High integrity earthing and ring final circuits.

[mattylad]

Spark123, what did you use to draw that picture?

And what is the rightmost fitting? looks like a double lightswitch?
Cheers,
matty

 

[ban-all-sheds]

So BAS, just to clarify things, is this picture more in agreement with what you are saying?

Untitled

• Grizzly
• 24 Jul 2008
• 1

Yup.

And if I can out this diagram up without some frustrated petty twonk saying "ooh that doesn't comply either because the colours are wrong" you can see more clearly what is meant by "two individual protective conductors"



And how either one of the two individual protective conductors can be removed, leaving one remaining protective conductor which complies with Section 543.

 

[Spark123]

Spark123, what did you use to draw that picture?

And what is the rightmost fitting? looks like a double lightswitch?
Cheers,
matty

MS paint, it is meant to be a switched fcu.

 

[Spark123]

"The" cpc is the problem You must have two of them, not one. And if you're going to argue that you do have two protective conductors at each point then you have automatically admitted that it's not complying with 543.7.1.3 (iii), because you can't count them as two AND show that EACH ONE is a ring with BOTH ENDS connected to the earth terminal at the origin.

543.7.1.3 (iii) does not ask for two separate independant circuit protective conductors, it asks for two individual protective conductors. As they are protective conductors they need to meet the criterion for protective conductors, not necesserally CPCs.
So as far as rings go, as long as the CPC is installed as a ring then it complies with 543.2.9, as long as there are two individual* protective conductors forming the CPC at each point** both complying with 543 then it gets the thumbs up from me.
The picture I drew (last april) is from guidance note 8 from the IET.

* individual as in separate i.e. if one is lost/broken, the other remains.
** teminated in separate terminals.

 

[ban-all-sheds]

543.7.1.3 (iii) does not ask for two separate independant circuit protective conductors, it asks for two individual protective conductors. As they are protective conductors they need to meet the criterion for protective conductors, not necesserally CPCs.

Would you please apply your same counting logic to the segments of a single protective conductor as in 543.7.1.3 (i) & (ii) and see if it works?

So as far as rings go, as long as the CPC is installed as a ring then it complies with 543.2.9, as long as there are two individual* protective conductors forming the CPC at each point** both complying with 543 then it gets the thumbs up from me.

But there aren't.

We keep coming back to the same stumbling block which you refuse to see, and which therefore you keep stumbling over.

The regulations require two individual protective conductors. It says so in black and white.

Individual is not given a special definition in the regulations, therefore it retains its usual English meaning, i.e. separate, distinct from others especially others of its kind.

If you've got two separate ones, each one of which complies with 543.2.9 (which each one, individually and separately must, as it says so in black and white) then you must be able to remove one and leave one remaining, which still complies with 543.2.9.

And you can't do that, because you don't have two separate and distinct protective conductors each one of which complies with 543.2.9.

The picture I drew (last april) is from guidance note 8 from the IET.

Read the disclaimer in the preface.

 

[mattylad]

PAINT! OMG.... OK cheers, methinks I'll get some sockets drawn in google sketchup then lol.

 

[mattylad]

The "2 separate" definition is a bit of a non issue really, if it needs 2 CPC conductors so that means that along with T/E cable you add an extra CPC cable, simple - whats so hard about that that it needs such a lot of discussion?

Unless they make T/E with 2 CPC cores in?

 

[ban-all-sheds]

The "2 separate" definition is a bit of a non issue really, if it needs 2 CPC conductors so that means that along with T/E cable you add an extra CPC cable, simple - whats so hard about that that it needs such a lot of discussion?

But people don't want to do that, and don't want to think that they have to, so they try to jump through hoops denying what "individual" means, and claiming that the term "protective conductor" doesn't mean "circuit protective conductor" when used in the phrase "the circuit shall have a protective conductor...."

 

[Spark123]

543.7.1.3 (iii) does not ask for two separate independant circuit protective conductors, it asks for two individual protective conductors. As they are protective conductors they need to meet the criterion for protective conductors, not necesserally CPCs.

Would you please apply your same counting logic to the segments of a single protective conductor as in 543.7.1.3 (i) & (ii) and see if it works?

Yep, works for me. There for (i) there needs to be one protective conductor of 10mm minimum. For (ii) there needs to be one protective conductor of 4mm minimum with additional mech protection.

We keep coming back to the same stumbling block which you refuse to see, and which therefore you keep stumbling over.

The regulations require two individual protective conductors. It says so in black and white.

Even though a ring already effectively has a double protective conductor? (albeit a normal ring doesn't incorporate double terminals on accessories).

Individual is not given a special definition in the regulations, therefore it retains its usual English meaning, i.e. separate, distinct from others especially others of its kind.

Yep, two separate protective conductors connecting the accessory to separate terminals on the MET via two separate routes.

If you've got two separate ones, each one of which complies with 543.2.9 (which each one, individually and separately must, as it says so in black and white) then you must be able to remove one and leave one remaining, which still complies with 543.2.9.

But do they both need to comply with 543.2.9 which is referring to the CPC (which would be complied with when installed)? Or do they both need to comply with the regs for an individual protective conductor?

 

[ban-all-sheds]

Yep, works for me. There for (i) there needs to be one protective conductor of 10mm minimum. For (ii) there needs to be one protective conductor of 4mm minimum with additional mech protection.

But you also say that because you can do this:

http://i215.photobucket.com/albums/cc91/Spark-123/rfc2.jpg

you have two protective conductors.

Now you're saying you have one.

Do you really not see that your whole argument rests on illogical and inconsistent grounds, and requires you to ignore what common English words mean?

Even though a ring already effectively has a double protective conductor?

It doesn't - it has one, in the shape of a ring. At any point there are two current paths, along different sections of the same conductor, but that doesn't mean there are two conductors.

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.

If you had two then you would be able to remove one and have one left, on the basis that 2-1=1. But you can't, because you don't have two.

Removing a segment of a ring and turning it into two separate radials doesn't show that you had two rings to start with.

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 whan you do it a 3rd time, etc?

Do you really not see that there is no logic underpinning your counting of conductors?

Yep, two separate protective conductors connecting the accessory to separate terminals on the MET via two separate routes.

Two separate conductors EACH ONE complying with 543.2, not with the combination of the two of them complying with 543.2.

But do they both need to comply with 543.2.9 which is referring to the CPC (which would be complied with when installed)? Or do they both need to comply with the regs for an individual protective conductor?

The individual protective conductor of a ring must be a ring.

 

[Spark123]

Yep, works for me. There for (i) there needs to be one protective conductor of 10mm minimum. For (ii) there needs to be one protective conductor of 4mm minimum with additional mech protection.

But you also say that because you can do this:

http://i215.photobucket.com/albums/cc91/Spark-123/rfc2.jpg

you have two protective conductors.

Now you're saying you have one.

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

Do you really not see that your whole argument rests on illogical and inconsistent grounds, and requires you to ignore what common English words mean?

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.

Even though a ring already effectively has a double protective conductor?

It doesn't - it has one, in the shape of a ring. At any point there are two current paths, along different sections of the same conductor, but that doesn't mean there are two conductors.

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

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.

Removing a segment of a ring and turning it into two separate radials doesn't show that you had two rings to start with.

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

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 whan you do it a 3rd time, etc?

If you should lose one through it being broken it will become 2 conductors.
Using the method you describe is over and above what is required by the regs.

Do you really not see that there is no logic underpinning your counting of conductors?

Yep, two separate protective conductors connecting the accessory to separate terminals on the MET via two separate routes.

Two separate conductors EACH ONE complying with 543.2, not with the combination of the two of them complying with 543.2.

Yep, both the protective conductors from each point need to comply with 543.2. The CPC which is made up of the protective conductors needs to be in the form of a ring.

 

[LiamPope]

Wouldn't it save a lot of time and keyboard wear if somebody just dropped a line to the BSI and asked them what they mean?

Liam

 

[ban-all-sheds]

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. 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.

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.

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.

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.

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.

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".

The problem is that when you work on that basis, so that you can count "protective conductors" in a variety of ways, you end up with inconsistencies.

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?

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.

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.

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.

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?

 

[ban-all-sheds]

Wouldn't it save a lot of time and keyboard wear if somebody just dropped a line to the BSI and asked them what they mean?

Liam

That would be interesting.

But what would happen if they said they didn't mean "protective conductor" and "circuit protective conductor" to be synonymous, and they didn't mean that a ring final had to have two separate protective conductors etc? Whatever they say they mean would not change what the wording in the regulations actually says, but it would mean that the wording of the regulations is wrong.

And what's the protocol for dealing with mistakes in the regulations? Can we all start doing things that don't comply with the BS as published on the basis of an email, or do we have to carry on doing what the published BS says until there is an official amendment?

 

[ban-all-sheds]

Here's another way of illustrating the inconsistency in Spark123's argument.

According to him the diagram posted at the start complies with 543.7.1.3 (iii) because of his interpretation of "two individual protective conductors", and the way he counts things.

But it must also comply with 543.7.1.3 (i) and (ii), as all the aspects of topology and connections are outside 543.7.1.3 - it would look the same no matter which of 543.7.1.3 (i), (ii) or (iii) you decided to go with for the specification of the protective conductor itself.

So what consistent meaning for "protective conductor", and consistent way of counting them are there such that that diagram shows a circuit with both a single protective conductor and two individual protective conductors?