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Wire Color Coding

Written by Steve Hudgik

When someone asks about wire color coding, we need to start with a number of questions. For example, there are many wire color coding standards. Which standard applies depends on where you are, the type of application, the voltage and other factors. In addition, are you talking about the color coding of the wire insulation, or the color coding of labels used to identify wires and cables?

We'll start with the wire color coding used for insulation, then finish with a discussion of color coding of wire markers and labels.

For example, in the U.S. the following is the typical wire color coding for wires used for power distribution:

Wire Color Coding Guide

120 and 240 Volt Wire Color Codes

  • phase 1 - black
  • phase 2 - red
  • phase 3 - blue
  • neutral - white or three white stripes
  • ground - green or green striped

277 and 480 Volt Wire Color Codes

  • phase 1 - brown
  • phase 2 - orange
  • phase 3 - yellow
  • neutral - gray or with 2 white stripes
  • ground - green with yellow stripe

When wires are larger than #6 AWG they all will have black insulation. Wire color coding should be added during installation using colored bands that wrap around the wire.

The individual wires within a cable have color coded insulation. The colors that are used are specified by law in some areas. In some areas only a few colors may be specified. In other locations there may be local laws or even local customs that determine the required wire color coding.

For example, most of the countries in Europe follow the wire color code established by the International Electrotechnical Commission IEC) for AC branch circuits. This standard requires:

IEC Wire Color Codes For AC Branch Circuits

  • phase 1 - brown
  • phase 2 - black
  • phase 3 - grey
  • neutral - blue
  • ground - green with yellow stripe

In Canada wire color coding standards are set by the Canadian Electric Code (CEC). As in the U.S. and Europe for AC power the ground is green with yellow stripe, but the neutral is white.

Canadian Wire Color Codes For AC Power

  • phase 1 - red
  • phase 2 - black
  • phase 3 - blue
  • neutral - white
  • ground - green with yellow stripe

U.S. DC Power Wire Color Coding Standard

Solar power systems generate DC power and DC power distribution is frequently required for large computer systems. In the U.S. the DC power standard (published by NEC) requires that the ground wire be bare or have green or green-yellow insulation. The neutral must be white or grey. The following recommended wire color coding applies to DC power systems:

All DC Power Systems
ground - bare, green or green-yellow

Two-Wire Ungrounded DC Power
positive - red
negative - black

Two-Wire Grounded DC Power – Negative Ground
positive - red
negative - white

Two-Wire Grounded DC Power – Positive Ground
positive - white
negative - black

Three-Wire Grounded DC Power
positive - red
center tap - white
negative - black

Non-Power Wire Color Coding

Wiring used for telecommunications or computer network applications uses a different color coding standard. For example, if we look at RJ21 cable, there are 25 twisted pairs. For the wire color coding there are two groups of five colors. Each twisted pair within the cable uses one color from the first group and a color from the second group of five colors. This provides enough color combinations for 25 pairs of wires.

The two groups of five wire color codes are:

Wire Color Coding Group One

Wire Color Coding Group Two

Wire Color coding - Wire Markers and Cable Labels

When it comes to the labels used to mark wires at the ends, you can do whatever works best. However, it is important to establish an consistent standard that is used within your facility, or better yet throughout your organization. The ANSI 606-A standard includes requirements for marking telecommunications wires that may provide a useful example:

ANSI/TIA/EIA 606-A defines itself as covering: “The ANSI/TIA/EIA 606-A Standard specifies administration for a generic telecommunications cabling system that will support a multi-product, multi-vendor environment. It provides a uniform administration approach that is independent of applications, which may change several times throughout the life of the telecommunications infrastructure.”

The following is what 606-A states about wire marker design:

Labeling Visibility and durability

“The size, color, and contrast of all labels should be selected to ensure that the identifiers are easily read. Labels should be visible during the installation of and normal maintenance of the infrastructure. Labels should be resistant to the environmental conditions at the point of installation (such as moisture, heat, or ultraviolet light), and should have design life equal to or greater than that of the labeled component.”

You'll need to establish a wire color coding system that works for your systems. Color communicates information rapidly, but the amount of information is limited. For example, the label color could identify the system, and then a code printed on the label identifies the specific wire or cable. This allows systems to be easily be visually identified by color.

Making Color Coded Wire and Cable Labels

Electrical systems, and their associated wiring and cables, have complex and unique designs. The best way to have the required durable, easy-to-read labels, is to be using a DuraLabel custom label printer. With DuraLabel you have the ability to print both shrink tube wire markers and self-laminating wire markers. Wire markers can be printed in batches, or individually as needed.

The information presented in this document was obtained from sources that we deem reliable; Graphic Products does not guarantee accuracy or completeness. Graphic Products, Inc. makes no representations or warranties of any kind, express or implied. Users of this document should consult municipal, state, and federal code and/or verify all information with the appropriate regulatory agency.

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