unusual cable - can anyone tell me what it is please

[ban-all-sheds]

Face it, on a PME system there is live and neutral/earth, just by calling them neutral and earth/cpc either side of the cut-out doesn't change what is connected to what

Nor does it change the fact that the ESQCR prohibit consumers from combining the neutral and protective functions in a single conductor in their installations.

Therefore the neutral of a split-con cable cannot, no matter what potential it is at wrt earth, be regarded as an earth.

The neutral of a split-con cable is not suitable for use as a protective conductor because the law prohibits us from using it as one.

You may not use split-con cable where the cable is required to have an earthed metallic sheath.

I'm sorry if that causes you any distress, and I can assure you I'm not arguing that black is white.

But it's what the regulations say.

 

[westie101]

But it's what the regulations say.

Which specific regulation says specifically that

You may not use split-con cable where the cable is required to have an earthed metallic sheath.

(bearing in mind that as far as ESCQR is concerned you can!

I suspect it is more a case of not wanting too than can't as regards BS7671

It doesn't cause me any distress at all BTW. I am happy to see any opinion but have yet to see any specific fact

 

[holmslaw]

..

 

[westie101]

Holmslaw I will accept that as a reason.

 

[bernardgreen]

My view of it is that "the regulations" were compromised by the requirements to

[1] remove the cost of reliable earth conductor in the networks.

[2] prior to PME being introduce remove the liability of the supply company for the effectiveness of the "earthing" of the system.

The introduction of PME ( I believe ) came about because some installations could not get good reliable earths from earth rods or metallic water mains and pressure was applied to find an alternative to true earthing. Instead of providing earths the PME systems provide a connection for the CPC which when used with a current operated RCD will provide acceptable ( to most ) safety for all people inside the equipotential zone serviced by the CPC.

People crossing the boundary of the equipotential zone will be at risk if the service provided connection for the CPC is not at true ground potential. Standing on the ground and touching an outside water tap is crossing the boundary, as is the gas man touching the outside gas meter and the person holding an "earthed" metal item in the garden.

Face it, on a PME system there is live and neutral/earth, just by calling them neutral and earth/cpc either side of the cut-out doesn't change what is connected to what

Strictly speaking the CPC in a circuit protected by a RCD is not connected to the neutral of that circuit as the connection is indirect via the neutral primary coil in the RCD sensor.

 

[JohnW2]

However, as I was suggesting before, do you really think that BS7671 would be satisfied if one 'earthed' exposed-conductive-parts to the neutral conductor (and, indeed, perhaps took the next logical step and 'did without' a CPC altogether)?

Electrically I would not disagree! A definition of earthed that is used is "connected to the greater mass of earth" If that is accepted then a neutral conductor in an installation is connected to the greater mass of earth by virtue of its connection to the supply network. Face it, on a PME system there is live and neutral/earth, just by calling them neutral and earth/cpc either side of the cut-out doesn't change what is connected to what

As I said before, 'electrically' I would not disagree very much, either - but we are talking about 'the regulations' (specifically, about BS7671).

However, to repeat my question, do you really believe that 2-core fixed wiring, with the neutral regarded as acting as the 'CPC' (and therefore used to 'earth' exposed-conductive parts) in a TN-C-S installation would be regarded by anyone (on the consumer's side of the meter) as being BS7671-compliant? Goodness only knows what a PIR/EICR would have to say about that!

Kind Regards, John.

 

[JohnW2]

... and, as I asked, where are all the electricians (doing their Christmas shopping)? It's all very well for BAS, Bernard and myself representing one side of the argument, but we really need some (downstream of meter) professional input!

Kind Regards, John.

 

[westie101]

However, to repeat my question, do you really believe that 2-core fixed wiring, with the neutral regarded as acting as the 'CPC' (and therefore used to 'earth' exposed-conductive parts) in a TN-C-S installation would be regarded by anyone (on the consumer's side of the meter) as being BS7671-compliant? Goodness only knows what a PIR/EICR would have to say about that!

As has been pointed out (and we know anyway) it is specifically prohibited, that is not to say that in theory rules could be changed.

I suspect there would be a lot of nervousness about it though!

(the surprised looks we get when we explain the concept of PME are bad enough)

 

[JohnW2]

As has been pointed out (and we know anyway) it is specifically prohibited ...

If you accept that BS7671 prohibits the combining of neutral and earth/CPC functionality in a single conductor (hence also, by implication, prohibiting the 'earthing' of anything by connecting it to the {'separate} neutral conductor), why do you think BS7671 would regard a sheath as 'earthed' if a discrete part of it was the neutral conductor, rather than a separate 'CPC'?

Kind Regards, John.

 

[ban-all-sheds]

If you accept that BS7671 prohibits the combining of neutral and earth/CPC functionality in a single conductor

Not just BS 7671.

See 8(4).

 

[JohnW2]

If you accept that BS7671 prohibits the combining of neutral and earth/CPC functionality in a single conductor

Not just BS 7671. See 8(4).

Indeed - but what westie does not seem to accept is that there is a problem (at least in terms of BS7671) if half the sheathing (which is required to be 'earthed') of a cable is connected to neutral, rather than earth. To my mind, that constitutes using the neutral for a 'protective function' - hence, as you imply, seemingly non-compliant with ESQCR as well as BS7671.

Kind Regards, John.

 

[westie101]

seemingly non-compliant with ESQCR as well as BS7671.

As we know that it is compliant with ESQCR I am at a loss to understand the supposed lack of compliance with BS7671, it does not appear to be specifically stated anywhere (or if it is the reference hasn't surfaced) that it does or does not comply but is a matter of various opinions.

And there stands my argument the cable has been used for 40 years on networks and complies.

Perhaps one of those questions that would take a court case to answer

 

[EFLImpudence]

where are all the electricians (doing their Christmas shopping)?

It's not Christmas Eve yet.

I suspect the lack of interest from electricians (although holmslaw, Bas and Bernard have hit the nail on the head since John first asked) is because we're not quite sure what you are arguing about.

John is stating what the regulations say about various arrangements and

Westie is saying with his usual one sided (corporate) view that we are allowed to do it another way which may be less safe but that's the way it is so it must be right.

 

[westie101]

Westie is saying with his usual one sided (corporate) view that we are allowed to do it another way which may be less safe but that's the way it is so it must be right.

Thank you sand goodbye

 

[ban-all-sheds]

As we know that it is compliant with ESQCR

Ye Gods.

It is NOT compliant with the ESQCR for a consumer to earth all of the outer conductors of a split-con cable.

And there stands my argument the cable has been used for 40 years on networks and complies.

Ye Gods.

BS 7671 does not apply to DNO networks.

What is OK for DNO networks can, and does, contravene BS 7671, but that's OK because they are not within the scope of BS 7671.


Why do you find it so hard to accept that that could be so?