Ban the sale of twin and earth ? ?

[Paul_C]

Why insulate the earth throughout the entire length of the reel when in essence only a few inches of each cut length require insulating?

It's not really even a case of requiring insulation, it's just sleeved as a matter of course these days because such a rule was added to the wiring regulations. It used to just be left bare in accessory boxes, where connected to the appropriate terminal on sockets, etc. As it's connected to the metal box anyway, there's really no technical reason for it to be sleeved. In other countries that's still often the case, e.g. when using Romex in the U.S. as mentioned earlier.

 

[JohnW2]

It's not really even a case of requiring insulation, it's just sleeved as a matter of course these days because such a rule was added to the wiring regulations. It used to just be left bare in accessory boxes, where connected to the appropriate terminal on sockets, etc. As it's connected to the metal box anyway, there's really no technical reason for it to be sleeved. In other countries that's still often the case, e.g. when using Romex in the U.S. as mentioned earlier.

Maybe, but given the 'unknown things' (probably best not to know, in some cases ) which probably happen to conductors when we scrunch everything into a backbox to get the front plate in place, I think it's very wise to not have bare wires which could bend and touch goodness knows what!

Kind Regards, John.

 

[SimonH2]

I've already given you enough information to find them if you actually cared.

And I notice that you still haven't answered my questions, while chiding others for not answering yours. In the above situations, change flat T&E to round cable, and what do you do then ? Come along now, surely it can't be hard because you keep telling us that everything is sorted for all cable types other than T&E.

 

[Paul_C]

Maybe, but given the 'unknown things' (probably best not to know, in some cases ) which probably happen to conductors when we scrunch everything into a backbox to get the front plate in place, I think it's very wise to not have bare wires which could bend and touch goodness knows what!

Ah, now that's another story! There seems to be a tendency in this country to try and use boxes which are far too shallow for the wiring which is to go in them.

 

[JohnW2]

Ah, now that's another story! There seems to be a tendency in this country to try and use boxes which are far too shallow for the wiring which is to go in them.

That's probably true, although I do try to be quite generous in my choice of box size. However, no matter how big the box, if one gives oneself enough cabe to work with (in making the terminations), there's still a fair bit of 'unseen/unknown happenings' when one pushes it all back in - and if one of the things connected to the accessory were a bare CPC, I still think there's a definite danger of it touching something it shouldn't touch, hence G/Y sleeving seems to be a pretty sensible idea!

Kind Regards, John.

 

[ban-all-sheds]

Yet more troll food

 

[SimonH2]

Yes, but you have to admit, it is kind of fun making him look stupid

Sorry, that should say helping him to make himself look stupid - it doesn't need much input from us

 

[bernardgreen]

Yes, but you have to admit, it is kind of fun making him look stupid Sorry, that should say helping him to make himself look stupid - it doesn't need much input from us

Be fair, he does have many valid points and in any discussion all opinions need to be considered.

Getting back to the original question I asked, Is twin and earth a false description under trading standards when in so many installations the CPC cannot be accurately described as earth.

 

[SimonH2]

Yes, but you have to admit, it is kind of fun making him look stupid Sorry, that should say helping him to make himself look stupid - it doesn't need much input from us

Be fair, he does have many valid points and in any discussion all opinions need to be considered.

But in this case the points aren't valid. There is nothing whatsoever about T&E that justifies the attack - every criticism is actually of the fittings being used, not the cable. He's also slagged off others for not answering his questions when he pointedly ignores those asked of him which would show this.

Getting back to the original question I asked, Is twin and earth a false description under trading standards when in so many installations the CPC cannot be accurately described as earth.

Well that is an interesting question. But then if you are going to take that line, what about all those accessories with an "earth" terminal ? In general discussions, it is normal for people to use the term "earth" when referring both to the terminals and conductors, and to the process of connecting conductive enclosures etc to "something safe".

So while in a strict technical sense, "earth" isn't always "earth", in general it is still referred to as "earth" even when it's not.

So no, I don't think there's a case for banning the name twin and "earth" since that CPC is connected to terminals marked E, or earth, or with an earth symbol - even at the DNO provided "earth" terminal.

 

[bernardgreen]

Hi Simon

I am being a pedantic about the possible mis-use of the term "earth".

Obviously it hase been accepted by the general public as an acceptable "title" for the CPC by common useage but since the introduction of PME and similar neutral derived "earths" assuming the CPC is earth and at true ground potential does create hazards when the CPC is exported out of the equi-potential zone.

It stems from trying to explain to a semi technical person why the earths from two buildings ( one TT and the other PME ) cannot be connected together and that water pipes and other services must have electrical isolation breaks in them. To him earth wires are earth and can be safely connected to each other by service pipes etc.

 

[holmslaw]

..

 

[Paul_C]

So no, I don't think there's a case for banning the name twin and "earth" since that CPC is connected to terminals marked E, or earth, or with an earth symbol - even at the DNO provided "earth" terminal.

And don't forget that for a good many years before the term CPC was introduced, it was called the ECC - Earth Continuity Conductor.

 

[bernardgreen]

as demonstrated by your assumption that my points regarding T&E cable clamping are invalid.

Your opinion is valid as a concern but based on risk analysis the concern is not great enough, the risk acceptable small to not require cable clamping in every type of junction box used with twin and "earth" cable.

If there is no relative movement between the cable and the accessory in which the cables conductors are terminated then cable clamping in the accessory in not necessary. A junction box fitted to a joist and a cable pinned to the joint or other fixed item cannot move relative to each other.

A loose junction box which can be moved ( such as those that are wired below the ceiling and then pushed back up through the hole ) definately does need to have clamps for all the cables that connect to its terminals.

It is true that loose un-pinned cables could be pulled, tugged or tripped over ( in the loft ) and move relative to the junction box. That is a poor installation and some one who did that is also likely to not bother with correctly clamping the cables if clamps were available.

 

[ban-all-sheds]

Then you start with the insults as do a lot of people when they realise they have lost an argument.

You are too moronic to take part in a sensible discussion.

 

[JohnW2]

I am being a pedantic about the possible mis-use of the term "earth". Obviously it hase been accepted by the general public as an acceptable "title" for the CPC by common useage but since the introduction of PME and similar neutral derived "earths" ....
It stems from trying to explain to a semi technical person why the earths from two buildings ( one TT and the other PME ) cannot be connected together ....

It's surely just an incredibly well-established and ubiquitous bit of terminology, the changing of which would do nothing but cause confusion for the vast majority of the population.

However, I think you're being unfair in using the general public / 'semi-technical persons' as the scapegoat. For example, even in these days of PME etc., BS7671 still requires electricians to call the connection between the DNO's 'earth' and the installation an 'Earthing conductor', and the place it connects to the 'Main Earthing Terminal' (MET) ... and, more generally, throughout Chapter 54 (and other places in the regs), you will find (from the Chapter title onwards) the words 'earth' and 'earthing' being used widely by BS7671. Then, as others have pointed out, the world is full of many millions of accessories and appliances with 'earth' terminals, and they continue to be produced.

Furthermore, I think that the 'earths' we use are, under non-fault conditions, not all that different from what 'earths' always have been - namely something fairly close to true earth potential. I'm not sure that one should get upset about the word because things can change under fault conditions - that's even true with TT earths.

If any criticism is called for, I think it's probably because the IEE/IET have seen fit to change (in some contexts) terminology which was incredibly well-estalished, highly ubiquitous and generally widely 'understood'

Kind Regards, John.