Your boiler has shut itself down as a safety precaution because it has detected an internal fault that could lead to overheating or unsafe operation.

REFHI TOO LOW ERROR Temperature measured not correct

What causes this fault?

This fault occurs when the boiler's internal temperature exceeds safe limits, triggering a safety shutdown to prevent damage. The most common reasons are a failure in the pump preventing water from moving through the system, or a faulty sensor incorrectly reporting an overheat. It can also be caused by a blockage in the heat exchanger or air trapped within the unit.