Your boiler has detected very cold temperatures and has turned itself on automatically to prevent the internal pipes from freezing.

Frost protection mode

What causes this fault?

This status occurs when the internal temperature sensor within the boiler drops below 5°C. To protect itself from frost damage, the boiler automatically ignites to warm the primary heat exchanger and circulate water until a safe temperature is reached. It is a built-in safety feature rather than a mechanical failure.