BoilerFaultCodesYour boiler has likely overheated, causing a safety switch to trip and shut down the system to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Limit thermostat
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a mechanical safety switch to cut off the burner. The most common reasons are a failed pump that isn't moving water efficiently, or a build-up of sludge and debris that is restricting flow through the heat exchanger.
This issue often surfaces in autumn when the heating is turned back on for the first time, as pump components can seize up after being idle over the summer.
DIY fix possible
Check that your radiator valves are open to allow water to flow.Ensure the system pressure is between 1 and 1.5 bar on the pressure gauge.Wait for the boiler to cool down, then turn the mode selector switch to 'OFF/RESET' for a few seconds before switching it back to 'ON'.
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Gas Safe Register →Protect yourself from future repair bills
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