A Question about Wiring Colour Code Conventions

[docboardman]

Hi everyone!

I think this is a fairly simple question, but so far I have never seen it explained. In a standard 2 core and earth cable, the normal convention is: Brown = Live and Blue = Neutral. Is there a standard convention for 3 core and earth (e.g. Brown, Black and Grey)?

Cheers!

 

[ericmark]

To start with Neutral is Live so your colour code is wrong it's
Brown = Line (Not Live)
Blue = Neutral

Brown = Line 1
Grey = Line 2
Black = Line 3
Blue = Neutral
Green/Yellow = Earth

Where a wire is used for other than colour would denote the sleeves are used.

The colours are not strictly adhered to for a split phase supply as used with UK 110v the cores should be Brown and Grey yet every yellow cable I have used has brown and blue cores. When using twin core and earth cable for switches two browns should be used yet this is rare. And it is easier to work with three different colours than three the same.

Because of other items in factories including DC industrial where Brown and Grey are Line 1 and Line 2 it is common to sleeve the Black wire blue and use as neutral as then only one wire needs a sleeve. This is carried on with other installations so often the black is used as neutral but there is no convention and you could sleeve any of the colours.

Exception is Green and Yellow this can never be sleeved and used for anything else. Green and Yellow is always earth.

 

[docboardman]

Thanks Ericmark.

Also, thanks for the correction about Neutral. I knew it was live, just forgot about it for some reason. Not sure where I got the term "Live" for the brown wire from. But I'll refer to it as "Line" from now on.

I asked the question because there is some 3 core + earth wiring in the house where the black wire is sleeved with blue. This looks like what you described for DC industrial. But in some diagrams I have been studying the black wire is sleeved with brown. This confused me.

It looks like the most important thing is that you keep consistent. I can use a grey or a black wire for neutral as long as it is sleeved appropriately. And, for that matter, I guess I could sleeve them in brown if they were line wires.

Cheers!

 

[dingbat]

Brown = Line 1
Black = Line 2
Grey = Line 3
Blue = Neutral
Green/Yellow = Earth

Check out Appendix 7 - page 342.

 

[ban-all-sheds]

it is common to sleeve the Black wire blue and use as neutral as then only one wire needs a sleeve. This is carried on with other installations so often the black is used as neutral but there is no convention and you could sleeve any of the colours.

AIUI the use of black for the neutral is deprecated, in order to break the black=neutral association in people's minds, and that the recommended way to use a Br/Bl/G cable for single phase is:

Brown - Line.
Grey, sleeved blue - Neutral
Black, sleeved G/Y - cpc.

 

[docboardman]

Thanks Dingbat and Bans!

The reason I asked the question originally is that I have been looking over some of the work done in this house over the last few years. The same electrician has done all of it.

In one instance (I haven't looked at all the similar circuits he's done) a single light on the landing was wired up to two switches. He used 3C + E. Both the black and grey wires were sleeved in brown. I decided that made sense since one or the other of them could be live depending on how the switches were set.

Then I noticed he used 3C + E to wire up an extractor fan so that it came on (through an isolator) when the bathroom light was turned on. In this case the L1 terminal was brown, the L2 terminal was grey (sleeved brown) and the N terminal was black (sleeved blue).

Since starting this thread, I've done a lot more research on this site. I don't remember the link now, but in my notes I have that there is no hard and fast standard, however black with a brown sleeve and grey with a blue sleeve are preferred by the NICEIC.

I'd like to conform to accepted standards. On the other hand, I'd also like to stay consistent within the house. So it's all a bit confusing right now.

Oh ... and just to muddy things a bit, I also found a diagram for the light switch/extractor fan combination where: L1 = black (brown sleeve), L2 = brown, N = grey (blue sleeve).

Thanks for all your help, everyone.

 

[kevindgas]

Black, sleeved G/Y - cpc.

my understanding of cables is that rarely is the CPC sleeved in flat cable and round flex is sleeved G/Y
i would be interested in knowing where you get your cable that is CPC free!

 

[Adam_151]

Ban is talking about 3-core SWA

 

[ban-all-sheds]

Or any cable with just brown black & grey...

 

[sparkwright]

it is common to sleeve the Black wire blue and use as neutral as then only one wire needs a sleeve. This is carried on with other installations so often the black is used as neutral but there is no convention and you could sleeve any of the colours.

AIUI the use of black for the neutral is deprecated, in order to break the black=neutral association in people's minds, and that the recommended way to use a Br/Bl/G cable for single phase is:

Brown - Line.
Grey, sleeved blue - Neutral
Black, sleeved G/Y - cpc.

The above is for a 3 core cable such as a SWA cable.

In a flat 3 core and earth cable that may find in a regular lighting circuits the coloured cores could be used as 3 lines (2-way switch for example).

However, in some cases the 3 core and earth cable will be required to supply line, switched line and neutral.

In this case the colours are
permanent line - brown
switched line - black sleeved brown
neutral - grey sleeved blue

Some electricians will tell you grey is switched line and black is neutral. They are WRONG. So if you ever come across a cable used for two lines and a neutral then you must make sure which colours have been used in case you end up making a wrong connection.

With the old colours
red = brown
yellow = black
blue = grey

Why people think it's ok to use a harmonised black as neutral is beyond me. You only have to compare the structure of an old cable to a new cable to tell what's what. Or go to college. Or read a book.

In a 3 phase installation
line 1 red = brown
line 2 yellow = black
line 3 blue = grey
neutral black = blue

I don't know if anyone's been killed yet with that reversal of blue and black.
Could be confusing in a singles installation for example.

 

[ericmark]

I can see that in a house where only a single phase supply is used that one may want to use grey and neutral and black as line when supplying items like bathroom fans where two line feeds are required.
However looking wider than the house as pointed out Page 342 to 344 when used with a split phase supply L- is grey and L+ is brown (page 344) yet L2 is Black on Page 342 so much depends on other equipment on site as to which is best colour to use.
Personally I think the whole idea of using cable coloured for three phase on single phase supplies is silly and what is wrong with the white numbered cores as used in industry I don't know.
I have lost count of how many houses I have been to where the thermostat on the hot water tank has been wired in three core and the earth wire has been sleeved. We all know it's a no no but it still happens and I suppose there is little or no chance of guy who did it ever being drawn to task.
So I don't think it really matters if grey or black is selected as a neutral as long as it is sleeved correct.

 

[docboardman]

Thanks again Ericmark.

Most of what I've read today suggests that, for a timed ceiling fan, I'll use:

Permanent Live = Brown
Switched Live = Black (sleeved Brown)
Neutral = Grey (sleeved Blue)

I guess my electrician didn't follow this convention, I don't know why, on the other hand everything is sleeved to indicate what it is so - as you say - "I don't think it really matters if grey or black is selected as a neutral as long as it is sleeved correct."

Cheers for now.

 

[sparkwright]

Perhaps it doesn't really matter if black or grey is used as neutral but there is more than enough guidance to confirm that grey should be used.

If it's harmonised cable then surely we should all be using the same colour. It's just not consistant to use differing colours.

Afterall, before 2004 we weren't sleeving our yellow black and connecting to neutral, were we?

If you don't mind me saying, people who use the black of a harmonised cable as neutral should be lined up against a wall and shot.

 

[docboardman]

Not sure about the shot bit, but otherwise I totally agree with what you say, Sparkwright.

 

[1john]

my NIC inspector told me that the sleeving of the grey for neutral as apposed to the black is to 'de-neutralise' black.