400vac/24vdc Wire Colours

Join Date
Nov 2007
Location
North Yorkshire
Posts
26
Hi there, i was hoping for some oppinions from you all with regards to colours on +24VDC and -0VDC wires should be?

To me the most common combination i have seen in a huge amount of panels and this is also in accordance with BS EN60204-1.

BLACK - AC POWER CIRCUITS (400V AC etc)
RED - AC CONTROL CIRCUITS (110V AC)
BLUE - DC CONTROL CIRCUITS (+24V DC)

Although there is no reference to Blue/White i would say its common place although i have seen the use of all blue for both +24V and -0V.


But why is there other combinations such as blue/red (common for phenoix contacts who have jumper bars and distribution terminals that use blue/red for +24VDC and -0VDC connections?

I use to work one place that always used white/red (+24V DC) and white/black (-0VDC) and white (switched +24VDC) - has anyone ever seen anything like this before? Never seemed to be appropriate to any standards i have read...


If anyone else has any oppinons especialy any regulation guidelines to US specifications i would be glad to hear your thoughts and oppinions?

Thanks,
Bri. :)
 
I have no idea what the standard is in the UK, expect IEC would be the norm. IEC and NFPA state blue for +dc and blue/white stripe for - dc.

In the past I got use to 24vdc being brown + and blue - but things have changed.
 
All the standards I have come across have a loophole built in somewhere that allows an OEM to use any wire colors they want (within reason) as long as they are consistent and they are well documented. This is especially true with DC under 60 volts. We recently built a machine for a customer in Ireland that use a customer-specified wire color scheme. It followed EN60204 with the ground, 230VAC single phase and 400VAC 3-phase supplies. After that, all bets were off.


Keith
 
Our cabinet builders use blue for all internal 24V DC cabinet wiring, and I like it that way. Colour coding makes the cabinet look a bit dodgy and when you use terminals with DC bus bars integrated (like the Weidmuller Z series) there are very few dedicated 0V cores to worry about. Black is used for all 230/380V internal wiring.

I've seen blue/brown more often than blue/red. A lot of OEM cables for proximity sensors and photoeyes etc use a brown/blue/black/white (24V/0V/Sig1/Sig2) colour pattern so I suspect that it is enshrined in a standard somewhere (DIN?).
 
It sure would be nice for someone to come up with a standard where colors do not conflict.
Not only that but I learned in Navy black red white ABC 123 is clockwise. Then they started labeling the shorepower black red blue. Then I became a civilian and got more confused.
In USA colors defined by Natl Elec Code are
Orange is dedicated supposedly for wild leg on delta with one phase centertapped and grounded to derive 120.
Green or bare is ground
White or gray is neutral

In USA the common practice is I believe
450 4 w 3 phase is brown orange yellow -- the orange conflicts with the high leg of delta I would think. Could get confusing in a plant where you have delta and 450 4 W three phase.
277 would be whatever phase is used ie brown or yellow etc and white (neut)
230 or 208 120 4W is black red blue
120 (from 208 3 phase) would be like 277 above
phase color and white for neut.

So what does one do for DC and where you have it various voltages ie 125 250 120 24 12 etc??

Then if you have aircraft what do you do with 400 cycle??

Dan Bentler
 
Brian Hamilton said:
BLACK - AC POWER CIRCUITS (400V AC etc)
RED - AC CONTROL CIRCUITS (110V AC)
BLUE - DC CONTROL CIRCUITS (+24V DC)

That would be the norm, although most copanies have 'their' standard colours, that combination I would say is the most common.


rsdoran said:
Quote:
Originally Posted by kittydog42
My company uses red for +24VDC and blue for 0VDC, in 16AWG.



Personally do not like that.

Nor do I, red usually means higher voltage than 24VDC.


This AWG thing gets me too since I've been over here. Like I had never heard of Ampacity and thought that funny (in the UK we still go the full hog 'current carrying capacity'), AWG seems odd to me, the higher the number the smaller the wire!!!

16AWG (1.5mm) or 17AWG (1mm) would be quite common, depends on the ampacity required. :p
 
In the UK, orange quite often mean't supplied from elsewhere, so could be live when the panel is disconnected (interface wiring).

Where I work now we use yellow for the same thing.
 
Using red isn't my personal choice, though I am used to it by now. Red can also be one of the 208V legs if it is a higher gauge than 16AWG. We use black and white for 120VAC. We color code based on context, not voltage, though most of our panels are all 24VDC, except for the power feed. We do almost no switching at 120VAC, to keep the panel running on the Class 2 power supply. On the control side of things, we use purple for relay switched wires, grey for analog inputs, orange for analog outputs, pink for digital inputs, brown for digital outputs, and yellow for alarm circuits. We also use orange and yellow for 24VAC if we have that power in the panel. Sometimes we have two separate 24VAC transformers in the panel, and if we do, the second one uses pink and brown.

Not too many of our panels go to industrial customers. Most go into commercial or institutional applications, such as schools or office buildings. If the panel is going to an industrial customer, we will choose colors based on their specifications, if they have any.

You guys would hate our panels!
 
Thanks for all the comments so far, some very intresting and somewhat bizzare combinations out there...

Here's another one for you all to think about, for example if you have a panel without any neutral connection; and use a transformer from 400VAC - 110VAC the two legs of the secondary would be what colours? For both control circuits and power circuits?

I would personally say RED for control circuits (both legs) and then black (both legs) for power circuits; but what if you tied one leg down to earth? Hence like a neutral - would you change one wire for light blue even though its not an "actual" neutral wire?

Food for thought...


Thanks,
Bri. :)
 
Our standard is Blue for +24vdc and Blue w/ white trace for 0vdc.

One of our customers has a spec with Brown for +24 and Blue or Blue/WHT for 0VDC.

I believe I've read (probably NFPA79) that Red is for the AC control voltage and Black is for voltages above that. Although that will lead to red being used for different AC voltages on different systems. Or, what if you have a bunch of AC contols but it makes sense to have once circuit of 220 control?

As with all standards, they are compromises. If one standard made sense for all situations, then there would only be one standard.
 
It seems in industry the shift has been to always make the "hot" wire BLACK, for consistency in troubleshooting. So, I see 24V and 110V circuits with Black Hot and White Neg/Neutral a lot. Actually, if there is any other color in the DC pair, it's always the negative. I have several installations I service that have red as negative. As long as the black positive is consistent, it's not an issue.

Also, I get the Red/Green run light issue brought up a lot, where Red is "RUN", and Green is "OFF". A lot of older operators don't like this scheme, as it is reverse of the "old" standard. I have to explain that, like the wiring, it's a saftey standard... not RUN/STOP, but ENERGIZED/DEENERGIZED. I'm told that comes from nuke plant saftey standards, but I've never traced it back.
 
tomalbright said:
It seems in industry the shift has been to always make the "hot" wire BLACK, for consistency in troubleshooting. So, I see 24V and 110V circuits with Black Hot and White Neg/Neutral a lot. Actually, if there is any other color in the DC pair, it's always the negative. I have several installations I service that have red as negative. As long as the black positive is consistent, it's not an issue.

Also, I get the Red/Green run light issue brought up a lot, where Red is "RUN", and Green is "OFF". A lot of older operators don't like this scheme, as it is reverse of the "old" standard. I have to explain that, like the wiring, it's a saftey standard... not RUN/STOP, but ENERGIZED/DEENERGIZED. I'm told that comes from nuke plant saftey standards, but I've never traced it back.

NFPA 79 Electrical Standard for Industrial Machinery states that Start or ON shall be Green but Black, White, or Gray is permissible but NEVER Red and vice versa for Stop i.e. it is Red and NEVER Green.

Lights; Red should indicate Danger, emergency, or fault. Amber/Yellow is warning, Green is safe or normal, Blue is required action.

OSHA uses NFPA standards in their regulations. NFPA 79 can be viewed online, chapter 10 covers this: http://www.nfpa.org/freecodes/free_access_document.asp
 
For buttons, and illuminated pushbuttons yes.

For status, RED can mean DANGER, and GREEN can mean SAFE, under the Safety section of Table 10.3.2. The lights I'm specifically talking about are MCC cubicle status indicators.
 

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