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Electric wire is made of copper and plastic insulation and is used to transport electricity to homes. There are four types of wire, including triplex cable and non-metallic sheathed wire. The National Electrical Code sets guidelines for wiring methods to protect people from improper use of electricity.
Electric wire is the medium by which electricity is transported to and through every single home that uses electricity. It is made of a metal that conducts electricity easily, usually copper, in a plastic sheath called an insulator. There are various types of this wire, each suitable for certain loads and conditions. Four main types are common in residential applications.
The first type is triplex cable, which is the cable that runs overhead between outdoor power poles. Often in triplex cable, there are three wires twisted together: two insulated carrying line voltage, and the other is a bare, neutral wire. The second type, main power cables, run between a power pole and the house to which power is carried. These cables are typically rated for 125% of the load they are intended to carry.
The other two types of electrical wire run through the walls and outlets of a house. Panel power cords are rated at 125 amps, to carry power to a main junction box or circuit breaker panel, and provide the connection from which other wiring branches out in a home. Non-metallic sheathed wire, also called Romex®, is the typical wiring used in most homes. It consists of two or three lead wires and a bare ground wire, all enclosed in a plastic sheath. It is economical and suitable for dry interior applications.
In the United States, acceptable wiring methods are specified by the National Electrical Code (NEC). Local jurisdictions usually adopt the NEC and thus vary the local code slightly from it. The NEC need not be the electrical code for any jurisdiction, but rather is simply an influential set of standards used by local governments for regulatory purposes. Its intent is to protect people from the dangers deriving from the improper use of electricity.
An example of an NEC guideline would be a stipulation that the ground wire in a circuit be bare or have green insulation. The NEC also states that large appliances such as ovens, stoves and central air conditioning units should be on a dedicated circuit. The NEC guidelines receive changes and updates from time to time, but existing installations are generally not required to make changes to comply with the new code. New buildings are required to comply with electrical wiring standards set by local authorities.
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