BoilerFaultCodesTechnical description
Indicates an overheat condition has occurred requiring a reset of the overheat thermostat.
What causes this fault?
This fault occurs when the water inside the heat exchanger reaches a temperature that is dangerously high, triggering a safety switch to cut off the gas. The most common reasons are a pump failure preventing water from moving through the system or a blockage caused by a build-up of sludge and debris. It can also be caused by a faulty sensor that is incorrectly reporting the temperature to the control board.
This issue is more common during the first cold snap of autumn when a pump that has been idle all summer fails to restart or struggles to move cold, thickened system sludge.
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.