Dangerous Henley Block!?

[JohnW2]

The grey mechanical protection layer should never be exposed to voltages.

I don't think anyone has suggested anything that would cause that to happen, but you seem to be persisting with your belief that there is something 'dodgy' about the outer layer of a PVC/PVC cable.

What exactly do you think might happen if the outer layer (grey or any other colour) of a PVC/PVC cable were "exposed to voltages"? (and, whilst I'm asking, "voltages" between where and where?).

Kind Regards, John

 

[AndyPRK]

Interesting Sunray.

 

[Harry Bloomfield]

What exactly do you think might happen if the outer layer (grey or any other colour) of a PVC/PVC cable were "exposed to voltages"? (and, whilst I'm asking, "voltages" between where and where?).

Likely, nothing at all, but the point is the sheath is there for mechanical protection, the inner is there for insulation.

 

[JohnW2]

Likely, nothing at all, but the point is the sheath is there for mechanical protection, the inner is there for insulation.

I realise that a good few people, including yourself, believe that, but are you are aware of anywhere where it is actually 'stated' that the outer layer is [only] there for mechanical protection **?

Does this mean that you believe that a 'single-insulated' conductor surrounded only by a non-insulating (e.g. metallic) outer layer which provided 'mechanical protection', with no intervening second 'insulating layer' would be considered acceptable? I personally wouldn't have thought so, and I certainly cannot recall ever having seen such an animal.

Does it also mean that you think BS7671 is wrong in saying that one of the approaches for an item of Class II equipment is for it to have "double insulation" (rather than "basic insulation plus mechanical protection", which you would seemingly think it should be)? Indeed, unless it has an outer earthed metallic covering, then I think one can reasonably regard a cable as essentially being a 'Class II item' - or, at least, analogous thereto.

[ ** I would have thought that, in addition to providing additional mechanical protection, the outer sheath of, say, a PVC/PVC cable is also there to provide 'belt and braces' insulation, in case there is a failure of the 'basic insulation'. Let's face it, if there happens to be a defect in the inner ('basic') insulation of a live conductor (which would be undetectable by testing if only one conductor were affected), the outer layer of PVC would then be the only thing preventing someone from touching the live conductor - so I would expect it to be required to have at least as good insulating properties as does the inner ('basic') insulation. ]

Kind Regards, John

 

[Lectrician]

I’m glad at four pages this has now ended .

Ffs guys, 4 pages on tails. More for the tools, less for the sat at home/office procrastinating.

 

[JohnW2]

I’m glad at four pages this has now ended .

What makes you think that it has ended? - it's not much over 24 hours since the last post .

(but we're only just onto page 4, so it would take quite a few posts to increase the number of pages)

Kind Regards, John

 

[SUNRAY]

Yes 4 pages but sadly all we've got to is differences of opinion on the correct way to do things.

At least we have no dispute that the OPs installation is wrong.

 

[JohnW2]

Yes 4 pages but sadly all we've got to is differences of opinion on the correct way to do things. At least we have no dispute that the OPs installation is wrong.

Yes, I think (hope) that we all agree that the issue the OP asked about (exposed copper) is wrong, potentially dangerous and warrants urgent rectification - but I imagine that the OP already knew that.

The other issues discussed (which I certainly didn't initiate!) relate to things which I personally regard as being pretty 'trivial' and with minimal safety implications, regardless of considerations of 'correct' and 'incorrect'.

Kind Regards, John

 

[SUNRAY]

The other issues discussed (which I certainly didn't initiate!) relate to things which I personally regard as being pretty 'trivial' and with minimal safety implications, regardless of considerations of 'correct' and 'incorrect'. Kind Regards, John

Yes aggreed.

I don't disagree with the current rule of not having the insulation showing but I'm not intending to make changes to my home installation where there are 8 examples.

 

[JohnW2]

Yes aggreed. I don't disagree with the current rule of not having the insulation showing but I'm not intending to make changes to my home installation where there are 8 examples.

I think the only real discussion/disagreement has been about practicalities. As I have said, I think that if 'conductor identification' is by insulation colour, then the implication of the requirement in BS7671 is that that insulation should be readily visible, which really requires that the insulation protrudes a little beyond the cut end of the sheath (within the enclosure).

However, more important (in my opinion) is that the inner insulation should not be visible outside of the enclosure - so if the mechanics of the enclosure are such that one has to choose between satisfying both of those requirements, then I would personally say, pragmatically, that the lesser of the evils would be to have insulation and sheath cut to the same length but with no insulation visible outside of the enclosure.

Kind Regards, John

 

[AndyPRK]

But separate insulation

https://www.ebay.co.uk/itm/184398471069

Can understand now why we now have coloured tails.

 

[JohnW2]

Can understand now why we now have coloured tails.

Looking at cables like that, one can't help but wonder why the PVC covering of such conductors has to be split into two layers - i.e. why not allow just a single layer of thicker (and/or 'better') PVC?

As I recently wrote, something like a PVC/PVC cable can, in many senses, be though of as analogous to an item of Class II equipment. For the latter, the requirement sis for "Double or Reinforced" insulation, so why not something similar for cables?

Kind Regards, John

 

[SUNRAY]

I think the only real discussion/disagreement has been about practicalities. As I have said, I think that if 'conductor identification' is by insulation colour, then the implication of the requirement in BS7671 is that that insulation should be readily visible, which really requires that the insulation protrudes a little beyond the cut end of the sheath (within the enclosure).

However, more important (in my opinion) is that the inner insulation should not be visible outside of the enclosure - so if the mechanics of the enclosure are such that one has to choose between satisfying both of those requirements, then I would personally say, pragmatically, that the lesser of the evils would be to have insulation and sheath cut to the same length but with no insulation visible outside of the enclosure.

Kind Regards, John

My personal view too.
The wall on these

is <3mm, possibly even <2mm and getting a copper free termination without it being too long and fouling the opposite cable is difficult enough without worrying about getting a bit of colour showing, especially as it doesn't show internally.