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In both those instances the white wire should be identified as being hot, usually with black tape inside junction boxes. The neutral wire is identified by gray or white insulated wire, perhaps using stripes or markings. With lamp cord wire the ribbed wire is the neutral, and the smooth wire is the hot. NEC 2008 400.22(f) allows surface marking ...
In North America, this type of cable is designated as NM cable. NM means "nonmetallic", referring to the outer sheathing; the conductors are still metallic. NM was first listed and described in the NEC in 1926, but it was invented a few years earlier by the Rome Wire Company in 1922 in Rome, New York, and marketed under the trade name "Romex". [2]
Electrical power cables are sometimes installed in raceways, including electrical conduit and cable trays, which may contain one or more conductors. When it is intended to be used inside a building, nonmetallic sheathed building cable (NM-B) consists of two or more wire conductors (plus a grounding conductor) enclosed inside a thermoplastic ...
Galvanized rigid conduit (GRC) is galvanized steel tubing, with a tubing wall that is thick enough to allow it to be threaded. Its common applications are in commercial and industrial construction. [1] It is designed to protect wire and connectors. Intermediate metal conduit (IMC) is a steel tubing heavier than EMT but lighter than RMC. It may ...
Non-metallic sheathed cable (or nonmetallic building wire, NM, NM-B) [6] Armored cable (or BX) [6] Multicore cable (consist of more than one wire and is covered by cable jacket) Paired cable – Composed of two individually insulated conductors that are usually used in DC or low-frequency AC applications
The first rubber-insulated cables for US building wiring were introduced in 1922 with US patent 1458803, Burley, Harry & Rooney, Henry, "Insulated electric wire", issued 1923-06-12, assigned to Boston Insulated Wire and Cable . These were two or more solid copper electrical wires with rubber insulation, plus woven cotton cloth over each ...
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A full-load wire does heat up slightly due to the metallic resistance of the wire, but this wire heating is factored into the cable's temperature rating. (NEC 310.10) [12] The NEC specifies acceptable numbers of conductors in crowded areas such as inside conduit, referred to as the fill rating.