Your boiler has been incorrectly set to a multi-boiler configuration even though it is operating as a single unit.

What causes this fault?

This fault occurs when the boiler's internal computer has been told to look for other boilers to work alongside, but it cannot find any connected. It is usually triggered by an incorrect setting during a software update or if the wrong configuration code was entered when the main circuit board was replaced. Essentially, the boiler is waiting for communication from a 'team' of units that does not exist.