BoilerFaultCodesYour boiler is overheating because the water inside is heating up too quickly, often caused by a lack of circulation or a blockage.
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 boiler heats up at an unsafe speed, causing the system to shut down to prevent damage. The most common reason is that the water isn't moving through the unit properly, often due to a pump failure, trapped air, or a buildup of sludge blocking the pipework.
This issue often surfaces when the heating is turned back on after summer, as circulation pumps can seize if they haven't been used for several months.
DIY fix possible
Check that all radiator valves are fully openCheck that the boiler pressure is between 1.0 and 1.5 barRestart the boiler to see if the fault clears
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 Response SE is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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