BoilerFaultCodesYour boiler has shut down because the water in the heating system has become too hot, usually due to 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: Max. CH flow temperature
What causes this fault?
This fault occurs when the water leaving the boiler exceeds its safe temperature limit, causing the system to shut down for safety. The most common reasons are a pump failure that prevents water from moving, or a physical blockage within the pipework or heat exchanger that traps heat inside the unit.
This issue is more frequent during the first cold spell of autumn, when central heating pumps that have been idle all summer often seize up or fail to start.
DIY fix possible
Check that all radiator valves (TRVs) are turned to the highest settingEnsure the system pressure is between 1 and 1.5 bar on the gaugeBleed all radiators to remove trapped air that could be blocking water flow
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 2.5 — no call-out fees, no surprises.
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Worcester Bosch Greenstar 25 HE Combi 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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