BoilerFaultCodesTechnical description
It will require manual re-setting if an overheat condition occurs (the LED will go Red).
What causes this fault?
This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety shut-off. The most common reasons are a failing pump that isn't moving water away from the boiler quickly enough or a buildup of debris and sludge that is restricting the flow. Essentially, the boiler is generating heat but has no way to vent it into your radiators.
This fault is more frequent in autumn when heating systems are first turned on after a long summer break, as internal pumps often seize 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.