faulty and send the wrong information to the boiler control board.
This issue often appears when you first turn the heating back on in autumn, as internal pump parts can seize up after being idle over the summer.
DIY fix possible
Check that your radiator valves are fully open to allow water to flow.Ensure there is enough water pressure in the system (typically 1.0 to 1.5 bar).Press the 'Reset' button (flame symbol with a cross) once the boiler has cooled down.
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A boiler cover plan would cover faults like F.20 — no call-out fees, no surprises.
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