Can THHN/THWN-2 conductors be installed directly buried in the ground?

• A. Yes, it is allowed
• B. No, it is not allowed
• C. Only in specific conditions
• D. Only with additional insulation

Answer: (B)

THHN/THWN-2 conductors are not suitable for direct burial in the ground because they lack the required insulation and moisture resistance necessary for such an application. When conductors are installed directly in the earth, they are exposed to moisture and other environmental conditions that can lead to insulation degradation over time.

For underground installations, conductors must have insulation that is rated for direct burial applications, typically using materials like UF (Underground Feeder) cable or equivalent. These cables have specific properties that protect them from moisture and chemical exposure. Therefore, it is important to select the right type of conductor based on its intended installation environment to ensure safety and reliability.