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 the water inside the boiler gets too hot too quickly, causing the system to pause to prevent overheating. It is usually caused by a blockage in the pipework or a failing pump that isn't moving the water away from the heat source fast enough. Sometimes it can also be triggered by air trapped in the system or sensors that are no longer reading temperatures accurately.
This issue is frequently seen in autumn when heating systems are turned back on after a long summer break, as internal pump parts can seize during periods of inactivity.
DIY fix possible
Check that all radiator valves (TRVs) are turned to the highest settingEnsure the boiler pressure is between 1.0 and 1.5 bar on the digital displayCheck for any noises that suggest trapped air and bleed your radiators if necessary
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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