Fill in the blank

When working with electrical systems, including multi-conductor cables, identification of conductors is an important issue. For example, on a new 480/277V, 3-phase, 4-wire system, the NEC requires you to identify conductors by phase or line and system [210.5(C)]. It is common practice to identify these ungrounded conductors with an outer finish (i.e., insulation color) that is: brown, orange, and yellow; gray for the grounded conductor; and green, green with one or more yellow stripes, or bare for the equipment grounding conductor. But when working on existing electrical systems, such as 480/277V, 3-phase, 4-wire systems, you should take care because the color __________ may have been used for an ungrounded conductor. Hint: See the Fine Print Note.

  1. white
  2. white with one or more colored stripes, other than green
  3. black with three distinctive white stripes on its entire length
  4. gray

Answer: D

As noted in the Fine Print Note of 200.6(E), "The color gray may have been used in the past as an ungrounded conductor. Care should be taken when working on existing systems." Although the FPN is cautioning electricians to be aware of the conductor with the outer gray color, it's possible that other colored conductors that are not normally used to identify ungrounded conductors may have been used as ungrounded conductors. So be careful out there!

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at necexpert@aol.com.