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Electrical Wires & Cables |
To do electrical work in your home, you can use either a combination of single conductors (individual wires) or a multiconductor cable. Though wire sizes and wiring techniques were developed for single conductors, today most people find cable more convenient to use.
Two common single conductors are type THW and type THWN/THHN. Both are rated for either dry and wet locations and for temperatures up to 75 degrees Centigrade (167 degrees Fahrenheit). Typically, you run these individual wires inside protective metal or plastic conduit. You can buy either solid-core or stranded wire; solid-core is stiffer, which makes it more difficult to snake through conduit, but it makes better connections. Wire is usually sold by the foot and in 50- to 500-foot spools.
Cable typically combines a neutral wire, one or two "hot" wires, and a grounding wire inside a plastic or metal covering. The individual conductors within a cable are usually insulated from one another by a color-coded thermoplastic material that doesn't carry current (we say usually because a grounding wire may be bare, particularly when it is contained within a cable). White or gray insulation indicates neutral wires, green is used for grounding wires, and all other colors (black, red, blue, etc.) are used to identify hot wires.
Several types of cable are shown here. Type NM (nonmetallic sheathed cable) is the standard choice for most interior projects; it's sold by the foot or in boxes that house from 25 to 250 feet of coiled cable. The current version, called NM-B, is rated for dry locations only and temperatures to 60 degrees Centigrade (140 degrees Fahrenheit)--even though it houses 90-degree conductors. A beefier, black- sheathed version, sometimes called large appliance cable, has stranded wires to facilitate bending. Durable AC (armored cable) and its updated cousin, MC, are still used for some interior jobs but are expensive.
In addition to type of use, cable is identified by the number and size of the conductors it contains. For example, a cable with two #14 wires (one neutral and one hot) and a grounding wire is called two-wire cable or, more specifically, 14-2 with ground. The number 14 is an American Wire Gauge (AWG) designation that refers to the diameter of the metal conductor not including the insulation. The larger the wire's diameter, the larger its current-carrying capacity, or ampacity, and the lower its gauge number. These numbers appear on the cable sheathing, as well as on the individual wires protected within.
Although copper is the best and most commonly used metal for conductors, aluminum and copper-clad aluminum are also sometimes used. Because aluminum is not as efficient a conductor as copper, an aluminum or copper-clad aluminum wire must be larger than a copper wire in order to conduct the same amount of electricity. If you're considering one of these wires, first check your local electrical codes.
 Complete Home Wiring
Electricity provides us with comfort and conveniences that we often take for granted until something goes wrong. Fortunately for the do-it-yourselfer, electrical work is one of the easiest kinds of home improvement and repair.
Copyright Sunset Publishing Corporation
Photographs by Mark Rutherford |
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Got a question about Electrical Wires & Cables? Ask or search the HomeTips Forums
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