It doesn't. However, 120.3 says that the work will be compliant with BS7671 if the designer can demonstrate that whatever is being supplied by the circuit makes the circuit no less safe than it would have been if the words of 433.1.204 had been followed literally and rigorously.
I, for one, would ask you to point out exactly where it says that it's only for new inventions (however they might be defined) and can't be applied to existing types of apparatus. Does it actually say any such thing? (Perhaps somebody would quote the precise wording of 120.3 at present.)
It may not, but does that matter if there's something which overrides that?
It very much doesn't. It merely talks about 'deviations', with no qualification at all. As I wrote last night, there IS a corresponding (and very similar) regulation which is specifically about "new materials and inventions" (133.5) - which, to me, underlines the fact that BAS's suggestion/interpretation regarding 120.3 makes little sense.
Maybe it was, but so what? What concerns us is what the regulations in Amd3 of the 17th edition actually say.
You are the one who is usually criticising people for guessing that the intent behind a regulation was what they would like the regulation to say.
Oh dear - is that the sound of a penny dropping for you?
Why does the change matter?
I asked you if it was unreasonable.
Isn't that what I have been trying to get you to understand?
How so? I was pointing out that you seem to be applying a double standard, saying that one regulation should be taken to mean exactly what it says without room for interpretation as to what you or I might think it was intended to mean, while at the same time claiming that it's acceptable to "interpret" another rather than just taking it exactly as written.
Because, presumably, if there had been no intent to change the meaning, or at least to clarify what meaning was intended, then it wouldn't have been changed?
To think that it was intended to allow for new types of apparatus? No, that's not unreasonable. Neither is it unreasonable to take it that it is referring to the use of existing types of apparatus which provide a similar level of safety.
But you think that interpretating is acceptable. Are you saying that, in general, it is OK for people to "interpret" regulations in a way which supports your position, but not when it undermines it?
Oh, I see.
Indeed so, but it is apparent that BAS's main point is nothing to do with the degree of cable protection per se. The point he is labouring is that, because of what 433.1.204 "actually says" (and doesn't "actually say"), a ring final loses its dispensation to be wired in cable with CCC ≥20A protected by a 32A OPD if anything other than "an accessory to BS1363" is connected to the ring. In other words, he would presumably say that the whole ring became 'non-compliant' if it (amongst other things) supplied a load via, say, a 1A or 3A MCB.
Where has this come from?
I presume it comes from his belief that (from the words of 433.1.204) if a ring final ("with or without spurs") 'supplies' something which is not a BS1363 accessory (i.e. if the first thing the electrons hit {either in the ring itself or in a spur} is a non-BS1363-accessory) that it invalidates the OPD/CCC dispensation for ring finals.
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