High integrity earthing

[ban-all-sheds]

You haven't answered my question BAS - define cable and define conductor.

Conductor - something that conducts electricity.
Cable - a wire or bundle of wires that conducts electricity.

BTW 543-02-02 is not the definition of a protective conductor it merely tells you what it may consist of. It does NOT rule out the possibility of of the protective conductor (abstract) being formed by any number of physical conductors.

Allelujah - the penny has finally dropped for you. You finally realise that more than one physical conductor does not necessarily mean more than one cpc.

As in Spark123's diagram - 6 lengths of cable, 5 metal straps, one individual protective conductor, not the two that 607-02-04 requires.

 

[NotHimAgain]

Allelujah - the penny has finally dropped for you. You finally realise that more than one physical conductor does not necessarily mean more than one cpc.

I haven't finally realised it - it has always been obvious, but the converse of your definition is not ruled out so that means that more than one protective conductor can be used to form the (abstract) single cpc.

Now that I can have more than one conductor in different multicore cables - you see where this is going don't you .

Now those definitions - the word is inadequate, another is imprecise. In terms of electrical installations we need to discriminate between a lump of steel (conductor) and that part of a cable that is intended to conductor electric current.

We might try:
conductor: that part of a cable that provides the conducting path for electric current.

cable: a conductor or group of conductors to transmit electric current normally contained within a single enclosure of insulating and protective coverings.

 

[ColJack]

Since you totally ignored my earlier post because it didn't agree with your argument, then I'll repeat it here and see if you reply BAS..

[code:1]607-03-01
blah, blah, blah.... The following arangements of the final circuit are acceptable:

i) blah.. blah.. blah..

ii) A radial final circuit with a single protective conductor:
a) the conductor being connected as a ring; or
b) a seperate protective conductor being provided at the FINAL socket outlet by connection to the metal conduit or ducting; or
c) ( paraphrasing ) cross connecting the earth at the end of 2 radials...[/code:1]

so if it's acceptable to use one earth along the length of a radial circuit and only take a single earth back from the last socket on it to the board , then why do you say it's not acceptable for a ring to be considered the same?



basically the reg requires that there is either 2 paths back to the earth in case one fails, or that the earth is of such a size or mechanically protected to prevent it's failure due to damage..

so again i ask.. if it's ok for a radial to be considdered as having a high integrity earth if the last socket on the radial has it's earth connected back to the board, makint the earth a ring, then why do you thing that the earth on a ring is not ok connected the same..

the picture that spark123 posted somewhere above my original post can be a picture of either a ring, or a radial that complies since no phase or neutral conductors are shown..

if they stop at the last socket, and only the earth returns to the board then it complies as a radial, but if they contunue to the board to form a ring then they don't?

 

[tim west]

It's you who can't look at a piece of wire, with two ends, both of which are in the CU, and only see one conductor.

Its you that keeps mentioning conductor not me so its you thats confused im certainly not in any way confused I know the difference between physical wires and conductors, and there are two wires not one.

 

[ban-all-sheds]

I haven't finally realised it - it has always been obvious, but the converse of your definition is not ruled out so that means that more than one protective conductor can be used to form the (abstract) single cpc.

"More than one protective conductor can be used to form the circuit protective conductor". Isn't that what I said, rather than the converse of it?

"As in Spark123's diagram - 6 lengths of cable, 5 metal straps, one individual protective conductor, not the two that 607-02-04 requires."

The thing is though, a cpc is not an abstract concept, it is a real physical entity, which has to have real end-end continuity, and in a ring final circuit has to be a ring itself. Yes, you can make it out of more than one conductor - this is what is always done. And yes, you could make two individual protective conductors out of more than one component. In fact you'd have to use at least two components to make two individual cpcs.

But what you cannot do is to make two individual protective conductors that share any of the multiple segments in a non-redundant fashion - if they do share any segment then they are not individual conductors.

Please note that 607-02-04 (iii) requires that each individual cpc complies with 543. And 543 requires the cpc of a ring final to be a ring.

In other words, if your RFC requires a high-integrity cpc, and it isn't large enough to comply with 607-02-04 (i) or (ii), then 607-02-04 (iii) plus 543-02-09 mean that you have to have two individual protective conductor rings.

Bear in mind that there is no way that two individual circuits can share one of their unique non-duplicated component conductors and still be individual. You have to be able to remove one complete individual cpc and still have one complete individual cpc remaining. If you can't do that, then you didn't have two individual cpcs in the first place.

And unless and until you can show, using Spark123's diagram, that there are two individual cpcs present, and that you could remove every component that makes up cpc #1 and still have a functioning, 543-02-09 compliant cpc #2 then your claim that Spark123's diagram contains two individual cpcs as per 607-02-04 (iii) plus 543-02-09 remains bogus.

All you have to do to show that I am wrong about what I believe the regulations clearly say is to show that you can do that.

You won't, of course, for the same reason that you haven't on any of the previous times I've asked - you know you can't and yet you persist in refusing to accept that the fact that you can't means you are wrong.

Now that I can have more than one conductor in different multicore cables - you see where this is going don't you .

It's going the same way as all your other arguments - towards utter failure to be able to show that a ring final with just two ends of a cpc, however you define or construct the cpc - you have complete freedom there - has two individual cpcs.

Now those definitions - the word is inadequate, another is imprecise. In terms of electrical installations we need to discriminate between a lump of steel (conductor) and that part of a cable that is intended to conductor electric current.

We might try:
conductor: that part of a cable that provides the conducting path for electric current.

cable: a conductor or group of conductors to transmit electric current normally contained within a single enclosure of insulating and protective coverings.

Use whatever definitions you are happy with.

Then show, using Spark123's diagram, that there are two individual cpcs present, and that you could remove every component that makes up cpc #1 and still have a functioning, 543-02-09 compliant cpc #2.

 

[NotHimAgain]

In other words, if your RFC requires a high-integrity cpc, and it isn't large enough to comply with 607-02-04 (i) or (ii), then 607-02-04 (iii) plus 543-02-09 mean that you have to have two individual protective conductor rings.

Absolute rubbish - this is your pretty diagram again BAS isn't. Why don't you send it to the committee that wrote this section of BS 7671 for comment. When they finally stop laughing they will tell you that it offers no technical merit and it does improve safety in the terms of this problem. In fact it probably reduces it because there would be so many cables crammed into each socket outlet enclosure that compression damage would be more likely.

Stick to your day job BAS

 

[tim west]

Ban you are confusing conductors and wires, if you believe that the diagram with the concentric circles is one wire the same as one conductor then why draw circles you should have drawn straight lines.
After all according to your explanation its just one conductor therefore no matter how it is distributed it still consists of one conductor.

But I have only mentioned wires and cables.

now tell me how you'll manage to run off a cable from a reel and make it a continuous circular cable? You can't!

So therefore you are confusing making several cables and links into a conductor of single entity whereas it is a circuit made up of several conductors joined together and even electrically when joined they are not the same conductor as each joint has a minimal resistance but still there.

What my argument with you is that you could potentially confuse the DIY'ers that use this forum by suggesting a single cable/wire is at each point when physically there are two T&E cables or two armoureds or two MICC's...... or six singles.

 

[ban-all-sheds]

Since you totally ignored my earlier post because it didn't agree with your argument, then I'll repeat it here and see if you reply BAS..

I didn't ignore it - I hadn't realised it was directed at me, as it did not address me, it did not contain a quote of mine and it did not occur anywhere near one of my posts, let alone follow one directly.

so again i ask.. if it's ok for a radial to be considdered as having a high integrity earth if the last socket on the radial has it's earth connected back to the board, makint the earth a ring, then why do you thing that the earth on a ring is not ok connected the same..

Because the regulations say it isn't.

the picture that spark123 posted somewhere above my original post can be a picture of either a ring, or a radial that complies since no phase or neutral conductors are shown..

Ah - wouldn't it be nice for you if Spark123 hadn't introduced his drawing with "Ring final circuits provide duplication of the protective conductor, and if the ends of the protective conductor are separately terminated at the distribution board and at the socket outlets, the requirements of 607 will be met, as shown in figure (below)".....

Actually it wouldn't matter if he hadn't, because this topic has been about the requirements for high-integrity cpcs in ring circuits.

if they stop at the last socket, and only the earth returns to the board then it complies as a radial, but if they contunue to the board to form a ring then they don't?

That's what the regulations say. And intuitively that makes sense - you increase the integrity of a radial cpc by making it a ring, and you increase the integrity of a ring cpc by adding a second ring cpc.

 

[Spark123]

The drawing which I posted, along with the wording is what is in GN8. Why would you need more cpc integrity for a ring than you would for a radial?

 

[ban-all-sheds]

Absolute rubbish

That's what the regulations say. Like it or not, and whether that is what they really meant to say, the regulations actually do say "two individual protective conductors each complying with the requirements of Section 543".

this is your pretty diagram again BAS isn't. Why don't you send it to the committee that wrote this section of BS 7671 for comment. When they finally stop laughing they will tell you that it offers no technical merit and it does improve safety in the terms of this problem.

That's what the regulations say. Like it or not, and whether that is what they really meant to say, the regulations actually do say "two individual protective conductors each complying with the requirements of Section 543".

In fact it probably reduces it because there would be so many cables crammed into each socket outlet enclosure that compression damage would be more likely.

Use deep boxes then.

Stick to your day job BAS

I see.

So totally unable to produce, or label, a diagram to show that I am wrong, you just decide to call my argument rubbish and then say something dismissive like that.

I don't know whether you think that means that you could take a circuit wired like Spark123's and remove one individual cpc ring and still have one individual cpc ring present, but I suspect you don't, just as I suspect you have known all along that you can't.

 

[ban-all-sheds]

The drawing which I posted, along with the wording is what is in GN8. Why would you need more cpc integrity for a ring than you would for a radial?

For the same reason that you need more integrity for a radial than a radial cpc?

i.e. you increase the integrity of a radial cpc by making it a ring.

If the cpc is already a ring because the circuit is a ring, then you increase the integrity by adding a second ring.

And GN8 does not agree with what the regulation says, which has been my consistent position all along.

Would you care to post the appropriate paragraph from the Preface to GN8? You'll know which one I mean as soon as you read it.

Then perhaps you could explain why everyone is so sure that a Guidance Document which explicitly states that it does not ensure compliance with BS7671 and that people should always consult BS7671 to satisfy compliance, must be right, and BS7671 must be wrong, and that GN8 must mean what it says and that BS7671 must not mean what it says?

 

[Spark123]

The drawing which I posted, along with the wording is what is in GN8. Why would you need more cpc integrity for a ring than you would for a radial?

For the same reason that you need more integrity for a radial than a radial cpc?

i.e. you increase the integrity of a radial cpc by making it a ring.

If the cpc is already a ring because the circuit is a ring, then you increase the integrity by adding a second ring.

Maybe but does it need to be increased anymore? Surely if you needed 2 ring CPCs for a High integrity earthing RFC then why wouldn't you need the same for a radial circuit?

Would you care to post the appropriate paragraph from the Preface to GN8? You'll know which one I mean as soon as you read it.
Then perhaps you could explain why everyone is so sure that a Guidance Document which explicitly states that it does not ensure compliance with BS7671 and that people should always consult BS7671 to satisfy compliance, must be right, and BS7671 must be wrong, and that GN8 must mean what it says and that BS7671 must not mean what it says?

You mean this paragraph:
"This guidance note does not ensure compliance with BS7671. It is merely intended to explain explain some of the requirements of BS7671. Readers should always consult the full text of BS7671 to satisfy themselves of compliance and must rely on their own skill and judgement when making use of the guidance provided here."

The guidance note will not ensure compliance with BS7671 as it only covers earthing and bonding, none of the guidance notes cover the full scope of BS7671. Differing locations may also require different regulations to be met. It does however generally aid in explaining the aim of a number of the regs regarding earthing and bonding.

 

[THRIPSTER]

17th - not word for word but might help

543.7.1.3

The wiring of every final circuit and distribution circuit intended to supply one or more items of equipment , such that the total CPC current is likely to exceeed 10mA, shall have a high integrity protective connection complying with one or more of the following:-

(i) A single protective conductor having a cross-sectional area of not less than 10mm squared complying with the requirements of regulations 543.2 and 543.3

(ii) A single CPC of not less than 4mm squared complying with 543.2 and 543.3, the CPC being mechanically protected, eg; within conduit

(iii) Two individual CPC's each complying with section 543. The two CPC's may be of different types eg; metallic conduit together with a cable CPC. One of the CPC's may be formed by metallic sheath , armour or wire braid within the cable.

(iv) An earth monitoring system may be installed...........

(v) Use of a double wound transformer......................

543.7.1.4 Where two CPC's are used the ends shall be terminated independently of each other................


Regards

 

[ban-all-sheds]

Ban you are confusing conductors and wires, if you believe that the diagram with the concentric circles is one wire the same as one conductor then why draw circles you should have drawn straight lines.

I've drawn it as a circle.

I've drawn it as a straight line.

I've drawn it as a loop with ends.

I've drawn it as a closed loop.

Spark123 has drawn it as a collection of wires and metal straps.

The only consistent thing running through all this is your complete inability to use your eyes and count the presence of a single circuit conductor, not two circuit conductors.

After all according to your explanation its just one conductor therefore no matter how it is distributed it still consists of one conductor.

If you believe otherwise then show, using Spark123's diagram, that there are two individual cpcs present, and that you could remove every component that makes up cpc #1 and still have a functioning, 543-02-09 compliant cpc #2.

But I have only mentioned wires and cables.

Fine - then draw a diagram like Spark123's but only using wires and cables and show that there are two individual cpcs present, and that you could remove every component that makes up cpc #1 and still have a functioning, 543-02-09 compliant cpc #2.

now tell me how you'll manage to run off a cable from a reel and make it a continuous circular cable? You can't!

I did postulate the existence of some magical molecular welding technique that would allow a continuous circular cable to be made, but that doesn't matter. If it confuses you too much, or if you want to focus on that artifice as a way to avoid having to deal with the nature of the circuit then a bit of choc-block will do just as well. The drawing below shows, at A, a length of copper wire.

At B, C, D etc it shows the wire cut in one or two places, and joined or not in one or two places with a piece of choc-block. For each of B - H could you please state how many conductors there are, and why.

So therefore you are confusing making several cables and links into a conductor of single entity whereas it is a circuit made up of several conductors joined together and even electrically when joined they are not the same conductor as each joint has a minimal resistance but still there.

OK - so how many cpcs does the drawing posted by Spark123 have? Please tell us, and please explain how you arrive at that number, and if and how that number would change in the following circumstances:

a) The addition of another socket.

b) The removal of a socket and the cables connected to it joined with solder/crimps/choc.

c) The removal of a socket and the cables connected to it replaced with a contiguous one.

Then perhaps you'd like to explain your meaning of conductor in the context of the tests that are required for continuity of ring final circuit conductors.

What my argument with you is that you could potentially confuse the DIY'ers that use this forum by suggesting a single cable/wire is at each point when physically there are two T&E cables or two armoureds or two MICC's...... or six singles.

Dunno about DIYers, but you seem totally confused by the notion that a conductor might have more than one wire in it.

Forget high integrity earthing - imagine you are wiring a plain old ordinary ring final circuit using singles. It has 10 socket outlets on it.

By my reckoning the circuit will contain 11 brown-sleeved wires, 11 blue sleeved wires and 11 G/Y sleeved ones. Do you think that means that the circuit has 11 phase conductors, 11 neutral conductors and 11 cpcs?

 

[NotHimAgain]

BAS why do you keep saying that is what the regulation say - that is what you say that they say.

In any event my first post on this topic indicated that changes in the text may lead to confusion.

Lets flag up some of the errors in their text for you .

The problem starts with 607-02-04. It begins - The wiring of every final circuit and distribution circuit .... Thus including all final circuits.

Earlier versions specifically offered the standard ring main with appropriate modification as an ALTERNATIVE to 607-02-04.

However, all is not lost because I can make 607-02-04 (iii) para 2 fit, even if you can't.

This error is followed by the removal from 607-03-01 of the specific indication of permitted protective conductor size (1.5 mm²).

607-03-01 (i) makes clear that spurs must have a high integrity protective
conductor connection complying with 607-02 but it does not make clear the status of the conductors forming the ring. Note that the talk is of a protective conductor connection - it is not just about the protective conductor.

Now if you had argued that 1.5mm² could not be used and that 2.5mm² is required I could probably have agreed with you - but your take on this is frankly ridiculous - your interpretation of what is required does not make engineering sense and you would know that if you actually understood the problem.