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Quite a number of answers to electrical questions (like this answer) indicate that a standard /2 cable can be used for a 240V load so long as the white wire is taped (or colored with a marker or paint pen, heat-shrink, etc) to indicate that it is being used as a hot, not a neutral. Other questions, for instance those about wiring 3-way switches, indicate remarking the wires with yellow tape to indicate the travelers.

When remarking a wire to indicate that its use in this instance is not as the original insulation color would lead one to believe, is the entire amount of wire visible in the box (at each end) required to be covered, or is it sufficient to make a band by wrapping one or two layers of tape around the wire?

As I see it, the difference would be:

  • Completely covered -> a quick glance in the box shows 2 black or a black and a red, therefore it's obviously two hots.
  • A band -> a quick glance could show a black and a white leading one to believe there's a hot & neutral. However, a more thorough inspection would show that the white has a band of colored tape, therefore it's two hots.

What is the NEC requirement for thoroughness in remarking a wire to a different color for a different purpose?

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    Interesting question. I'd try to mark the last few inches of the wire, and I've seen some people just wrap one turn of electrical tape and call it good (1/2" or so). Would be nice to know if it's in the code, or maybe just a standard from trained electricians.
    – JPhi1618
    Dec 1, 2021 at 17:34
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    I am betting for completely covered, just because I usually use a band.
    – crip659
    Dec 1, 2021 at 18:10
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    It seems clear to me that you want to make it clear that you have for example a white conductor marked as yellow. If you completely cover the conductor, you make that less clear. Additionally, if I saw a completely wrapped conductor my first assumption would be NOT that it's marked, but that its insulation was damaged. Looking forward to an answer to the actual question, if code has anything to say on this.
    – jay613
    Dec 1, 2021 at 19:15
  • Interesting thought, @jay613, that one hadn't occurred to me. I'm over here waiting for some sort of code quote as patiently as I can... :) Fortunately, this is a theoretical question ATM, not an urgent need.
    – FreeMan
    Dec 1, 2021 at 19:24
  • Found this, but it only goes to 2014. Does not seem to give a good answer to the question. ncwhomeinspections.com/Re-Identifying+white+conductors
    – crip659
    Dec 1, 2021 at 20:19

1 Answer 1

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+100

In the context of the question (mains wiring, greater than 50 volts, etc) NEC stipulates that white-marked conductors be used only as a grounded conductor (ie neutral). Referring to the 2017 edition, the requirement is found in 200.7(A):

200.7 Use of Insulation of a White or Gray Color or with Three Continuous White or Gray Stripes.
(A) General. The following shall be used only for the grounded circuit conductor, unless otherwise permitted in 200.7(B) and (C):
(1) A conductor with continuous white or gray covering
(2) A conductor with three continuous white or gray stripes on other than green insulation
(3) A marking of white or gray color at the termination

Exceptions immediately follow. Paragraph 200.7(C)(1) is applicable to this question:

(C) Circuits of 50 Volts or More. The use of insulation that is white or gray or that has three continuous white or gray stripes for other than a grounded conductor for circuits of 50 volts or more shall be permitted only as in (1) and (2).
(1) If part of a cable assembly that has the insulation permanently reidentified to indicate its use as an ungrounded conductor by marking tape, painting, or other effective means at its termination and at each location where the conductor is visible and accessible. Identification shall encircle the insulation and shall be a color other than white, gray, or green. If used for single-pole, 3-way or 4-way switch loops, the reidentified conductor with white or gray insulation or three continuous white or gray stripes shall be used only for the supply to the switch, but not as a return conductor from the switch to the outlet.

These citations do not address the extent to which the mark may or must conceal the original marking of the conductor. It might be useful to survey the code for other instances in which re-marking is addressed to look for a pattern. In 250.119(B)(3), regarding the marking of a conductor in multi-conductor cable for equipment grounding, the code states Identification shall encircle the conductor. In section 690.31, regarding wiring methods permitted for PV systems, there is mention of separate color coding, marking tape, tagging, or other approved means but again no discussion on the extent of coverage of the original conductor marks. One can understand that tagging would provide a very minimal degree of coverage, however.

Absent specific guidance on the topic, the general requirements of being durable, of good quality, executed in a workman-like manner, etc should be maintained. I see nothing that would lead a person to believe it is necessary to make any effort to conceal the original markings of the conductor.

In my opinion, it would be good practice not to fully conceal the original color or markings of the conductor so as to create awareness that the conductor is reidentified. This can serve as warning in case the cable should become exposed in a new place, or in case its marking in another place should become removed.

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  • Thank you! It seems that a couple of wraps of tape is sufficient. That's handy, as it saves on tape. ;)
    – FreeMan
    Jan 17, 2022 at 16:31

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