Support spacing for cable trays must align with the manufacturer's instructions, as outlined in NEC 392. Generally, standard trays require supports every 6 to 10 feet, while heavy-duty, long-span trays can handle distances of up to 20 feet between supports. screw tie) is used to external fastening element fasten support elements to supporting parts of the build-ing structure and, in. us-trations without notice. All illustrations, descriptions and technical information included in this document are provided as indications and can cable trays are equivalent. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned. Prohibited Areas: Cable trays cannot be used in hoistways or enclosed spaces and must remain accessible. Grounding: Metallic trays can serve as equipment grounding conductors (EGC) if they meet NEC requirements. Specifiers should be aware that some cable tray. Where products of five metre lengths or above are packed in bundles, they shall be supported with a minimum of three timber bearers which provide sufficient clearance to accommodate the forks of a forklift truck. The NEC has a requirement for ladder-type cable trays.