IT radial circuit

garlicbread · Posted: Sat Jul 04, 2009 12:22 pm Post Subject: IT radial circuit

can anyone tell me with regards to a radial circuit which will have IT equipment on it, what do you do with the last socket regarding the cpc, obviously on a ring all sockets will have 2 separate cpc's to terminate in separate earting terminals, but what about the last socket on a radial. Is it just a case of linking them.
also im struggling to find out the correct procedure when it comes to earthing galv steel back boxes. if there is a fixed lug on the back box, is a link between socket and back box not required? Struggling to find anything in the regs
cheers

Adam_151 · Posted: Sat Jul 04, 2009 12:31 pm Post Subject:

Quote:

but what about the last socket on a radial. Is it just a case of linking them.

Just to clarify, you are not talking about 2no. radial circuits are you?... just the one? (before someone comes in, skim reads the post and goes off down the wrong track!)

Recessed boxes in the wall do not require an earth flylead to the front plate as long as they have at least one fixed lug (this does not work the other way... a front plate cannot be earthed by screws from an earthed box)

garlicbread · Posted: Sat Jul 04, 2009 12:33 pm Post Subject:

yeah just 1 No radial

Adam_151 · Posted: Sat Jul 04, 2009 12:53 pm Post Subject:

In that case, you'll need a separate earth wire from the DB (minimum size 4mm²), if its a circuit for something like a data cabinet, take the 4mm² earth through the FCU, but dont terminate it there, have it come out and follow the flex to the cabinet and have it bolted to an ECP on the equipment. If its for a socket outlet circuit, then take it to the last socket so that the cpc is effectivly a ring, and do as you would on a ring; use separate terminals

garlicbread · Posted: Sat Jul 04, 2009 12:55 pm Post Subject:

cheers thanks for the info

Chri5 · Posted: Sat Jul 04, 2009 12:56 pm Post Subject:

Standard radial without high integrity earthing (seperate CPC in addition to the one in TE).

Last socket will just have the 1 x CPC, the sockets may have 2 x earth terminals but they WILL link via metalwork manufactured in to the socket.

Good practice is to have a earth 'strapper' cable between the metal back box earth terminal and the socket in ADDITION to the earth that connects via the box -> fixed lug -> screw.

It's a better earthing method and although unlikely, the screw making the earth could become loose, rust, break or be changed for a nylon screw.