When electricians do electrical work, they call it "electrical wiring," which presupposes that wires are involved. However, what they actually fish through the walls from device to device are cables. So what happened to the wires? They're obviously still there, or no connections could be made. When it comes down to it, it's pretty easy to define wire and cable.
Electrical cables are simply bundles of wires coated with fire- and moisture-resistant insulation. This arrangement provides extra protection for the actual conducting wires, which — except for ground wires — are individually coated with insulation. It also makes it easier to keep track of them. When you buy electrical cable, it's identified by the size of the wire as well as the number of wires inside the cable sheathing.
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Different Types of Electrical Wires
Electrical wires have to be made of a conducting metal, and since copper is one of the best conductors there is, it's the preferred material. Aluminum is an alternative for industrial and high-voltage applications, but it isn't one of the electrical wiring types for a house, although it was for a short time in the 1900s.
The most important wire characteristic for an electrician is the diameter of the wire as measured by its AWG number. (AWG stands for American wire gauge, so it's equivalent to the wire gauge). Lower gauge numbers correspond to larger-diameter wires, and the lower the gauge number, the more current the wire is able to handle without overheating. In residential wiring, some common wire gauges are 14, 12, 10, and 8 AWG, with 12 AWG being the most common. Typically, only electricians handle wire gauges lower than 8.
Different Types of Electrical Cables
The most important characteristic of a wire cable is the number of conducting wires it contains. These days, all residential circuits are grounded, and every device has to be connected to a ground wire, but that wire isn't counted as a conductor. Therefore, two-conductor cable contains two insulated wires (usually white and black) and a ground wire, and three-conductor cable contains three insulated wires (usually red, black, and white) and a ground wire.
Electrical cable is also categorized by the sheathing. Interior residential cable generally has a nylon coating and can be classed as THHN (heat-resistant) or THWN (water-resistant). It's common to find dual-rated cables that are both heat- and water-resistant. If you're looking for electrical cable to do outdoor wiring or to bury, you need UF-B (underground feed) cable, which is coated with PVC sheathing. If you want to do wiring in a wet location indoors, such as a laundry room, you need NM-B (nonmetallic) cable. NM-B is suitable for most indoor wiring, but you can't use it outdoors.
How to Find the Wire Cable You Need
The electrical code is very specific about which wire gauge and which type of cable you need for specific circumstances, so if you're in doubt about this, consult a licensed electrician. Once you know what you need, here's how to identify it on the store shelves.
The label on a roll of electrical cable specifies the AWG and the number of conductors with a pair of numbers separated by a slash. For example, 12/2 cable has two 12 AWG conductors, while 10/3 cable has three 10 AWG conductors. The unspecified ground wire is included in all but some low-voltage cables. Look for the UF-B designation if you want to use the cable outside or the NM-B designation if you are wiring a bathroom or laundry room. Some low-voltage cable used for landscape lighting is labeled DBR, which means it's suitable for direct burial.