Socket earthing yeah or neah

[Darkwood]

Doing a pir at mo and on checking the sockets (ring) noticed the earths had been terminated as a pair into the backbox with a 1.5mm tail to socket, ive knocked this as i see it as a weak link and requires the pair to terminate onto socket with tail link to the back box. Whats your feed back?

 

[Phil Mumford]

CPC's to primary means of earthing which is the earth terminals on the socket.

No need to earth the back box as it not an extraneous conductive part and them there two M3.5's cover it anyways. I always do, though.

Code 4 ?

 

[Mr Mark Sparks]

agree
only need to flylead box if it has 2 adjustable lugs

 

[Darkwood]

I was expressing the manner in which the socket got an earth and that the ring earth didnt run through the socket, and back boxes do need earthing but if they have at least one fixed thread on them then you can rely on the 3.5 screw to achieve this, but its looked on as good practice to earth it anyway.

 

[oldtimer]

Guys tell me if I am getting it wrong here but I served my time in the 14th edition yes I know and running a seperate earth cable was not done as the containment system ie trunking and conduit were classed as "electricaly and mechanically sound" so you had no option but to put in a lead from the box earth terminal to the socket also if you wired in T&E you still had to put the lead in.Now this is where it gets interesting as some sparks would twist both earths and the lead and terminate it on the stud on the back box others would do the reverse. So why put the lead in ? well the whole idea was that when you took the screws out and pulled the socket back the socket still had to be earthed. So do you still have to put the link in with ref to the 17th

 

[Des 56]

We are not supposed to remove the socket live,so the need for an extra earth to the back box would not arise
It does seem to be good practice,but not any sort of requirement, unless the earthing cant be maintained whilst live by dodgy movable lugs,hence the one fived lug quotes

 

[patricklondon]

both cpc into seperate earth terminals of socket (if there are two) not twisted, seperate earth sleeeving for each and addidional cpc to terminal in metal back box

 

[Spudnik]

The CPC's only need terminating into separate earths terminals on the sockets if the circuit has to incorporate high integrity earthing arrangements.

Must admit, good idea regardless though.

 

[Darkwood]

It seems no-one has picked up on my original question, the point i was making was you cant run the earth ring through the backbox with a 1.5mm tail to the socket, the earth ring must go to the socket and the 1.5mm tail to the backbox if you fit one, i well aware of the regs with tailing backboxes but the point of my question was the manner in which a socket i came across had its earthing terminated. As i pulled the ring main for this in the PIR i just wanted your feedback.

 

[Sintra]

It seems no-one has picked up on my original question, the point i was making was you cant run the earth ring through the backbox with a 1.5mm tail to the socket, the earth ring must go to the socket and the 1.5mm tail to the backbox if you fit one, i well aware of the regs with tailing backboxes but the point of my question was the manner in which a socket i came across had its earthing terminated. As i pulled the ring main for this in the PIR i just wanted your feedback.

That is correct as you say Darkwood. Cpc conductors from ring must be terminated at socket not back box. Then fly lead if required.

If i came accross sockets terminated like that whilst doing a PIR i would code 2 it and therefore PIR would be unsatisfactory.

 

[Mr Mark Sparks]

what about 1leg in box 1leg in socket and a link between
seen this often

 

[Darkwood]

what about 1leg in box 1leg in socket and a link between
seen this often

Cant argue with this one as it still has the ring earth going through the socket and have seen this a few times myself although not my preferred choice as damp in the wall would create a corroded terminal as ive also seen this many times.

 

[andyb]

Was R1+R2 ok? was Ze ok?
How can you give this a code anything? this was a pir you were doing, you can't give it an unsatisfactory report just because it doesn't measure up to your interpretation of good practice.

 

[Darkwood]

Was R1+R2 ok? was Ze ok?
How can you give this a code anything? this was a pir you were doing, you can't give it an unsatisfactory report just because it doesn't measure up to your interpretation of good practice.

Its not an interpretation of good practice its a weak link in the circuit as an example if a a short circuit occurs L/E on the ring main then it normally has 2 X 1.5mm paths to run the high current through until the fuse operates but as we know the standard practice of a ring is to front end with a 32amp mcb/rcbo which overates the cable but is allowed due the nature of load sharing around the ring. If you earth ring the backbox then tail the socket to earth it if the fault is on a item plugged into this socket then then the earth tail has to cope with the full fault current which is then shared when it joins the earth ring.
So in effect the fault path has to go through a undersized link which may not withstand the fault current in this case 1500amps, the solution is simple by just fitting 4mm links but i was putting the issue forward to see what others like yourself thought.
Ps this is only to the 16th so no rcd protection so only the time/current curve of the mcb can be relied on.

 

[andyb]

What about the cpc in a spur? do you run a seperate 4mm earth.

 

[Darkwood]

What about the cpc in a spur? do you run a seperate 4mm earth.

You make a good point and thats what i threw this question out there for, a thought i overlooked so assuming that spurs off ringmains have been deemed safe for earth size then the 1.5mm tail dosnt pose a earthing issue under fault. The real question behind all this is does the fuse operate fast enough for the 1.5mm to cope but as you point out about spurs it must have been deemed safe enough to allow spurs off rings so i will not issue a code on it.

 

[Des 56]

A good example by andyb
It removed the coding desicion

Also a good example of a situation that became clear through discussion between the parties
The benefit of the forum shown up with this question and responses conclusion

My thought is that the high fault current would be at such a short period flowing in the cpc of the spur, that it may not cause thermal damage
Comparing the standard current carrying capacity of a 1.5 tail to a 2x1.5 mm cpc may be where the doubt arose

The original post about connecting the cpcs at the back box would leave me uneasy about the installers methods,not something that would fill me with confidence in their methods if I were doing the PIR

 

[andyb]

I suppose that the correct answer is to do an adiabatic equation for the sockets in question.
I think my 1st post was a trifle ott, most observations on pirs are subjective, other than obvious dangers of risk to life or property.
As an electrician I would ask myself if the instalation was safe and complies with the regs, the second part is not so easy to answer and as I am just back from the pub I will not even try to answer it now. But I will have a kip and then give it some more thought.
Cheers.

 

[EddieB]

It would seem to me that in most cases here the answers that Darkwood recieved were not for the the question asked, Hocome on lads read the question properly before answering

 

[Guest123]

It would seem to me that in most cases here the answers that Darkwood recieved were not for the the question asked, Hocome on lads read the question properly before answering

Care to share your views then Eddie???