Your boiler has lost power or has a major electrical fault, meaning it cannot provide any heating or hot water despite the fuse board appearing normal.

No red lights (Green light functioning)

What causes this fault?

This fault occurs when the boiler's internal brain loses the ability to distribute power to key components like the fan or pump. It is usually caused by a surge that has blown the internal glass fuses or a complete failure of the transformer on the main circuit board. Because the boiler cannot verify that its safety systems are powered, it shuts down entirely as a precaution.