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. 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. Our free calculator helps you determine the correct tray size based on NEC and IEC standards. Select Fill Standard: Choose 40% for power cables (NEC compliant) or 50% for. The spacing between trays, whether horizontal or vertical, depends on various factors like cable type, environment, and tray material. The NEC has a requirement for ladder-type cable trays.