BoilerFaultCodesYour boiler is taking longer than expected to heat up your hot water tank, causing the system to stop as a precaution.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Maximum charging time for a storage without own controller
What causes this fault?
This fault happens when the boiler fails to heat your hot water cylinder within a set time limit, usually because the internal sensors haven't detected a sufficient rise in temperature. The most common cause is a faulty sensor giving an incorrect reading, or a mechanical failure in the diverter valve which prevents heat from actually reaching the water tank.
DIY fix possible
Check that the valves on your hot water cylinder are fully openEnsure your thermostat is calling for hot waterTry resetting the boiler to see if the error clears
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like D.75 — no call-out fees, no surprises.
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