Your boiler has detected an internal error or has become too hot and has safely shut itself down as a precaution.

If the red fault indication light is illuminated, it indicates a fault or overheat condition requiring a reset procedure.

What causes this fault?

This fault occurs when the boiler's internal safety sensors detect that the water temperature has exceeded safe limits or if a component has failed. The most common reasons include a blockage in the system, a pump failure that prevents water from moving, or a build-up of limescale within the heat exchanger. Because the unit cannot safely cool itself down, it shuts off to prevent damage to the internal parts.