THWN or THHN

Application

CU THHN/THWN(-2) Building Wire is intended for general-purpose electrical wiring in accordance with the applicable requirements of the National Electrical Code (NEC). With a rated voltage of 600V, it is designed for installation in conduit or other approved raceway systems. Depending on the conductor type and product rating, it can also be used in machine tool wiring, electrical appliances, and control circuits.

The permitted conductor temperature varies according to the wire designation and operating environment:

THHN / T90 Nylon:Rated for maximum conductor temperatures of 90°C in dry locations.
THWN-2:Suitable for wet and dry locations at conductor temperatures up to 90°C, subject to applicable conditions of use. When exposed to oil, the applicable temperature rating must be verified.
THWN:Generally rated for up to 75°C in wet locations and 90°C in dry locations, with oil-exposure limitations determined by the product marking.
TWN75:Designed for wet-location applications with a maximum conductor temperature of 75°C.
MTW:Temperature ratings depend on the environment. Typical ratings include up to 60°C in wet or oil-exposed conditions and up to 90°C in dry locations, with ampacity limitations where required by NFPA 79.
AWM:May be rated for temperatures up to 105°C in dry locations when manufactured, marked, and used in accordance with the applicable Appliance Wiring Material requirements.

The actual temperature rating and permitted application must be confirmed by the product markings and relevant electrical codes.

Construction

CU THHN/THWN(-2) Building Wire is manufactured using soft-drawn copper conductors to provide electrical conductivity and flexibility appropriate to the selected conductor construction.

For sizes from 14 AWG through 4/0 AWG, a combination-unilay stranding design may be used. Larger sizes of 250 kcmil and above may feature compressed stranded copper conductors, depending on the specified construction.

The copper conductor is insulated with durable PVC material designed to provide heat and moisture resistance. An overall nylon jacket is applied to the specified product types to provide an additional protective layer.

Available insulation or jacket colors may include black, white, red, blue, purple, green, yellow, orange, brown, and gray. Color availability depends on the selected specification, production requirements, and order quantity. Certain colors may require a minimum order quantity.

Standards

The following industry standards may apply to the conductor materials and construction of CU THHN/THWN(-2) Building Wire, depending on the specified product design:

ASTM B3:Standard Specification for Soft or Annealed Copper Wire.
ASTM B8:Standard Specification for Concentric-Lay-Stranded Copper Conductors.
ASTM B787:Standard Specification for 19 Wire Combination Unilay-Stranded Copper Conductors for Subsequent Insulation.
UL 83:Standard for Thermoplastic-Insulated Wires and Cables.

Product compliance and certification should be verified against the applicable specifications and documentation for the supplied wire.

Technical Parameter