Wireway Depth: The maximum permitted distance for the through (wireway) beyond the front of panelboard is 6 inches, the trough's depth is 12 inches and switchboard's depth is 24 inches. Choosing the right electrical junction box size is crucial for safety and code compliance in your US projects. This guide helps you determine the correct dimensions based on wire fill capacity, device requirements, and installation environment, ensuring a safe and efficient electrical system. Common uses: ceiling lights, fans, smoke detectors. 5 is an article in the National Electrical Code that addresses requirements for underground electrical installations, including minimum cover requirements—the measurement used to determine the distance from the top of an underground cable or raceway to the finished grade.