BoilerFaultCodesYour boiler is overheating because the water inside it is getting too hot too quickly or isn't circulating properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Temperature difference/pressure too high
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water is heating up much faster than it can be moved away into your radiators. The most common reason is a blockage in the pipework or a failing pump that is no longer able to push the water through the system efficiently. It can also be caused by a build-up of limescale inside the heat exchanger, which acts like a physical barrier to the water flow.
This issue often comes to light in autumn when the heating is turned back on after a long summer break, as pumps can seize and sludge can settle during periods of inactivity.
DIY fix possible
Check that your radiator valves are fully open to allow water flowCheck that the boiler pressure is within the green zone (typically 1 to 1.5 bar)Restart the boiler to see if the fault clears
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A boiler cover plan would cover faults like AA — no call-out fees, no surprises.
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Worcester Bosch WR325 RSF 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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