BoilerFaultCodesWhat the manual says
Manufacturer manualwaiting time: temperature difference flow - return sensor too high (Check thermistor fit)
What causes this fault?
This fault occurs when heat is building up inside the boiler faster than the water can carry it away to your radiators. The most common reasons are a pump that is beginning to fail, a blockage of sludge in the pipework, or sensors that are providing incorrect temperature readings to the control board.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after being idle all summer, which can cause internal pump components to seize.
DIY fix possible
Check that all radiator valves are fully openEnsure the system pressure is between 1.0 and 1.5 bar on the gaugeBleed all radiators to remove trapped air that could be blocking water flow
Avoid the next call-out bill
A cover plan would handle faults like S.53: no call-out fees, no surprise bills.
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