Dado 3 compartment or Maxi trunking - home office - use singles?

[EFLImpudence]

 

[JohnW2]

No more and no less than I can explain why a normal, standard-integrity ring has to have a ring cpc. It it not supposed to carry any significant current, and we all know that with just one path for pc current it is perfectly OK for fault protection, so there is no conceivable electrical reason that I can think of why a string of sockets needs a ring cpc when L&N are a ring. Can you?

Not really - that is an interesting, but totally different, question. Were they perhaps concerned that if one had one of eric's infamous "106m rings" (or even just a longish non-eric ring) with the CPC only connected at one end, one could run into Zs problems? By my reckoning 106m of 1mm² has a resistance of about 2.3Ω (at 70°) (which would make it impossible to achieve required disconnection times with a B32 or 30A 3036), whereas with a 106m ring CPC, the maximum resistance from any point to CU is only about 0.58Ω.

But it does - the regulations say so, so it has one. The integrity of the earthing that that provides is often cited as an advantage of ring finals, BTW, and that is what is considered to be "standard integrity earthing".

I think we've done this one to death. 543.7.2.201 says "... shall be provided with a high integrity protective conductor connection complying with 543.7.1. The following arrangements of the final circuit are acceptable: (i) A ring final circuit with A ring protective conductor...". Is that not saying that "a ring final circuit with A ring protective conductor" is one acceptable way of achgieving the required compliance with 543.7.1?

Maybe it is, and maybe it isn't. But that is what the regulations say - there are different ways to achieve HI earthing. ......... adding a second ring cpc to a circuit which normally has one ring cpc.

I think we've reached the point at which I have to say that I don't really care what the regulations precisely say. There is, as you know, no compulsion to comply with BS7671, and I would be prepared to stand in front of anyone and present my argument that (a) I believe my interpretation to be correct, certainly in terms of the spirit, and probably with the word, of BS7671, but if 'they' took your view that it was non-compliant with BS7671, then (b) present the electrical argument that a ring final with a single CPC ring (and 'separate terminals') was as safe as (and essentially identical to, CPC-wise) a (BS7671-compliant) radial circuit whose CPC had been turned into a ring, and a lot safer than a (apparently BS7671-compliant) radial circuit with a 10mm² (or mechanically-protected 4mm²) single radial CPC. Do you believe that you could successfully contest that electrical argument (if I choose that route rather than BS7671-compliuance)??

Kind Regards, John

 

[333rocky333]

This months PE magazine has an ad for JTEL and looks like there connecting a HI ring, cant tell the earth configuration though

http://professional-electrician.com/features/jtl-explains-its-electrical-apprenticeship-schemes/

 

[ban-all-sheds]

No, it makes no difference whatsoever what the L&N are - please answer the simple question.

Of course it makes a difference.

Either you really don't understand that, in which case I suggest you leave this discussion, as it is beyond you, or you do realise it but think you can get away with pretending that it doesn't matter.

In the diagram, as drawn, is there one CPC or two CPCs - or some other answer. It's a simple question that you should have no trouble answering.

I'll answer it when you tell me how many line and neutral conductors there are in this:

I can understand you refusing to answer it

I'm not refusing to answer it - I'm saying it depends.

You can clear up the dependence by telling me how many L & N conductors there are in the drawing above.

and doing your usual diversionary tactics to obfuscate your refusal (or inability) to answer,

Neither.

but it does matter. How many CPCs in the diagram ?

It depends.

I didn't ask anything about what regs it may or may not meet, just how many CPCs in the diagram.

So can it not even be assumed that what you have drawn is compliant with any regulation?

 

[ban-all-sheds]

... a high-integrity radial needs either two radial cpcs or one ring cpc, and a high-integrity ring needs two rings cpcs. No anomaly.

No anomaly?

No.

 

[ban-all-sheds]

or, in slightly difference language, there are two protective conductors back to the earth bar. Are you quibbling about some perceived difference between "Protective Conductor" and "Circuit Protective Conductor"??

Not at all. I think the only time I've used "protective conductor" here without "circuit" is in the context of "protective conductor current". But if I am wrong about that then I apologise if it confused you.

Indeed not, but when they are connected at the socket, those two protective conductors, together, become a ring.

Indeed.

A ring.

Not two individual ones.

Any chance you might consider, and answer, my question to you about the rope, or will that be another one you ignore as you have the request to draw a diagram showing a ring final circuit with two individual cpcs where both of them comply with the requirements in Section 543 for ring final cpcs, and then a second one showing one of the two individual cpcs removed leaving one remaining individual cpc which complies with the requirements in Section 543 for ring final cpcs?

 

[ban-all-sheds]

In terms of the sort of thing we are talking about here, one advantage of ring final circuits is that they have CPC redundancy. This means that (unless you subscribe to the BAS viewpoint) a standard ring final circuit is well on the way to being acceptable as a HI earthing system

No, it has standard (for a ring final) integrity earthing. If you want to do HIE, you have a number of options, one of which is doubling the number of compliant cpcs. A concept which you accept for radials but brand an anomaly when applied to rings.

(requiring only the 'separate terminal' addition to be fully 'HI', except for BAS)

It only requires that?

What about 543.7.1.203(iii), which says it needs two individual cpcs?

And it's not "except for me", it's except for what the regulations actually say. You can argue until you are blue in the face that you think they don't mean what they actually say, and that it's OK to certify compliance with BS 7671 by ignoring what they actually say because you think you should do something different to what they actually say, but none of that effort will ever change what they actually say.

 

[EFLImpudence]

(i) A ring final circuit with A ring protective conductor..

Well, that would seem to be definitive.

After reading and deciphering 543.7.1 and all its referrals to other sections, it boils down to that (for a ring).
Would it not have been clearer to place that at the beginning of the section?

So, anyone reading that would not necessarily think that it required using separate earthing terminals.

 

[JohnW2]

... a high-integrity radial needs either two radial cpcs or one ring cpc, and a high-integrity ring needs two rings cpcs. No anomaly.

No anomaly?

No.

You obviously have a different understanding of 'anomoly' than I do.

A 'leak' from L to exposed-c-ps in something plugged into a socket doesn't have a clue as to whether it's plugged in to a ring or radial circuit, and even if it were able to 'talk' to the socket then (unless it were the last socket on a radial), the socket wouldn't have a clue, either. All the socket 'knows' is that it is connected to at least two L conductors, at least two N conductors and a number of protective conductors, and if any of those protective conductors represents an effective path to earth, it will achieve the required goal of minimising the pd between the exposed-c-p and earth. However, it is being suggested that the required number of protective conductors connected to the socket differs according to the type of circuit - even though that is something which is impossible to ascertain by any amount of inspection or testing at the position of the socket (i.e. the situation at the socket is identical, whether it is part of a radial or ring circuit).

I would call that anomalous, even if you wouldn't.

Kind Regards, John

 

[JohnW2]

And it's not "except for me", it's except for what the regulations actually say. You can argue until you are blue in the face that you think they don't mean what they actually say, and that it's OK to certify compliance with BS 7671 by ignoring what they actually say because you think you should do something different to what they actually say, but none of that effort will ever change what they actually say.

As I said, I really don't care what the regulations actually say. (even though I believe that they "actually say" the same as what I believe). I would be totally comfortable with forgetting about BS7671-compliance (in relation to this particular issue) and, instead (e.g. to demonstrate compliance with Part P) to present my own electrical argument as to why a ring final circuit with a single protective conductor ring (and 'separate terminals') is satisfactory as high-integrity earthing. ... and, although you have not replied to my question, I doubt that you (or anyone) would be able to successfully contest my (electrical) argument.

Kind Regards, John

 

[JohnW2]

(i) A ring final circuit with A ring protective conductor..

Well, that would seem to be definitive.

Quite - and that's all I've been trying to say, all along

Kind Regards, John

 

[ban-all-sheds]

That's where we disagree. As one can tell by looking at other parts of 543.7, the main concept for achieving HIE is (very reasonably) for there to be more than one path back to the CU earth bar (i.e. 'CPC redundancy'). A radial circuit does not have that, so one has to add something to make it HIE.

Not so - one can simply increase the size of the cpc, and still retain a single radial one (for a radial circuit).

Perhaps you should read what 543.7.1.203 (i) & (ii) actually say.

However, a standard ring final (with one CPC ring) already has two paths, so does not need anything additional to create 'CPC redundancy'

Yes it does, because a ring final is required to have a ring cpc. If you want cpc redundancy you have to have two ring cpcs.

- which is presumably why 543.7.2.201(i) says that a ring final circuit is acceptable as HIE

What 543.7.2.201 actually says is that you have to have a high integrity protective conductor connection (not circuit, please note) which complies with 543.7.1.

And what do we see are the requirements when we look at 543.7.1?

We see that what 543.7.2.201 requires you to have is:

(i) a high integrity protective conductor connection consisting of a single protective conductor (which for a radial would be a radial cpc, and for a ring would be a ring cpc - if you read 543.2.9 you will see that the latter is undeniably the case) with a csa of not less than 10mm².

or

(ii) a high integrity protective conductor connection consisting of a single protective conductor (which for a radial would be a radial cpc, and for a ring would be a ring cpc - if you read 543.2.9 you will see that the latter is undeniably the case) with a csa of not less than 4mm² and with additional mechanical protection.

or

(iii) a high integrity protective conductor connection consisting of two individual protective conductors, both of which have to comply with (inter alia) 543.2.9, and that means that both of them have to be a ring.

So yes - you can indeed have a single ring cpc qualify as a HIE. But not unless you make it bigger or/and better protected than normal.

In other words, a standard ring final is (give or take the 'separate terminals' requirement) HIE by design (IMO, one of the very few 'pros' of ring finals!), and therefore needs nothing more to bring it up to the same level of HIE as a radial circuit with 'the necessary additions' (or modifications).

So has your "well they don't actually mean that" now expanded to include "well they don't actually mean that 543.7.1.203 (iii) is an option for ring finals"?

 

[ban-all-sheds]

As I wrote yesterday, I think one of the confusions is resulting from the fact that BAS seemingly perceives a difference between "Protective Conductor" and "Circuit Protective Conductor", accepting that the former represents "A path" back to the CU (hence there are two), but regarding the latter ('CPC') as referring to the entire ring of protective conductors (with joints) - in which case there is only one. Where he got those different 'definitions' from, I haven't got a clue.

Neither have I, because all of that is an invention of yours.

Just like your invention that 543.7.1.203 (iii) is not an option for ring finals.

Just like your invention that having two individual protective conductors does not mean that you could remove one of the individuals and be left with the remaining individual.

Just like your invention where if Reg A says that you can have two individual things, lets call then T1 & T2, both of which comply with Reg B, and Reg B says that each thing has to have property P, that that combination does not mean that T1 has to have property P and T2 has to have property P.

Just like your invention that if you asked me to bring you "two individual pieces of rope, both of them 5m long", and I brought you one piece, 10m long, I would have done what you asked.

 

[ban-all-sheds]

I think this really is getting a bit silly.

Blimey - has the penny finally dropped for you about what the regulations actually say?

We're not talking about geometry but, in context (since it's what matters to HIE), about multiplicity/redundancy of paths from a point on the ring back to the CU earth bar. Although, geometrically, a ring/circle is only one line, there are two (curved) 'lines' (aka 'paths') between any two points on the ring/circle.

Yes.

The ring.

THE ring.

Singular.

And 543.7.1.203(iii) requires that there be two individual ones. Not one. Two. Not singular.

Because nowhere does it talk about paths. 543.7.1.203(iii) does not require two individual paths, it requires two individual protective conductors, and a segment of a ring is not an individual protective conductor in the form of a ring with both ends connected to the earthing terminal at the origin of the circuit. The segment only has one end so connected, and therefore the segment does not comply with the requirement in 543.2.9 for the protective conductor of a ring circuit, and therefore the segment is not an individual protective conductor which complies with 543.7.1.203(iii).

 

[ban-all-sheds]

If I understand BAS's reasoning (and use of the terms) correctly, I think he probably believes that a standard circuit has just one "CPC" (no matter what topology/configuration it may have),

Err, if it does not have only one, how can you verify end-to-end continuity of it?

Unless you want to postulate a cpc of infinite length it is going to have to have two ends. So if you have more than one cpc you'll have to have more than two ends.

Does a standard circuit have more than two ends of cpcs?

but that it may consist of two or more "protective conductors". Hence all this tedious "one or two" debate!

No, just more tedious inventions by you.