BoilerFaultCodesTechnical description
Flow temperature overheat lockout or no water flow lockout
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature limit or stops moving entirely, triggering a safety shutdown to prevent damage. The most common reasons include a seized pump that isn't circulating the water, a blockage in the pipework caused by sludge, or a faulty sensor that is incorrectly reporting the temperature.
This issue often surfaces when the heating is first turned on in autumn, as central heating pumps can seize up if they have been left inactive throughout the summer.
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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