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The 2014 National Electrical Code (NEC) process received more proposals—including a total of 45 generated by the NEC Correlating Committee Task Group on direct current (DC)—and comments to insert DC into the Code than any other NEC cycle in history. There were proposals dealing with DC branch circuits and feeders; grounding requirements for DC circuits; a new article on DC low-voltage suspended ceiling power distribution; spacing requirements for DC-rated switchboards and panelboards; lighting equipment connected to Class 2 DC power sources in Article 411; requirements for DC circuits, conductors, and systems in Article 480 covering storage batteries (22 proposals were generated from installation requirements deleted from NFPA 70E, the Standard for Electrical Safety in the Workplace); DC changes in Article 690 covering photovoltaic systems; and a new Article 646 covering modular data systems. This magazine article only covers the requirements for color coding and marking for DC branch circuits and DC feeders in the 2014 NEC.
The addition of DC branch circuits into the NEC can be found in 210.5(C) as a new general statement covering alternating current (AC) circuits in 210.5(C)(1) and DC circuits in new 210.5(C)(2) as follows: “(C) Identification of Ungrounded Conductors. Ungrounded conductors shall be identified in accordance with 210.5(C)(1) or (2), as applicable.”
In the following paragraphs, new Code text is red, and explanations are in brackets and italicized. The new text reads as follows: “(2) Branch Circuits Supplied From Direct-Current Systems. Where a branch circuit is supplied from a DC system operating at more than 50 volts,” [The reason for more than a 50-volt range is both the NEC and NFPA 70E generally do not consider less than 50 volts DC to be a shock hazard.] “each ungrounded conductor of 4 AWG or larger shall be identified by polarity at all termination, connection, and splice points by marking tape, tagging, or other approved means” [Generally, a 4 AWG or larger insulated conductor provides enough surface area to ensure tape or tags maintain a secure hold. Each ungrounded conductor must be identified by polarity, such as positive or negative.] “each ungrounded conductor of 6 AWG or smaller shall be identified by polarity at all termination, connection, and splice points in compliance with 210.5(C)(2)(a) and (b).” [Conductors, in sizes 6 AWG and smaller, must be identified using alternative methods with subsections (a) and (b) providing the methods of marking these smaller conductors.] “The identification methods utilized for conductors originating within each branch circuit panelboard or similar branch-circuit distribution equipment shall be documented in a manner that is readily available or shall be permanently posted at each branch circuit panelboard or similar branch-circuit distribution equipment.” [The documentation or posting for DC branch-circuit conductors is the same for AC branch-circuit conductors as can be found in 210.5(C)(1)(b).]
Section 210.5(C)(2)(a) provides the following requirement for positive polarity on 6 AWG or smaller conductors: “Where the positive polarity of a DC system does not serve as the connection point for the grounded conductor, each positive ungrounded conductor shall be identified by one of the following means: (1) a continuous red outer finish; (2) a continuous red stripe durably marked along the conductors entire length on insulation of a color other than green, white, gray, or black; or (3) imprinted plus signs (+) or the word ‘Positive’ or ‘Pos’ durably marked on insulation of a color other than green, white, gray, or black and repeated at intervals not exceeding 24 inches in accordance with 310.120(B).”
Section 210.5(C)(2)(b) provides the requirement for negative polarity on 6 AWG or smaller conductors as follows: “Where the negative polarity of a DC system does not serve as the connection point for the grounded conductor, each negative ungrounded conductor shall be identified by one of the following means: (1) A continuous black outer finish (2) A continuous black stripe durably marked along the conductor’s entire length on insulation of a color other than green, white, gray, or red (3) Imprinted minus signs (–) or the word ‘Negative’ or ‘Neg’ durably marked on insulation of a color other than green, white, gray, or red, and repeated at intervals not exceeding 610 mm (24 in.) in accordance with 310.120(B).”
Section 215.12 provides the similar identification for DC feeder conductors as outlined in the above paragraphs with the titles and text in 215.12(C)(2) addressing feeders rather than branch circuits. These conductor insulation identifiers and color coding should help provide safety for both AC and DC systems where more than one nominal voltage system is present in a premise.