Types of Copper Wire Insulation

Considerations

• Since electrical wire is used to carry electric current from one point to another within an electric circuit, the insulation must be able to withstand the heat generated by the wire, as well as withstanding voltage differentials between the wire and the outside environment. Some wires are exposed to chemical hazards; therefore the insulation on these wires must be chemical resistant.

Polymer-Based Insulation Types

• Many polymer-based materials -- commonly known as plastics -- may be used as insulation material for copper electrical wire. These materials are used because of their high dielectric values, heat resistance, cost, chemical resistance and physical flexibility. Some common polymer-based insulation materials are Teflon, Tefzel, nylon, polyvinyl chloride, silicone rubber and polyethylene. Some of these materials may be used in tandem, such as nylon-jacketed polyvinyl chloride insulation.

Non-Polymer Insulation Types

• Non-polymer dielectric materials may also be used to insulate copper wire. These materials are typically used for specialty applications such as transformer windings and electromagnets. Some of these materials include enamel, ceramic and paper.

Building-Specific Copper Wire Insulation

• Wire used in residential and commercial buildings is insulated with polyvinyl chloride with a secondary nylon jacket. Insulated copper wire that is used for this purpose may have designations such as TFFN, THHN or THWN. The TFFN designation stands for "thermoplastic flexible fixture wire nylon-jacketed," which indicates that the wire insulation is suitable for use in dry environments where the temperature will not exceed 105 degrees Centigrade or in environments where oil is present and where the temperature of the environment will not exceed 80 degrees Centigrade. The THHN designation stands for "thermoplastic high heat-resistant nylon-coated," which indicates this insulation type is well suited to dry environments where the temperature may reach 90 degrees Centigrade or wet environments where the temperature may reach 75 degrees Centigrade. The THWN designation stands for "thermoplastic high water-resistant nylon-coated," which indicates that this insulation type is well suited to wet environments where the temperature will not exceed 75 degrees Centigrade.