BoilerFaultCodesWhat the manual says
Manufacturer manualWaiting time: Water shortage (Product is within the waiting period of the modulation block/operating block function as a result of water deficiency (flow/return spread too large))
What causes this fault?
This fault occurs when the water temperature increases too rapidly within the heat exchanger because it isn't moving through the pipes fast enough to carry the heat away. The most common reasons are a failing internal pump, a build-up of sludge blocking the narrow waterways, or air trapped within the system preventing proper circulation.
This issue is most common when you first switch the heating back on for autumn, as pump components can seize or sludge can settle after being inactive over the summer.
DIY fix possible
Check that all radiator valves (TRVs) are fully openEnsure the boiler pressure is between 1.0 and 1.5 bar on the displayCheck for any blocked magnetic filters or air locks in the radiators
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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