We all know the blue when used as line in a ceiling rose should be over sleeved, and we have seen many times where the sleeve has fell off, .... so it is not an unknown problem, so if when investigated the green/yellow is not sleeved at the fan, then it is impossible to tell if the electrician installing it ever fitted the sleeves...
True, and that's why it is not a very desirable practice, even if compliant with BS7671....
... shrink sleeve is unlikely to fall off once shrunk on, and also any future user will not even see the original green/yellow marking, but the example shows a very short length of over sleeving with the majority of the cable showing original colour.
Again, indeed. On the rare occasions I've done this, I have used significant lengths of heat-shrink for the over-sleeving, for this very reason.
The problem is the courts seem loathed to blame the occupant, when either that occupant or his family has been killed, they want to blame some tradesman who should have known better, not a ordinary person.
Probably - but, as I said before, if the G/Y had been over-sleeved by the tradesman, in compliance with BS7671, it's hard to see how a court could 'blame' them. If the sleeving had subsequently 'fallen off', that must have been due to actions of someone other than the person who put it on.
However, you now seem to be questioning whether over-sleeving a G/Y conductor in a multi-core cable
actually is BS7671-compliant ...
What you need to do is consider the full stop. So how do you read "Single-core cables that are Coloured green-and-yellow throughout their length shall only be used as a protective conductor and shall not be over-marked at their terminations, except as permitted by Regulation 514.4.3."? I see this as an addition to the first statement and it allows the over sleeving of the single core cable when part of a PEN conductor, it does not say if not a single core cable you can over sleeve. ... Maybe BS7671:2018 has different wording?
The wording of BS7671:2018 is essentially the same:
BS7671:2018 said:
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 identified by 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
I don't think many people would agree with your interpretation. As for the first sentence, one needs to remember that 514.3.2 allows conductors to be 'identified' by the insulation colour OR by 'overmarking' at the terminations. A G/Y-insulated conductor with brown (or red) over-sleeving is therefore 'identified' as a line conductor. Perhaps more to the point, if your interpretation were correct (i.e. saying that a G/Y conductor must
never be over-sleeved), then the sentence about single-core cables would surely be unnecessary - by including it, they are surely indicating/implying that 'overmarking' of a G/Y is permitted for conductors which are not single-core?
As said before it is down to the English student to interpret what it says, but I would say "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." is quite explicate, and what follows it clearly refers to PEN conductors and does not distract from the first statement.
It is only the very last clause of that sentence (indicating one exception to what the rest of the sentence says) that relates to PEN conductors. The main part of the sentence says "
Single-core cables that are Coloured green-and-yellow throughout their length
shall only be used as a protective conductor and
shall not be over-marked at their terminations
I may be wrong but, as I have said, I believe that you are somewhat out-on-a-limb in your interpretation of this regulation. That doesn't mean that I regard over-sleeving of G/Ys (in multi-core cables) as remotely desirable, but that's not what we're talking about - we are discussing what is, and is not, BS7671-compliant (and which hence could be used by a hypothetical court to decide whether or not something which had been done was "wrong").
Kind Regards, John