Your boiler is struggling to detect a stable electrical signal from the mains power supply, causing it to shut down as a safety precaution.

Mains supply frequency incorrect - There may be a problem with your power supply.

What causes this fault?

This fault occurs when the boiler's internal computer detects that the incoming electricity from your home is not at the steady frequency it requires to operate safely. The most common reason is an issue with the local power grid or faulty electrical wiring within the property that is interfering with the power signal. In some cases, the boiler's main control board may have developed a fault, causing it to misread an otherwise healthy power supply.