BoilerFaultCodesYour boiler has shut down because it has detected an unsafe build-up of heat or a lack of water circulation within the main unit.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Safety temperature limiter in heat exchanger or flue gas temperature limiter has been activated.
What causes this fault?
This fault occurs when the internal temperature of the boiler rises above a safe limit, causing the system to shut down to prevent damage. The most common reasons are a lack of water flow due to a seized pump, a blockage in the heat exchanger, or air trapped within the pipework. Effectively, the heat being produced by the burner is not being carried away into your radiators quickly enough.
This fault often appears during the first cold spell of autumn when the heating is turned on after a long summer break, as internal pump components can seize during periods of inactivity.
DIY fix possible
Check the pressure gauge on the front of the boiler; if it is below 1 bar, top it up to 1.5 bar using the filling link.Ensure all radiator valves are fully open to allow water to circulate through the system.Press and hold the 'Reset' button for five seconds to see if the error clears once the boiler has cooled down.
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A boiler cover plan would cover faults like E9 — no call-out fees, no surprises.
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Worcester Bosch Greenstar 25i (ZWB 7-25) 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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