What type of wiring method is approved for underground installations?

For underground installations, the use of rigid conduit is a highly reliable and approved wiring method. Rigid conduit offers significant protection against environmental factors such as moisture, soil intrusion, and physical damage that can occur when wiring is buried underground. The conduit itself is made of durable materials like metal or PVC, providing a strong barrier that safeguards the electrical conductors within from external elements.

In addition to physical protection, rigid conduit allows for proper grounding and supports the safe routing of electrical wires, ensuring compliance with the National Electrical Code (NEC) for underground wiring systems. It is essential for maintaining the integrity and longevity of electrical installations in less accessible or harsh environments.

While other types of wiring methods may have their specific applications, they may not be suitable for direct underground installation due to limitations in protection, moisture resistance, or structural integrity when underground. For instance, non-metallic sheathed cable is typically not rated for direct burial unless it is specifically designed for that purpose, and flexible cords are not considered suitable for permanent installations. Therefore, rigid conduit stands out as the most appropriate choice for underground wiring applications.