Working on a large chain of stores,there lights are controlled by 240v contactors,
They have employed another company to fit a large timer control box to work them.
This has its own 240v supply, could be any phase!
They then run a multicore to the contacter box using seperate core for some of the contactor coils and removing existing live control wires.
some contactors are left on the old circuits with same existing neutral.
Instead of using a new core for the neutrals. they have left existing control circuit neutrals on the contactors.
This neutral now does the old circuits as well as the new supply contactors.
My concern is to replace the contactors or break the neutrals you would have to isolate both supplys, however if you did not know you would still have voltage and possibly 415v between neutrals
I think this is wrong as they are now bridging across two circuits and in some case two boards, and if old board turned off it would become live due to there neutral feeding back.
I am sure there must be a reg regarding this
does anyone know the number of it so I can prove them this