In nonmetallic sheathed cable (NM) used for residential and commercial wiring, the outer sheath color indicates the wire gauge or size and amperage rating of the wire within. Before about 2001, most NM cable had a white outer jacket, but beginning in 2001, most NM-B cable is jacketed with a vinyl out insulation that is colored to identify it for both consumers and inspectors. This color coding of the wire sheath is strictly voluntary, but most manufacturers have now followed suit in adhering to... the color scheme.
The five basic color schemes used for the NM cable in residential construction are white, yellow, orange, black and gray. These colors are seen in the solid vinyl outer jacket that enclose the individual conductors within the cable, and are easily identified at a glance.
Be aware that black is used as a color for two different wire gauges, so some care is needed when interpreting black cable.
01 of 07
Cable with white sheathing houses 14-gauge wire. This type wire is used for 15-amp circuits in your home. General lighting circuits are normally the primary use of 14-gauge cable, although many homes are now wiring these circuits as 20-amp circuits.
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Yellow color-coded cable sheathing encloses 12-gauge wire, which is rated for 20-amp circuits. General power for outlets and appliances is the main use for this 12-gauge cable.
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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.
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Black-sheathed cable is used for both 6- and 8-gauge wire. 8-gauge wire is rated for 45-amp circuits, while 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.
If you need black cable, make sure to read the sheathing and packaging carefully to determine if you are buying 6-or 8-gauge wire.Continue to 5 of 7 below.
05 of 07
Gray-colored sheathing is used to designate cable intended for underground installation. It has excellent water resistance and may also be rated for resistance to oil and sunlight. In this cable, the conductors are embedded in solid vinyl rather than running loosely inside the jacket.
Because the gray coding does not indicate wire size, read the packaging and jacket printing to make sure you are buying the right wire size.
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Outer Jacket Labeling
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.
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Color Coding on Individual Conductors
The wires inside a sheathed cable will also have plastic insulation that is color-coded for easy recognition. All cables will have a white insulated wire and a black insulated wire; these identify the neutral and the hot wires, respectively.
The bare copper wire in the cable is the ground wire. (In rare instances, you might find cable in which the ground wire is covered with green insulation—green is a color designated for ground wires.)
In a three-wire cable, there will be a red wire in addition... to the white and black wires. Red is also designated as a hot color.