Can THHN conductors be used for direct burial installations?

• A. Yes
• B. No
• C. Only with special approval
• D. Only in dry conditions

Answer: (B)

THHN conductors are primarily designed for dry locations and are not suitable for direct burial applications. This type of wire has an insulation that does not have the necessary properties to withstand moisture over time, which is critical for any conductor that is to be buried underground. Direct burial wire must be able to resist moisture and corrosion to ensure safety and longevity. As such, using THHN conductors in direct burial installations would be against electrical code requirements and safety standards since they would not provide adequate protection in the soil's wet conditions. For underground installations, it is essential to use conductors that are specifically rated for direct burial, such as UF (Underground Feeder) or other types specifically designed to endure such conditions.