Yup.So BAS, just to clarify things, is this picture more in agreement with what you are saying?
MS paint, it is meant to be a switched fcu.Spark123, what did you use to draw that picture?
And what is the rightmost fitting? looks like a double lightswitch?
Cheers,
matty
"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.
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?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.
But there aren't.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.
Read the disclaimer in the preface.The picture I drew (last april) is from guidance note 8 from the IET.
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...."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?
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.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?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.
Even though a ring already effectively has a double protective conductor? (albeit a normal ring doesn't incorporate double terminals on accessories).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.
Yep, two separate protective conductors connecting the accessory to separate terminals on the MET via two separate routes.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.
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?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 you also say that because you can do this: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.
http://i215.photobucket.com/albums/cc91/Spark-123/rfc2.jpg
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.Even though a ring already effectively has a double protective conductor?
Two separate conductors EACH ONE complying with 543.2, not with the combination of the two of them complying with 543.2.Yep, two separate protective conductors connecting the accessory to separate terminals on the MET via two separate routes.
The individual protective conductor of a ring must be a ring.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?
Nope, that pic shows a high integrity ring earthing system with a single fault taking out a protective conductor.But you also say that because you can do this: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.
http://i215.photobucket.com/albums/cc91/Spark-123/rfc2.jpg
you have two protective conductors.
Now you're saying you have one.
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.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?
It has one circuit protective conductor made up of a number of protective conductors.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.Even though a ring already effectively has a double protective conductor?
You can't do this with a bog standard radial circuit, but that doesn't mean it doesn't have a protective conductor.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.
I have never claimed there to be 2 ring protective conductors though.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 should lose one through it being broken it will become 2 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 whan you do it a 3rd time, etc?
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.Do you really not see that there is no logic underpinning your counting of conductors?Two separate conductors EACH ONE complying with 543.2, not with the combination of the two of them complying with 543.2.Yep, two separate protective conductors connecting the accessory to separate terminals on the MET via two separate routes.
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.Nope, that pic shows a high integrity ring earthing system with a single fault taking out a protective conductor.
I interpret it how it was written.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.
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).It has one circuit protective conductor made up of a number of protective conductors.
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.You can't do this with a bog standard radial circuit, but that doesn't mean it doesn't have a protective conductor.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.
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 have never claimed there to be 2 ring protective conductors though.
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?If you should lose one through it being broken it will become 2 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?
No - it's exactly what the regulations as written require.Using the method you describe is over and above what is required by the regs.
Ah - so if both the protective conductors fro each point comply with 543.2 then both of them must be rings.Yep, both the protective conductors from each point need to comply with 543.2.
That would be interesting.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
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local