BoilerFaultCodesYour boiler has shut down because it is getting too hot inside, likely due to a lack of water or a circulation problem.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Heat exchanger overheat: Water pressure/dry; All air vented; Pump/cables/connections; Water leaks/blockages; Safety thermostats/cables/connections; Otherwise replace control board.
What causes this fault?
This fault occurs when the water inside the boiler’s heat exchanger exceeds a safe temperature limit, causing the system to shut down for safety. It is usually triggered by a circulation failure, such as a seized pump or a blockage, which prevents heat from being moved away from the boiler and into your radiators. In some cases, it can also be caused by low water pressure or trapped air preventing the water from flowing correctly through the internal pipework.
This issue is more common during the first cold spell of autumn, when pumps that have been sitting idle all summer can seize up upon restarting.
DIY fix possible
Check the system pressure gauge and top up the water if it is below 1.5 barEnsure all radiator valves and isolation valves are fully openBleed all radiators to remove trapped air from the system
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Slow flash (normally on, flashes off) - 2 — no call-out fees, no surprises.
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Worcester Bosch Greenstar 12Ri 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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