High integrity earthing and ring final circuits.

[Spark123]

Nope, that pic shows a high integrity ring earthing system with a single fault taking out a protective conductor.

But then you do not have a protective conductor remaining which complies with 543.2.9.

No you wouldn't as it is in effect in a fault condition. Nor would you in a normal ring though. The risk is still reduced as the other of the two paths to the MET still maintains the connection to earth.

543.7.1.3 says that you must have two separate ones, each of which complies with 543.2.9. If you have two individual conductors, each of which complies with 543.2.9, then if, as you say, you take one of them out, you must have one left which complies with 543.2.9.

But you don't.

No you don't, but did you ever need the two to comply with 543.2.9 on their own? In a healthy ring state it will comply.

If you claim that your diagram shows two protective conductors, each of which complies with 543.2.9, why when you remove one of them are you not still left with one which complies with 543.2.9?

If x-1 /= 1, then x /= 2.

I don't claim them both to comply with 543.2.9, I claim there to be two protective paths via conductors from each accessory and in a healthy state it to comply with 543.2.9.

Nope, how I interpret it is obvoiusly different to the way you interpret it. I have taken on board what the on site guide and the guidance notes say on the matter also.

I interpret it how it was written.

So do I, also taking into account what is written in the guidance notes and the on site guide.

I read the words with their normal everyday meaning - words like "individual", "two", "each". I don't have to start saying "Ah but in this case it doesn't mean that" to get my explanation to hang together.

I don't have inconsistencies with counting and simple arithmetic every time I explain one thing and then try to use the same rules to explain something else.

I obviously have a different viewpoint from you, and read and interpret english differently. Maybe everyone reads things an interprets things differently, doesn't necesserilly mean everyone else is wrong.

It has one circuit protective conductor made up of a number of protective conductors.

OK - so let's go with that for a while, and assume that when the regulations talk about the requirements for the protective conductor(s) of a circuit they don't actually mean the circuit protective conductor(s).

You say that there are a number of protective conductors, and that it's these to which 543.7.1.3 refers.

So how do we resolve the inconsistency between that, and 543.7.2.1 (ii) (a) where it also uses the term "protective conductor", but says "a radial final circuit with a single protective conductor" and "the protective conductor being connected as a ring"?

You can't take one of your multiple protective conductors and claim that it is also the single protective conductor for a radial final circuit, nor can you take one of your multiple protective conductors and form it into a ring.

But if we regard "protective conductor" and "circuit protective conductor" as synonymous (which is really hard not to when faced with phrases like "a ring final circuit with a ring protective conductor", or "a radial final circuit with a single protective conductor") then all of the inconsistencies just disappear, and we are left with a perfectly clear, logical and unambiguous set of requirements which all fit together.

In the pic I drew the protective conductors were formed together and connected as a ring. It still doesn't alter the fact that there are two paths for current to flow through two different and independant of each other legs. A protective conductor can connect together an exposed conductive part and the MET. It can also connect together two exposed conductive parts.

If you had two then you would be able to measure two different continuities between two sets of ends at the CU. But you can't, because you don't have two.

You can't do this with a bog standard radial circuit, but that doesn't mean it doesn't have a protective conductor.

I was talking about ring cpcs. You can measure the continuity between the two ends of a bog standard radial cpc, just not at the CU. And if the radial circuit had two separate cpcs then you could measure two separate continuities.

I have never claimed there to be 2 ring protective conductors though.

No you haven't, but then that is the basis of your argument, that "protective conductor" and "circuit protective conductor" are not the same thing, even when the regulations say "a ring final circuit with a ring protective conductor".

I am not saying they are completely different, just the circuit protective conductor can be made up of protective conductors.

If you were wiring in singles you could, at the cost of considerable time, do it without cutting any of the cables at all, just removing a section of sleeving and bending the cable into a 'U' at that point to get it into the terminal. At what point in that operation would your single unbroken conductor become two conductors? Are there any topology theories which explain that? Are there any which explain why if there is such an operation it doesn't create 3 conductors when you do it again, or 4 when you do it a 3rd time, etc?

If you should lose one through it being broken it will become 2 conductors.

Could you please answer the actual question asked? With a continuous length of copper wire with little U shaped bends in various places, when does it become two conductors and how, and why when whatever the operation is that takes it from one to two is carried out another n times doesn't it take it to n+2 conductors?

This is over and above what the regs require, what if the circuit was wired as you seem adamant on it being necessary via two ring CPCs, a single length of copper used for one ring doing the thing so it remains unbroken at each socket, then when it returns to the CU it remains unbroken into and back out of the MET, then does the rounds on the other CPC ring? Would you still consider that a single protective conductor?

Of course, if we consider it as a single circuit protective conductor no matter how many times it's bent and connected to a socket terminal then we don't have that inconsistency to deal with.

Yep, I would consider it a single CPC.

Using the method you describe is over and above what is required by the regs.

No - it's exactly what the regulations as written require.

Where does it say the CPC has to remain unbroken throughout its length?

Yep, both the protective conductors from each point need to comply with 543.2.

Ah - so if both the protective conductors fro each point comply with 543.2 then both of them must be rings.

Notice the use of the word protective conductor as opposed to Circuit protective conductor though

Could you please pick one of the rings at any of the points in your diagram and remove it, and show how at that point there's only one ring left?

I don't need to remove a ring though, just one protective conductor. Each accessory will still be connected to the MET via protective conductors.

 

[ban-all-sheds]

No you wouldn't as it is in effect in a fault condition. Nor would you in a normal ring though.

But if you had started out with two separate protective conductors, each of which complied with 543.2.9 then removing one would still leave you with one remaining protective conductor complying with 543.2.9.

The fact that you don't have one left proves that you didn't have two in the first place, because the solution to

x-1=0

is that x = 1, not 2.

No you don't, but did you ever need the two to comply with 543.2.9 on their own?

No you don't - you only need one.

But to comply with 543.7.1.3 (iii) you need two, each of which complies with 543.2.9.

I don't claim them both to comply with 543.2.9, I claim there to be two protective paths via conductors from each accessory and in a healthy state it to comply with 543.2.9.

But that's not what the regulations say you must have.

543.7.1.3 (iii) two individual protective conductors each complying with the requirements of Section 543.

I don't claim them both to comply with 543.2.9

Then your interpretation leads to an arrangement which does not comply with 543.7.1.3 (iii).

So do I, also taking into account what is written in the guidance notes and the on site guide.

Do you take into account the disclaimers in those?

And do you take into account that there are clearly a lot of people who cannot or will not read what the regulations actually say?

And do you take into account that what the guidance documents say clearly contradicts what the regulations say?

And do you take into account that it is the Wiring Regulations which define BS 7671, not any guidance publications?

I obviously have a different viewpoint from you, and read and interpret english differently. Maybe everyone reads things an interprets things differently, doesn't necesserilly mean everyone else is wrong.

So do you not accept the dictionary definition of "individual"?

Do you not accept the conventional numerical definition of "two"?

In the pic I drew the protective conductors were formed together and connected as a ring. It still doesn't alter the fact that there are two paths for current to flow through two different and independant of each other legs.

I'm not saying it does.

But the wording of the regulations is not "two individual current paths" it is "two individual protective conductors".

I am not saying they are completely different, just the circuit protective conductor can be made up of protective conductors.

So how does your diagram show compliance with 543.7.1.3 (i) and (ii) which require a single protective conductor?

What consistent meaning for "protective conductor", and consistent way of counting them are there such that the diagram posted at the start shows either a circuit with a single protective conductor or one with two individual protective conductors?

This is over and above what the regs require,

I never said, or suggested, that it was what the regs required. It was a scenario I created to try and get to the heart of your theory of protective conductor counting.

what if the circuit was wired as you seem adamant on it being necessary via two ring CPCs, a single length of copper used for one ring doing the thing so it remains unbroken at each socket, then when it returns to the CU it remains unbroken into and back out of the MET, then does the rounds on the other CPC ring? Would you still consider that a single protective conductor?

No, I'd consider it two cpcs, because once it's returned to the MET it has become a ring, so if you take it on another journey you create a second ring. And if you take it on a 3rd journey you create a third ring. And so on - perfectly consistent. I could cut, or remove by cutting, one of the rings and still be left with the others - perfectly consistent.

Using the method you describe is over and above what is required by the regs.

No - it's exactly what the regulations as written require.

Where does it say the CPC has to remain unbroken throughout its length?

It doesn't, I thought that you were referring to "my method" as in having two ring cpcs. It never occurred to me that you could possibly imagine that I was suggesting that the regulations require the cpc to be unbroken.

So now that we've got that little diversion out of the way, if I could ask you again to consider a circuit with the cpc unbroken (without assuming I'm saying it has to be to comply with the regulations), if you had a continuous length of copper wire with little U shaped bends in various places, when does it become two conductors and how, and why when whatever the operation is that takes it from one to two is carried out another n times doesn't it take it to n+2 conductors?

Notice the use of the word protective conductor as opposed to Circuit protective conductor though

Yes, I have noted it. And I have noted that you do not believe that "protective conductor" is synonymous with "circuit protective conductor" even when used in the phrase "a ring final circuit with a ring protective conductor".

But that's fine - if your reading is that "protective conductor" means any arbitrary component of the circuit protective conductor, and therefore 543.7.1.3 (iii) isn't calling for two individual circuit protective conductors, let's look again at the diagram:

With the explanatory text removed this could be showing a ring cpc for a ring circuit, complying with 543.7.1.3 (i) or (ii), or according to you (iii).

It could also be showing the cpc for a radial circuit complying with 543.7.2.1 (ii) (a).

Can you please show how a consistent definition, and method of counting, could be applied to that diagram to label

1. 543.7.1.3 (i) a single protective conductor
2. 543.7.1.3 (ii) a single protective conductor
3. 543.7.1.3 (iii) two individual protective conductors
4. 543.7.2.1 (ii)(a) a single protective conductor connected as a ring

 

[ColJack]

ok, so for a radial... the following holds true according to your definition?

543.7.1.3
(i) if it's a 10mm cpc than you don't need to connect back from the last socket..

(ii) if it's a 4mm cpc ( with mechanical protection ) you don't need to connect back form the last socket..

(iii) if it's less than 4mm then you need to connect it back from the last socket ( via metal trunking / conduit, a seperate earth wire, or by connecting to the last socket of a similar radial

for (iii) you then have 2 individual conductors connected in the form of a ring.
by your definition then, as soon as you connect the ends of the conductors at the sockets and earth terminal, you no longer have 2 individual conductors, just a single one..

 

[ban-all-sheds]

ok, so for a radial... the following holds true according to your definition?

543.7.1.3
(i) if it's a 10mm cpc than you don't need to connect back from the last socket..

Yes you do - 543.7.1.3 (i) defines the characteristics of the conductor, 543.7.2.1 (ii)(a) tells you to connect it as a ring.

(ii) if it's a 4mm cpc ( with mechanical protection ) you don't need to connect back form the last socket..

Ditto

(iii) if it's less than 4mm then you need to connect it back from the last socket ( via metal trunking / conduit, a seperate earth wire, or by connecting to the last socket of a similar radial

Not quite - you need to do that whatever.

for (iii) you then have 2 individual conductors connected in the form of a ring.

Which makes one ring.

by your definition then, as soon as you connect the ends of the conductors at the sockets and earth terminal, you no longer have 2 individual conductors, just a single one..

Yes - one single ring conductor.

Which is OK in 10mm², or 4mm²+protection, but if not (e.g. the circuit is wired in 2.5/1.5mm² T/E you need two individual rings.

 

[ColJack]

again you have me at a disadvantage, I don't have a copy of the 17th edition yet...

however, it does not mention a single protenctive conductor connected as a ring for a radial in the 16th edition..
a single 10mm cpc is acceptable as a high integrity earth.
a single 4m cpc that is mechanically protected is acceptible as a high integrity earth..
2 individual conductors of less than 4mm is acceptable as a hgh integrity earth..

 

[Spark123]

No you don't, but did you ever need the two to comply with 543.2.9 on their own?

No you don't - you only need one.

But to comply with 543.7.1.3 (iii) you need two, each of which complies with 543.2.9.

This is where my thoughts differ in the interpretation from you.

I don't claim them both to comply with 543.2.9

Then your interpretation leads to an arrangement which does not comply with 543.7.1.3 (iii).

If the individual protective conductors are sized in accordance with section 543 and they form a ring then I don't see the problem.

So do I, also taking into account what is written in the guidance notes and the on site guide.

Do you take into account the disclaimers in those?

Yes, I do. I also take into account they are written by engineers from the IET and are aimed at the likes of myself to help comply with the regulations.

And do you take into account that there are clearly a lot of people who cannot or will not read what the regulations actually say?

Yep, and those that try to understand what the regulations say and apply them in real life situations. Using the guidance notes and on site guide help cross this boundry - the regs state what needs to be done, the guidance notes and OSG aid in how to do it.

And do you take into account that what the guidance documents say clearly contradicts what the regulations say?

I wouldn't say clearly contradicts.

And do you take into account that it is the Wiring Regulations which define BS 7671, not any guidance publications?

Like I said above, it is the regs which say what needs to be done. The guides offer assistance in how to accomplish it.

I obviously have a different viewpoint from you, and read and interpret english differently. Maybe everyone reads things an interprets things differently, doesn't necesserilly mean everyone else is wrong.

So do you not accept the dictionary definition of "individual"?

Individual as in separate from each other? 2 protective conductors at each point each providing a separate and independant path back to the MET.

In the pic I drew the protective conductors were formed together and connected as a ring. It still doesn't alter the fact that there are two paths for current to flow through two different and independant of each other legs.

I'm not saying it does.

But the wording of the regulations is not "two individual current paths" it is "two individual protective conductors".

The current is flowing through 2 separate paths through separate protective conductors.

I am not saying they are completely different, just the circuit protective conductor can be made up of protective conductors.

So how does your diagram show compliance with 543.7.1.3 (i) and (ii) which require a single protective conductor?

I don't claim the diagram to show any sort of compliance with 543.7.1.3 (i) and (ii), these require a protective conductor to connect the item back to the MET in the sizes stated.

So now that we've got that little diversion out of the way, if I could ask you again to consider a circuit with the cpc unbroken (without assuming I'm saying it has to be to comply with the regulations), if you had a continuous length of copper wire with little U shaped bends in various places, when does it become two conductors and how, and why when whatever the operation is that takes it from one to two is carried out another n times doesn't it take it to n+2 conductors?

So it is OK for the conductors to be classed as separate conductors if connected but looped at the MET, but not if they are connected and looped at an accessory? The idea of high integrity earthing is to either ensure the path to earth is not lost or to provide another path should one be broken.

Untitled

• Spark123
• 26 Jul 2008
• 1

 

[ban-all-sheds]

This is where my thoughts differ in the interpretation from you.

I read "two individual protective conductors, each complying with...." as meaning two individual protective conductors, each complying with...
i.e. "this individual protective conductor, complying with... and this other individual protective conductor complying with...".

There really is no more reasonable interpretation, and in fact I'd hardly call it an "interpretation" at all - English is my first language, and it's written in English. I just read it, and understand it, in the same way that if I read "two individual fillets of white fish, each weighing about 250g" or "you'll need two individual pieces of 4x2, each 8' long" I'd know exactly what it meant without engaging in tortuous "interpretation".

Maybe the fact that you feel you need to "interpret" what is written rather than just simply reading it is part of the problem here?

If the individual protective conductors are sized in accordance with section 543 and they form a ring then I don't see the problem.

The problem is that if in 543.7.1.3 you decide that "protective conductor" means one of the individual links, that doesn't allow you to just have a single one as per (i) and (ii), nor two of them as per (iii), nor does it allow you to have each one complying with 543.2.

Do you take into account the disclaimers in those?

Yes, I do. I also take into account they are written by engineers from the IET and are aimed at the likes of myself to help comply with the regulations.

Maybe they too are written by people who cannot or will not read "two individual protective conductors, each complying with..." in the simplest, most obvious and most normal way.

And do you take into account that there are clearly a lot of people who cannot or will not read what the regulations actually say?

Yep, and those that try to understand what the regulations say and apply them in real life situations.

There is no "try to understand", or at least there wouldn't be if you didn't insist on artificially creating a need. "When we go camping we'll need two tents, each capable of sleeping 4 people" does not need any effort to understand it - you read it, it's plain what it means and you understand it.

"We're looking for for volunteers for transport duty - we'll need two drivers, each with a vehicle that can carry 3 passengers" does not need any effort to understand it - you read it, it's plain what it means and you understand it.

"Two individual protective conductors, each complying with the requirements of Section 543" does not need any effort to understand it - you read it, it's plain what it means and you understand it.

Or at least, you should.

Using the guidance notes and on site guide help cross this boundry - the regs state what needs to be done, the guidance notes and OSG aid in how to do it.

But you are using guidance documents, or if tasked would write guidance documents yourself, which do not show you how to do what the regulations state - they show you how to do something different.

And do you take into account that what the guidance documents say clearly contradicts what the regulations say?

I wouldn't say clearly contradicts.

However you define and count them, this diagram:



does not show two individual protective conductors.

And do you take into account that it is the Wiring Regulations which define BS 7671, not any guidance publications?

Like I said above, it is the regs which say what needs to be done. The guides offer assistance in how to accomplish it.

So in other words what is written in the Regulations is what defines compliance with BS7671, not what's written in the guides.

Hence the disclaimers in the latter.

Individual as in separate from each other? 2 protective conductors at each point each providing a separate and independant path back to the MET.

But that's not what the regulations say.

They don't say you must have "two protective conductors at each point each providing a separate and independent path back to the MET", they say that the circuit must have a high integrity protective connection consisting of two individual protective conductors...

The current is flowing through 2 separate paths through separate protective conductors.

But if that is how you decide that there are two individual protective conductors you don't then have a situation where each of them complies with the requirements of Section 543.

And 543.7.1.3 (iii) says that each of them must.

I don't claim the diagram to show any sort of compliance with 543.7.1.3 (i) and (ii), these require a protective conductor to connect the item back to the MET in the sizes stated.

OK - assuming that the sizes are OK, do you claim that the layout of the protective conductor(s) complies with 543.7.1.3 (i) and (ii)?

So it is OK for the conductors to be classed as separate conductors if connected but looped at the MET, but not if they are connected and looped at an accessory? The idea of high integrity earthing is to either ensure the path to earth is not lost or to provide another path should one be broken.

Never mind what the reasons for high integrity earthing are - will you please stop evading a request for you to explain how you designate and count individual conductors.

If you had a continuous length of copper wire with little U shaped bends in various places, when does it become two conductors and how, and why when whatever the operation is that takes it from one to two is carried out another n times doesn't it take it to n+2 conductors?

Untitled

• Spark123
• 26 Jul 2008
• 1

Can you clarify what the numbers mean?

I can see individual lengths of protective conductor with:
. a 1 at each end
. a 2 at each end
. a 1 at one end and a 2 at the other

so they can't be saying "this is protective conductor #1 and this is protective conductor #2"

Also that drawing has 5 components each labelled "protective conductor" - can you explain how they relate to either the requirement in 543.7.1.3 (i) and (ii) for "a single protective conductor" or the one in 543.7.1.3 (iii) for "two individual protective conductors"?

 

[Spark123]

This is where my thoughts differ in the interpretation from you.

I read "two individual protective conductors, each complying with...." as meaning two individual protective conductors, each complying with...
i.e. "this individual protective conductor, complying with... and this other individual protective conductor complying with...".

There really is no more reasonable interpretation, and in fact I'd hardly call it an "interpretation" at all - English is my first language, and it's written in English. I just read it, and understand it, in the same way that if I read "two individual fillets of white fish, each weighing about 250g" or "you'll need two individual pieces of 4x2, each 8' long" I'd know exactly what it meant without engaging in tortuous "interpretation".

Maybe the fact that you feel you need to "interpret" what is written rather than just simply reading it is part of the problem here?

The first time I ever read that regulation I envisaged having two separate conductors between each accessory and the main earthing terminal. This would have meant a reduculous amount of protective conductors at the MET, for example if there were 10 sockets then there would need to be 20 conductors at the MET. Then I read the guidance documentation which pointed me in the correct direction.

If the individual protective conductors are sized in accordance with section 543 and they form a ring then I don't see the problem.

The problem is that if in 543.7.1.3 you decide that "protective conductor" means one of the individual links, that doesn't allow you to just have a single one as per (i) and (ii), nor two of them as per (iii), nor does it allow you to have each one complying with 543.2.

I don't see a problem with there only being one ring, it seems the people who write the OSG and the guidance notes also don't see a problem with it.

Do you take into account the disclaimers in those?

Yes, I do. I also take into account they are written by engineers from the IET and are aimed at the likes of myself to help comply with the regulations.

Maybe they too are written by people who cannot or will not read "two individual protective conductors, each complying with..." in the simplest, most obvious and most normal way.

Maybe they are, but then maybe they understand what the requirements are about and the best way about achieving them.

"Two individual protective conductors, each complying with the requirements of Section 543" does not need any effort to understand it - you read it, it's plain what it means and you understand it.

Or at least, you should.

The guidance issued by the IET says that ring final circuit provide duplication of the protective conductor. Read into this however you like, I take it to mean this as there are two paths via two protective conductors as I have drawn on a diagram on a number of occasions.

Using the guidance notes and on site guide help cross this boundry - the regs state what needs to be done, the guidance notes and OSG aid in how to do it.

But you are using guidance documents, or if tasked would write guidance documents yourself, which do not show you how to do what the regulations state - they show you how to do something different.

I have written guidance documents myself yes, I have read numerous documents produced by other people. Everyone has a different approach at putting a piont across, some are more clear than others. You know yourself at times regs can be a bit of a minefield!

And do you take into account that what the guidance documents say clearly contradicts what the regulations say?

I wouldn't say clearly contradicts.

However you define and count them, this diagram:



does not show two individual protective conductors.

It shows a duplication of a protective path which the people at the IET who write the guides appear to deem to be an acceptable method.

And do you take into account that it is the Wiring Regulations which define BS 7671, not any guidance publications?

Like I said above, it is the regs which say what needs to be done. The guides offer assistance in how to accomplish it.

So in other words what is written in the Regulations is what defines compliance with BS7671, not what's written in the guides.

There are always going to be grey areas, I'm not denying that. Maybe if you feel so strongly about the difference between what is in the regs, your method of complying with them and what is in the guidance notes or on site guide then you can start a post over on the IET forum and see what the boys over there have to say on the matter.

Individual as in separate from each other? 2 protective conductors at each point each providing a separate and independant path back to the MET.

But that's not what the regulations say.

Maybe not, but maybe it is an accepted method of looking at the subject.

They don't say you must have "two protective conductors at each point each providing a separate and independent path back to the MET", they say that the circuit must have a high integrity protective connection consisting of two individual protective conductors...

A ring final employing accessories with 2 terminals with a protective conductor in each terminal provides duplication of the protective conductor. They are separate from each other as in they provide a separate route for current to flow. In the event of one being lost the other one maintains the protective path.

The current is flowing through 2 separate paths through separate protective conductors.

But if that is how you decide that there are two individual protective conductors you don't then have a situation where each of them complies with the requirements of Section 543.

You'd have to check each of them complies at each point.

I don't claim the diagram to show any sort of compliance with 543.7.1.3 (i) and (ii), these require a protective conductor to connect the item back to the MET in the sizes stated.

OK - assuming that the sizes are OK, do you claim that the layout of the protective conductor(s) complies with 543.7.1.3 (i) and (ii)?

If the conductors were larger then they would comply, I don't rate the idea of using the 2 screws in the back of the sockets to extend the protective conductor of the circuit around. A bus bar system or individual protective conductors from an earthing terminal may be a better idea for (i) and (ii).

So it is OK for the conductors to be classed as separate conductors if connected but looped at the MET, but not if they are connected and looped at an accessory? The idea of high integrity earthing is to either ensure the path to earth is not lost or to provide another path should one be broken.

Never mind what the reasons for high integrity earthing are - will you please stop evading a request for you to explain how you designate and count individual conductors.

I'd count them between their terminations and/or change in use. The diagram before clearly shows the conductors to be separate conductor lengths though.

Untitled

• Spark123
• 26 Jul 2008
• 1

Can you clarify what the numbers mean?

I can see individual lengths of protective conductor with:
. a 1 at each end
. a 2 at each end
. a 1 at one end and a 2 at the other

so they can't be saying "this is protective conductor #1 and this is protective conductor #2"

Also that drawing has 5 components each labelled "protective conductor" - can you explain how they relate to either the requirement in 543.7.1.3 (i) and (ii) for "a single protective conductor" or the one in 543.7.1.3 (iii) for "two individual protective conductors"?

I think I have covered this a number of times now, so many it is becoming tedious.
There are two protective paths via the various protective conductors back to the MET from each point. Point 1 on the each socket is providing a path back to 1 on the MET. Point 2 is providing a path to 2 on the MET via a separate protective conductor route to that of 1.

 

[ban-all-sheds]

The first time I ever read that regulation I envisaged having two separate conductors between each accessory and the main earthing terminal. This would have meant a reduculous amount of protective conductors at the MET, for example if there were 10 sockets then there would need to be 20 conductors at the MET.

Surely if 1 ring cpc gets you 2 connections at the MET, irrespective of how many accessories there are, 2 ring cpcs would get you 4 connections at the MET, irrespective of how many accessories there are....?

Then I read the guidance documentation which pointed me in the correct direction.

But not a direction described by The Wiring Regulations.

I don't see a problem with there only being one ring, it seems the people who write the OSG and the guidance notes also don't see a problem with it.

The problem is that The Wiring Regulations say otherwise.

Maybe they are, but then maybe they understand what the requirements are about and the best way about achieving them.

Then their understanding diverges from what the words in The Wiring Regulations actually say.

The guidance issued by the IET says that ring final circuit provide duplication of the protective conductor. Read into this however you like, I take it to mean this as there are two paths via two protective conductors as I have drawn on a diagram on a number of occasions.

And to which I have replied on a number of occasions that yes, it provides two paths but no, two paths is not the requirement described by the words in The Wiring Regulations.

I have written guidance documents myself yes, I have read numerous documents produced by other people. Everyone has a different approach at putting a piont across, some are more clear than others. You know yourself at times regs can be a bit of a minefield!

Yup, and illogical and inconsistent.

It seems perverse therefore to read a clearly worded requirement and then to seek to interpret it in a way that adds to the inconsistencies rather than a way which is follows the actual wording and doesn't create inconsistencies.

It shows a duplication of a protective path which the people at the IET who write the guides appear to deem to be an acceptable method.

But it does not show a method deemed acceptable by the people who wrote and ratified The Wiring Regulations.

There are always going to be grey areas, I'm not denying that.

But in this case you chose to regard something as grey when the black and white was perfectly clear.

Maybe if you feel so strongly about the difference between what is in the regs, your method of complying with them and what is in the guidance notes or on site guide then you can start a post over on the IET forum and see what the boys over there have to say on the matter.

The boys and girls over there are no different from the boys and girls over here.

But in any event I wasn't aware that expressing opinions on Internet fora was the way that changes were made to the ratified and published versions of national standards such as BS 7671.....

Maybe not, but maybe it is an accepted method of looking at the subject.

It is not a method deemed acceptable by the people who wrote and ratified The Wiring Regulations.

A ring final employing accessories with 2 terminals with a protective conductor in each terminal provides duplication of the protective conductor. They are separate from each other as in they provide a separate route for current to flow. In the event of one being lost the other one maintains the protective path.

Two separate routes is not what The Wiring Regulations say is required.

You'd have to check each of them complies at each point.

So at each point you believe that there are two conductors, each of which complies with the requirements of Section 543?

I've checked, and I can't see that there is. Yes there are two individual current paths back to the MET, but there are not two rings at each point, and that is what is required by one of the paragraphs in Section 543.

Furthermore, if you are now to use "two independent current paths" as what is really being asked for by 543.7.1.3, then please use the same interpretation in the rest of Section 543 and show how the circuit has two independent current paths each of which complies with Section 543.

If the conductors were larger then they would comply,

So you say that it shows an arrangement which complies with a requirement for a single protective conductor.

And with one which requires two individual protective conductors.

And you really don't see any inconsistency there?

If that circuit was installed with just a 10mm² cpc being done first, and then phase & neutral added in a radial design then you say it would comply because it had the single protective conductor required by 543.7.1.3.

If it were then turned into a ring final by extending the phase & neutral conductors back to the origin then you say it would comply because it had the two individual protective conductors required by 543.7.1.3.

Can you please show how turning the phase and neutral conductors into a ring and doing absolutely nothing to the cpc would double the number of protective conductors?

I'd count them between their terminations and/or change in use. The diagram before clearly shows the conductors to be separate conductor lengths though.

But how many does it show, in your scheme?

Does it show the single protective conductor required by 543.7.1.3 (i) and (ii) or the two individual protective conductors required by 543.7.1.3 (iii)

I think I have covered this a number of times now, so many it is becoming tedious.

What you've done, possibly to the point of tedium is to take a very clearly worded requirement, just as clear as "Into this box you will place two individual bars of chocolate, each weighing 200g", and claiming that it means something other than what the words say, despite the fact that as soon as you do that you end up with a whole stack of inconsistencies that you simply would not if you just stuck to what the words actually say.

There are two protective paths via the various protective conductors back to the MET from each point. Point 1 on the each socket is providing a path back to 1 on the MET. Point 2 is providing a path to 2 on the MET via a separate protective conductor route to that of 1.

But 543.7.1.3 doesn't say that from each point of use there shall be two protective paths back to the MET.

It says that the circuit shall have two independent protective conductors.

 

[Spark123]

The first time I ever read that regulation I envisaged having two separate conductors between each accessory and the main earthing terminal. This would have meant a reduculous amount of protective conductors at the MET, for example if there were 10 sockets then there would need to be 20 conductors at the MET.

Surely if 1 ring cpc gets you 2 connections at the MET, irrespective of how many accessories there are, 2 ring cpcs would get you 4 connections at the MET, irrespective of how many accessories there are....?

Like I have said all along, it is open to interpretation. If what I originally thought was true then there would be 2 completely independant conductors at each point, I'll hold my hand up that was completely wrong on that front!

Then I read the guidance documentation which pointed me in the correct direction.

But not a direction described by The Wiring Regulations.

Maybe in your eyes not, but in the eyes of the IET who write the guidance notes it complies.

Maybe they are, but then maybe they understand what the requirements are about and the best way about achieving them.

Then their understanding diverges from what the words in The Wiring Regulations actually say.

It is probably the difference between someone sitting in an office writing a document and someone having to follow the said document in the field. I don't know what your line of work is but I have, as a tradesman, tried to follow documents written by people who have never seen the work before and a lot of the time I find them not a lot of use and full of errors.

It shows a duplication of a protective path which the people at the IET who write the guides appear to deem to be an acceptable method.

But it does not show a method deemed acceptable by the people who wrote and ratified The Wiring Regulations.

And yet it is the people from the same place who write the guidance on the document...

But in any event I wasn't aware that expressing opinions on Internet fora was the way that changes were made to the ratified and published versions of national standards such as BS 7671.....

It probably won't make any difference, but at least it will probably have more input than from a DIY forum.

Maybe not, but maybe it is an accepted method of looking at the subject.

It is not a method deemed acceptable by the people who wrote and ratified The Wiring Regulations.

The same organisation who wrote the guidance notes and the on site guide too.

If the conductors were larger then they would comply,

So you say that it shows an arrangement which complies with a requirement for a single protective conductor.

Not really, the protective conductors do not need to form a ring when they are larger.

I'd count them between their terminations and/or change in use. The diagram before clearly shows the conductors to be separate conductor lengths though.

But how many does it show, in your scheme?

It shows a single ring circuit protective conductor which is made up of a number of lengths of protective conductors. The integrity of which is doubled as it has two connections with the MET.

Does it show the single protective conductor required by 543.7.1.3 (i) and (ii) or the two individual protective conductors required by 543.7.1.3 (iii)

Nothing to do with (i) or (ii). It shows two paths for protective currents to flow through separate conductors.

There are two protective paths via the various protective conductors back to the MET from each point. Point 1 on the each socket is providing a path back to 1 on the MET. Point 2 is providing a path to 2 on the MET via a separate protective conductor route to that of 1.

But 543.7.1.3 doesn't say that from each point of use there shall be two protective paths back to the MET.

It says that the circuit shall have two independent protective conductors.

The two protective conductors at each point are independant of each other

 

[Bahco]

So, who won in the end?

If you pair need something to do you can help me put my coving up!

 

[ban-all-sheds]

But not a direction described by The Wiring Regulations.

Maybe in your eyes not, but in the eyes of the IET who write the guidance notes it complies.

Well then here we have a very real and serious problem. Because even the IET intended exactly what you say, that is not what they wrote in The Wiring Regulations, which are also a British Standard.

National standards cannot be amended by non-standards body publications. GNs are published by the IET - they are not BS documents, and they neither define nor amend formal standards.

But it does not show a method deemed acceptable by the people who wrote and ratified The Wiring Regulations.

And yet it is the people from the same place who write the guidance on the document...

GNs are published by the IET - they are not BS documents, and they neither define nor amend formal standards. And they have disclaimers.

The same organisation who wrote the guidance notes and the on site guide too.

GNs and the OSG are published by the IET - they are not BS documents, and they neither define nor amend formal standards. And they have disclaimers.

Not really, the protective conductors do not need to form a ring when they are larger.

543.7.2.1 (ii) (a).

It shows a single ring circuit protective conductor which is made up of a number of lengths of protective conductors.

In which case for it to comply with 543.7.1.3 (i) and (ii), then "protective conductor" in the phrase "a single protective conductor" in those two must be synonymous with "ring circuit protective conductor", in order to match your "a single ring circuit protective conductor".

I suggest that it would be utterly preposterous to decide that within one regulation a term varies in meaning from one sentence to the next, so in 543.7.1.3 (iii) it's also synonymous, and therefore 543.7.1.3 (iii) requires two individual ring circuit protective conductors.

Nothing to do with (i) or (ii). It shows two paths for protective currents to flow through separate conductors.

How can it be nothing to do with a regulation you say it illustrates?

If it's supposed to tell you how to comply then it must show something which does comply.

And no matter how many times you talk about current paths that will not change the words printed on the pages of BS 7671:2008.

The two protective conductors at each point are independant of each other

But that's not the requirement written in The Wiring Regulations.

 

[Spark123]

Not really, the protective conductors do not need to form a ring when they are larger.

543.7.2.1 (ii) (a).

Doesn't (iii) allow you to refer to 543.7.1, 543.7.1.3 (i) and (ii) which are the regs relating to using larger protective conductors which don't mention using ring conductors?

I suggest that it would be utterly preposterous to decide that within one regulation a term varies in meaning from one sentence to the next, so in 543.7.1.3 (iii) it's also synonymous, and therefore 543.7.1.3 (iii) requires two individual ring circuit protective conductors.

Yet in 543.7.2.1 it requires a ring protective conductor, as in one ring protective conductor?

 

[ban-all-sheds]

Doesn't (iii) allow you to refer to 543.7.1, 543.7.1.3 (i) and (ii) which are the regs relating to using larger protective conductors which don't mention using ring conductors?

543.7.2 Socket-outlet final circuits. The following arrangements of the final circuit are acceptable:
(i) a ring final circuit with a ring protective conductor
(ii)(a) a radial final circuit with a single protective conductor connected as a ring

i.e. you can meet the requirement for a radial with a ring cpc.

i.e. the diagram showing a ring cpc could be showing a compliant cpc for a radial circuit, which is what I said.

Yet in 543.7.2.1 it requires a ring protective conductor, as in one ring protective conductor?

543.7.2.1 (i) + 543.7.1.3 (i) a ring final circuit with a ring protective conductor having a cross-sectional area of not less than 10mm²...

543.7.2.1 (i) + 543.7.1.3 (ii) a ring final circuit with a ring protective conductor having a cross-sectional area of not less than 4mm²...

543.7.2.1 (iii) + 543.7.1.3 (iii) a ring final circuit with two individual ring protective conductors...

 

[Spark123]

Doesn't (iii) allow you to refer to 543.7.1, 543.7.1.3 (i) and (ii) which are the regs relating to using larger protective conductors which don't mention using ring conductors?

543.7.2 Socket-outlet final circuits. The following arrangements of the final circuit are acceptable:
(i) a ring final circuit with a ring protective conductor
(ii)(a) a radial final circuit with a single protective conductor connected as a ring

i.e. you can meet the requirement for a radial with a ring cpc.

i.e. the diagram showing a ring cpc could be showing a compliant cpc for a radial circuit, which is what I said.

I'm not disputing the fact you can use a ring CPC on a radial, this is generally for when the CPC is smaller than required by 543.7.1.3 (i) or (ii).
If you decide to want to install a conductor sized in accordance with 543.7.1.3 (i) or (ii) then 543.7.2.1 (iii) will be complied with hence there is no requirement to form a conductor of those larger sizes into a ring conductor.

Yet in 543.7.2.1 it requires a ring protective conductor, as in one ring protective conductor?

543.7.2.1 (i) + 543.7.1.3 (i) a ring final circuit with a ring protective conductor having a cross-sectional area of not less than 10mm²...

543.7.2.1 (i) + 543.7.1.3 (ii) a ring final circuit with a ring protective conductor having a cross-sectional area of not less than 4mm²...

543.7.2.1 (iii) + 543.7.1.3 (iii) a ring final circuit with two individual ring protective conductors...

I don't like the way the OSG 16th ed changes the wording of the regs! It has (iii) as duplicate protective conductors each complying with section 543. Talk about a mess. It also shows 1.5mm² cpcs, so it is back to two individual vs duplicate protective conductors!