BoilerFaultCodesYour boiler is heating up too quickly and has shut down to prevent overheating, likely because the water isn't moving through the system properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Maximum temperature - Flow temperature T1 increase too fast
What causes this fault?
This fault occurs when the water inside the heat exchanger reaches its maximum safe temperature almost immediately after the burner ignites. The most common reason is a blockage or a failed pump preventing water from circulating, which causes the stationary water to boil instantly. It can also be triggered by a faulty sensor sending incorrect temperature readings to the boiler's control board.
This issue often surfaces when the heating is first turned on after summer, as the internal pump can seize up during long periods of inactivity.
DIY fix possible
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 bar on the gaugeCheck if the secondary heating pump is running or if there is a blockage in the external pipework
Find a Gas Safe engineer
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A boiler cover plan would cover faults like 925 — no call-out fees, no surprises.
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Ideal Systemiser SE is discontinued — time for a new one?
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