BoilerFaultCodesWhat the manual says
Manufacturer manualOverheat fault
From this model's manual
Verified against the Glow Worm Cxi Csi System installation & service manual, page 37.
What causes this fault?
This fault occurs when the internal temperature of the boiler exceeds safe limits, triggering a safety sensor to cut the power. It is usually caused by a lack of water flow, often due to a pump failure or a blockage in the main heat exchanger that prevents heat from being carried away from the burner.
This issue often surfaces when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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