A wire color chart tells you what colors to use. The code does something narrower and more useful: it reserves three specific markings for one job, prohibits their use for anything else, and then lists eight methods by which a grounded conductor may be identified. Which method you use is mostly your choice. What you may not do is use white, gray or three white stripes for something else.
There is also a clause in this subject that surprises electricians who have worked with it for years, and it is not about color at all.
White, gray and three white stripes are reserved
The identification article does not begin with a list of permitted colors. It begins with a prohibition, and the prohibition names three markings.
A conductor with a continuous white covering, a conductor with a continuous gray covering, or a conductor with three continuous white stripes on insulation other than green shall be used only for the grounded circuit conductor. The rule permits two ways out, and only two: circuits of less than 50 volts, which are required to be grounded only where the general grounding article requires it, and the two cases set out further below.
Green is not on that list because green belongs to a different conductor, and the reservation is written so that the two never collide. Three white stripes are permitted only on insulation other than green, and a white or gray marking used to re-identify a conductor must be a color other than white, gray or green. Green is walled off from the grounded conductor system in both directions.
Eight permitted methods at 6 AWG and smaller
For an insulated grounded conductor of 6 AWG or smaller, there are eight permitted means. They divide into markings applied along the whole length of the conductor and markings applied in the field.
Method | What it is |
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Continuous white outer finish | A whole-length marking |
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Continuous gray outer finish | A whole-length marking |
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Three continuous white stripes along the entire length, on insulation other than green | A whole-length marking |
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A white or gray outer covering with colored tracer threads in the braid identifying the source of manufacture | A whole-length marking; the tracer threads do not disqualify it |
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The grounded conductor of a mineral-insulated, metal-sheathed cable, identified at the time of installation by distinctive marking at its terminations | A field marking |
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A single-conductor, sunlight-resistant, outdoor-rated cable used as a grounded conductor in a photovoltaic system, identified at the time of installation by distinctive white marking at all terminations | A field marking |
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Fixture wire, complying with the identification requirements for that product | By reference to the fixture wire article |
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Aerial cable, identified as above or by a ridge on the exterior of the cable | A whole-length marking, by shape rather than by color |
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Two of those eight are worth separating from the rest. The tracer-thread allowance means a white conductor is not disqualified by the presence of colored threads woven into its braid, which is how a manufacturer’s name ends up inside a neutral without violating the rule. And the photovoltaic case is the only one in the list that requires the marking at all terminations rather than at terminations generally.
Four at 4 AWG and larger, and the size ladder
Above the smaller sizes the list shortens, because a large conductor is difficult to mark along its whole length in the factory and easy to mark at the point where somebody will look.
Method | What it is |
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Continuous white outer finish | A whole-length marking |
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Continuous gray outer finish | A whole-length marking |
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Three continuous white stripes along the entire length, on insulation other than green | A whole-length marking |
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At the time of installation, a distinctive white or gray marking at its terminations | A field marking, and this marking must encircle the conductor or the insulation |
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The fourth method is the one an installer is most likely to use and most likely to install wrongly. The requirement is not that a mark be present at the termination. It is that the mark encircle the conductor or its insulation, so that the identification is visible from any angle rather than only from the side the installer happened to be facing.
The two size lists do not overlap. One applies to 6 AWG and smaller and the other to 4 AWG and larger, so a conductor is governed by one list or the other and never by both.
The two size lists do not overlap
Three of the methods are not colors
Four entries across the two tables identify a conductor by something other than a color applied along its length, and each of them is a shape or a field mark.
Provision | Method |
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Mineral-insulated, metal-sheathed cable | Distinctive marking at its terminations, applied at installation |
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Single-conductor outdoor-rated cable used as a grounded conductor in a photovoltaic system | Distinctive white marking at all terminations, applied at installation |
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Aerial cable | A ridge on the exterior of the cable, which identifies it by feel |
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Multiconductor flat cable, 4 AWG or larger | An external ridge on the grounded conductor |
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The aerial and flat-cable ridges are the interesting pair, because they move the identification out of the visual channel entirely. A conductor marked with a ridge can be identified in the dark, at the end of a run, with a hand rather than a light — which is exactly the situation a conductor identification rule exists for. Nothing in the article requires color. What it requires is that a person can tell the conductors apart.
Two product-specific references complete the set: a grounded conductor inside a flexible cord is identified by a white or gray outer finish or by the methods that apply to cords, and fixture wire follows its own identification requirements.
The only way out of the reservation, and its four conditions
The prohibition on using white, gray or three white stripes for anything but a grounded conductor has a narrow exception, and it is the clause that lets a white conductor in a cable assembly serve as an ungrounded conductor. In circuits of 50 volts or more it is permitted only where all of the following are true.
Condition | Requirement |
|---|
The conductor’s context | It must be part of a cable assembly |
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Permanence | The insulation must be permanently reidentified by marking tape, painting or other effective means |
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Where the marking goes | At its termination and at each location where the conductor is visible and accessible |
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How it is applied | The identification must encircle the insulation |
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What color it may be | A color other than white, gray or green |
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There is then a restriction on how a reidentified conductor may be used that has nothing to do with its color. Where it is used for a single-pole, three-way or four-way switch loop, the reidentified conductor may be used only for the supply to the switch, and not as the return conductor from the switch to the outlet.
Read the conditions as a set and the logic is consistent with the rest of the article. A marking that is permanent, that appears wherever the conductor is exposed, and that encircles the insulation is functionally equivalent to a factory-applied color for the purpose of not confusing anyone.
Three markings are reserved, and there are two ways out
Three cross-references and one requirement of its own
The branch circuit identification section is short, and its first two paragraphs contain no rule at all — only pointers.
Branch circuit conductor | Identified in accordance with |
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The grounded conductor | The grounded conductor article |
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The equipment grounding conductor | The equipment grounding conductor article |
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The third paragraph is different, and it is the only one that creates an obligation of its own.
Where the premises wiring system has feeders supplied from more than one nominal voltage system, each ungrounded conductor of a feeder must be identified by phase or line and by system at all termination, connection and splice points. The permitted means are separate color coding, marking tape, tagging or other approved means.
That is worth reading twice, because of what it does not say. The code never states which colors the phase conductors of a system must be. What it requires is that the scheme in use distinguishes the phases from one another and distinguishes one system from another. A building with 480-volt and 208-volt feeders can satisfy the paragraph with almost any consistent scheme, and cannot satisfy it by using brown, orange and yellow in both.
The requirement almost nobody expects
Two clauses in this subject require something other than marking conductors, and both of them are records requirements.
Where grounded conductors of different systems are installed in the same raceway, cable, box, auxiliary gutter or other enclosure, each grounded conductor must be identified by system. The means permitted include giving one system’s grounded conductor an outer covering meeting the general identification rules, giving the others a different outer covering or a white or gray covering with a readily distinguishable colored stripe other than green, or using other distinguishing means. And then the sentence that is the point of this section:
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.
The ungrounded conductor rule reaches the same place. Where a feeder panelboard or similar distribution equipment supplies conductors whose identification method is used, that method must be documented in a manner that is readily available or permanently posted at each feeder panelboard.
So there are two separate places in the code where the identification scheme itself becomes a document, and an inspection can ask for the document rather than for the conductor. Most identification failures on a job are not a wrong color. They are a scheme that existed in one electrician’s head and was never written down.
The two places where the scheme becomes a document
Article 200 carries one more piece of field advice, and it appears twice in the same article, which is a fair indication of how often it matters. The color gray may have been used in the past as an ungrounded conductor, and care should be taken when working on existing systems. A gray conductor in an older installation is therefore not self-identifying, and the rule that reserves gray for a grounded conductor is a rule about new work rather than a description of what is already in the wall.
FAQ
How many ways are there to identify a grounded conductor?
For an insulated conductor of 6 AWG or smaller, eight methods are permitted. For 4 AWG and larger, four are permitted. The two lists do not overlap, and neither depends on using a color along the whole length — four of the permitted methods identify the conductor by a marking at its terminations, by an external ridge, or at installation.
Does the code say which colors the phase conductors must be?
Not in the identification provisions read here. What it requires is that where more than one nominal voltage system supplies feeders, each ungrounded conductor be identified by phase or line and by system at every termination, connection and splice point. The scheme must distinguish the phases from each other and the systems from each other, and the method must be documented or posted.
Conclusion
White, gray and three white stripes are reserved for one conductor by a prohibition rather than by a recommendation, and green is walled off from that system in both directions. Within the reservation there is real latitude: eight permitted methods at 6 AWG and smaller and four at 4 AWG and larger, four of which do not involve a color along the length at all. The one route out of the reservation requires a permanent marking that encircles the insulation and appears wherever the conductor is exposed, plus a restriction on how the reidentified conductor may be used in a switch loop.
And the part that is easiest to overlook is that two clauses require the identification scheme to be written down or posted. Those are the only two, they sit in different sections, and they are the reason an inspector can ask for paper in a subject that otherwise lives entirely on the surface of the insulation.
Cable marked the way the drawing calls for it
ZONG Cable prints conductor identification to the scheme a project specifies, and can stripe, ridge and color a construction so that the marking survives the pull rather than only the factory. Tell us the identification scheme and the sizes, and we will confirm what the construction can carry. The range sits under cable, the grounding and bonding practice these conductors feed into is set out in the guide to telecommunications grounding and bonding, the separate pair-color system used for data cable is covered in T568A and T568B wiring, what sits around a conductor inside a finished cable is described in network cable anatomy, the size question behind the two identification lists is worked through in voltage drop and conductor sizing, and private-label construction to a specified scheme is handled under OEM support.
Sources
- NFPA 70, National Electrical Code, 2011 edition. Read directly for this article: Article 200, Use and Identification of Grounded Conductors — 200.6 Means of Identifying Grounded Conductors, paragraph (A) Sizes 6 AWG or Smaller with its eight permitted means, paragraph (B) Sizes 4 AWG or Larger with its four permitted means, paragraph (C) Flexible Cords, paragraph (D) Grounded Conductors of Different Systems with its three permitted means and its documentation or posting requirement, and paragraph (E) Grounded Conductors of Multiconductor Cables with its external ridge provision and both exceptions, together with the informational note on the historic use of gray that appears in paragraph (E); 200.7 Use of Insulation of a White or Gray Color or with Three Continuous White Stripes, paragraph (A) General, paragraph (B) Circuits of Less Than 50 Volts and paragraph (C) Circuits of 50 Volts or More with subparagraphs (1) and (2), including the four conditions on permanent reidentification and the restriction on the use of a reidentified conductor in single-pole, three-way and four-way switch loops, together with the same informational note on gray; 200.9 Means of Identification of Terminals. Article 210, Branch Circuits — 210.5 Identification for Branch Circuits, paragraph (A) Grounded Conductor, paragraph (B) Equipment Grounding Conductor and paragraph (C) Ungrounded Conductors with its documentation or posting requirement. Source text read from a full-text copy of the 2011 edition.
- ZONG Cable range. https://zh-zong.com/cable/
