BoilerFaultCodesYour boiler has shut down because a safety sensor has detected that the internal heat exchanger is getting 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: Safety sensor of the heat exchanger is overheated.
What causes this fault?
This fault occurs when water cannot travel through the boiler fast enough to take the heat away, causing the internal temperature to spike. The most common reasons are a failed pump that isn't pushing water round or a blockage caused by a buildup of sludge and debris in the system. Small air pockets trapped within the heat exchanger can also trigger this safety shutdown.
This issue often appears when the heating is first turned on in autumn, as pumps can seize up after being inactive over the summer months.
DIY fix possible
Check that your radiator valves (TRVs) are fully open to allow water to flow.Ensure there are no blockages or blankets covering the boiler casing.Press the reset button once to see if the fault clears after the system has cooled.
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