Your boiler has detected that the water coming back from your radiators is too hot, which usually means the heat isn't being released into your rooms properly or water isn't flowing 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 too high
What causes this fault?
This fault occurs when the water returning to the boiler is almost as hot as the water sent out, meaning heat isn't being transferred to your rooms. The most common reasons are a pump failure that has stopped water from circulating, or a blockage in the pipework that is trapping hot water inside the boiler. It can also be caused by all your radiator valves being turned off at once, leaving the hot water with nowhere to go.
This issue often surfaces during the first cold spell of autumn when pumps can seize up after being inactive all summer.
DIY fix possible
Check that at least two or three radiators have their valves fully openEnsure your Thermostatic Radiator Valves (TRVs) are not all turned to zeroReset the boiler using the reset button once the system has cooled down
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