What is the minimum trade size of RMC permitted for installation between two panelboards that are 5 feet apart?

The minimum trade size of rigid metal conduit (RMC) permitted for installation between two panelboards that are 5 feet apart is 2.5 inches. This size is determined by the need to ensure adequate space for conductors while considering factors such as bending radius and fill capacity.

RMC is often chosen for its durability and ability to protect electrical wiring from physical damage, and the size directly affects its ability to accommodate conductor types and quantities. According to the National Electrical Code (NEC), specific installations, especially those involving panelboards, may require a minimum conduit size to ensure safety and functionality.

For installations where two panelboards are located close together, like 5 feet apart, the choice of 2.5 inches provides enough room for conductors, ensuring compliance with the NEC’s fill requirements and allowing for efficient operation. If smaller sizes were used, they could result in overcrowded wiring or issues with heat dissipation, increasing the risk of electrical failure or safety hazards. This is why 2.5 inches is established as the minimum size for such installations.