CPC as live conductor now OK?

[scousespark]

I'd much rather have someone like John on here giving out knowledgeable advice than someone like yourself giving out not just wrong, but dangerous advice to DIYers.

I'm sure you do, as he/she doesn't question your competence. You'd rather listen to a DIYer than a senior engineer at the IET.

That dear readers is how low the trade has sunk, and why you are getting ripped off daily by course cowboys.

In the post where you quoted the IET, their post started with IET wrote.

I am required to preface my remarks by saying that I have no authority to interpret the requirements of BS 7671:2008(2011), Requirements for Electrical Installations, however, within that constraint, I hope you will find my comments helpful.

It's a jump to now claim this was advised by a senior IET engineer.
Just how are sparks ripping people off on a daily basis?

 

[JohnW2]

[In the post where you quoted the IET, their post started with IET wrote.
"I am required to preface my remarks by saying that I have no authority to interpret the requirements of BS 7671:2008(2011), Requirements for Electrical Installations, however, within that constraint, I hope you will find my comments helpful."
It's a jump to now claim this was advised by a senior IET engineer.

It is. However, to be fair to the person who wrote that reply, what they went on to say (in response to the specific question posed by doitall) was totally in keeping with virtually all our interpretations of the what the regs say about oversleeving G/Y for use as a live conductor.

The problem is that, not unreasonably, doitall only got a reply to the question he had asked. I would be very interested to hear from the person at the IET would have to say (albeit with caveats!) if (s)he were asked whether it is acceptable to ignore the requirements of 411.3.1.1 of BS7671:2008(2011) (which requires a CPC to be run to 'every point and accessory') if one doesn't have enough cores in one's cable for a CPC, because one has oversleeved the G/Y core for use as a live conductor. ... but doitall seems reluctant to ask them that question.

Kind Regards, John

 

[EFLImpudence]

In the post where you quoted the IET, their post started with IET wrote.

I am required to preface my remarks by saying that I have no authority to interpret the requirements of BS 7671:2008(2011), Requirements for Electrical Installations, however, within that constraint, I hope you will find my comments helpful.

It's a jump to now claim this was advised by a senior IET engineer.
Just how are sparks ripping people off on a daily basis?

Also in that quote was -
"Twin and earth cables should equally never have the CPC sleeved with any colour other than green and yellow."

which, of course, why doitall is now limiting the argument to 3 core flex (which could easily be replaced with four core) unlike the original question which related to replacing thermostats at points wired with T+E. (if my memory serves me correctly, I can't be bothered to look for it).

 

[ban-all-sheds]

and, as someone with a keen interest in human behaviour, I am primarily interested in discovering why you are behaving in the way you are.

Is is cos he is a t**t?

 

[ban-all-sheds]

Exact question coppied and pasted.

As a Plumbing and heating consultant I come across an infinate number of properties where the green and yellow insulated core has been oversleeved and used as a switch wire, (normal multicore flex as used in heating controls)

The trade seems to be 50/50 ok or not ok, I have asked the NICEIC and Napit with conflicting replies.

New installations I would say no, but the million already installed is the question.

Your opinion would be appreciated before I loose what little hair I still have.

signed Me.

Really? Exact question copied and pasted?

How come then that this search:

https://www.google.co.uk/search?q="...s+been+oversleeved+and+used+as+a+switch+wire"
only finds this thread, not the IET one?

 

[ban-all-sheds]

No I know I'm right

You are mistaken

and have it in writing.

From someone who is byhis own admission not qualified to give an official answer

I can sleep well at night thank as what you think is irrelevant, you're not even a sparky

Neither are you.

How can you give advice to DIYers when you admit you're not a sparky JohnW2.

Because he is much cleverer and much more knowledgeable than you.

Obviously one wont get an intelligent discussion.

You've seen to that.

 

[JohnW2]

Also in that quote was -
"Twin and earth cables should equally never have the CPC sleeved with any colour other than green and yellow."
which, of course, why doitall is now limiting the argument to 3 core flex (which could easily be replaced with four core) unlike the original question which related to replacing thermostats at points wired with T+E. (if my memory serves me correctly, I can't be bothered to look for it).

Just as well, since the bare CPC of T+E is clearly a no-no as a live conductor, regardless of any sleeving at its ends. Apart from anything else, for most of it's length, it would only be 'single insulated' - which, as I need not tell you, is not acceptable (or reg-compliant) for a live conductor unless the cable is in conduit.

Kind Regards, John

 

[sparkwright]

FWIW, I could not bring myself to do it, as that cable could be tapped into somewhere along its length and a connection made to the green/yellow conductor. It would be reasonable to assume this conductor to be connected to earth.

I agree, and also wouldn't do it for that very reason. However, as we have agreed, the practice of oversleeving a G/Y only at its terminations, so as to use it as a live conductor, is not, in itself, non-compliant with BS7671 - but the installation as a whole would be non-compliant if one can't find some other way to run a CPC to whatever is at the end of the cable.

Kind Regards, John

Suppose a central heating system had two 3 core flexes run next to each other to supply a programmer. Would it be reasonable to use one green/yellow core as the earth, and the other green/yellow core over-sleeved as a live or neutral?

 

[Iggifer]

Suppose a central heating system had two 3 core flexes run next to each other to supply a programmer. Would it be reasonable to use one green/yellow core as the earth, and the other green/yellow core over-sleeved as a live or neutral?

I would think no, as if you were to break into flex b with the oversleeved G/Y (for whatever reason) it's not actually a cpc, and there is no protection from the CPC in flex b. It would make much more sense to use 1x multicore flex

 

[EFLImpudence]

Why not just use the correct cable?

 

[JohnW2]

Suppose a central heating system had two 3 core flexes run next to each other to supply a programmer. Would it be reasonable to use one green/yellow core as the earth, and the other green/yellow core over-sleeved as a live or neutral?

That's the difficult question, which I've been waiting for someone to ask It's obviously better than having no CPC run to the programmer, and one could certainly read the regs as saying that it is compliant (so long as both cables remain in place).

However, the same argument obviously cannot be applied to things like thermostats, that have only one cable- which is the sort of scenario which started this whole discussion.

Kind Regards, John
Edit: typos corrected

 

[sparkwright]

But they are saying you can over-sleeve a green and yellow core in a multi-core cable.

Don't like the idea, particularly as flex is available to suit any job, but there will always be a time where one is a core short.

 

[JohnW2]

Don't like the idea, particularly as flex is available to suit any job, but there will always be a time where one is a core short.

If, as I suspect, you wouldn't dream of using 3-core cable if you had 4-core available (even if the 3-core could be argued to be technically reg-compliant), would you be professionally comfortable using 3-core just because that was all you had, and going to get the proper cable would be an inconvenience?

Kind Regards, John

 

[sparkwright]

Though I would not be comfortable using the green/yellow core as a L or N, one has to consider instances on existing installations where it may be very impractical to install what has been called the 'correct cable'. So if it is perfectly permissible to over-sleeve the green/yellow, then it would seem acceptable to do so, providing the accessories have a suitable earth run to them.

Having said that, it wouldn't sit well with me to do this, as to me earth is earth.

I suppose a short run of surface run cable is perhaps at less risk of the green/yellow being tapped into to earth something. But then a short run of surface cable would be the easiest to replace anyway.

The point I'm trying to make is what can you legally 'get away with'. In fact, if it's allowed, is it actually 'getting away with it'? If it's allowed, it's allowed, isn't it?

Fortunately, I think most of us can usually find a painless way to get the best possible job, by fishing the 'correct' cable from A to B.

 

[JohnW2]

Though I would not be comfortable using the green/yellow core as a L or N, one has to consider instances on existing installations where it may be very impractical to install what has been called the 'correct cable'. So if it is perfectly permissible to over-sleeve the green/yellow, then it would seem acceptable to do so, providing the accessories have a suitable earth run to them. Having said that, it wouldn't sit well with me to do this, as to me earth is earth.

Exactly. Although it would probably be acceptable to the regs, provided that a CPC got to the accessory by some other route, you would not feel comfortable and it "wouldn't sit well with you".

In any event, what about the infamous (3-wire) thermostat, or other single-cable control/accessory? Would you ever feel it acceptable to use 3-core cable for that, hence not complying with the regs' requirement that a CPC be run to the control/accessory?

I suppose a short run of surface run cable is perhaps at less risk of the green/yellow being tapped into to earth something. But then a short run of surface cable would be the easiest to replace anyway.

As you imply, that's a situation in which, ironically, failing to replace with 'proper cable' would probably be the least excusable.

The point I'm trying to make is what can you legally 'get away with'. In fact, if it's allowed, is it actually 'getting away with it'? If it's allowed, it's allowed, isn't it?

Yes, 'allowed is allowed', but we all know that 'acting under orders' is a very dicy way to try justify acts which are contrary to one's conscience (professional or otherwise). This is where professionalism comes (or should come) into the equation. A professional obviously cannot undertake work to a lower standard than the relevant regulations require, but if (s)he is not comfortable that something which just satifies the regulations is satisfactory, or adequately safe, then they should work to a (self-imposed) higher standard than that of the regulations. ... and that applies in almost any walk of life, not just to electricians. Professionals are responsible for their own actions and cannot (should not) try to hide behind regulations which allow things they are not happy to do.

Kind Regards, John