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. Most NM-B cable made after 2001 is sheathed with different-colored wire sheathings 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 adhering to the color scheme
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The Five Basic Colors Of Nonmetallic Cable
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. The colors 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.
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White-colored Nonmetallic Sheathed Cable
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.
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Yellow-colored Nonmetallic Sheathed Cable
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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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.Continue to 5 of 8 below.
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Black-colored Nonmetallic Sheathed Cable
Black-sheathed cable is used for both 6- and 8-gauge wire. 8-gauge wire is good 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.
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Gray-colored Nonmetallic Sheathed Cable
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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With this information, the next time that you look at nonmetallic-sheathed cable, a single glance at the color of the cable sheathing will tell you many of the details you need. But always make sure to double-check and verify the wire’s gauge rating and the installation areas it is approved for.