Conductor identification requirements are located in articles throughout the National Electrical Code (NEC). The first such requirement is in Article 110, and it pertains to a specific type of electrical system. In accordance with 110.15, on a 4-wire, delta-connected system where the midpoint of one phase winding is grounded, only 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. In a three-phase, 4-wire, delta-connected transformer, the neutral conductor is connected to the midpoint of one of the transformer’s single-phase portions. In this type of transformer, one conductor will have a higher voltage to ground than the other two conductors. Some of the slang terms for the conductor having higher voltage to ground include “high leg,” “wild leg,” “stinger leg” and “red leg.” While the conductor can be marked by other effective means, such as tagging, most of the time, this conductor is marked by an orange outer finish (see Figure 1).


This section continues by requiring the identification to be placed at each connection point on the system if the grounded conductor is also present. If conductors in a three-phase, 4-wire, delta-connected voltage system are installed in a junction box used as a pull box, it is not required to identify the high-leg conductor as long as no connections or terminations are made. If conductors in a three-phase, 4-wire, delta-connected voltage system are installed in a junction box and connections are made, the conductor having the higher phase voltage shall be durably and permanently marked by an orange outer finish or by other effective means (see Figure 2).


The next requirements for conductor identification are in Article 200, Use and Identification of Grounded Conductors, which provides requirements for terminal identification, grounded conductors in premises wiring systems and the identification of grounded conductors (200.1). A grounded conductor, as defined in Article 100, is a system or circuit conductor that is intentionally grounded. Section 200.6, Means of Identifying Grounded Conductors, is divided into five subsections: Sizes 6 AWG or Smaller, Sizes 4 AWG or Larger, Flexible Cords, Grounded Conductors of Different Systems, and Grounded Conductors of Multiconductor Cables. The first two subsections cover most grounded conductors. Section 200.6(A) pertains to sizes 6 AWG or smaller insulated grounded conductors and 200.6(B) pertains to sizes 4 AWG or larger insulated grounded conductors.


For conductor sizes 6 AWG or smaller, there are eight options for identifying grounded conductors. However, the first three are the ones used most often. The first option states that a grounded conductor shall be identified by a continuous white outer finish. The second option is similar in that a grounded conductor shall be identified by a continuous gray outer finish. The third option states that a grounded conductor shall be identified by three continuous white or gray strips along the conductor’s entire length on any color insulation except green. It is important to note that the color on the insulation for conductors 6 AWG or smaller shall be continuous (see Figure 3).


For conductor sizes 4 AWG or larger, there are only four options for identifying grounded conductors. The first three options in 200.6(B) are exactly the same as the first three options for conductor sizes 6 AWG or smaller. These larger grounded conductors can also be identified by a continuous white or gray outer finish or by three continuous white or gray strips along the conductor’s entire length on any color insulation except green. The fourth option states that conductor sizes 4 AWG or larger shall be identified at the time of installation by a distinctive white or gray marking at the conductor’s terminations. When using this option, the marking shall encircle the conductor or insulation. While the marking can be any marking that encircles the conductor, white phasing tape is usually used (see Figure 4).


While field-marking grounded and neutral conductor sizes 4 AWG and larger is permissible, it is not permissible to field-mark grounded and neutral conductor sizes 6 AWG and smaller. At times, 8 AWG and 6 AWG conductors with black insulation are installed as grounded or neutral conductors, and then white or gray marking tape is used at the terminations. This type of installation is a violation of 200.6(A) unless the grounded conductor is a mineral-insulated, metal-sheathed cable or a single-conductor, sunlight-resistant, outdoor-rated cable used as a grounded conductor in photovoltaic power systems as permitted by 690.31 (see Figure 5).


Where grounded conductors of different systems are installed in the same raceway, cable, box, auxiliary gutter, enclosure, etc., the grounded conductors of each system must be noticeably different. The grounded conductors from one system must meet the outer-covering specifications required by 200.6(A) or (B). The other systems shall have a different outer covering conforming to 200.6(A) or (B) or by an outer covering of white or gray with a readily distinguishable colored stripe—other than green—running along the insulation. 


For example, feeder conductors from two different voltage systems are entering the same junction box where connections will be made. A neutral conductor is included with each set of feeder conductors. All of the conductors are larger than 6 AWG; therefore, the use of marking tape is permitted. One system is a 208Y/120-volt (V), three-phase, 4-wire, wye-connected system, and the other is a 480Y/277V, three-phase, 4-wire, wye-connected system. The grounded conductor for the 208Y/120V system has been marked or identified by encircling white color-coding or phasing tape around the conductor. Gray color-coding or phasing tape has been used to identify the grounded conductor for the 480Y/277V system (see Figure 6).


The industry standard for identifying conductors in a three-phase, 208Y/120V system is black, red and blue for the ungrounded conductors and white for the grounded conductor. Likewise, the industry standard for identifying conductors in a three-phase, 480Y/277V system is brown, orange and yellow for the ungrounded conductors and gray for the grounded conductor. While these colors are the industry standard, the NEC does not require them. Also in accordance with 110.6(D), the means of identification shall be documented in a manner that is readily available or shall be permanently posted where the conductors of different systems originate.


Another essential requirement pertaining to conductor identification is in Article 250, Grounding and Bonding. Requirements for the identification of equipment grounding conductors are in 250.119. Unless required elsewhere in the NEC, equipment grounding conductors can be bare, covered or insulated. Individually covered or insulated equipment grounding conductors shall have a continuous outer finish that is either green, or green with one or more yellow stripes, except as permitted in 250.119. Like grounded conductors, an insulated or covered equipment grounding conductor 4 AWG and larger shall be permitted, at the time of installation, to be permanently identified as an equipment grounding conductor at each end and at every point where the conductor is accessible [250.119(A)(1)]. Also like grounded conductors, the identification shall encircle the conductor. The identification shall be accomplished by one of the options listed in 250.119(A)(2). The first option states that the insulation or covering can be stripped from the entire exposed length. The second option states that it can be colored green at the termination. The third option states that the insulation or covering can be marked with green tape or green adhesive labels at the termination.


Next month, the discussion of temperature limitations continues.


THHN (90°C) conductor

Motor marked with a design Letter D

THWN conductor (larger than 1 AWG)

1/0 AWG THHN
conductor

Do not exceed the 75°C for this conductor.

90°C


termination

THHN (90°C) conductor

Motor marked with a design Letter D

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