BoilerFaultCodesYour boiler has switched itself off because it has detected that it is getting too hot, likely due to a circulation issue 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: Flue overheat, Heat exchanger overheat, or Flue blockage. Possible solution/check: Heat exchanger blocked, Heat exchanger baffles removed, Water pressure, All air vented, Pump / harness / connections, Water leaks / blockages, Safety thermostats / low voltage wiring harness / connections, Blockage in flue system, Otherwise replace control board.
What causes this fault?
This fault occurs when internal sensors detect that the boiler's heat exchanger or flue gases have reached a dangerously high temperature. It is most commonly caused by a lack of water flow, which prevents the heat from being carried away from the unit, or a physical blockage within the pipework or flue system.
This issue often surfaces during the first cold snap of autumn when heating systems are turned back on after a long summer break, causing older pumps to seize.
DIY fix possible
Check if your central heating pressure is between 1 and 1.5 bar on the pressure gauge.Ensure all radiator valves are fully open and any air has been bled from the radiators.Press and hold the reset button for five seconds to see if the fault clears.
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A boiler cover plan would cover faults like Blue light: Slow flash (normally on, flashes off), Lockout reset button: Flashing (reset required) — no call-out fees, no surprises.
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Worcester Bosch Greenstar 12i System 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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