Your boiler has detected that the water temperature has risen too quickly or reached an unusually high level, causing it to shut down to prevent overheating.

Actual temperature: Flow temperature at the flow temperature sensor

What causes this fault?

This fault occurs when water cannot travel through the boiler’s heat exchanger fast enough to carry the heat away, causing a rapid temperature spike. The most common reasons are a failed internal pump, a blockage caused by sludge or debris in the pipework, or air trapped within the system preventing proper circulation.