Which statement about THHN conductors is accurate?

• A. THHN conductors are individual conductors used in conduit, rated for higher temperatures.
• B. THHN conductors are a shielded cable used for indoor applications.
• C. THHN stands for Thermoplastic Heat Resistant Nonmetallic.
• D. THHN conductors are used only in outdoor locations.

Answer: (A)

THHN is a single conductor with thermoplastic insulation and a nylon-coated finish, designed for use in raceways like conduit. Because it’s an individual conductor meant to run inside a conduit, it’s used where conductors are pulled through conduits rather than in shielded cables. The nylon coating adds abrasion resistance and enables the insulation to handle higher temperatures, which is why THHN is specified for higher-temperature service than many other common conductors. It isn’t shielded cable, and its name isn’t what some might think—THHN stands for Thermoplastic High-Heat-Resistant Nylon-coated. It can be used indoors or outdoors in conduit, depending on the application, but its key feature is the combination of being an individual conductor and having a high-temperature rating.