BoilerFaultCodesYour boiler has detected that the water returning from your radiators is too hot, which has caused it to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Central heating return sensor overheating
What causes this fault?
This fault occurs when the water traveling back into the boiler from your radiators becomes excessively hot, causing the system to shut down to prevent internal damage. The most common reason is a lack of water circulation, often caused by a failing pump or a buildup of sludge and debris that blocks the main heat exchanger.
This fault is more common when the heating is first turned on after summer, as circulation pumps can seize up during long periods of inactivity.
DIY fix possible
Ensure all radiator valves (TRVs) are fully open and not stuck.Check that the internal boiler pressure is between 1 and 1.5 bar.Reset the boiler using the control knob or button to see if the fault clears.
Find a Gas Safe engineer
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