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THHN (Thermoplastic High Heat-resistant Nylon-coated)
Designated for a specific insulation material and temperature rating for electrical wire and cable. Wires with THHN insulation are commonly used in the alternating current (AC) electrical distribution systems of buildings of all types and sizes throughout North America, usually at voltage levels (potential difference or electromotive force) ranging from 110-600 Volts. This type of insulation is used for both copper and aluminum wires which are either solid or stranded, depending on size.