Your boiler has shut down completely because its internal computer has lost power or suffered a serious electrical fault.

Appliance lockout and power failure

What causes this fault?

This fault occurs when the boiler's main control board loses its electrical connection or suffers a complete internal failure. It is often caused by a blown fuse, loose wiring, or a power surge that has damaged the electronic components. Without a stable power signal, the boiler's computer cannot manage the safety checks and must shut down for security.