Lights off a Fire Alarm

[EFLImpudence]

I know you feel strongly about that and I disagree so won't argue again, but -

From side to side one could say the sequence is Red, Yellow, Bare earth, Blue.

A new cable goes Brown, Black, Bare earth, Grey.

wouldn't it be better for protection if the conductors were:

L E L N ?

Or is there a reason that I'm missing?

 

[OwainDIYer]

wouldn't it be better for protection if the conductors were:
L E L N ?
Or is there a reason that I'm missing?

The reason is that it's really 3-phase cable with no neutral. Blue used to be a phase and Brown Black and Grey are all phases now. On smoke detector interconnects all wires are to be treated as 240v phase. On two-way light switching the third wire can be either a switched live or a neutral depending on the location of the lamp in the circuit.

 

[sparkwright]

I know you feel strongly about that and I disagree so won't argue again, but -


wouldn't it be better for protection if the conductors were:

L E L N ?

Or is there a reason that I'm missing?

Good, no need to argue.

If it was to be L E L N, then I suppose that would mean grey and black would be the lives, and brown the neutral!!

I seems to me if in 3 phase
Red = Brown
Yellow = Black
Blue = Grey
then those interpretations should logically follow for a 3 core and earth cable, which as far as I am concerned, they do.

Also, if we have to verify every time which colour has been used for the neutral, would it be nice to at least verify that it is the colour we may expect it to be?

 

[EFLImpudence]

If it was to be L E L N, then I suppose that would mean grey and black would be the lives, and brown the neutral!!

I did not mean that in any relation to the colours but just as a better safety factor.
It makes no difference in three phase with only one CPC, where it is.

Put it another way - If you want the Grey (or Blue) to be Neutral, then wouldn't it have been better to have the CPC between the Brown and Black (Red and Yellow)?

It seems to me if in 3 phase
Red = Brown
Yellow = Black
Blue = Grey
then those interpretations should logically follow for a 3 core and earth cable, which as far as I am concerned, they do.

They may do, but that may not have been the reason for the order of RYB. There may have been no reason.
Lucky it wasn't Red Blue Yellow.

Also, if we have to verify every time which colour has been used for the neutral, would it be nice to at least verify that it is the colour we may expect it to be?

As you do have to verify, it doesn't matter.

 

[333rocky333]

When harmonised cable came out in 2004 there was LOADS of information informing us which colours to use - in 3 phase situations, and regular single phase use - including 3 core and earth cables where a neutral may be included.

There were leaflets, key rings etc with it all shown.

I dont recall ever seing one regarding single phase and never seen any actual tech info, even now, saying use yellow earth, blue neutral (sleeved), let alone black earth grey neutral nowadays (sleeved)

Yellow and blue became the norm as they slightly resembled whats found in flex and its true what you say about the old colours to the new regarding the 3 phases, but as said some people opted that aproach, whereas in the 2 year changeover period many kept the black as neutral sleeving the brown as RED to match the existing circuits, hence not causing two sets of colours unnecassary.
Afaik It was some time on, when a large installer that used a lot of 3 core turned for advise and they adressed the issue, but to this day apart from a magazine article I have never seen it official.
Im happy to be proved wrong if you can find any official literature though

 

[333rocky333]

Incidently, i will try and get a picture, I know of a 12way fuse board that is on the old blue phase supply, its a conduit instalation and the only cables in it are Blue and Black, nowadays it looks so strange

 

[Risteard]

Incidently, i will try and get a picture, I know of a 12way fuse board that is on the old blue phase supply, its a conduit instalation and the only cables in it are Blue and Black, nowadays it looks so strange

Interestingly that was never permitted for final circuits. Only single phase distribution circuits were ever permitted to be wired in phase colours (and even they haven't been for quite some time).

 

[sparkwright]

Incidently, i will try and get a picture, I know of a 12way fuse board that is on the old blue phase supply, its a conduit instalation and the only cables in it are Blue and Black, nowadays it looks so strange

Yes, seen that before, in a leisure centre. Sockets wired with red and black, yellow and black, or blue and black.

Could be a problem if anyone wanted to shift things about in the DB, but so what.

Also seen in a 70s block of flats lighting conduit with all yellow switched live cores, and strangely white (previously a 1950s colour) used for the same in an 80s block of flats.

You have to admire these ****-proof ideas.

 

[333rocky333]

Interestingly that was never permitted for final circuits. Only single phase distribution circuits were ever permitted to be wired in phase colours (and even they haven't been for quite some time).

It was a very old install,one of the first uk tesco stores in hendon london , im sure at the time i did check and it was once permitted long long ago, before then being allowed only for 3 phase circuits, but maybe i misread and it was as you say, one of those things you will never likely see again, bit like a house round here that had lead meter tails.

 

[SUNRAY]

Interestingly that was never permitted for final circuits. Only single phase distribution circuits were ever permitted to be wired in phase colours (and even they haven't been for quite some time).

What has never been permitted?
AFAIC the norm in 3ph buildings was to use the phase colour for 1ph circuits.
Ironically a good friend of mine nearly lost his life a couple of years after harmonisation: A 1ph 'fuse box' on blue phase needed to be replaced and it was removed by one guy but replaced by another the following day. This was in a services passage and on the other side was several layers of tray supported on unistrut.
My friend went in to do the testing and managed to get his hand on the neutral bar with all the blue wires, he was thrown backwards against the end of a strut between his shoulderblades, cracking several vertebrae then he dropped unconcious and scraped loads of skin and flesh off his back and head. He spent several months in hospital and is now handicapped.

 

[SUNRAY]

When harmonised cable came out in 2004 there was LOADS of information informing us which colours to use - in 3 phase situations, and regular single phase use - including 3 core and earth cables where a neutral may be included.

There were leaflets, key rings etc with it all shown.

In the case of a 3 core and earth cable, one barely even has to be told - because it's so obvious. Look at the structure of three core and earth cable. From side to side one could say the sequence is Red, Yellow, Bare earth, Blue.

A new cable goes Brown, Black, Bare earth, Grey.

So that alone shows us grey should be neutal, if we used the blue and the neutral before. And people did always use the blue for neutral.

I seem to remember all this stuff you describe came out later (maybe 2 years). Certainly all of the neutrals that I knew of were the black wire for a long time.

Why don't we bring back cables with Red, Yellow and Black. no confusion there.

 

[Risteard]

What has never been permitted?
AFAIC the norm in 3ph buildings was to use the phase colour for 1ph circuits.

The use of phase colours for final circuits has never been permitted. It was only ever allowable on the supply side (and even at that not for a great many years) up to the final distribution board (i.e. for distribution circuits). That is the position with BS7671.

Other national standards do permit the practice, but that's not what we are discussing here.

 

[SUNRAY]

The use of phase colours for final circuits has never been permitted. It was only ever allowable on the supply side (and even at that not for a great many years) up to the final distribution board (i.e. for distribution circuits). That is the position with BS7671.

Other national standards do permit the practice, but that's not what we are discussing here.

Wow that means there are thousands of buildings across the country that have been wired in the wrong colours for at least fifty years.
Only a couple of months ago we were debating whether to use Brown or Black in a board that was otherwise white or yellow. in the end we went for brown so the black didn't get confused with the neutral. We did not have the same option in the ph3 board where we had to use blue for neutral but fitted 'N' markers. To see a dozen or so blacks and one blue on the N bar looked so wrong when the rest of the board was full of blue going to the fuses.

 

[SUNRAY]

The use of phase colours for final circuits has never been permitted. It was only ever allowable on the supply side (and even at that not for a great many years) up to the final distribution board (i.e. for distribution circuits). That is the position with BS7671.

Other national standards do permit the practice, but that's not what we are discussing here.

My high schools new school building Circa 1966 was wired in phase colours even the pyros.

 

[Risteard]

My high schools new school building Circa 1966 was wired in phase colours even the pyros.

I never said it was terribly uncommon. That isn't the same thing as it not being an allowable practice.