Wire Color Codes

[jsi]

I've done a fair bit of household wiring (USA building codes if that matters) and I was taught to never use the black wire for anything but power. (except for the exceptions )  Now my new hobby in low voltage electronics is making me a bit crazy because black seems to be the standard for ground. Is there a standard for wire colors in low voltage stuff the same way there is for the mains?

(I'll get over it, but everytime I connect a black wire to ground I have to think really hard, this is OK, this is OK.)

[dom0]

No

[liquibyte]

I always use red for positive and black for negative and green for ground with exceptions.  If I want to wire an off board transistor for instance, I use black for the collector, red for the emitter, and green for the base.  There is no standard that I'm aware of so it boils down to preference or even what you have on hand for that matter.

[Andy Watson]

No

+1

Where possible, you could twist live and neutral together. This would aid identification and reduce EM fields generated by the mains current. Otherwise, keep a clear head and double and triple check  your wiring!

[Brumby]

I always use red for positive and black for negative and green for ground ...

I tend to follow this basic approach - with using yellow as a higher supply voltage (blame my exposure to computer PSUs).

Mains wiring in Australia used to be Red (active) Black (Neutral) and Green (earth), but now we use the Brown/Blue/Green with Yellow stripe.

The only other practice I like to follow is when using flat rainbow cable, to follow some logical mapping of the colours to the numeric values associated with the resistor colour code.  eg Data line 0, 1, 2, 3 ..... etc  to black, brown, red, orange .... 
But that's just one of my personal quirks.

[Dinsdale]

PCs are "low voltage". Most power supplies in that application have settled on a standard. I try to follow that.
I'm trying to locate the "Bomber's Color Code". You know, "Cut the red wire... No, No, the yellow wire,
the yellow wire!"

[Richard Crowley]

The North American standard for power where white = neutral and "hot" is black (or red or blue or orange, etc.) isn't all that intuitive. But, honestly, why the Europeans chose blue for "neutral" and brown for "hot" is even more bizarre and arbitrary, IME. Even as I write this I wouldn't bet my life that is correct because it just seems so completely random.

For DC power wiring inside gear, my standard is black for common, and red for the primary positive rail. While violet is the primary negative rail. 
Other positive voltages can be yellow, orange, etc, while other negative power rails can be blue, gray, etc. 
Green is reserved for chassis ground, mains safety ground, etc.

[bills]

I use white, black ,green for AC.
red for + dc biack for - dc .
HV Same as AC.
hope this makes sense.

[obiwanjacobi]

Look at a PC PSU - I believe it uses some sort of standard...



[2c]

[Simon]

No there is no standard although black seems to be fairly standard for negative which we tend to call ground in our circuits although it's not the same ground as earth ground. If you want real complication you can ask the Germans who decided to make brown negative and black positive which is really mad. I think a lot of people would probably follow power supply coding from computers and use red for positive and if there is more than one positive probably read for 5 V and yellow for 12 V or any other major high-voltage but that's just what I would do if I had a choice and had to make a decision. There is no code.

[Shadetreeprops]

I have used yellow with a red stripe to indicate pos, and regular yellow for neg. I have also used White for everything, normally it just boils down to how much of what wire i found in a dumpster, and how much do i need for said project.

My homemade PSU, would drive anyone mad, cause i have colors cris crossing each other. if i was not the one who made it, i would not make head or tails of what was going on with it..

but for alot of low volts i have seen this. RED pos, Black Neg, Yellow or Green as Ground.. but for my PSU, the power brick, the 12v is yellow, and the 5v is red, black is ground, and blue is what i have to short red to, to get it to stay on, or use it as my switch.

[miceuz]

There is no standard, but It's a good practice to design your own and stick to it

For me it's like this:
red, orange - vcc
black - gnd
yellow - sck
blue - data coming from slave
green - data coming from master

etc

Makes debugging much easier

[German_EE]

My standard color scheme is:

Red     +12V
Orange + Anything above 12V
Yellow + Anything below 12V
Green     Audio
Blue   -12V
Violet   Power switch
Black    Used for internal wiring
White   Used for internal wiring
Brown  Low voltage AC

Copper colored coax    RF circuits
Black colored coax       Audio circuits

Mains wires follow the standard European color code of blue/brown/green & yellow but are wrapped in either transparent heatshrink or plastic spiral wrap to differentiate them from standard voltages.

[android]

I always use orange for SCK ... easy way to remember: Clockwork Orange 

[LordHexahedron]

no objective standard, typically red for hot, black for neutral, green for ground.

I use the standard:
reds (pink, red, orange) - power
blacks (black, dark green, dark blue, other dark?) - neutral
greens (green, yellow, beige) - ground

everything else (light blue, purple, white, others) is either data or to make it easier to debug - if it's ambiguous I mark it.
My wiring must be hard to read for colorblind people, I use all the colors I can get my hands on

[dom0]

The North American standard for power where white = neutral and "hot" is black (or red or blue or orange, etc.) isn't all that intuitive. But, honestly, why the Europeans chose blue for "neutral" and brown for "hot" is even more bizarre and arbitrary, IME. Even as I write this I wouldn't bet my life that is correct because it just seems so completely random.

Blue is neutral. Phases are brown, black and grey (in that order L1... L3). Doesn't matter for normal appliances, though, because you generally can't know which one is hot and which one is neutral.

I don't think there is any way to make these colours not arbitrary. Okay, "red" for "hot", maybe, but other than that...

[Jeroen3]

Most of the time I encounter this:
Ground - Green/Yellow. Not allowed to carry current.
Neutral - Blue.
Phase 1- Brown.
Phase 2- Black.
Phase 3- Grey.
If three phase, they come in pairs. Should be easy to recognize.
Switched phase - black.

Often you'll find just Blue and Black for 3 phase. The standards are not very strictly enforced. Could just be what cables are in discount that month.
Apart from ground, everyone uses the same for ground, green/yellow wire. Which is good.

But I've recently seen an installation using Blue, Brown-Grey-White for 3 Phase, removing the ambiguity of black. DC 24V was red/black. Other colors were sensing and signalling.
The first page of the schematic often tells you what color "standard" they used.

[tooki]

The North American standard for power where white = neutral and "hot" is black (or red or blue or orange, etc.) isn't all that intuitive. But, honestly, why the Europeans chose blue for "neutral" and brown for "hot" is even more bizarre and arbitrary, IME. Even as I write this I wouldn't bet my life that is correct because it just seems so completely random.

Blue is neutral. Phases are brown, black and grey (in that order L1... L3). Doesn't matter for normal appliances, though, because you generally can't know which one is hot and which one is neutral.

I don't think there is any way to make these colours not arbitrary.

I thought I read somewhere that those colors (blue/brown/black/gray plus striped green-yellow for ground) were chosen because they can be distinguished by people who are color-blind.

(That's also the reason the default color scheme in early versions of OS/2 was so hideous. It wasn't chosen for aesthetics.)

[Zero999]

No there is no standard although black seems to be fairly standard for negative which we tend to call ground in our circuits although it's not the same ground as earth ground.

There is no standard for the colour of wiring inside appliances, whether it be AC or DC, regardless of the voltage.

In the EU, there is a standard for DC wiring inside buildings. The colours are identical to AC wiring, with blue being the earthed current carrying conductor, brown for positive, grey for negative and green/yellow for protective earth.

http://electrical.theiet.org/wiring-regulations/cable-colours/harmonised.cfm?type=pdf
https://www.eca.co.uk/filelibrary/download/?FileID=1295

[Neilm]

There is no standard for the colour of wiring inside appliances, whether it be AC or DC, regardless of the voltage.

Not quite true - IEC61010 specifies that earth is only on Green / Yellow wire, and the wire should not be used for anything that is not earth.

[vk6zgo]

There used to be one:-

http://wikibin.org/index2.php?option=com_content&do_pdf=1&id=8689

I tend to use a modified version of this,with the highest DC +ve voltage ----Red,
The next highest --Orange
The one below that--Pink
All are "sort of" versions of Red

I can't ever remember us using Grey for Mains in Oz---usually it was whatever the power cable used to the power switch,then whatever the transformer primary was,after that.

PMG/Telecom Aust used Red & Black for their 24v supplies.

One place I worked decided it would be a wonderful idea to use Blue for +24v----go figure!

[Muttley Snickers]

The plate pictured below is not one of mine and I only grabbed it for the rotary switch and sometimes you just have to deal with what the fellow that went before you did, in our industry we deal with a wide variety of multicore cables and there are some adopted practices but we never take it for granted that someone else does the same.

It might be the black wire ?.......

[cs.dk]

Yes,
It's always the black wire, when somethings wrong

From a day at work - 1x80 core + 1x25 core all black;
(Before dressing it up, and make it look nice)

[PTR_1275]

I work on caravans a lot here in Western Australia, we always use red is positive, black is negative. There are standard "other colours" for trailer plugs and wiring, but nothing further than that.

Some of the big van manufacturers are pains in the ass because they have adopted the American 110v wiring code for their 12 volt systems, therefore black is positive and white is negative. Because of this I never trust anything I work on, whether it be on the bench or in a van. I always check the polarity of anything I've not done myself within the last day.

[cs.dk]

I work on caravans a lot here in Western Australia, we always use red is positive, black is negative. There are standard "other colours" for trailer plugs and wiring, but nothing further than that.

Some of the big van manufacturers are pains in the ass because they have adopted the American 110v wiring code for their 12 volt systems, therefore black is positive and white is negative. Because of this I never trust anything I work on, whether it be on the bench or in a van. I always check the polarity of anything I've not done myself within the last day.

I agree.. Volvo trucks also uses white as negative. Every manufacturer does it their ways. Sad there isn't a standard.
In general on trucks or cars I use red as B+ (Kl.30), black or purple as Ign+ (Kl.15), brown for ground/chsssis, yellow (Kl.58) light, blue reverse-signal, green handbrake-signal.
On mains i have to follow the code; Blue for neutral, brown/grey/black for fases, and yellow/green for PE.. In some older Danish installations, red are PE

[mtdoc]

It's particularly confusing here in the USA when working on PV systems where you are often transitioning back and forth between DC (black negative, Red Positive) and AC, where black is "live" and white is "neutral" and usually tied to earth ground.  Code specifies bonding DC battery negative to earth ground - further confusing things.

[Jeroen3]

I can understand that the negative of a DC circuit is tied to ground at the battery since AC Neutral is also tied to ground at the transformer.

[SL4P]

The mashup described in the preceding comments - explains why mains wiring should be done by a locally licences electrician!

For ELV projects, I stick with
Vas/0V/GND black
+5Vcc red
+12V yellow
then I start looking for 'as close as I can' standards...

[Dave Atom]

Red to Red,
Black to Black,
Plug it in,
And stand well back.

Always worked for me

[Zero999]

The plate pictured below is not one of mine and I only grabbed it for the rotary switch and sometimes you just have to deal with what the fellow that went before you did, in our industry we deal with a wide variety of multicore cables and there are some adopted practices but we never take it for granted that someone else does the same.

It might be the black wire ?.......

If you look closely, the cable cores are numbered which is quite common in multicore cables.

There is no standard for the colour of wiring inside appliances, whether it be AC or DC, regardless of the voltage.

Not quite true - IEC61010 specifies that earth is only on Green / Yellow wire, and the wire should not be used for anything that is not earth.

That doesn't apply to domestic/office equipment though, so something like a PC could use any colours.

I don't have access to the standard you've referenced to but EN60204 says:

Black = AC or DC power
Red = AC control
Blue  = DC control
Orange = safety
Green & yellow PE and nothing else, which agrees with you.


Link:
http://www.yuntongglass.com/upfile/2012031917030348602.pdf
Pages 76 & 77.

[dom0]

I'm pretty sure the IEC standard says that green-yellow must only be used for PE, independent of context.

[richard.cs]

But, honestly, why the Europeans chose blue for "neutral" and brown for "hot" is even more bizarre and arbitrary, IME. Even as I write this I wouldn't bet my life that is correct because it just seems so completely random.

It's the compromise you get when trying to select colours that aren't ambiguous when mixed with the many different previous systems across multiple countries. Blue had never been a phase colour in single phase systems (but had been L3 in the UK) so it was a reasonable choice. Brown is a bit worse, it was earth in the UK though not for long (1934-1939). Red had been used for just about everything, as had black. But the blue/brown combination hadn't been used anywhere before. Black L2 and Grey L3 were the result of the UK pushing for different phase colours, in much of Europe it's normal to use 1 phase colour and a rotation tester (which is usually good enough but doesn't get you absolute phase).

Personally I liked the old UK system with the three primary colours as the three phases, it seemed reasonably logical and with colours for phases black follows as a sensible choice for neutral.

[Zero999]

Personally I liked the old UK system with the three primary colours as the three phases, it seemed reasonably logical and with colours for phases black follows as a sensible choice for neutral.

Me too. There was no need to standardise with the EU for fixed wiring. I can understand the need for equipment exported to the EU but the colour of the wires, in buildings here in the UK, is none of their business

[LaurentR]

Even though a lot of car OEM harnesses use totally random colors, basic car audio aftermarket harnesses are fairly standard (Metra/EIA).
http://www.the12volt.com/caraudio/headunitharness.asp

Memory / Constant 12V(+)   Yellow
Switch / Accessory   Red
Ground   Black
Illumination   Orange/White
Antenna Remote   Blue
Amp Remote   Blue/White
Left Front (+)   White
Left Front (-)   White/Black
Right Front (+)   Grey
Right Front (-)   Grey/Black
Left Rear (+)   Green
Left Rear (-)   Green/Black
Right Rear (+)   Violet
Right Rear (-)   Violet/Black

[retrolefty]

It can be very disheartening the lack of standards sometimes. At the refinery I worked at the various plants, maybe a dozen, each had a different central control house with many many 4-20ma 50 pair cables running from house to plant instruments and valves. 50 pair twisted shield white/black was the most frequent cabling used. However some plants used white for the +24 loop power and black for the loop common/ground. At the next plant it would be the opposite. It came down to when the plant was built which project 'standards' were used. Best to always measure over assuming. Kind of a measure twice cut once thing.

[ROBOT]

Not really a standard but whenever working with low voltage stuff black is almost always ground and red would be +5v. I tend to use orange for 3.3v.

[N2IXK]

Back in the vacuum tube era there was a RETMA standard color code for internal wiring of electronic gear:

Black - Grounds, grounded elements and returns
Brown - Heaters or filaments, off ground
Red - Power Supply B-plus
Orange - Screen grids
Yellow - Cathodes
Green - Control Grids
Blue - Plates
Violet - not used
Gray - AC power lines
White - Above or below ground returns, AVC, etc.

[Cerebus]

Personally I liked the old UK system with the three primary colours as the three phases, it seemed reasonably logical and with colours for phases black follows as a sensible choice for neutral.

Me too. There was no need to standardise with the EU for fixed wiring. I can understand the need for equipment exported to the EU but the colour of the wires, in buildings here in the UK, is none of their business

The argument would be:

1) Free mobility within the EU. If you're an electrician it lets you move between EU countries more easily.
2) Market equalities. If you make cable in the UK you can sell the same cable in France, Germany etc. etc. You only have to meet one set of regulatory requirement for the whole EU, rather than one for each country. I've noticed that people are starting to specify cables by european type numbers rather than the UK IEE/BASEC numbers, which used to be standard practice in the UK. (e.g. H07V-R instead of 6491X)