Re What is a "Live conductor"?

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ban-all-sheds said:

That is really going to depend on the definition of "energise". .... But when you intentionally supply something which in normal operation creates a potential difference between the cpc and true earth so that you intentionally cause current to flow in the cpc......

JW2: OK - so you appear to be saying that the BS7671 definition of a live conductor (live part) does, or may, include CPCs. Is that correct? ....

Well, I have never looked at, or considered, what the definition of a live conductor or a live part is. Nor "energise".

But if doing something which causes current to flow in a conductor is not "energising" it, then what is it, and what is "energising"?

Whatever the definitions say, or do not say, I really don't see how one can look at 543.7 and not see requirements associated with situations where the cpc is expected to carry current in normal operation.


ban-all-sheds said:

I'm sure it is.

JW2: Fair enough - so you agree that the authors of BS7671 did not intend that the definition of a 'live conductor' should include CPCs? ...

I would say so, on the grounds that all sorts of things become a nonsense if it does, and the classification becomes almost pointless because what conductors would then not be live?

ban-all-sheds said:

So maybe those who claim a definition for "live conductor" which ends up making a cpc one should reconsider their definition rather than falsely claim that cpcs are not intended to carry current during normal operation.

JW2: Maybe. I certainly don't know where 'intended to carry current during normal operation came from.

It came from this exchange:

bernardgreen said:

Then so is the CPC a Live conductor, or do the electrons change uniforms when they cross the border between Neutral tails and CPC in the cutout ?
Risteard said:

No it isn't. It is a protective conductor as it is not intended to carry current during normal operation.

To which I pointed out that 543.7 is stuffed full of things you have to do when you expect the cpc to carry current, and we all know how Risteard took that.

But again - look at what 543.7 says, and the words it uses. It's not talking about abnormal or fault conditions. It says things like "... total protective conductor current is likely to exceed ...". Something which is likely is something which is normal.


JW2: However if, as above, you think that the BS7671 definition of 'live conductor' does/may include CPCs, yet are sure that such was not the intention of the authors, are you suggesting that they simply got the definition wrong?


Something is wrong. If the definition of a "live conductor" means that a cpc is sometimes one, and that is not the intention, then the definition must be wrong.
 
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JohnW2 said:
However if, as above, you think that the BS7671 definition of 'live conductor' does/may include CPCs, yet are sure that such was not the intention of the authors, are you suggesting that they simply got the definition wrong?
Something is wrong. If the definition of a "live conductor" means that a cpc is sometimes one, and that is not the intention, then the definition must be wrong.
Well, I think we are all agreed that it is very unlikely that such was the intention, so the definition (of a live conductor/part) is 'wrong' IF it means that a CPC is sometimes one. Whether that is the case depends, in turn, on the meaning of "energize", which is not defined in BS7671, so we can merely guess/speculate. I can but presume that, rightly or wrongly (and despite your argument), those who wrote the definition did not mean/intend that 'energizing' is something that would ever been done deliberately to a CPC. One would certainly not normally talk about "energizing a CPC".

Kind Regards, John
 
So when you intentionally apply a voltage wrt earth to a cpc, what are you doing to it?
 
If your neutral is connected to the met within your installation, you have a fault that needs rectifying.
No - electrically a TN-C-S supply does have the neutral connected to the MET.


I was under the impression that connection belongs to the supplier and isn't part of the customer's installation.
That's an artificial distinction, the making of which appears to have little or no value in this discussion.

Arbitrary dotted lines through parts of an electrical diagram are of no consequence to electrons - they will cross them as if they were not there.
 
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I think the problem is that none of the materials involved in an electrical installation is a superconductor, so you can have potential differences between things that are connected together.
No - electrically a TN-C-S supply does have the neutral connected to the MET.
Yes, specifically at a point where it won't cause a hazard as it is all bonded properly downstream of that point. Your neutral becomes progressively less close to your equipotential level as you get further into your installation. Your cpcs should not.
Arbitrary dotted lines through parts of an electrical diagram are of no consequence to electrons - they will cross them as if they were not there.
But if you have enough of them crossing at a time, you'll end up with a potential difference depending on the resistance of the path. Hence why the connection is before the supplier provided earth is connected to the met.
 
But if you have enough of them crossing at a time, you'll end up with a potential difference depending on the resistance of the path. Hence why the connection is before the supplier provided earth is connected to the met.
What I meant was if you draw an electrical circuit and then no matter how many dotted lines you draw on it to divide it into sections of "ownership", none of them will make a blind bit of difference to how the circuit behaves electrically speaking.
 
Ok fair enough I'll remove that red herring, it's no coincidence the bit where the cross connection is made is provided upstream of the consumer's met. If it came under bs7671 instead of the supplier's domain, it would still be upstream. It couldn't just tee off at the consumer unit.
 
So when you intentionally apply a voltage wrt earth to a cpc, what are you doing to it?
I just don't know whether that qualifies as "energising". I'll try looking up the dictionary definition (given that BS7671 doesn't have one), but suspect that will probably not help too much.

However, aren't we just wasting our time - given that, despite discussions about words, we seem to be agreed that it makes no sense to regard CPCs as "live conductors"?

If we did regard CPS as "live", I would struggle to think of any conductors which did not qualify as "live", which would render that qualification redundant. Even a lightning conductor is 'intended' to acquire a potential during a lighning strike.

Kind Regards, John
 
It is important to remember that not only is ban-all-sheds not an Electrician, indeed he never has been an Electrician.
 
It is important to remember that not only is ban-all-sheds not an Electrician, indeed he never has been an Electrician.
It's probably important to remember that the majority of participants in this DIY forum are not, and never have been, electricians, or even 'electricians'.

Kind Regards, John
 
It's probably important to remember that the majority of participants in this DIY forum are not, and never have been, electricians, or even 'electricians'.

Kind Regards, John
I am aware of that, but the majority do not pretend to be. However someone who has such a strong opinion on all manner of Regs has limited experience in their application. Indeed I recall a post not very long ago where he wanted to know how to fit a grid switch.
 
I am aware of that, but the majority do not pretend to be.
I don't believe he does, any more than do I or other of the non-electrician 'regulars'. I would also say that his knowledge of the regulations and many aspects of matters electrical equals or exceeds that of many electricians.
However someone who has such a strong opinion on all manner of Regs has limited experience in their application.
I would say that the same is true of myself, and a good few others here. I also suspect that a good few of those on the committee that writes the regulations also have limited (or no) experience of their application.

Kind Regards, John
 

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