Your boiler has shut itself down because it became too hot, likely due to a circulation problem or a component failure.

Overheat cut off device tripped. Thermostat, Overheat cut off device, Water differential pressure switch, or faulty Pump.

What causes this fault?

This fault occurs when the water inside the boiler reaches an unsafe temperature, 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 debris in the pipes that blocks flow. In some cases, the sensor itself may have failed and is incorrectly reporting that the boiler is overheating.