BoilerFaultCodesYour boiler has detected that the water coming back from your radiators is hotter than the water going out, which usually means the water isn't flowing correctly or the sensors are confused.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Return temperature higher than flow
What causes this fault?
This fault occurs when the internal sensors detect that the water returning from your heating system is hotter than the water leaving the boiler, which defies the laws of physics under normal operation. It is almost always caused by a lack of water circulation, meaning the heat cannot escape the boiler and is 'backing up' inside the heat exchanger. The most common reasons are a failed pump, a blockage in the pipework, or a sensor that has developed a fault and is sending the wrong temperature reading to the main board.
This fault is more common when the heating is first turned on after summer, as the circulation pump can often seize or stick after long periods of inactivity.
DIY fix possible
Check that all radiator valves are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barBleed all radiators to remove trapped airRestart the boiler using the reset button
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