Your boiler has stopped working because the electricity supply coming into the unit has dropped below the minimum level required to operate safely.

Low supply voltage

What causes this fault?

This fault occurs when the electrical current entering the boiler drops below 175V, which is too low for the internal components to function. It is usually caused by a temporary fluctuation in the local power grid or an issue with the electrical wiring leading to the boiler. In some cases, a failing main control board inside the unit can also incorrectly detect a voltage drop that isn't actually there.