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. To determine the proper spacing, consult the manufacturer's load capacity chart, which accounts for the total weight of the. We recognize the need for a complete cable tray reference source for electrical engineers and designers. The following pages address the 2014 National Electrical Code® requirements for cable tray systems as well as design solutions from practical experience. These systems, made from metal or plastic, are open structures designed to support electrical conductors, ensuring proper organization and safety.