multi core cable

[luap]

had an argument at work today about a 12 core cable and now hes made me unsure. as iv done this many times b4. i ran a 12 core cable in to a junction box from a control panel using 5 for lives 5 for neutrals and using a common earth fusing the lives and using disconect terminals for the neutrals then ran mains rated flex to the instruments which in this case were just monitors. and some bigwig spouted this cant be done as all circuits need there own earth.and this i cant seem to find in the regs book. any help apreciated. thanks

bump..

 

[The Truth]

had an argument at work today about a 12 core cable and now hes made me unsure. as iv done this many times b4. i ran a 12 core cable in to a junction box from a control panel using 5 for lives 5 for neutrals and using a common earth fusing the lives and using disconect terminals for the neutrals then ran mains rated flex to the instruments which in this case were just monitors. and some bigwig spouted this cant be done as all circuits need there own earth.and this i cant seem to find in the regs book. any help apreciated. thanks

bump..

a common earth is allowed for mulitple circuits run in a multicore cable or conduit providing the shared CPC is of adequate size for at least ONE of those circuits treated as if it were on its own. The thinking behind this is that the chance of a simultaneous fault on more than 1 of those separate circuits is miniscule. this is in the book somewhere. i havent checked that in a while but its stuck in my memory

 

[Notsosmart]

The harsh reality is unfortunately that if the company where you are installing the equipment into have specifications that state an earth for each feed, then an earth for each feed you will install, or maybe risk non payment.