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. Support spacing for cable trays must align with the manufacturer's instructions, as outlined in NEC 392. Proper installation can significantly reduce electromagnetic interference, prevent fire hazards, and improve overall efficiency. This article provides an in-depth. Actual width of the cable tray.