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Electrical wiring color code standards
Looking for color standards for control wiring.
By Larry Grayson on 3 August, 2004 - 4:05 pm

I have a Eng. that is trying to use color coding different to what I was always told to use as the standard. Can any one direct me to a book or web site with such coding or tell where to find it in the code book. Red is AC and Blue is DC.

By Verhappen, Ian on 3 August, 2004 - 9:54 pm

This thread has been posted before and includes reference to several international standards.

Ian Verhappen

By Matthew Hyatt on 3 August, 2004 - 11:26 pm
1 out of 1 members thought this post was helpful...

For all of the UL listed panels I have worked on, designed and such I used the following:

Black = AC hot
Red = switched AC hot
Yellow = AC hot from a another source - another control panel as an example.
White = neutral
red w/white tracer = switched neutral
Green or green w/ yellow tracer = ground/earth ground

blue = DC voltage, ie, 12vdc, 24vdc
white w/blue tracer = dc common

Brown = AC 3 pahse - phase A
Orange = AC 3 pahse - phase B
Yellow = AC 3 Phase - phase C

shileds: think of current loops
2 cond
clear or red = +
black = -(neg)
3 cond
red = power (24vdc typically for transducers)
clear = + (signal output)
black = - (signal common)

Hope this helps, oh, and any panel I have design and wired this way is easily understaood by 99% of all service and electrical people I have worked with.

By Richard Gue on 5 August, 2004 - 5:43 pm

Since our control panels are fabricated and listed under
Industrial Control Panels - UL508A, I have to use the
following color coding.

In section 66.5.3, the UL508A standard lists the following
color coding for internal power wiring.

Black - all ungrounded control power circuit conductors
regardless of voltage
White or natural grey - grounded AC current-carrying power
circuit conductor, regardless of voltage

In section 66.9, the UL508A standard lists the following
color coding for internal control wiring.

Black - all ungrounded control circuit conductors operating at the supply voltage
Red - ungrounded AC control circuits operating at a voltage less than the supply voltage
Blue - ungrounded DC control circuits
Yellow - ungrounded control circuits or other wiring, such
as for cabinet lighting, that remain energized when the main disconnect is in the "off" position
White or natural grey - grounded AC current-carrying control circuit conductor, regardless of voltage
White with blue stripe - grounded DC current-carrying
control circuit conductor
White with yellow stripe - grounded AC control circuit
current-carrying conductor that remains energized when the
main disconnect is in the "off" position

The UL508A standard does not apply to wiring outside the
industrial control panel.

Richard Gue
Controls Engineer
North Star Ice Equipment Corp.
Seattle, WA
(206) 763-7300 voice
(206) 763-7323 fax

By Chris Berhost on 24 August, 2004 - 10:39 pm
1 out of 1 members thought this post was helpful...

Please note that section 66.9 applies to industrial machinery such as:

Metalworking Machine Tools
Plastic Machinery, (injection molding, extrusion, blow molding, etc.)
Woodworking, Laminating and Sawmill machines
Assembly machines
Material handling machines and robots
Inspection and testing machines

They do not apply to general use industrial control panels.

I read another posting and i thought i understood it. Here, i read again and now i'm confused. Have u ever thought that ur posting might be read by a lay man (like me who wants to fix the plug of my washing machine and not sure which to connect to which)?

A very colorful discussion indeed and like Ruf, I am a bit confused too. This is what happens when you've numerous standards! Why can't all these highly professional bodies come together and agree on common color code standards of wires for use in various applications? Will save lot of confusion and, maybe, accidents. Is it ego that prevents this from happening or is it really a more complex issue? Remember the problem the Hubble telescope's mirror encountered when it was realized that engineers forgot to do the correct conversion from inches to centimeters (or visa-versa)?!

By Bob Peterson on 27 February, 2012 - 10:13 pm

There are color coding standards. They are just different for different areas of the world and different applications.

You're right!

What we need is one standard to rule them all!

(This is how we get one more standard.)

See also:

If you are in the U.S., the color codes are printed in NFPA 79 for industrial machinery. I'm not sure where, or if, it is listed in the NEC.

Also, Matthew's post looks correct to me.

By Bob Peterson on 6 August, 2004 - 12:36 am

There are various such standards. IEC uses one set of colors, NFPA79 uses another. Depends on what part of the world you are in.

Here in the US only certain colors are specified by the electrical code (NEC or NFPA70) (such as green or bare for ground and white or gray for neutral). Others are left to the imagination but in practice most of the time red or black is used for hot wires for 120V circuits, and usually black is used for 3 phase circuits with bands of colored tape to differeniate the phases.

Keep in mind that different standards might well apply to different pieces of your wiring, and that in some cases there is no applicable standard (for instance NFPA79 only applies to machine tools).

You refereed to different color bands for different phases, Is there any code about how many bands per wire or spacing of those bands?

dlecheler [at]

>There are various such standards. IEC
>uses one set of colors, NFPA79 uses
>another. Depends on what part of the
>world you are in.
--- SNIP ---

By Richard Benton on 12 August, 2004 - 2:27 pm

The color code that you are talking about is set up in the JIC electrical standards for machine tools and industrial equipment. The JIC is the Joint Industrial Council. YOU ARE 100% RIGHT!

The national electrial code does not address wire colors except to identify ground (green), grounded neutral (white), high voltage neutral (gray), and the highest voltage lead of a three phase delta four wire system (orange).

You need a copy of the JIC electrical standards. These standards, though outdated, have not been superseded by any other code or standard.

By Daren Drohman on 1 May, 2006 - 8:21 pm

I thought the NFPA79 supersedes the JIC?

By J. Ulinski on 22 May, 2008 - 1:23 am

JIC was rolled into NFPA 79 many years. New revisions of NFPA-79 should be reviewed for current specifications, however, most industrial equipment manufacturing companies and blue their customers have their own internal build specs that provide direction on what specifications are applicable.

By infra482002 on 6 October, 2004 - 9:54 pm

I guess you are in the US. If you connected Active (hot) to a black conducter here in Australia you would lose your license... lol

By Reuben Gonzales on 24 November, 2004 - 1:44 pm

Hello, I am relocating to South Australia and I am in dire need of information concerning books, for the codes and other information that pertains to the testing that is involved in obtaining an electrical license. I will be hopefully be testing for an electrician special class license. I hope that you can help thanks.

By Jim Everhart on 17 April, 2009 - 12:15 pm

2009 NFPA 79 Electrical Standard for Industrial Machinery dictates wiring colors for industrial machinery - go for ordering info

Black = AC power at line voltage

Red = AC power at less than line voltage

White; neutral Gray = AC Neutral conductor at less than line voltage

Blue = Ungrouded DC power

Blue/white stripe or white/blue stripe = DC grounded voltage

Orange or Yellow = excepted voltage that may be energized while the main disconnect is in the off position

Green; Green w/yellow stripe = equipment grounding conductor

Jim Everhart
Power Lab Controls
Welcome NC

RHEC Industrial Controls
Lexington NC

1 out of 1 members thought this post was helpful...

This is a topic which I am attempting to address with the NEC/NFPA/UL. An ABB 'White Paper', "NFPA79 and UL508A
Industrial Machinery Operating Handle Requirements a White Paper by ABB, Inc." published in April 2007 states:

[begin quote]
What is an Industrial Machine? According to NFPA79 and UL508A, the following types of machines are classified as Industrial Machinery:

a) Metalworking machine tools
b) Plastics machinery
c) Wood working machinery
d) Assembly machines
e) Material handling machines
f) Inspection and testing machines

What is not an Industrial Machine? The following types of machines are not classified as Industrial Machinery.

b) Pumps
c) Fans
d) Wastewater treatment
e) Portable machines of any kind.

[end quote]

If it not classified as such, it is NOT covered by these codes/standards! As such, a control panel for an oil or gas SCADA/control panel or RTU is NOT associated with Industrial Machinery!

Since the original Instrumentation engineers and technicians usually had DC electronic backgrounds, 'Black' is always the DC return/ground wire.

In 2-wire transmitter cables, 'White' is usually associated with DC 'signals' or mA loops 'positive' wire. In a 3-wire transmitter, Red would be the DC positive power wire. OK, since transmitters are DC circuits, +24VDC usually comes out on the White wire to the transmitter and the controlled mA signal leaves/comes back on the Black wire eventually to the DC negative. This is traditionally through a 250 Ohm resistor located somewhere in the return path. Recently 'Electrical' engineers and AC electricians have been trying to design and install according to what they know - AC, which is different from DC and also NOT found in most existing instrumentation installations.

Bottom line is that this threads codes/standards are very EQUIPMENT specific. Industrial Instrumentation installations need to be specifically addressed by NFPA/NEC/UL. I will be making proposals/recommendations this year. In a separate thread I will start a discussion on the specific wording.

By Kurt Hanke on 3 June, 2010 - 8:46 pm

Kudos to Mr. Richard Gue and Mr. Jim Everhart for getting it right.

I've designed and been inside a lot of industrial equipment over the last 20 years - including much in the list you describe as "not" industrial machines - never have I seen the wire color schedule that you describe.

Stick with NFPA 79 as described by the above 2 gentlemen and you can't go wrong.

Kurt Hanke, P.E.
Turbocraft, Inc.
Everett, WA

Kudos to Mr. Everhart. For those wishing exact references to NFPA 79, it can be found in Chapter 13.

13.2 Identification of conductors. & deal with Green and Yellow deals with White and Gray White/Blue and White/Orange applies to the specific use of Orange applies to the use of Black, Red and Blue.

Also, many thanks to Mathew for confirming the convention that is currently in use with current loop instrumentation circuits.

Tim Reese
Everest College, San Bernardino, CA

My question is in regards to the UL color code " Orange - ungrounded control circuits or other wiring, such as for cabinet lighting, that remain energized when the main disconnect is in the "off" position".

If the external wire is connected to a breaker on the subpanel of an enclosure, then wired to a 24vdc power supply, is the wire between the breaker and the power supply still orange?

Also, are the wires on the load side of the 24vdc power supply orange(+) & orange w/ white stripe(-)? Or, should they be blue(+) and white w/ blue stripe(-)?

By Bob Peterson on 21 January, 2016 - 12:51 pm

Take a close look at what 66.9.1 f says versus 66.9.1 g.

Orange with a white stripe is not listed anywhere. White with an orange strip is only used for AC grounded control circuits not disconnected by the disconnecting means. the DC circuits would still be covered by 66.9.1 c and f.

I understand that there are some differences with UL and NFPA 79. Generally we design the panels and have a UL shop manufacture them and label them. The question is whether BLUE wires shall be permitted to be used for ungrounded dc control conductors per in NFPA 79, or whether ORANGE wire must be used per

Note that the power supply within the control enclosure has a separate 120vac feed which allows the emergency stop functions to remain operable in the enclosure when the the main supply circuit disconnecting means is in the off position.

By Steve Myres on 27 January, 2016 - 8:47 am

I've used blue with an orange stripe for that scenario. Blue for voltage, orange for before-the-disconnect.

And, since the voltage is very low, the hazard intended to be communicated by the distinct color before the disconnect is low as well.

By Bob Peterson on 27 January, 2016 - 11:45 am

now you have changed your question from what UL508a says to what a different standard says.

I don't have a current copy of NFPA79, and in my 2002 version wire color codes are found in 14.2. In my version it is unclear what the requirement actually is for the specific question you ask.

> 2009 NFPA 79 Electrical Standard for Industrial Machinery dictates wiring colors for industrial machinery - go for ordering info <

Is there a 2009 edition?

The 2007 edition states the color orange for excepted voltage that may be energized while the main disconnect is in the off position. The 2002 accepted orange or yellow, has this been changed back to either color or is orange the only accepted color?


I like having DC+ and DC- distinguishable. DC+ is conventionally solid blue. Blue with white stripe is fine for DC-, but it's a special order. For a medium or large panel shop that's no problem.

I build some simple control panels in my garage, the others I send to a panel shop. It's not worth my while to buy a spool of blue/white, so I use gray for DC- in that case.

One glitch in wire coloring schemes arises with solar powered panels. You can chain two 12VDC solar panels together to make 24VDC, but one 12VDC solar panel with 12to24DC converter for analog loop power is simpler and less expensive. Control Microsystems has a niche market with 12VDC controller and an internal 12to24VDC converter to power analog loops. So you're left the problem of clearly identifying both 12VDC and 24DVC wires. There's no shortage of colors, but I'm not aware a convention to deal with that. To make matters worse, telecom equipment uses 48VDC with a positive ground as a standard.

> I have a Eng. that is tring to use color coding differnt to what I was always told to use as the standard. Can any one direct me to a book or web site with such coding or tell where to find it in the code book. Red is AC and Blue is DC. <

Doesnt it seem odd to anyone that we have written standards, codes, and the damn CFR, yet we cannot even decipher any of them enough to agree on what colors should be used?

This thread gives more credance to thoughts that much of the 'code' is driven and developed to fuel corporate interests associated with wiring devices. So go ahead and wave the code book in the air, stomp your feet some, quote chapter and verse with fire and brimstone.

Any written standards that are so vague and interpretive that leave room for smart folks like us to disagree are not effective and become relegated as a guide, not a regulation. Imagine trying to enforce these vague 'standards'!

I'm just wiring up a control circuit for a lighting control cabinet, the coils are 120VAC and the 2 wire control is 24VAC. Normally I wouldn't give it a second thought and just use red & white for both. But then I thought it would be helpful to make the 24VAC a different color to make it easy to trace inside the duct.....
Went looking and I can't find anything that CLEARLY states anything!

Google ...

Electrical wiring - Wikipedia, the free encyclopedia and down to Colour code common wiring safety code

By Amish Electrician on 26 April, 2011 - 9:33 pm

> Google ...

> Electrical wiring - Wikipedia, the free encyclopedia and down to Colour code
> common wiring safety code

Really? If you are using wikipedia or google for a reference guide to electrical work, then you shouldn't be performing the work.....period!

Neutrals and grounds are the only colors specified, once a color scheme is established, then it must be continued throughout the facility.

i agree, and make sure your schematic is clearly stated with wire colors and then all questions should be answered

While most posts are correct regarding UL508A for the wire colors the best advice I would give is that anyone wanting to design/build enclosures and machines to spec should purchase the UL508A, NEC and NFPA-79 revisions currently approved and released. For example I have had customers use orange wire for interlocking power sources (both AC and DC) while others have insisted on use of a color stripe to note the power type as defined in UL508A. Although this does not follow the letter of UL508A it demonstrates that yellow is not the only color approved for power sources not removed with the system/panel disconnect means. I also noted that DC grounded systems also require white/blue stripe common whereas ungrounded DC circuits need blue/white stripe. A copy of current specifications is money well spent.

James Ulinski
Controls Engineering
ROI Industries.

I don't get it, so many replys, but i did not find what I was looking for.

Control panel for 3 Phase electric motors.

-Supply Voltage 480V 3Ph
-Transformer inside the Panel for "CONTROL VOLTAGE" 220V for example
-Now inside this panel there is Supply High voltage AND control voltage.

Don't you think you want to have a different color wire for the control voltage than the supply voltage????

And what would be the wire colors for this panel???

By Bob Peterson on 14 February, 2013 - 8:43 am

If you are in the US, you could use UL508a or NFPA79 for wire color coding inside of control panels.

NFPA79 can be viewed at the NFPA web site for free.

Normally in the US we would not use 220V as a control voltage.

The US national electrical code does not specify color coding of conductors other than for equipment grounding conductors (green) and grounded conductors (white or gray). There is also a color code for the high leg on some power systems. But that is it. Nothing else is required. You can wire the power feeds in purple if you want to. You just cannot use green or white (gray) for anything but their intended purposes.


By Curt Wuollet on 14 February, 2013 - 12:45 pm

Let me help you. Yes, there should be standards. And there are, lots of conflicting standards. Even the recognized standards bodies seldom agree. Control systems are sold by anyone to anyone and the better vendors have a standard, their own. And many buying companies have standards. It's quite likely my standard wouldn't pass inspection in your area. In the end, I do what I think is right, based on the schemes that make the most sense I've seen over a broad range of foreign and domestic equipment along with requirements of the NFPA and if necessary the whim and fancy of local authorities. But. no matter what you do, it probably matches someone's standard. I've seen entire systems done with black wire.


By Bob Peterson on 14 February, 2013 - 6:01 pm


There are no major conflicts between the consensus standard NFPA79 and UL508a. Between them, they represent the most commonly used control panel wiring standards. They grew out of older standards that were quite similar.

You have to remember that you are involved in a fringe area of control systems by doing your own thing. It is not by even a remote stretch something that is the norm.

I would also point out that NFPA79 only applies to machines and would not apply to process systems or gas turbines, among other things.

I do not know of any standards bodies in the US that have any conflicting standards for wiring of control panels. They were long ago harmonized. Perhaps if you know of any such anomalies you could point them out. I am aware of a single minor issue between NFPA79 and UL508a. NFPA79 requires certain wires be orange while UL508a allows them to be either orange or yellow. That is it to my knowledge.

perhaps you could list the "lots" of conflicting standards you claim to be aware of.


By Curt Wuollet on 14 February, 2013 - 11:31 pm

Hi Bob

We are global these days and the majority of packaged systems I am seeing are from the EU. And while the two most quoted American standards bodies are in harmony, if not complete agreement, they are at odds with IEC or whom-so-ever picks coloring schemes in the member countries of the EU. And a lot of the older equipment seemed not to have any particular standard at all. And for that matter I haven't seen a great deal of compliance here either. Beyond the safety mandated grounding and house power connections, small systems tend to be all over the map with no color coding, all black for example seen from time to time. One US company I've seen even likes to change colors along a signal line and use yellow (power from outside the enclosure) for ESTOP and safety interlocks. The stuff I build does lean on the US standards. But it you see a variety of systems, from a variety of places and a variety of vendors you can't make any assumptions. Guess what a white wire with orange and purple stripes means.


By Bob Peterson on 15 February, 2013 - 10:31 am

If you are buying packaged equipment from the EU that does not meet US standards, whose fault is that?

I agree there are some very low end suppliers of control systems and/or machines that will give you junk. Whose fault is it for accepting that?

But the fact is that those kind of systems just are not the norm in US industry in general. Maybe they are where you work, but they just are not in the US in general.

BTW, how do you manage to meet the various safety requirements if the products you are accepting do not meet accepted US standards? Including the OSHA requirement that control panels be listed? How would you even go about making a proper safety evaluation of them?

If they do not meet US standards for one thing they probably don't meet it in others. Do they have US short circuit current ratings? If not, how could you even wire them up?

By Curt Wuollet on 15 February, 2013 - 1:52 pm

Excellent questions, Bob.

The problem is that for example, I don't think you can buy a printing press made here. And they are massive and complex, a huge undertaking and not made to order. So if you want to be in the business........ Often it requires working with the local officials and a few adaptations. I don't know how they satisfy OSHA but those things are negotiated on installation. Many other specialty machines are like that. Take it or leave it. If you are commissioning a system to be built, you may have a choice. An yes, it is lunacy to have a dozen different brands of PLC, but that's how it happens. I had a little influence on the semi custom items, but.....


By Bob Peterson on 18 February, 2013 - 3:57 pm

> I don't think you can buy a printing press made here.


You might be right, but you can get them made with control systems that
meet US standards. But, the company has to want to do it.


By Kitchener on 21 March, 2013 - 5:47 pm

Did you ever get an answer? This is the standard I inspect for, if the client(AHJ)does not have their own standard specified. It is generally recognized by municipalities, water & wastewater, and city utilities for MCCs, industrial control panels & field wiring.

480V A phase = Brown
480V B phase = Orange
480V C phase = Yellow
480VAC neutral = grey

Ground is always green, green w/ yellow stripe or bare copper.
Use tape at every termination, to color code wire, only if colored insulation is not available due to large AWG.

3 phase 240 / 208 VAC Power
A phase = Black
B phase = Red (orange if high leg)
C phase = Blue
1 phase 240/120VAC Power
L1 = Black
L2 = Red
Neutral = White

120VAC Panel = Red, Field = Violet, Foreign circuit = Yellow
DC Control Generally =Blue, or light blue
After this it varies much more than the above list.
DC power supply wiring:
SHIELDED PAIR +red, or white, or clear, -black.

I work for a specifying electrical engineer in Northern California. I am a licensed ICC electrical inspector & an OSHA Outreach Safety Trainer. I hope this helps & be safe.