The acronyms "THHN" and "THWN" refer to the National Electrical Code requirements these wires meet. "T" indicates the wire has thermoplastic insulation, while "H" stands for both heat resistance and high heat resistance up to 194 degrees Fahrenheit. "W" shows the wire is approved for use in wet or damp locations, while "N" indicates that oil and gas cannot harm the wire. These wires can carry up to 600 volts and are made of copper, and their colors indicate their use. White wires are neutral; green and bare wires are used as ground wires; and black, blue and red wires are located in residential wiring and indicate the wires may be hot.
Cables used in residential settings carry 600 volts, but those used in industrial applications vary. NM-B cable, which is non-metallic cable that can withstand up to 194 degrees Fahrenheit, is the most common cable available for residential use. It includes two thermoplastic insulated wires inside a thick sheath on which the cable's gauge and maximum voltage capacity is printed. Other popularly used cables include the UF cable for use in damp areas; the armored cable, which is wrapped in a metal sheath and often found in older homes; the metal-clad cable, which is primarily used in industrial settings; the coaxial cable used to transfer television signals; and category 5e cables used for computer networks and phones.Learn more about Electrical