You need to know your cable count first. They will sit in the tray together. Never. Article Summary: A compliant cable tray installation requires a thorough understanding of NEC Article 392, proper structural support, and precise installation techniques. But before you lay the first tray or clamp down a single cable, you need a solid plan. Spacing. This method statement describes a detailed procedure for properly installing cable trays and conduits for the Feeder System.