skts x 2 earth terminals

[driverman]

Been 2nd fixing today, which i've not done for many years. I've noticed that both Volex 13A twin & single sockets have 2 x earth terminals. Is that now standard? I thought that requirement was only applied to sockets that served a lot of IT equipment. Even years ago i would sleeve the earths separately, but then into one terminal. Is there any electrical reason for the change? Thanks

 

[Doomed]

Been 2nd fixing today, which i've not done for many years. I've noticed that both Volex 13A twin & single sockets have 2 x earth terminals. Is that now standard? I thought that requirement was only applied to sockets that served a lot of IT equipment. Even years ago i would sleeve the earths separately, but then into one terminal. Is there any electrical reason for the change? Thanks

Just so the socket can be used for any situation.
Just get into the habit of using both terminals when doing a ring main, it only takes a few seconds more.

 

[Tidy Max]

Why should you use both terminals when doing a ring main?

 

[ayjay]

same q as t/max?

 

[driverman]

Just so the socket can be used for any situation.
Just get into the habit of using both terminals when doing a ring main, it only takes a few seconds more.

Ohh i've no problem with it at all. I've used them both today. Even bent each wire earth wire back 3 times to ensure good connection/strength. Just wondered why they are being introduced

 

[Deleted member 26818]

There's no reason to use both terminals, unless there are 2 separate CPCs.

 

[Tidy Max]

If you used both terminals for the ring main the earth within the socket would be completing the cpc continuity. I always put both cpcs in one terminal and the other terminal for the back box bonding.

 

[driverman]

There's no reason to use both terminals, unless there are 2 separate CPCs.

As you know, 2 x CPC's in a ring final circuit

 

[driverman]

If you used both terminals for the ring main the earth within the socket would be completing the cpc continuity. I always put both cpcs in one terminal and the other terminal for the back box bonding.

Right, understand. so no requirement as such then to use both separately on a ring. I suppose if both used could make fault finding bit easier as you could disconnect 1 x earth as opposed to untwisting/ separating the 2 cpc's

 

[Tidy Max]

There is only one CPC in a ring final? You would use two protective conductors in a circuit with high protective conductor current?

 

[Doomed]

Why should you use both terminals when doing a ring main?

I didn't say you should, its just a habit to get into that hardly takes any extra time.

 

[Tidy Max]

Right, understand. so no requirement as such then to use both separately on a ring. I suppose if both used could make fault finding bit easier as you could disconnect 1 x earth as opposed to untwisting/ separating the 2 cpc's

I never twist, i always sleeve them separately then put both in the same terminal. Tighten until it squeaks with pleasure then tug test

 

[Doomed]

ugh, twisted earths, the bane of fault finding / testing!

 

[Tidy Max]

I didn't say you should, its just a habit to get into that hardly takes any extra time.

But why get into the habit at all? I am not trying to be smart or funny with thee if it is coming across that way. I just don't understand the reasoning. Which is true for alot of the stuff i read on here and 99 times out of 100 i come away having learnt something so i thought that may be the case here!

 

[Doomed]

So when you do a IT related circuit (assuming you do commercial) you are already in the habit - one of my colleagues has been heard muttering to himself when on commercial installs because he has 'got into the rhythm' and then forgot to use both terminals.

 

[Deleted member 26818]

2 terminals and 1 CPC = twice as many terminations which may fail.

 

[Tidy Max]

Never done one mate! The bulk of my work is domestic and sub contract. Interesting to know What sort of earth leakage do you get on commercial IT circuits. I did some aesthetic lighting on a large health centre a couple of years ago and noticed they had run a 4mm earth to all of the sockets even though they had been wired in T+E

 

[Deleted member 26818]

So when you do a IT related circuit (assuming you do commercial) you are already in the habit - one of my colleagues has been heard muttering to himself when on commercial installs because he has 'got into the rhythm' and then forgot to use both terminals.

There does appear to be a misinterpretation of the requirements for 2 separate CPCs for such circuits.
One conductor run in a ring formation and terminated at separate terminals does not equate to two CPCs.
It needs two separate conductors, each connected to a separate terminal in order to comply.

 

[driverman]

ugh, twisted earths, the bane of fault finding / testing!

Exactly, never have liked twisting conductors together. As an apprentice years ago, it was the norm to twist (was imperial then) conductors together. When metric cables came out, many electricians still twisted conductors together. In my opinion very bad practice. I doubt if many twist conductors together nowdays! Or do they ?

 

[Doomed]

Never done one mate! The bulk of my work is domestic and sub contract. Interesting to know What sort of earth leakage do you get on commercial IT circuits. I did some aesthetic lighting on a large health centre a couple of years ago and noticed they had run a 4mm earth to all of the sockets even though they had been wired in T+E

The circuits have never been 'loaded up' while I have been on site, someone else plugs the computers in (normally). If we are not working to a designers drawing we base our installs on what we have known designers to do, limiting the number of machines on each circuit etc, and once again we don't get involved in plugging the machines in (normally). We have never been called back because of a problem, so the designers / our copying must be working OK.

 

[Deleted member 26818]

There are arguments for both.
Twisting together would allow for continuity of the conductors, if the terminal became loose.
Twisting together restricts the number of conductors that can be terminated.
Twisting together is a pain when it comes to testing.

 

[Tidy Max]

The only conductor twisting i do is when i am installing or building an induction loop!

 

[Guest77]

I cannot see the problem myself, if you connect the CPCs into seperate terminals and one breaks or isn't tight the socket is still protected, if in one terminal then the same as it always has been, who cares, it is no big deal either way on a standard domestic outlet.

 

[Guest77]

Why should you use both terminals when doing a ring main?

Why Not?

 

[Deleted member 26818]

Some sockets have 2 terminals for each of the circuit conductors.
This increases installation times and increases the likelihood of a termination loosening.
If one terminal fails, then yes the conductor is still connected, though using a plug in tester would not show that a conductor had fallen out.

 

[driverman]

I cannot see the problem myself, if you connect the CPCs into seperate terminals and one breaks or isn't tight the socket is still protected, if in one terminal then the same as it always has been, who cares, it is no big deal either way on a standard domestic outlet.

i can't see it making any difference what so ever. However, as not in the game as such I just wondered why the introduction. Surly must be more expensive to produce, therefore there must be a reason why. Could it be an EU instruction?

 

[Risteard]

Presumably it is to enable the socket outlet to be used where there are high protective conductors currents.

Personally I would always use both terminations.

 

[Deleted member 9648]

i can't see it making any difference what so ever. However, as not in the game as such I just wondered why the introduction. Surly must be more expensive to produce, therefore there must be a reason why. Could it be an EU instruction?

EU are not interested in UK sockets....the reason is manufacturers dont have to manufacture both types....cheaper to tool for one only,and the extra cost of the two terminals is sneaked onto us.

 

[SJD]

In fault-finding an RFC with a higher-than-expected value for r2, on at least a couple of occasions it has turned out to be due to relying on the socket internal metalwork.

One end of the RFC into one terminal, the other end of the RFC into the other terminal. Screws done up tight. But the sockets had riveted bits of metal work, not always making good contact. I've seen sockets with the best part of an Ohm measured between the two terminals.

 

[Tidy Max]

I had the exact same issue about 6 months ago. It was a single socket that had been connected up that way causing the issue. I re terminated them and the lowered the value however after reading this thread i was thinking the terminations just may have been a bit crap!

 

[driverman]

Awww now i'm thinking put both earths into one terminal! Which is what I have been doing for years!

 

[Doomed]

No matter what you do it will be wrong somehow.

Especially if your married.

 

[driverman]

No matter what you do it will be wrong somehow.

Especially if your married.

Baffled....although had a few drinks hic

 

[wildgoose]

Decent sockets with double pole switching, will have 2 earthing terminals. The cheaper single pole switched sockets - which I stay away from, normally have just the one earth terminal.

I personally will use both earth terminals on a newly wired sockets only because it looks better. On a refurb/replacement socket, I'll use whichever terminal is best for the existing cable length.

Earthing of the metal knockout boxes in domestic applications, is of course not required providing one of the mounting lugs is fixed.

 

[ayjay]

use tenby sockets
they have very fine terminal threads and don,t loosen

 

[Engineer54]

Well i would personally use one of the socket earth terminals for the rings circuit conductors, and the other for a flying lead to the back box. I don't really care what BS7671 has to say about relying on a face plate fixing screw, i was taught to use flying leads to the back box and see no reason not to continue to do so!!

 

[shanky887614]

Baffled....although had a few drinks hic

nothing rong with that, just got back fron pub myself.

not completely out of it yet, but i need to take extra care wiyh spelling

 

[wildgoose]

Nothing wrong with flying earth leads inside the boxes - I was taught that way back too. However, back in the old days of the 60's & 70's, you really did need flyleads. Limited use of rcd's and no knockout box grommets was common place - how many original socket boxes from this era do you find without any grommets?

 

[Simlec]

There does appear to be a misinterpretation of the requirements for 2 separate CPCs for such circuits.
One conductor run in a ring formation and terminated at separate terminals does not equate to two CPCs.
It needs two separate conductors, each connected to a separate terminal in order to comply.

Im not sure what your saying Spin?
Are you saying the image (for example) in Guidance note 8 page 132 is incorrect!
As it says on page 131 that if the ends of the protective conductor are separately terminated at DB & sockets then Reg 543.7 will be met as shown in image

 

[onions1066]

Hey guys. Haven't been on in a while but is this really what it's come to arguing over how many earth terminals to use in a domestic socket. Does it actually matter. ...........

Sent from my GT-I9505 using Tapatalk 4

 

[UNG]

ugh, twisted earths, the bane of fault finding / testing!

You forgot the twisted live and neutrals for extra grief just weakens the cable IMO

Exactly, never have liked twisting conductors together. As an apprentice years ago, it was the norm to twist (was imperial then) conductors together. When metric cables came out, many electricians still twisted conductors together. In my opinion very bad practice. I doubt if many twist conductors together nowdays! Or do they ?

There are people who still do it they should have their pliers confiscated

There are arguments for both.
Twisting together would allow for continuity of the conductors, if the terminal became loose.
Twisting together restricts the number of conductors that can be terminated.
Twisting together is a pain when it comes to testing.

I think people who do are just twisted

i can't see it making any difference what so ever. However, as not in the game as such I just wondered why the introduction. Surly must be more expensive to produce, therefore there must be a reason why. Could it be an EU instruction?

It probably won't make much difference to the Bob's in the factory whether it has one earth terminal or two

EU are not interested in UK sockets....the reason is manufacturers dont have to manufacture both types....cheaper to tool for one only,and the extra cost of the two terminals is sneaked onto us.

The mouldings on a lot of sockets these days universal so they can have one or two earth terminals, the extra cost of the second earth terminal is probably only a few pence

In fault-finding an RFC with a higher-than-expected value for r2, on at least a couple of occasions it has turned out to be due to relying on the socket internal metalwork.

One end of the RFC into one terminal, the other end of the RFC into the other terminal. Screws done up tight. But the sockets had riveted bits of metal work, not always making good contact. I've seen sockets with the best part of an Ohm measured between the two terminals.

Had this a few times I also find the switches can be a bit hit and miss when doing R1 - R2 tests

 

[Deleted member 9648]

You forgot the twisted live and neutrals for extra grief just weakens the cable IMO



There are people who still do it they should have their pliers confiscated



I think people who do are just twisted



It probably won't make much difference to the Bob's in the factory whether it has one earth terminal or two



The mouldings on a lot of sockets these days universal so they can have one or two earth terminals, the extra cost of the second earth terminal is probably only a few pence



Had this a few times I also find the switches can be a bit hit and miss when doing R1 - R2 tests

Those few pence per socket add up when you are mass producing.

 

[Tidy Max]

Im not sure what your saying Spin?
Are you saying the image (for example) in Guidance note 8 page 132 is incorrect!
As it says on page 131 that if the ends of the protective conductor are separately terminated at DB & sockets then Reg 543.7 will be met as shown in image

That is specifically for circuits that have high protective conductor currents. Which is what Spin is saying.

In the post that you quoted he is saying in a normal RING circuit there is only ONE cpc.

 

[Simlec]

That is specifically for circuits that have high protective conductor currents. Which is what Spin is saying.

In the post that you quoted he is saying in a normal RING circuit there is only ONE cpc.

​Are you sure?

 

[Tidy Max]

Yes i am sure! You may have two ends but its two ends of the same cpc! There aren't two seperate circuit protective conductors! Once again i will totally hold my hands up if i am getting the wrong end of the stick which is usually the case!

 

[Simlec]

Ring circuits, by their design, provide duplication of all conductors, including the protective conductor unless this is formed by metallic conduit and/or trunking. Regulation 543.7.1.104 requires that each protective conductor is terminated separately at each connection point; the regulation also requires that each wiring accessory has two separate earth terminals. At socket-outlets, this is a very easy requirement to meet – simply select accessories with dual earth terminals.

 

[Deleted member 26818]

As far as I can recall, the requirement is for a CPC with a minimum CSA of 4mm, or for there to be 2 CPCs both of which must satisfy the requirements to be considered as a CPC.
RFCs are effectively a circuit with conductors run in parallel so in a standard RFC run in 2.5mm T&E the conductor sizes can be considered as 4mm line, 4mm neutral but only 3mm CPC.
3mm as I am sure you are aware, is less than the 4mm required.
Some people say that because it's 2 conductors, it is therefore 2 CPCs.
That's ok, as long as both of the conductors would satisfy the requirements to be considered as CPCs.
When RFCs are run in singles, all of the conductors are usually the same CSA, so if the CSA of the CPC is 2.5mm, then when doubled, we have 5mm which is greater than the minimum 4mm required.

 

[Silly Sausage]

Ring circuits, by their design, provide duplication of all conductors, including the protective conductor ..................

It's not though, is it?!?! The conductors carry differing currents along their lengths.

Also, if you whip out a section of the ring (or get a break ), what do you get????
Two undersized Radials!

Yes i am sure! You may have two ends but its two ends of the same cpc! There aren't two seperate circuit protective conductors!

I completely agree!

 

[Guest55]

It's not though, is it?!?! The conductors carry differing currents along their lengths.

not being balanced with regards to load carrying doesnt exclude them from being duplicated........

;-)

edit ;

if you break a ring at any point , you have 2 radials , thereby you must have 2 cpc's.......

 

[Maddison]

i was always taught one cpc from each leg into each terminal then link between the two so not relying on the socket as the link, that way if one comes loose there is still another terminated and socket is still protected rather than losing both earths.