Why this extra wire?

[amfisted]

Yesterday I slightly enhanced the number of electrical points in my house by fitting convertors to change two single sockets for doubles.

The first socket had three conductors, but when I opened the second one, it had an additional, short length of wire which was connected to a terminal in the metal mounting box and secured to the earth terminal of the socket, along with the mains earth.

Is there any particular reason why that second socket might be earthed to the metal box when the first wasn't?

 

[EFLImpudence]

Is there any particular reason why that second socket might be earthed to the metal box when the first wasn't?

Yes, someone has connected the back-box on one and not the other.

It is a good idea to connect the back-box but not actually a requirement.

 

[Taylortwocities]

It is a good idea to connect the back-box but not actually a requirement.

It is not a requirement if one of the used fixing lugs in the back box is fixed. Most (but not all) are like this nowadays.
Older back boxes had sliding lugs on both sides and these back boxes must be earthed.

 

[riveralt]

Did the second socket also have three conductors plus the hopefully sheathed earth wire to the back box?
If the answer is yes, what is the size of the MCB/Fuse protecting this circuit?

 

[sparkwright]

Here we go.

 

[EFLImpudence]

Did the second socket also have three conductors plus the hopefully sheathed earth wire to the back box?
If the answer is yes, what is the size of the MCB/Fuse protecting this circuit?

Wouldn't the MCB rating only be significant if the answer is 'no'?

 

[JohnW2]

Did the second socket also have three conductors plus the hopefully sheathed earth wire to the back box? If the answer is yes, what is the size of the MCB/Fuse protecting this circuit?

Wouldn't the MCB rating only be significant if the answer is 'no'?

I suspect that there may be thoughts afoot that if both sockets have only 3 conductors (rather than 6) it might be a radial circuit (although they both could be legitimate spurs from a ring) (or, of course, one or both could be a spur off a spur off a ring!).

Kind Regards, John

 

[riveralt]

Did the second socket also have three conductors plus the hopefully sheathed earth wire to the back box?
If the answer is yes, what is the size of the MCB/Fuse protecting this circuit?

Wouldn't the MCB rating only be significant if the answer is 'no'?

I raised the questions, not to start a 'here we go' debate but more to clarify the situation that the OP may find himself in.
The OP seems to imply that the second (or is the first) socket is the same as the first - so is it a radial circuit? Is it spur on spur etc.
Finding out what type of circuit it is might be beyond the OP but the size of the MCB might be a starting point - followed up by trying
to determine the size of the cable.

 

[EFLImpudence]

So, with three conductors at each socket, what relevance is the MCB rating?

(Sorry sparkwright - bored )

 

[JohnW2]

I raised the questions, not to start a 'here we go' debate but more to clarify the situation that the OP may find himself in. The OP seems to imply that the second (or is the first) socket is the same as the first - so is it a radial circuit? Is it spur on spur etc. Finding out what type of circuit it is might be beyond the OP but the size of the MCB might be a starting point - followed up by trying to determine the size of the cable.

Indeed, as I just wrote, I suspected that's what you were getting at. However, I'm not really sure what any of this has got to do with the OP's question - as to whether there would be a reason why one back box would be earthed and the other not!

Kind Regards, John

 

[sparkwright]

I raised the questions, not to start a 'here we go' debate but more to clarify the situation that the OP may find himself in. The OP seems to imply that the second (or is the first) socket is the same as the first - so is it a radial circuit? Is it spur on spur etc. Finding out what type of circuit it is might be beyond the OP but the size of the MCB might be a starting point - followed up by trying to determine the size of the cable.

Indeed, as I just wrote, I suspected that's what you were getting at. However, I'm not really sure what any of this has got to do with the OP's question - as to whether there would be a reason why one back box would be earthed and the other not!

Kind Regards, John

 

[riveralt]

Yes just realised that you had posted as well, trying to watch the budget debate at the same time.
I suppose my question alludes to what I believe should be the wider function of this site.
A one line answer would have more than satisfied the OP - indeed the back box issue was already answered.
But clearly his description appears to raise potential red flags.
As an electrician if while I was adding two new sockets as per the OP and came across the wiring
as described I would investigate further. That is why I was seeking to clarify what he had said.

 

[sparkwright]

What's wrong with the wiring the op described? Seems normal to me.

 

[JohnW2]

I suppose my question alludes to what I believe should be the wider function of this site.
A one line answer would have more than satisfied the OP - indeed the back box issue was already answered. ... But clearly his description appears to raise potential red flags.

Yes, I'm inclined to agree, but I tend to get criticised for raising issues which were not asked about

As an electrician if while I was adding two new sockets as per the OP and came across the wiring as described I would investigate further. That is why I was seeking to clarify what he had said.

Yes, as I said before, I understand your reason and, even though a non-electrician, I would also probably 'investigate further'. However, that is getting into the "whilst I was doing it, I noticed ...." territory. Even if there is some issue, the OP has not really made it any less safe than it was before - since he has not 'added' sockets but merely changed two from singles to doubles.

Kind Regards, John

 

[JohnW2]

What's wrong with the wiring the op described? Seems normal to me.

riveralt is concerned that, with two sockets both having only one cable, he is uncertain about the nature of the circuit - which is a valid observation (albeit the OP has not really changed anything, so has not really made anything 'worse' or 'less safe'). As I said, this could theoretically be due to 'a problem', but it's equally possible that both are legitimate spurs from a ring, or that it is a 20A radial circuit (maybe even possibly a satisfactory 32A radial - we haven't been told about the cable size).

Kind Regards, John