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Colour codes USA 3 phase ?

Colour codes USA 3 phase ?

Colour codes USA 3 phase ?

I would like to know the colour codes for USA wiring 3 phase ?

                 David Gowland

RE: Colour codes USA 3 phase ?


For 208/120V systems:  Black, Red, Blue for A,B,C phases
For 480/277V systems:  Brown, Orange, Yellow for A,B,C phases


RE: Colour codes USA 3 phase ?

I generally agree with mpparent, that is a very common spec, perhaps the single most common spec out there.

But beware, there is no single "standard" published in any code in the US for phase insulation colors (NEC does have specific requirements for neutral & ground insulation colors).  And there are many conflicting color codes in use.

One notable exception is the Dept. of Energy, where they use Red-Blue-Black for ABC for both 208 & 480 volt systems.

RE: Colour codes USA 3 phase ?


 Many thanks,
             I have another question , but that may have been answered by the reply ,some American households have two phases , for 240v across the phases  and a neutral. If the normal code is black for phase and white for neutral what colour is used for the other phase ?

             regards  David

Orchard Electronic

RE: Colour codes USA 3 phase ?

I have seen red used.  I believe this is really 240V single phase, with center tap to give 120V


RE: Colour codes USA 3 phase ?

I hestitate to step into this after seeing the 100+ message thread a few weeks ago, but the US residential service is a SINGLE PHASE 240V supply with a center-tapped neutral point providing 120V to either "hot leg".  The neutral MUST be white and white may not be used for anything other than neutral.  Black is typically used for both hot legs although other colors may be used.  Ground MUST be green.  

I second peebee's admonition that there is no universal standard in the US for phase colors on three phase systems.


RE: Colour codes USA 3 phase ?

Yup.  The only code-reserved colors are white, gray, and green (for neutrals and grounding).

The phases can be any color you please so long is it's not white, gray, or green.

There's lots of houses wired with all hot wires black.  There's plenty of houses wired with all the colors of the rainbow, too.

RE: Colour codes USA 3 phase ?

Again, generally
For 208/120V systems:  Black, Red, Blue for A,B,C phases
For 480/277V systems:  Brown, Orange, Yellow for A,B,C phases

No code for most conductors except ground, neutral (as stated) and then some other "oddball" applications.  

For an isolated power system in a health care facility, orange, brown and yellow are required for the isolated conductors. Article 517

110.15 High-Leg Marking.
On a 4-wire, delta-connected system where the midpoint of one phase winding is grounded to supply lighting and similar loads, the conductor or busbar having the higher phase voltage to ground shall be durably and permanently marked by an outer finish that is orange in color or by other effective means.

424.35 Marking of Heating Cables.
Each unit shall be marked with the identifying name or identification symbol, catalog number, and ratings in volts and watts or in volts and amperes.
Each unit length of heating cable shall have a permanent legible marking on each nonheating lead located within 75 mm (3 in.) of the terminal end. The lead wire shall have the following color identification to indicate the circuit voltage on which it is to be used:   
(1) 120 volt, nominal — yellow
(2) 208 volt, nominal — blue
(3) 240 volt, nominal — red
(4) 277 volt, nominal — brown
(5) 480 volt, nominal — orange

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