https://professional-electrician.com/technical/identification-electrical-wiring/


You would not sleeve the new black conductor blue to use as the neutral and use the new blue as L3 would you?


Andy B

hopefully you'd be very careful not to assume however that the wiring was as shown above, without checking for volts..

Not long after the change over, I  witnessed the aftermath of just such a cockup where  a large number of portable shower 'tardises' had been dropped onto a camp site, along with a 1MVA genset to power them.

The cable tail on the hired  genset was 'old colours' and perhaps the yellow core was a bit dirty looking, and may have been mistaken for a badly made  grey, or it may have been wired by someone very tired. The dis board taking the 3 phase to lots of 32A commando sockets was however very much  wired to expect the new colours.


By transposing 2nd phase and neutral,  essentially the black/blue confusion ensued.

Once the genset was started, some of the showers were between 2 phases and ran very hot but failed very quickly.. Although the mistake was quickly rectified, a number of the showers were then 'cold only' for the rest of the event. Disappointing and expensive, for the sake of a quick flick on the volts range. (all dead tests had looked OK of course.)

The extractor fan requires a L and N switch for isolation purposes. I have installed two recently and seen two different circuits shown in instructions. One shows a 2-pole switch prior to the single pole service switch the other after. Both demanding that a 3 Amp fuse be fitted. For the first circuit you can simply use a 2-pole switched / fuse spur. For the second a dedicated and extractor annotated 3 -pole  switch is used. This is both expensive and and not fused, so you have to provide this separately and also use 3 core and earth cable. However I think second maybe the preferred method as the industry supplies the annotated 3 pole switch, but I have not seen an annotated 2-pole switch. Another advantage of the 2-pole switched circuit is that it isolates the whole circuit and not just the branch to the extractor. The switch is however supplied to give safe isolation of the fan for maintenance / removal.

However I think second maybe the preferred method as the industry supplies the annotated 3 pole switch, but I have not seen an annotated 2-pole switch.

Arguably there's little need to produce a dedicated fan-symbol marked 2-pole isolating device - as you can always employ the 3-pole version and leave one pair of terminals unused.  It's the same with simple lightswitches - if you want a 2-gang one you can only get it in 2-way versions - so you just have to leave the extra terminals unused for 1-way switching. The waste of the extra metal etc is far offset by the savings of not having multiple different products (and lower volumes of each).

 

Another advantage of the 2-pole switched circuit is that it isolates the whole circuit and not just the branch to the extractor.

But has the disadvantage of isolating the light as well as the fan - which can be a nuisance especially in bathrooms with no window.


  - Andy.

ebee:

I`d never use Black in a 3 core for N and that stems partly from the phase rotation jobby I mentioned.


Mind you I am out of kilter with a lot of folk with my 3 core for two way switching configuation. I know I`ve mentioned it before but Both Browns say L1 = perm L., Black sleeved Brown and Blue sleeved BrBrown into L2 and Finally Grey sleeved Brown as C. Of course I was brung up with Reds for L and Black for N, and R/Y/B for 3 phase, well I know some might think I`m old enough for white as 2nd phase but no I am not quite that old.

I was initially attracted to this thread by its reference to toilets etc., and recollections of my "oh dear!" moment. However I have followed the subsequent progression to identification colours with interest.


I don't know quite how old is meant by "old", but the idea of white for one of the phases seems to have occurred at various times.


It was around 1970, I think, that the new colours, i.e. brown for live, blue for neutral, green and yellow for earth, were introduced for flexible cords, round about the time also that sizes moved to metric. I wondered at the time why fixed wiring colours were remaining unchanged but nobody seemed able to answer that question.


I seem to recall at some stage subsequently a proposal that the three phase identification change to brown, white and grey. There seemed some sense in selecting white; it was not used for another purpose, it was bright, like yellow, and there seemed to be a historical link.


The present use of black as in identifier does seem to beg confusion with the old neutral. Much fixed wiring with the old red and black colours still exists and will continue to be there for a long time, so inevitably there will be cases of new wiring joining older with old colours.


Can anyone else remember the proposal for white, and why it "gave way" to black?

I wondered at the time why fixed wiring colours were remaining unchanged but nobody seemed able to answer that question.

My guess would be that the change was driven by European trade requirements - manufacturers wanted to be able to sell the same (esp single phase domestic) appliance across Europe (single  market and all that) - each country having its own flex type makes that painful for the production line and distribution. (In those days of course they didn't have to fit an appropriate plug). Fixed installations were much less of a trade issue - they didn't move about so much - and more complicated to solve as it had to address various 3-phase requirements too - so that problem got deferred.

 

Can anyone else remember the proposal for white, and why it "gave way" to black?

Probably because most of the continent already used black (or combinations of black and brown) for line (phase) - and white (well officially cream, but usually very white looking in practice) was already established as a functional earth. The continentals really weren't bothered about a third colour - they tended not to preserve phase rotation in wiring - often L1/L2/L3 were brown and two blacks or two browns and one black - that way they could reverse one pair at the motor to ensure correct rotation without anything looking wrong. It was the UK that insisted on a 3rd colour and I gather once you'd eliminated all the colours that had been used for something else in recent history across Europe (the Germans used to use red for earth for example) you were left with only pink or grey. They picked grey.


   - Andy.

If memory serves (might just be folklore and mee old heed though) , some of the continent used Brown as L1, Black as L2 & also Black as L3, which meant join two Blacks could short 2 phases, then instead of being sensible and adopting the best colours (ours) they did not want to favour or disfavour any single country so they compromised on the colours we get today. A political bodge.

Thanks for your take on this, Andy. It accounts for quite a lot.