In home wiring that implements nonmetallic sheathed cable (NM), the outer sheath color indicates the wire gauge or size and amperage rating of the wire within. Most NM-B cable, made after 2001, is sheathed with different colored wire sheathed to make identification easier for both consumers and inspectors. This color coding of the wire sheath is strictly voluntary, but most manufacturers have followed suit in producing such a color scheme.
The Five Basic Colors Of Nonmetallic Cable
The five basic color schemes used primarily in home construction are white, yellow, orange, black and gray. Actually, black is used twice, but it is used for two different wire gauges, so beware when selecting the appropriate wire size. These colors are the solid color of the insulation housing cover that coats the insulated and uninsulatede individual wires within.
White-colored Nonmetallic Sheathed Cable
The white color-coded wire sheath houses 14-gauge wire. This type wire is used for 15-amp circuits in your home. Lighting circuits are normally the primary use of this sized wire.
Yellow-colored Nonmetallic Sheathed Cable
Yellow color-coded wire sheath encloses 12-gauge wire that is rated for 20-amp circuits. General power for outlets and appliances is the main use for this sized wire feed.
Orange-colored Nonmetallic Sheathed Cable
The orange-colored wire sheathing is set aside for 10-gauge wire. It is able to handle 30-amp circuit loads. These loads include air conditioner, water heater feeds, and any other 30-amp loads.
Black-colored Nonmetallic Sheathed Cable
As far as black-coated wire, this is shared for both 6- and 8-gauge wire. As you may know, 8-gauge wire is good for 45-amp circuits and 6-gauge wire is capable of handling 60-amp circuits. The 6-gauge wire is better for a feeding a sub panel, an electric range, or a double oven, depending on the amperage rating listed on the appliance.
Gray-colored Nonmetallic Sheathed Cable
Now there is another colored sheathing that has more to do with installation areas than with wire size. This would be gray-colored NM wire. It is used for underground installations and comes in varying sizes. It has water-resistant qualities and is sometimes resistant to other things like oil and sunlight.
Nonmetallic Sheathed Cable's Outer Jacket Labeling
As with all nonmetallic sheathed cable, the outer jacket is labeled with letters that show how many insulated wires are concealed within the sheath. This wire count does not, however, include the uninsulated wire that is used as a ground wire. For instance, if the cable lists 12-2 WG, it means there are two insulated 12-gauge wires (a black and a white wire), plus a ground wire. If the label says 12-3, this is a three-conductor, 12-gauge cable with a bare copper ground wire included.
Identifying Wire Size At A Glance
So the next time that you look at nonmetallic-sheathed cable, you’ll have a leg up on someone who doesn’t know the inside tip of distinguishing the wire size and its load rating just by looking at the color of its cable sheathing. Even then, be sure to look at the labeling to double-check what the wire’s gauge rating is and the installation areas it is approved for.