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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] Today, the name "Romex" is a trademarked brand of the Southwire Company. [3]
A laser wire stripper is a computer-controlled machine, much like a CNC router, which uses a laser to burn off the insulation of the wire. Laser wire stripping machines are used mostly for very fine gauge wires since they do not damage the conductor.
Topside of firestop with penetrants consisting of electrical conduit on the left and a bus duct on the right. The firestop consists of firestop mortar on top and rockwool on the bottom, for a two-hour fire-resistance rating. For very high currents in electrical apparatus, and for high currents distributed through a building, bus bars can be used.
Another issue is the joining of aluminum wire to copper wire. In addition to the oxidation that occurs on the surface of aluminum wires which can cause a poor connection, aluminum and copper are dissimilar metals. As a result, galvanic corrosion can occur in the presence of an electrolyte, causing these connections to become unstable over time.
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 ...
Flexible metallic conduit (FMC, informally called greenfield or flex) is made by the helical coiling of a self-interlocked ribbed strip of aluminum or steel, forming a hollow tube through which wires can be pulled. FMC is used primarily in dry areas where it would be impractical to install EMT or other non-flexible conduit, yet where metallic ...
Twist-on wire connectors are available in a variety of sizes and shapes. While their exterior covering is typically made from insulating plastic, their means of connection is a tapered coiled metal insert, which threads onto the wires and holds them securely.
The NEC specifies acceptable numbers of conductors in crowded areas such as inside conduit, referred to as the fill rating. If the accepted fill rating is exceeded, then all the cables in the conduit are derated, lowering their acceptable maximum ambient operating temperature. Derating is necessary because multiple conductors carrying full-load ...