Extra earths

[Cj24]

Iv been workin on a job and noticed that on the ring in each of the rooms all the sockets for the computers are wired in 4mm twin but there is also another 2.5 earth pulled round all the sockets too so there is obv 4 earths at each socket, do you knw why this is?

 

[Spudnik]

http://www.electriciansforums.net/e...-electrical-regulations/16348-return-cpc.html

 

[Cj24]

Return cpc? Wat do u mean

 

[Guest123]

Click on it.....

 

[acat]

If you click on return cpc in Jasons post it will open a new thread and explian it to you

Shucks you beat me to it


Chris

 

[Adam W]

Basically when data is 'deleted' the computer dumps it down the cpc, so there can be a relatively high current on the cpc. Off the top of my head it's section 504 in the regs (or at least I think it was it was in 16th ed, when i last looked it up) which requires the cpc to be at least the same csa as the live conductors, known as "high integrity earthing".
T&E uses a smaller csa cpc than live, hence the extra cpc being wired alongside it.

 

[Cj24]

Cheers lads that's really helpful

 

[Cj24]

So u need a same size or slightly bigger cpc then the n and l conductors because of earth leakage on a data ring, so if you dnt pull extra earth in and just use earth out of twin wat will happen, will it trip when all computers are on

 

[nickblake]

high integrety earthing i think , used on IT equipment that has high leakage currents