Brown - Live Grey (sleeved Blue) - Neutral Black (sleeved Gn/Y) - Earth I believe that is the "usual" way rather than Bn-Live, Bk-Neutral, Gy-Earth. However, is there a "standard" which defines this or is it just accepted, best practice? Just sorting out an install where there may be two differing implementations and want to harmonise it.
Cable cores do not know what they are. They are just colours. It is up to you to denote what they are, what they do and mark them approprietely. When the colours changed, the IET put out guidance which is, as you say: The reason was to drive people away from using black as neutral, and avoid confusion. So that worked, didn't it. The convention is Line = brown Neutral = blue earth = green/yellow AND you must colour sleeve/mark any conductors of varying colours to confirm their use to the next guy/girl along. So. Use the grey as neutral, but it must be sleeved/marked with blue and use the black as earth, but it needs green/yellow sleeve. If you use a colour other than brown for a live function (eg a switched live in a lighting circuit) this conductor should be tagged with a brown marker. Simples!
This is the key thing I recall when looking into this topic. It really is that simples unless of course you're a DIYer asking about how to run a cable to his shed/shack at t'other end of t'garden.
No one has actually answered the OPs question as to whether there is a standard, except for Bazza's comment about IET guidance. I do not know the answer either, so is it just best/accepted practice based on the IET recommendations?
In the old colours red,yellow and blue,yellow was always used as the earth, oversleeved green then green and yellow.Blue was used as the neutral. Although the IEE issued guidelines about brown,black and grey, the logical and sensible thing to do was make black earth oversleeved and grey neutral oversleeved
Its an accepted best practice standard Or put it another way - if you, a professional spark, fitted an SWA with the black as the neutral with appropriate sleeving, would it still be "OK"? Would you still be able to sign it off?
I corrected myself just after you posted... Or put it another way - if you, a professional spark, fitted an SWA with the black as the neutral with appropriate sleeving, would it still be "OK"? Would you still be able to sign it off?
I'd say it's more than guidance then, but I'm not getting into a debate as to whether that constitutes it being a standard. More standard than guidance I'd say. No different in my eyes to using standard T&E but swapping so brown-neutral and blue-live with appropriate blue/brown sleeving. Such practice would at least be frowned upon. Or using old black/red T&E in a new install.
The on-site guide Table 11b provides GUIDANCE as to the old/new colour equivalents for both single and three phase whirring. I'm not going to recite the whole thing, but it effectively says what I wrote above.
You wouldn't believe how many times I find the black being used as neutral, contrary to the recommendations and published advice. What you forget is many electricians don't read anything. They work solely by what their mate tells them and believe everything they are told, never questioning anything by checking it out for themselves. To these types it is usual to use the black as neutral because that's what it used to be. The logic there is typical of these idiots. I lose my patience with it all. You arrive to do a job where these morons have been and you always have to work against your better knowledge.
There is no published guidance or Regulations regarding this. The NICEIC advise a particular colour because they want to de-neutralise the black. Sounds like a good idea, but really there is no evidence to suggest that it is. The IET don’t care what colour is used, as long as it’s not a single core G/Y and the terminations are marked appropriately. Whenever I go on a new site, I always try to remember to ask which colour is being used for earth. Occasionally I get told it’s G/Y. As to whether it’s black or grey, depends.