Poll - Ring final circuits with high integrity earthing

[JohnW2]

First, I must apologise for this: .... I realised after I'd posted it that I'd done wrt you exactly what I'd asked you not to do wrt me, but I was out all day yesterday and couldn't do anything about it.

I'm not sure that I fully understand, but your apology, although I think unnecessary, is happily accepted! As I explained yesterday, although I do fully understand the "consistency and logic" (per se) of what you posted, I believe it to be based on a false premise (that a 'standard' ring final, with separate terminals', is not already "HIE").

Kind Regards, John

 

[ban-all-sheds]

I believe that (in the context we are discussing) 'high integrity' relates to redundancy of 'paths to earth' - i.e. that two or more 'paths to earth' constitutes 'high integrity earthing'.

I believe that that is not what the regulations actually say. But then you don't care a jot what they actually say, do you.

I therefore believe that a standard ring final (if it has 'separate terminals') is already 'high integrity', and therefore does not require anything to be "doubled" to create 'high intensity earthing' - and I believe (subject to confirmation from IET) is that is what 543.7.2.201(i) is trying to say.

543.7.2.201.

That explicitly requires compliance with 543.7.1.

And 543.7.1.203 is a part of 543.7.1.

And 543.7.1.203 requires that circuits which have the characteristics which trigger the applicability of 543.7.2.201 be provided with high integrity protective connection which is one of:

(i) A single protective conductor ≥ 10mm²
(ii) A single protective conductor ≥ 4mm² with extra mechanical protection
(iii) Two individual protective conductors each complying with Section 543
[(iv) or (v) - provisions not relevant to this discussion]

So in the standard ring final with "separate terminals", which of 543.7.1.203 (i), (ii) or (iii) are you claiming compliance?

In other words, I would present your table as:

In other words you would present my table as saying that normally a ring final has "separate terminals" which is untrue.

In other words you would present my table as saying that the number of paths in the cpc of a normal ring final is not applicable, despite your opening statement (and many previous ones) that it is the number of paths to earth which matters.

In other words you introduce untruths into my table to stop it showing the logic and consistency of normal:HI for radial and ring circuits.

Way to go.

 

[JohnW2]

In other words you would present my table as saying that normally a ring final has "separate terminals" which is untrue.

No. If I had been prepared to spend the time creating a new table from scratch (rather than just editing yours), I could have included a third row in the middle, for a 'normal' ring final (without "separate terminals"), which would not have been described as HIE. As it was, I was very clear in indicating that the bottom row related to a ring final with just one 'CPC ring' but with "separate terminals" (which, as I understand it, you still do not accept as being "HIE").

Kind Regards, John

 

[JohnW2]

Well, I didn't have to wait 14 days but, as I feared, all I have got is a 'personal opinion' ....

Thank you for your email. I am required to preface my remarks by saying that I have no authority to interpret the requirements of BS 7671:2008(2015), Requirements for Electrical Installations, however, based on the information you have provided, I hope you will find my comments helpful.

Hmmmm !!

..... As you are aware the basis of the high integrity problem is the security of the earth connection – to stop hazardous voltages (perhaps 90V to earth) appearing on equipment metalwork if the earth connection is lost, so really it is a matter of secure connections and regular inspection of the installation to ensure they remain secure, rather than conductor size.

All true, but not actually anything to do with the explicit regulations about "HIE".

In the light of my opening paragraph above I can only say that it has always been my opinion, and discussion in technical committees has agreed with this, that the ring formed by the protective conductor in a ring final circuit is two conductors from any outlet on the ring back to the DB. I trust that my comments are of some assistance.

That 'opinion' is clearly consistent with my view (and not with BAS's view), but it still is only 'an opinion'. Whilst I am sure that we will never get anything more than 'an opinion', I will attempt to press him a little further and see if I get get his opinion (and agreement from "discussion in technical committees") to go a little further than that emboldened statement and add to the end of it something like "... and therefore would satisfy the requirements for an "HIE" circuit. ... so continue watching this space!

Kind Regards, John

 

[JohnW2]

OK, I think I've pushed the man at the IET as far as he dare go! I asked:

As you will realise from my previous e-mail, that has also always been my opinion. As a result, it has always been my opinion that those "two conductors from any outlet on the ring back to the DB" mean that such a circuit can be regarded as having "high integrity earthing". Whilst again accepting that you have no authority to interpret BS7671, I wonder if you are able to tell me whether your personal opinion about this is the same as mine?

... and the man at the IET replied:

Thanks for your reply, and bearing my former comment about interpretation in mind I would consider that if your ring final circuit protective conductor connections complied with regulation 543.7.1.204 it would be adequate. Most good quality 2 gang 13A socket-outlets have two earth terminals.

I presume that's as close as I am going to get to "the IET" confirming that they agree with my interpretation of the regs - namely that a ring final with a single 'CPC ring' and 'separate terminals' qualifies as "HIE" !!

Anyone who wishes to change their vote is free to do so (and can do so with this forum's software)

Kind Regards, John

 

[EFLImpudence]

For clarification, I did vote 'no' because I do not see how you can comply with one ring of 2.5/1.5 - the actual poll question.





Has anyone mentioned the second paragraph of 543.7.1.203(iii) with regard to the poll question?

 

[SimonH2]

And 543.7.1.203 is a part of 543.7.1.

And 543.7.1.203 requires that circuits which have the characteristics which trigger the applicability of 543.7.2.201 be provided with high integrity protective connection which is one of:

(i) A single protective conductor ≥ 10mm²
(ii) A single protective conductor ≥ 4mm² with extra mechanical protection
(iii) Two individual protective conductors each complying with Section 543
[(iv) or (v) - provisions not relevant to this discussion]

So in the standard ring final with "separate terminals", which of 543.7.1.203 (i), (ii) or (iii) are you claiming compliance?

I'll turn that around to you.
Lets assume for a moment that you are correct, would you please state how the single YELLOW ring in your earlier diagrams meets 543.7.1 (specifically 543,7,1,203(iii)), and also how the single green ring in the same diagrams also meets 543.7.1 ?

Because, according to your logic, each of those rings must on it's own meet the requirements of 543. And since you are adamant that a single ring cannot comply, then neither can either of your two rings individually. So each one, on it's own, must be two rings - so now a total of 4 rings. But then, each of those rings must on it's own comply with 543, and therefore must be two separate rings - so now a total of 8 rings. I think we can all see where this is headed.

But you also have to consider something else. 543.7.2.201 could not be clearer. It says that "A (note the singular) ... with a ring protective conductor ... is acceptable".

So at the very best, all you have proved is that the regs are not consistent within themselves.

 

[ban-all-sheds]

Not IMO. With only two terminals, people could attempt to argue that 'what was connected to which terminal' somehow identified which conductor was part of which ring.

One thing I'm not clear about is what you feel about a radial converted to HIE by turning its CPC into a ring (which I think you agree is acceptable as HIE). Since you would presumably regard that ring as being "one CPC" do I take it that you would therefore believe that 543.7.1.204 doesn't apply - i.e. that there is no 'separate terminals' requirement?

I believe that it does not apply to the situation of a single ring cpc because it clearly says "Where two protective conductors are used in accordance with 543.7.1.203(iii)..."

 

[ban-all-sheds]

I believe it to be based on a false premise (that a 'standard' ring final, with separate terminals', is not already "HIE").

What's the csa of the cpc of a "standard" ring final?

If neither ≥ 10mm² (543.7.1.203(i)) nor ≥ 4mm² with extra mechanical protection (543.7.1.203(ii)) then it does not comply with 543.7.1.203 therefore it does not comply with 543.7.1 therefore it does not comply with 543.7.2.201

 

[EFLImpudence]

And 543.7.1.203 is a part of 543.7.1.

And 543.7.1.203 requires that circuits which have the characteristics which trigger the applicability of 543.7.2.201 be provided with high integrity protective connection which is one of:

(i) A single protective conductor ≥ 10mm²
(ii) A single protective conductor ≥ 4mm² with extra mechanical protection
(iii) Two individual protective conductors each complying with Section 543
[(iv) or (v) - provisions not relevant to this discussion]

So in the standard ring final with "separate terminals", which of 543.7.1.203 (i), (ii) or (iii) are you claiming compliance?

I'll turn that around to you.
Lets assume for a moment that you are correct, would you please state how the single YELLOW ring in your earlier diagrams meets 543.7.1 (specifically 543,7,1,203(iii)), and also how the single green ring in the same diagrams also meets 543.7.1 ?

Because, according to your logic, each of those rings must on it's own meet the requirements of 543. And since you are adamant that a single ring cannot comply, then neither can either of your two rings individually. So each one, on it's own, must be two rings - so now a total of 4 rings. But then, each of those rings must on it's own comply with 543, and therefore must be two separate rings - so now a total of 8 rings. I think we can all see where this is headed.

But you also have to consider something else. 543.7.2.201 could not be clearer. It says that "A (note the singular) ... with a ring protective conductor ... is acceptable".

So at the very best, all you have proved is that the regs are not consistent within themselves.

So, why have you decided that a full page of regulations is irrelevant because of one sentence - which itself could be the mistake?

 

[JohnW2]

For clarification, I did vote 'no' because I do not see how you can comply with one ring of 2.5/1.5 - the actual poll question.

Fair enough - and if you still believe that, it is obviously appropriate that you leave your vote as 'No'. However, if that is the case, I'd be interested to know what you think would be necessary to make a ring final compliant as "HIE" - are you agreeing with BAS that two separate rings of protective conductors would be required, or what?

Also, since you mentioned "2.5/1,5", this seems to imply that you feel that the protective conductors' CSA is part (or all?) of the reason why a single (1.5mm²) CPC ring wouldn't comply as "HIE". If that is the case, can you explain what makes you think that?

Has anyone mentioned the second paragraph of 543.7.1.203(iii) with regard to the poll question?

The second paragraph of 543.7.1.203(iii) is irrelevant to a standard ring final, since the two "patrhs to earth" would be in different cables, wouldn't they?

Kind Regards, John

 

[ban-all-sheds]

No. If I had been prepared to spend the time creating a new table from scratch (rather than just editing yours), I could have included a third row in the middle, for a 'normal' ring final (without "separate terminals"), which would not have been described as HIE.

That was what the last row already described, for a standard-integrity circuit.

As it was, I was very clear in indicating that the bottom row related to a ring final with just one 'CPC ring' but with "separate terminals" (which, as I understand it, you still do not accept as being "HIE").

Not strictly true.

I do accept it as being HIE if the csa of that one cpc ring is either ≥ 10mm² (543.7.1.203(i)) or ≥ 4mm² with extra mechanical protection (543.7.1.203(ii)).

 

[JohnW2]

I believe it to be based on a false premise (that a 'standard' ring final, with separate terminals', is not already "HIE").

What's the csa of the cpc of a "standard" ring final? ... If neither ≥ 10mm² (543.7.1.203(i)) nor ≥ 4mm² with extra mechanical protection (543.7.1.203(ii)) then it does not comply with 543.7.1.203 therefore it does not comply with 543.7.1 therefore it does not comply with 543.7.2.201

The requirement is only to comply with one ("or more") parts of 543.7.1.203, not all parts. Although you disagree, 'we' (including 'the man at the IET') are complying with 543.7.1.203 via 543.7.1.203(iii), which has no requirements as regards CSA (unless more than one protective conductors are in the same cable, which won't be the case) - so there is no requirement to also comply with 543.7.1.203(ii).

Kind Regards, John

 

[ban-all-sheds]

That 'opinion' is clearly consistent with my view (and not with BAS's view)

Nor is it consistent with what the Regulations actually say.

 

[JohnW2]

No. If I had been prepared to spend the time creating a new table from scratch (rather than just editing yours), I could have included a third row in the middle, for a 'normal' ring final (without "separate terminals"), which would not have been described as HIE.

That was what the last row already described, for a standard-integrity circuit.

OK, in that case, had I been bothered to do it, I could have added my row below your ring one. The only difference between those two rows would be the presence/absence of 'separate terminals' which would, in turn, have made one "HIE" and the other not!

I do accept it as being HIE if the csa of that one cpc ring is either ≥ 10mm² (543.7.1.203(i)) or ≥ 4mm² with extra mechanical protection (543.7.1.203(ii)).

As I've just written, that is not necessary. One does not have to comply with (i) or (ii) if one is complying with (iii).

Kind Regards, John