Why? The earth loop integrity surely is potentially compromised by a single accessory failure, but if you take the ring in and ring out cpcs to the same terminal then the loop is more robust against long term failure by (for instance) corrosion on the hollow rivets on the strap across the back of a twin socket. (Yes I have seen it)
AWEM
On Thursday 07 March 2013 15:00 Andrew Mawson wrote in uk.d-i-y:
Counter argument: Earth integrity to the accessory is dependent on one terminal, whereas with two terminals both would have to fail.
You might argue you do not worry with radial sockets and lighting, but the option is not there. It is with a ring, so it makes sense to add it in to the safety factors available.
Loop integrity is not important compared to earth integrity at every accessory.
On Thursday 07 March 2013 14:56 Mike Tomlinson wrote in uk.d-i-y:
I was trying to remember where I got it from. It's not in the IEE On Site or the NIC Snags and Solutions for Earthing and Bonding.
Now I remember it was taught by the bloke who did my EAL Installers course. However, I do agree with him and prefer to use multiple terminals in a ring circuit. However, if you think the other way is better, there's no regulation or guide that makes "my" way better :-o
Presumably that's why there are two earth terminals on a double socket?
I've never seen both of them used - bear in mind I only do like for like swaps, not installations.
Not all double sockets have two earth terminals.
Maybe I should sit here doing nothing but thinking up new ways of describing things that have been perfectectly acceptable for eons as some seem to be doing.
+1.
Isnt that the EU's job?
Buried in te back of my mind is the SF story about a society in which no one works except the very few that can get government funding for projects...two chaps decide that the solution is to apply for funding for a projectt to determine and asist people in finding new catepgores of things that attract government fudning.
I laughed.
Till I actually visited a company funded by the EU...
Of the ten staff, nine were employed in getting funding, and the tenth didnt appear to be doing anything at all..
I only had a quick read but the example about metal cases on computes going live made sense; I had never understood what high integrity earth was before.
However, I think it says to use 4mm^2 for the separate CPC. Why is that when the "first" one will be 1.5mm^2?
TIA
So do I, but that's because it's just one uncut wire, folded over in the screw terminal, and same with the live and neutral. I have installed several ring circuits, each conductor being a single uncut length of copper around the whole ring. That way, you can't get a situation where only one of the conductors is properly connected in the terminal, and there's no summing of contact resistances around the ring - you have at most 2 connections in the path (in each conductor), one at the CU and the other at the socket.
Is that not a little bit OTT and must take ages to install?
You only need to test the ring to check the resistance readings.
John, as you and I have discussed the cpc/earth terminology usage in the wiki articles I know how you and I feel about the correct usage of the name cpc - well we agreed where to use the term. But if you were to call in at my local electrical wholsalers and ask for "cpc sleeving" they would either insult you or stand there looking blank and say "what?":-)
Now is it cpc or CPC and can you use either?:-)
I'm sure I've seen "c.p.c." in a book recently.
Well indeed - although I would point out I was not the one to introduce the term in this thread.
(in fact in my local TLC the other day I had to explain to the chap serving what a roll of mini trunking was - although they sell they stuff he had never seen it, and gave me a rather blank look when I asked for it!)
and can you order it from CPC? ;-)
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