Cable Types: Only use conductors rated for open-air environments, such as Tray Rated (Type TC) or Metal-Clad (Type MC) cables. Proper installation of cables in trays is critical for maintaining an efficient and safe electrical system. This is why proper planning and execution are. But before you lay the first tray or clamp down a single cable, you need a solid plan. Mark the cable tray route based on your electrical cable tray design and site. Article Summary: A compliant cable tray installation requires a thorough understanding of NEC Article 392, proper structural support, and precise installation techniques. 14 AWG though 1000 kcmil, insulated for operation from 600 volts though 35 kilovolts. Here's what you need to know: Cable Types: Only use.