Cable Management Tray Size: Choose a tray size that will hold the desired amount and length of cable. The NEC requires that cable trays must be supported by members at an interval specified by the cable tray manufacturer, but not more than 5 feet for horizontal runs to support the weight of the cables and other loads. The NEC has a requirement for ladder-type cable trays. Proper installation can significantly reduce. Article Summary: A compliant cable tray installation requires a thorough understanding of NEC Article 392, proper structural support, and precise installation techniques. These systems, made from metal or plastic, are open structures designed to support electrical conductors, ensuring proper organization and safety. Insert legs of duct support into bases and attach with 2-1/2” bolt and 1/2” nut. Space. The National Electrical Manufacturers Association (NEMA) Standards and guideline publications, of which the document herein is one, are developed through a voluntary Standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in.