Flat twin cable with sheathed CPC.

Marvo · Feb 15, 2024

I see they're introducing a new type of flat twin cable with a sheathed CPC. In my location there's no requirement to sleeve CPC/bonding conductors and you never see it done. We just install and arrange wiring in enclosures or DB's in such a way that there's no realistic chance of the uninsulated earth wires contacting live components or terminations. To be honest I can't ever recall seeing a fault due to an uninsulated earth having strayed into contact with a live or neutral. The closest thing I have seen is screw damage to wiring or flash damage due to an installer causing accidental contact between a live and chassis ground whilst working live but I'm a firm believer there's no tablet that cures stupid and no amount of insulating things would ever stop that happening.

When was the requirement for sleeved CPC's introduced in the UK? Was there a particular event or accident that prompted the rule or was it just decided it would be a good thing to do? Do you think the rule makes an important contribution to safety or it's just something that had good intentions behind it but actually makes no difference and just adds time and ballache to an installation?

pc1966 · Feb 15, 2024

AFIK the requirement to sleeve the CPC here goes back to before the 1970s, but I don't have copies of older regs to know when that became the norm.

While the UK T&E style of cable has bare CPC that is typically smaller than the live (but still to meet adiabatic) and expectation of adding some sleeving where stripped for use, in the ROI they have the CPC that is sleeved and I think follows the EU norm of same size as live.

The USA seems to have unsleeved CPC cable (Romex?) similar to the UK and I have never seen sleeving used, even though a lot of their sockets have far more exposed live connections behind the faceplate!

Pretty Mouth · Feb 15, 2024

The reg requiring sleeving at terminations etc. is in the 1976 edition, but not in the 1966 edition, so was introduced some time in between. I do come across the occasional fault caused by bare CPC to live part, that could have been avoided by use of sleeving, but not often

R-fur · Feb 15, 2024

I thought the sleaving was for identification as much as insulation. You definatly used to get green sleaving before the green/yellow came in. I think that was about 68.

IAmSparkytus! · Feb 15, 2024

Would probably buy this depending on price. Can get quite annoying trying to put 3mm sleeving on long lengths of stripped earth when making off a 24TP distribution board

Marvo · Feb 15, 2024

From the info I saw they said it will be the same price as the uninsulated version..... but don't quote me on that.

Marvo · Feb 15, 2024

I also heard that it's for helping with identification of the CPC but I think no matter how bad someone's eyesight or how colourblind they may be you couldn't mistake a bare CPC or bonding wire for anything other than what it is.

nicebutdim · Feb 15, 2024

IAmSparkytus! said:
Would probably buy this depending on price. Can get quite annoying trying to put 3mm sleeving on long lengths of stripped earth when making off a 24TP distribution board

6193B (I'm assuming you need LSF) has been available for years. While it doesn't meet any British Standard, I can think of nothing that prohibits its use.

Other cable types are also available with insulated CPC and are widely used in 3ph installations. I do occasionally come across T&E in 3ph boards, but it's a very rare occurrence.

nicebutdim · Feb 15, 2024

Marvo said:
I also heard that it's for helping with identification of the CPC but I think no matter how bad someone's eyesight or how colourblind they may be you couldn't mistake a bare CPC or bonding wire for anything other than what it is.

Unlikely cost would be the same considering additional material required in manufacture and that's excluding tooling costs.

6193Y/B used in southern Ireland has CPC sized the same as L&N, which obviously make it quite a bit more expensive.

loz2754 · Feb 15, 2024

It's the same price. Interestingly, they had to reformulate the sheath to accommodate the overall increase in size, so standard clips would still fit.

Marvo · Feb 15, 2024

The CPC remains a size smaller than the line conductors although sufficient to fulfil rfequirements of the adibiatic formula and the thin sheath on the CPC doesn't qualify as 'insulation' ie it doesn't carry a 1kv IR spec, it's just a thin sheath designed to prevent accidental contact. The outer cable dimensions will remain unchanged so all stripping tools, glands, fastnenings etc will still work.

They're also making the 3-core and earth version as well which I assume you use mainly for 2-way lighting arrangement cabling.

loz2754 · Feb 15, 2024

They also plan to make all sizes up to 16mm²

ipf · Feb 15, 2024

nicebutdim said:
I do occasionally come across T&E in 3ph boards, but it's a very rare occurrence.

I've come across loads of it, mostly for additional circuits to existing DB's, not nice.
I'm not totally against it in some cases. LSF T+E feeding single phase equipment in commercial kitchens, for example. Can be a basic, quick way of wiring through metal trunking and flexible conduit, in some situations.
Better than SY...

'Pie eater' territory

Pretty Mouth · Feb 16, 2024

R-fur said:
I thought the sleaving was for identification as much as insulation. You definatly used to get green sleaving before the green/yellow came in. I think that was about 68.

Interestingly, the reg in the '76 edition specifically mentions the word 'insulating', but doesn't mention the colour green. What I take from it is, that its primary purpose was to insulate, and green was used because any other colour would be inappropriate for an earth-continuity conductor (as it was known as back then)

R-fur · Feb 16, 2024

Pretty Mouth said:
Interestingly, the reg in the '76 edition specifically mentions the word 'insulating', but doesn't mention the colour green. What I take from it is, that its primary purpose was to insulate, and green was used because any other colour would be inappropriate for an earth-continuity conductor (as it was known as back then)

Yes it had to be insulating as opposed to conductive but it wasn't there as an insulator.

R-fur · Feb 16, 2024

I was an apprentice in 76 and cant remember what colour the sleaving was, I think it was green/yellow but always referred to as green sleaving.

loz2754 · Feb 16, 2024

The combination of green and yellow was introduced in 1978 according to the IET.

Pretty Mouth · Feb 18, 2024

R-fur said:
Yes it had to be insulating as opposed to conductive but it wasn't there as an insulator.

Here is the regulation:

D29 (ii)
Where the sheath of earth-continuity conductors complying with reg D28(i) is removed adjacent to joints and terminations, earth continuity conductors of CSA up to and including 6mm2 shall be protected by insulating sleeving complying with bs2848.

D28(i) refers to CPCs within cables (not flex).

Make of it what you will, but to me its main purpose is as an insulator.

IAmSparkytus! · Feb 18, 2024

nicebutdim said:
6193B (I'm assuming you need LSF) has been available for years. While it doesn't meet any British Standard, I can think of nothing that prohibits its use.

Other cable types are also available with insulated CPC and are widely used in 3ph installations. I do occasionally come across T&E in 3ph boards, but it's a very rare occurrence.

What are the alternatives with the sheathed earth?

nicebutdim · Feb 18, 2024

IAmSparkytus! said:
What are the alternatives with the sheathed earth?

6193B

timhoward · Feb 18, 2024

I bet they are delighted at Quickwire, they finally get a 2.5 sq mm junction box out and then the every day standard cable spawns an alternative!

IAmSparkytus! · Feb 18, 2024

nicebutdim said:
6193B

I’m sure I’ve seen an LSF round cable used on sites before as well with an insulated earth. Not flex, something a bit more substantial but not FP either, didn’t seem to have the outer sheath where you can sort of score then bend slightly to make to snap and strip (if that makes sense)