BoilerFaultCodesTechnical description
Maximum delta t
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the temperature is rising too rapidly or is too high compared to what the system can handle. The most common reason is a lack of water circulation, often caused by a failing pump or a blockage in the pipework that prevents heat from being carried away from the boiler.
This issue is most frequent when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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