High integrity earthing and ring final circuits.

[RF Lighting]

This is from my 17th edition training manual, written by the NICEIC, and endorsed by city and guilds:

It also seems the regulation has been rewritten in the 17th edition to remove any ambiguity which was present in the 16th edition.

543.7.2.1 For a final circuit with a number of socket-outlets or connection units intended to supply two or more items of equipment, where it is known or reasonably expected that the total protective conductor current in normal service will exceed 10 mA, the circuit shall be provided with a high integrity protective conductor connection complying with the requirements of Regulation 543.7.1. The following arrangements of the final circuit are acceptable:

(i) A ring final circuit with a ring protective conductor. Spurs, if provided, require high integrity protective conductor connections complying with the requirements of Regulation 543.7.1

(ii) [relates to radial circuit(s)]
(a) [relates to radial circuit(s)]
(b) [relates to radial circuit(s)]
(c) [relates to radial circuit(s)]
(iii) [relates to radial circuit(s)]

 

[ban-all-sheds]

This is from my 17th edition training manual, written by the NICEIC, and endorsed by city and guilds:

So it would seem that neither organisation can read, or if they can they don't know what the word "individual" means..

It also seems the regulation has been rewritten in the 17th edition to remove any ambiguity which was present in the 16th edition.

There was no ambiguity in the 16th.

543.7.2.1 For a final circuit with a number of socket-outlets or connection units intended to supply two or more items of equipment, where it is known or reasonably expected that the total protective conductor current in normal service will exceed 10 mA, the circuit shall be provided with a high integrity protective conductor connection complying with the requirements of Regulation 543.7.1.

And what are the requirements of 543.7.1, in the context of a circuit wired with a 1.5mm² cpc?

The following arrangements of the final circuit are acceptable:

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

Yes, but not a 1.5mm² ring cpc.

543.7.1.3 (i) says that one option is a cpc of at least 10mm².

543.7.1.3 (ii) says that one option is a cpc of at least 4mm² if it's protected against physical damage.

If you want to use a 1.5mm² cpc in the shape of a ring, complying with 543.2 & 543.3, then 543.7.1.3 (iii) says that you have to have two individual cpcs.

You might as well just go and read through this again, for my reasoning is unchanged - i.e. "two individual protective conductors" means two individual protective conductors, not one protective conductor comprised of several lengths of wire and several lengths of socket earth terminal straps. Connecting your cpc to different terminals in each socket may well increase the reliability of the connections but it does not magically turn one ring into two.

 

[jockspark]

hi lads does 543.7.1 (ii) help this could be where the confusion of installing
an other cpc
sorry lads 543.7.2.1 (ii)

 

[RF Lighting]

there is no 543.7.1 (ii)

I'm off to bed now as I have an early start tomorrow, but I'm certainly not running scared

 

[ColJack]

RF, you had to go and poke the beast again didn't you?

no matter what your interpretation of the regs BAS, the "official line" is that stated above..

a ring by it's very nature has 2 cpc's at any given point.. 2 cpc's leave the board, travel different directions from the board and meet at the given point..

it's no different to adding an extra cpc to a radial or cross connecting the ends of 2 seperate radials.. the 2 cpc's still leave the board and go different directions round the sockets untill they reach the given socket..

adding the extra cpc to the end of a radial makes the earth a ring, so does cross connecting the cpc's of seperate rings..

all they want is that there is at least one connection to earth from a given socket should one of the 2 connection points fail..

 

[jockspark]

that was my interputation but if i am wrong more than willing to have
it explained to me

 

[ColJack]

it all comes down to BAS's interpretation of the word "individual"..

to me if you disconnect the 2 earths at a socket on a ring, then there are 2 individual paths back to earth.
2 seperate lengths of copper ( albeit made up of various lenghts of wire and bar as part of the sockets ).
as long as they are not under the same screw in the earth bar then it's 2 seperate earths.. if they are under the same screw then they can be interpreted as being "strands" of a larger conductor..
which is how I think BAS's sees it....

 

[ban-all-sheds]

hi lads does 543.7.1 (ii) help this could be where the confusion of installing
an other cpc
sorry lads 543.7.2.1 (ii)

And 543.7.2.1 (ii) says you can have a ring cpc for a radial final circuit, not a ring final....

 

[jockspark]

yes and thats where i think poeple get confused with running an extra cpc in a ring final

 

[ban-all-sheds]

no matter what your interpretation of the regs BAS, the "official line" is that stated above..

"Official"???

This is from my 17th edition training manual, written by the NICEIC

And I'm not "interpreting" the regulations, I'm simply reading what they actually say. The interpretation is being done by those who cannot or will not grasp the very clear and simple thing that they actually say.

a ring by it's very nature has 2 cpc's at any given point.. 2 cpc's leave the board, travel different directions from the board and meet at the given point..

No - that's one cpc in the shape of a ring - Topology 101.

Let me ask you this - how many ends does a single conductor of finite length have?

it's no different to adding an extra cpc to a radial

An extra one?

If you are claiming that extending the cpc of a radial back to the start in order to make it a ring has somehow added an extra one, perhaps you'd like to explain why 543.7.2.1 (ii)(a) says "the protective conductor being connected as a ring" and not "the protective conductors being connected as rings" if there are two of them.

Maybe you could find a way to explain why the regulations use singular forms when you say they mean plural, and plural forms (e.g. "two individual protective conductors") when they don't mean it...

adding the extra cpc to the end of a radial makes the earth a ring

Yes - a ring, as in just one. Not two. So why does the same shape become two individual rings just because the live conductors are also rings?

so does cross connecting the cpc's of seperate rings..

Not an arrangement we're discussing...

all they want is that there is at least one connection to earth from a given socket should one of the 2 connection points fail..

But that's not what they SAY, and they have had plenty of opportunity to SAY that if that's what they want, but in the latest version they still SAY "two individual protective conductors"

 

[jockspark]

look at page 61 osg and before you say it i know its the 16th as the 17th
is not out yet well i am off to bed we will pick this up again tomorrow
try and chill out you are right or you are wrong but by the end of this thread
someone will go away with a better understanding goodnight

 

[ban-all-sheds]

it all comes down to BAS's interpretation of the word "individual"..

individual adj separate or distinct, esp. from others of its kind.

to me if you disconnect the 2 earths at a socket on a ring, then there are 2 individual paths back to earth.

Yes, but you haven't got two rings, have you?

2 seperate lengths of copper ( albeit made up of various lenghts of wire and bar as part of the sockets ).

Yes - 2 separate lengths of copper.

Neither of which is a ring.

as long as they are not under the same screw in the earth bar then it's 2 seperate earths..

Yes - 2 separate earths.

Neither of which is a ring.

if they are under the same screw then they can be interpreted as being "strands" of a larger conductor..
which is how I think BAS's sees it....

No - how/where/what they are screwed into at the earth bar is irrelevant. If you remove them from under their screw/screws how many rings have you got?

If you have two individual protective conductors, which is what the regulations say you should have, then with exactly the same degree of counting complexity that toddlers can cope with you must have "one plus one" individual protective conductors. Therefore you must be able to remove one individual protective conductor and still have one individual protective conductor remaining.

Unless for some reason 2-1 no longer = 1....

I'd love to see you annotate the diagram posted by RF to show which is which individual protective conductor complying with 543.2.9, and how you could remove one individual protective conductor and be left with the other individual protective conductor complying with 543.2.9.

 

[ban-all-sheds]

look at page 61 osg

I've seen that.

How can I put this clearly....


That diagram, and those words, are NOT WHAT THE REGULATIONS SAY.

They do not describe or explain or illustrate the requirements AS DEFINED IN THE REGULATIONS.

Have a good night's rest, and when you get up look at p8 of the OSG, 3rd paragraph.

 

[jockspark]

bas before i go to bed i have got 2 valium left i will give you my last valium
for christ sake man chill

 

[ColJack]

ok, writing aside, the diagram in the photo above shows a high integrity earth.. if the sockets were part of a radial then the last socket is connected back to the earth bar... yes?

so by it's very nature of already having the earth at the last socket connected back to the earth bar, a ring also has a high integrity earth ( assuming that the earths are in seperate terminals at the socket and board, and leaving the 1.5mm cpc in T+E issue asside since I don't do domestic and generally wire in singles.. )

the

If you have two individual protective conductors, which is what the regulations say you should have, then with exactly the same degree of counting complexity that toddlers can cope with you must have "one plus one" individual protective conductors. Therefore you must be able to remove one individual protective conductor and still have one individual protective conductor remaining.

which is exactly what you have in a ring if you use the dual earth terminal sockets and terminate one cpc into each terminal.. if you take one out, you still have the other..

you yourself above have agreed with my statement that you have 2 cpc's at each socket.. but then insist on adding "neither of which is a ring".

do you then terminate the additional earth from the end of a radial into each and every socket on it's path back to the board?

so if I looked in the back of any of your sockets that you have wired to have high integrity earth, I would see 4 earth wires, 2 into each earth terminal?