BoilerFaultCodesYour boiler has sensed that the water returning from the radiators is hotter than the water leaving the boiler, which usually indicates that water isn't flowing through your system correctly.
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 temperature
What causes this fault?
This fault occurs when the internal sensors detect that the cooling water returning to the boiler is hotter than the water leaving it, which is physically impossible under normal conditions. The most common reason is that the water is stationary due to a pump failure or a blockage, causing heat to build up unevenly around the sensors. In some cases, the sensors themselves may have become faulty or unclipped, sending incorrect temperature readings to the main computer.
This issue often surfaces when the heating is first turned on in autumn, as circulation pumps can seize up after being inactive throughout the summer.
DIY fix possible
Check that all radiator valves are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barRestart the boiler to see if the error clears
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