Your boiler has detected very cold temperatures and is running its internal pump to prevent the water inside from freezing.

Frostprotectionmodeactive

What causes this fault?

This fault occurs when the boiler’s internal sensors detect that the water temperature has dropped to a level where there is a genuine risk of the heat exchanger freezing. It typically happens because the boiler is located in a very cold area, such as a garage or outbuilding, or because a faulty sensor is sending an incorrect freezing signal to the control board. When this happens, the boiler pauses operation as a safety measure to prevent the internal pipework from cracking.