Using CPC as live conductor.... ok i know, but...

[uksparks]

Hi,

Had to change a bathroom fan at the weekend for someone and they wanted it to be on a timer, but couldnt as the cable was buried in the wall and wouldn't move etc..

the cable that fed it was a three core flex, I the earth was not being used anyway due to the load on the end etc.

I know you are not meant to use the CPC as a live conductor, but if its flex and the same CSA and you were to correctly identify it with brown etc, would it have then been acceptable?

I didn't do it, but it made me think, oh i so could have used it, but it just seemed wrong. I can understand why you wouldn't do it in twin and earth, but surely where its flex or all conductors are the same CSA and have their own sheathing on them inside the outer, would it have been acceptable or not?

I am going to say not on the basis CPC is CPC and nothing else, any thoughts would been welcomed.

 

[Simonslimline]

I am pretty sure the NIC mentioned this a while ago and said you can. They do seem to make it up as they see fit though.

Also i am fairly sure that you should not bury flex in a wall!

 

[Plonker 3]

Reg 514.4.2 says no you cant do that.

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I am pretty sure the NIC mentioned this a while ago and said you can. They do seem to make it up as they see fit though.

So what do the NIC know about anything, you do know they dont write the regs dont you?

 

[Pete999]

It's not up to the NICEIC it's a regulation they don't make the regulations

 

[Simonslimline]

Yes i am aware of that... i was simply mentioning what i had read

Reg 514.4.2 says no you cant do that.

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So what do the NIC know about anything, you do know they dont write the regs dont you?

 

[Plonker 3]

Simonslimline and uksparks feel to buy a copy of this book and read it sometime rather than listen to the NIC or any other CPS.



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Yes i am aware of that... i was simply mentioning what i had read

I read in the beano you can fall along way off a high cliff and walk away unhurt, does it make it true?

 

[DPG]

I am pretty sure the NIC mentioned this a while ago and said you can. They do seem to make it up as they see fit though.

Also i am fairly sure that you should not bury flex in a wall!

Is there a specific reg for this??? Daz

 

[Darkwood]

Check your regulations under cable Identy 514.4.2

Theoretically yes its just a colour but a big no no for various reasons.

 

[Silly Sausage]

Also, last sentence of 411.3.1.1

 

[Plonker 3]

Also i am fairly sure that you should not bury flex in a wall!

Do you own a copy of the regs?

 

[Simonslimline]

I am trainee and do own BS7671, if you read my post it does say that the NIC make it up as they see fit. I mentioned it only as i remember reading about it a while back.

Simonslimline and uksparks feel to buy a copy of this book and read it sometime rather than listen to the NIC or any other CPS.

View attachment 23389

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I read in the beano you can fall along way off a high cliff and walk away unhurt, does it make it true?

 

[telectrix]

as long as the fan was classII and there was no alternative, i might be tempted.

 

[Plonker 3]

I am trainee and do own BS7671, if you read my post it does say that the NIC make it up as they see fit. I mentioned it only as i remember reading about it a while back.

Well then you need to read it, threads like this will help you understand it more. Only say something you have read by providing a link to it to prove your point.

 

[Hawkmoon]

I remember a story going round a while back (90s) about a plumber who cut into an existing boiler wiring flex that had cpc as live - can't remember details but he connected the cpc to earth term somewhere in his jb and result was fatal shock for homeowner off the kitchen sink.

 

[Simonslimline]

yep fair enough, i cant find the article link but found this on a forum page......

Well then you need to read it, threads like this will help you understand it more. Only say something you have read by providing a link to it to prove your point.

 

[telectrix]

I remember a story going round a while back (90s) about a plumber who cut into an existing boiler wiring flex that had cpc as live - can't remember details but he connected the cpc to earth term somewhere in his jb and result was fatal shock for homeowner off the kitchen sink.

i can only see that happening if there was no earthing on the installation.

 

[Hawkmoon]

Bear in mind he would have used this 'earth' terminal to earth whatever he was installing (new boiler/whatever) making it live and anything metallically connected to it (eg copper pipes to sink)

As I say I don't remember details but there could have been other factors contributing.

 

[telectrix]

then if the installation was earthed, the OCPD would have operated as soon as he'd connected it to a line conductor.

 

[Plonker 3]

yep fair enough, i cant find the article link but found this on a forum page......

View attachment 23390

I have no idea who wrote that, but the reg they quoted applies to PEN conductors. So even the diagram used is a load of baloney.

 

[Pete999]

yep fair enough, i cant find the article link but found this on a forum page......

View attachment 23390

Might be barking up the wrong tree but doesn't the Class two logo mean anything to anyone, just saying

 

[Hawkmoon]

Tel...
The way I understood it the plumber thought that the cpc in the flex was his earthing source so everything he did from that point on was isolated from the actual earth (no real cpc present in his jointing box) - no reason for OCPD to operate

 

[itselectric]

I remember a story going round a while back (90s) about a plumber who cut into an existing boiler wiring flex that had cpc as live - can't remember details but he connected the cpc to earth term somewhere in his jb and result was fatal shock for homeowner off the kitchen sink.

It was in the papers in the nineties as you say. the plumber got time for it.

 

[eddielarge]

Omg Dillb is your glass half full such a negative response to a sensible question

 

[wayneob]

used to come across this when doing boiler upgrade work on the s-plan and y-plan systems, the way I see it is that the CPC is there to protect the cable aswell, bad practice.

 

[itselectric]

It was in the papers in the nineties as you say. the plumber got time for it.

I 've had another think on this and I'm almost certain it was an electrician, not a plumber, who was at fault.
When he was questioned in court he couldn't even say where the consumer unit was

 

[Badged01]

I 've had another think on this and I'm almost certain it was an electrician, not a plumber, who was at fault.
When he was questioned in court he couldn't even say where the consumer unit was

Probably been a Electrical Trainee "electrician" who did it then ............. hang-on, did they do Electrical Trainee courses in the 90's?

 

[Hawkmoon]

I 've had another think on this and I'm almost certain it was an electrician, not a plumber, who was at fault.
When he was questioned in court he couldn't even say where the consumer unit was

I think for the sake of forum harmony we should stick to blaming a plumber lol

 

[Brightspark2]

Reg 514.4.2 says no you cant do that.

It doesn't. If it's over sleeved at the end than its ok.

Unless it's a single core cable which can not be sleeved over.


But as darkwood says it's not good practice...

 

[iamelectric]

i would have had no problem using that flex , brown sleeving on both ends whats the problem , common sense over rules the the regs sometimes , tin hat firmly on

 

[DPG]

I have no idea who wrote that, but the reg they quoted applies to PEN conductors. So even the diagram used is a load of baloney.

Must a typo - I think they mean 514.4.2. Daz

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The diagram doesn't show a PEN conductor.

 

[Silly Sausage]

Must a typo - I think they mean 514.4.2. Daz

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The diagram doesn't show a PEN conductor.

Pretty sheite publication if they can't trap errors like that.
What rag was it anyway?

 

[SPARTYKUS]

i would have had no problem using that flex , brown sleeving on both ends whats the problem , common sense over rules the the regs sometimes , tin hat firmly on

Problem is when, as mentioned, someone taps into a cable, sees green & yeller, assumes its a cpc.....etc

 

[uksparks]

as long as the fan was classII and there was no alternative, i might be tempted.

Yes Class II, tempting isn't it. i didn't though as I felt it was just wrong. The problem was the flex was buried in the wall and I really wanted to swap it for a bit of three core, but though hmmm I could use that CPC as its not being used... It was a conductor like the others, so its not like it didnt have any insulation or a smaller CSA.

 

[MDJ]

It doesn't. If it's over sleeved at the end than its ok.

Unless it's a single core cable which can not be sleeved over.


But as darkwood says it's not good practice...

Thats not the way I read the reg, it says green and yellow cables throughout their length shall only be used as a protective conductor, the oversleeve bit is when you mark the ends with a blue indication for PEN conductors.

 

[uksparks]

yep fair enough, i cant find the article link but found this on a forum page......

View attachment 23390

This is exactly what I was looking at.

 

[uksparks]

Problem is when, as mentioned, someone taps into a cable, sees green & yeller, assumes its a cpc.....etc

That's where I was going with it, I know If I cut into a cable and i saw a green / yellow, I probably wouldn't give it any thought and think, yep that's the earth. I think its a good idea to use a CPC as a CPC only and nothing else.

 

[uksparks]

I think if you start using whats really seen to be an earth throughout its length as a live conductor, you are kind of cutting corners in a way and your standards (if you have any) will probably start going down hill, personally I would rather do the right thing and tell the customer, that's going to cost you, you need a new bit of cable.

 

[DPG]

The two regs in question are here, in case anyone hasn't got the regs with them:

514.4.2 Protective conductor

The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor

and this combination shall not be used for any other purpose. In this combination one of the colours shall cover at

least 30 % and at most 70 % of the surface being coloured, while the other colour shall cover the remainder of the

surface.

Single-core cables that are coloured green-and-yellow throughout their length shall only be used as a protective

conductor and shall not be overmarked at their terminations, except as permitted by Regulation 514.4.3.

A bare conductor or busbar used as a protective conductor shall be identified, where necessary, by equal green-andyellow

stripes, each not less than 15 mm and not more than 100 mm wide, close together, either throughout the

length of the conductor or in each compartment and unit and at each accessible position.

514.4.3 PEN conductor

A PEN conductor shall, when insulated, be marked by one of the following methods:

(i) Green-and-yellow throughout its length with, in addition, blue markings at the terminations

(ii) Blue throughout its length with, in addition, green-and-yellow markings at the terminations.

 

[Geoffsd]

Has it already been said?

Whether or not oversleeving the cpc is allowed, it cannot normally be done while complying with 412.2.3.2

 

[uksparks]

Single-core cables that are coloured green-and-yellow throughout their length shall only be used as a protective conductor and shall not be overmarked at their terminations

I think that really makes it quite clear.