Your boiler has shut down because its internal temperature has become too high, often caused by a lack of water flow or a blockage.

Overheat Lockout

What causes this fault?

This fault occurs when the water inside the boiler gets too hot, triggering a safety sensor to shut the system down to prevent damage. The most common reasons are a pump failure that stops water from moving or a buildup of sludge and debris that creates a blockage in the pipework.