A Colorful History

NEC’s conditional requirements have evolved

There are several conditions under which the National Electrical Code requires or permits conductors to be identified by the color of their insulation. These include the following:

• 230.56 for services, 215.8 for feeders, and 110.15 in general for the conductor having the higher voltage to ground, sometimes called the high leg or the stinger, on a three-phase four-wire delta system they must be identified by the color orange, or by other effective means.

• 424.35 requires the non-heating leads of electric space-heating cables to be identified for circuit voltage: 120V, yellow; 208, blue; 240, red; 277, brown and 480, orange.

• 400.22 permits the grounded conductor in a jacketed cord furnished with an appliance to be light blue.

• 504.80 permits conductors for intrinsically safe systems to be colored light blue.

• 517.160(A)(5) requires the conductors of an isolated power system in a hazardous flammable anesthetizing location in a hospital to be colored orange, brown and yellow.

The requirement more generally applied for conductor insulation color is to identify energized conductors to positively distinguish them from grounded or grounding conductors by colors other than white, gray or green.

The first mention of color code for the ungrounded conductors of a circuit is in Section 602.f. in the 1928 NEC, where, following the requirements for grounded conductors to be identified by white or natural gray, appears this: “The coverings of the other conductors shall be finished to show solid colors other than white or natural gray.” This requirement has finally been located at 310.12(c).

The first appearance of color coding of individual conductors—the identification of ungrounded conductors with relation to phase and voltage—was in the 1937 NEC Section 2104: “Multiwire Branch Circuits—Color Code. Branch circuits of any of the types recognized in this article may be installed as multiwire circuits provided one of the conductors of the circuit is an identified grounded conductor. Conductors of such multiwire branch circuits of multiphase systems shall conform to the following color code: three-wire circuits—one black, one white, one red; four-wire circuits—one black, one white, one red, one yellow; five-wire circuits—one black, one white, one red, one yellow, one blue.”

In the 1940 NEC, this was added to 2104: “If installed in raceways, as open work, or as concealed knob and tube work, the conductors of such multiwire branch circuit shall conform to the following color code:” Blue and yellow were interchanged.

Without further change, the section number is changed to 2112 in the 1947 NEC. In the ’53 Code, this fine-print note (FPN) was added: “Any conductor intended solely for grounding purposes shall be identified by a green color unless it be bare. Conductors having a green covering shall not be used for other than grounding purposes.” This FPN was changed to bold type in the ’56 NEC.

The first commentary on this subject in the eighth edition of Abbott based on the 1953 NEC: “The color coding of multiwire branch-circuit conductors is necessary in order that the loads may be properly balanced between the ungrounded conductors. Specific attention is called to the requirements that a green-colored conductor may not be used as a circuit wire.”

There were several proposals for the 1971 NEC, including a requirement for specific colors for 480Y/27 multiwire branch circuits, but Panel 2 removed the requirement for specific colors, allowing the ungrounded conductors for branch circuits to be any color other than white, natural gray, green or green with one or more yellow stripes. Different colors must be used for the ungrounded conductors of systems of different voltages, and the neutral conductor of different systems must be distinctly identified. The former requirement of black, white, red and blue has been retained as a recommendation. In the Preprint for the 1971 NEC, there is no insight provided for the panel position.

For the ’81 NEC, there were several proposals to restore a color-code requirement. The panel comment includes the following: “There are not enough colors to cover the variations in systems and voltages. The diverse practices in existing installations would cause incompatibility problems with the proposed color-coding requirements.

“Every conductor should be considered alive unless proven otherwise. The logistics and cost problems of Code manufacturing, shipping, stocking and installing the many colors of conductors would be unjustifiably severe.”

Based on an IBEW proposal, 210.4(D) is deleted, and new 210.5(C) is adopted in the ’05 NEC: “Ungrounded Conductors. Where the premises wiring system has branch circuits supplied from more than one nominal voltage system, each ungrounded conductor of a branch circuit, where accessible, shall be identified by system. The means of identification shall be permitted to be by separate color coding, marking tape, tagging or other approved means and shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment.”

This no longer limits the requirement to multiwire branch circuits, and it applies only where there is more than one voltage system on the premises. Also, note that the required identification is only by system, not by phase.

Similar requirements were adopted for the 2005 NEC, 215.12, for feeders. EC

SCHWAN is an electrical Code consultant in Hayward, Calif. He can be reached at creighton.s@sbcglobal.net.


About the Author

W. Creighton Schwan

Former Code Columnist
W. Creighton Schwan was a long-time contributor to ELECTRICAL CONTRACTOR magazine and an important figure in the electrical code world. His first article written for ELECTRICAL CONTRACTOR was published in January 1980 issue. He wrote a total of 326...

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