# Enclosure wiring colors for VDC



## jkaras (Mar 26, 2013)

Are there any NEC codes or rules relating to DC wires with specific regard to color? We will be installing a light sculpture in NY and we have to connect the wiring from the power supplies to the terminals within an enclosure. I know generally red is positive and black is negative, but if I use a different color for red such as white, could we encounter issues with our installation being not to code?

Thank you in advance!


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## Wirenuting (Sep 12, 2010)

The NEC doesn't mandate color for DC wiring.


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## ponyboy (Nov 18, 2012)

Typically round here as far as cabinets go- red is 120 volt control, blue is dc, yellow is outside source. Probably not what you mean though


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## Paulusgnome (Mar 28, 2009)

Although there are no NEC rules for DC wiring colours, I recommend that you do not use colours that are already used in AC wiring, this has the potential to confuse others further down the track.
Here, we build quite a lot of equipment that gets installed in US factories, and we tend to use plain blue for +24VDC, and blue with white stripe for 0VDC. Some US customers have asked for brown for +24VDC and blue for 0VDC.


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## varmit (Apr 19, 2009)

Normally in the US, blue is the color of choice for DC +. The the COM or DC- varies depending on the client. Normally I use gray for the COM. I have also seen/used blue with a white tracer or black.

There is no code mandated color code for DC. If necessary, you could post a legend on the panel showing your color code(s).

Most control panels will have black for power, red for 120 VAC control, and blue for 24 VDC control. This has been a common standard for as long as I have been around.


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## btharmy (Jan 17, 2009)

Paulusgnome said:


> Although there are no NEC rules for DC wiring colours, I recommend that you do not use colours that are already used in AC wiring, this has the potential to confuse others further down the track.
> Here, we build quite a lot of equipment that gets installed in US factories, and we tend to use plain blue for +24VDC, and blue with white stripe for 0VDC. Some US customers have asked for brown for +24VDC and blue for 0VDC.


I use invisible wire for 0vdc. :thumbup:


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## big2bird (Oct 1, 2012)

I would refrain from using white or green.


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## Paulusgnome (Mar 28, 2009)

btharmy said:


> I use invisible wire for 0vdc. :thumbup:


So does that make you half an electrician?:jester:


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## sparkywannabee (Jan 29, 2013)

Paulusgnome said:


> Although there are no NEC rules for DC wiring colours, I recommend that you do not use colours that are already used in AC wiring, this has the potential to confuse others further down the track.
> Here, we build quite a lot of equipment that gets installed in US factories, and we tend to use plain blue for +24VDC, and blue with white stripe for 0VDC. Some US customers have asked for brown for +24VDC and blue for 0VDC.


brown +ve, blue -ve. Hope that quake did'nt cause too much damage in your area.


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## uconduit (Jun 6, 2012)

I would seriously recommend getting those large sticker that say VDC and/or VOLTS D.C., and have those placed on any enclosures, panels or wherever there are terminations just for the simple fact that DC is not so common and non-contact testers aren't likely to give warning of voltage present. I worked on a large industrial project last year that had a fair amount of DC equipment, IIRC we were using black for positive and white for negative but I could be wrong.


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## btharmy (Jan 17, 2009)

Paulusgnome said:


> So does that make you half an electrician?:jester:


My point was, we have 24vdc, + & -. I have never seen it referred to a 0vdc. Around here, that means there is no voltage. "0" volts is no volts, thus no wire required. Anyway, I have been told, "If you have to explain your own joke, it wasn't that good of a joke to start with". Oh well.


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## Paulusgnome (Mar 28, 2009)

In using the designations +24VDC and 0VDC I am indicating that we have a 24VDC system where the -ve lines from the power supplies are all tied to ground at one central point.
In my work, we build large multi-station factory machines. These have an extensive 24VDC network in which it is vital that we avoid nasties such as ground loops, multiple connections between AC and DC grounds etc. 
To make this clear, for both our own build electricians and for the factory electricians who maintain the machinery, all of the schematics that I prepare use the designation 0VDC to distinguish from AC ground. This is just a convention taken from electronics and DC power industries that we have adopted, I guess we could use another label, but this works OK for us.
Note that we would not want to use +24VDC and -24VDC for the two rails because this would indicate a DC system of 48V centered on 0V.


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## Concept (Mar 30, 2012)

We have always wired with orange +24 and blue 0v. Twenty years now with no rule and no complaints.


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## Big John (May 23, 2010)

NFPA79:

Within a common enclosure:
Black = Supply power.
Red = Reduced voltage control power
Yellow = Power supplied from outside enclosure
Blue = Direct current
White = Any grounded conductor. Put a corresponding colored marker on it to indicate system (e.g.: Blue stripe = Grounded DC)
Green = EGC


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## DarthBurns (12 mo ago)

Paulusgnome said:


> Although there are no NEC rules for DC wiring colours, I recommend that you do not use colours that are already used in AC wiring, this has the potential to confuse others further down the track.
> Here, we build quite a lot of equipment that gets installed in US factories, and we tend to use plain blue for +24VDC, and blue with white stripe for 0VDC. Some US customers have asked for brown for +24VDC and blue for 0VDC.


Most (if not all) cables with 4 and 5 pin "Micro" connectors, commonly used for DC instruments, sensors, and switches, have a Brown wire for +24VDC and a Blue wire as Common. In the factory where I work, I have made this the standard, in order to assure that the color coding within the cabinet matches the color coding in the cables that run to the field devices. I have only ever seen the blue and blue/white combo used in phone and ethernet applications, but clearly there is no consensus on this issue.


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## Majewski (Jan 8, 2016)

DarthBurns said:


> Most (if not all) cables with 4 and 5 pin "Micro" connectors, commonly used for DC instruments, sensors, and switches, have a Brown wire for +24VDC and a Blue wire as Common. In the factory where I work, I have made this the standard, in order to assure that the color coding within the cabinet matches the color coding in the cables that run to the field devices. I have only ever seen the blue and blue/white combo used in phone and ethernet applications, but clearly there is no consensus on this issue.


thanks, we were waiting really long for that


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## emtnut (Mar 1, 2015)

Majewski said:


> thanks, we were waiting really long for that


Too bad, I heard the OP went under just 3 weeks ago ... Delay of contract was just too much after 8 1/2 yrs.


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## backstay (Feb 3, 2011)

Majewski said:


> thanks, we were waiting really long for that


Somethings are worth the wait.


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## Majewski (Jan 8, 2016)

backstay said:


> Somethings are worth the wait.


if only this were one of those things LOL


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## BillyMac59 (Sep 12, 2019)

Common Canadian findings - NOT code specified but more common practice - for DC control is : Blue-24V+ , Blue/white- 0v (com). For signal circuit wiring : Brown-24v+, Blue-0v/com, White-N.C.switch contact,Black- N.O. switch contact. Never, ever use red or white for DC especially when both voltages contained in same enclosure. Only bad things will happen....


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