BoilerFaultCodesYour boiler has detected that the temperature in your underfloor heating system has exceeded its safety limit, causing the boiler to shut down to prevent damage to your floors or pipework.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Under-floor system temperature fault
What causes this fault?
This fault occurs when the water temperature entering your underfloor heating loops exceeds a safe threshold, triggered by a safety thermostat. The most common reasons are a failure in the external mixing valve that regulates heat or a pump failure that prevents hot water from moving through the system quickly enough. It is designed to prevent excessive heat from warping floorboards or damaging sensitive pipework.
This fault is more common in autumn and winter when the underfloor heating is first switched on after a long period of inactivity, which can lead to seized pumps or stuck valves.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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