Your boiler has shut down because the internal exhaust gases have reached a dangerously high temperature, triggered by a safety sensor.

Exhaust gas temperature sensor error – excessive temperature alarm.

What causes this fault?

This fault occurs when the gases leaving your boiler's exhaust system become too hot, which can damage internal components. The most common reasons are a significant buildup of debris or limescale inside the heat exchanger or a blockage in the flue pipe that prevents heat from escaping properly. In some cases, the sensor itself may have failed and is sending an incorrect temperature reading to the boiler's computer.