BoilerFaultCodesTechnical description
Safety switch-off – overheating temperature reached
What causes this fault?
This fault occurs when the water inside the boiler reaches an illegally high temperature, triggering a safety sensor to shut the system down. The most common reason is that the water isn't moving through the unit quickly enough, often due to a pump failure or a blockage caused by sludge buildup in the pipework. It can also happen if there is trapped air in the system or if the internal divertor valve has become stuck.
This fault is more frequent when the heating is first turned on after summer, as pump components can seize up during months 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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