Your boiler has detected that the water inside the system is becoming dangerously hot and has shut itself down to prevent damage or overheating.

Flow temperature too high

What causes this fault?

This fault occurs when the boiler's main control board experiences a data processing failure or loses connection with internal sensors. It is typically caused by a genuine electronic failure within the computer chip or electrical interference disrupting the signal between components. While a simple reset may temporarily clear it, the code usually indicates that the internal hardware has reached the end of its reliable lifespan.