Cable tray spacing regulations

Cable tray supports should generally be spaced every 6 to 10 feet for standard trays, with heavy-duty or long-span trays allowing up to 20 feet, following NEC 392 and manufacturer guidelines.

Horizontal and Vertical Spacing

For horizontal runs, supports are typically installed every 6 to 10 feet, depending on tray type, load, and cable weight. Heavy-duty trays or long-span installations can extend support spacing up to 20 feet, but the manufacturer's load capacity chart must be consulted to ensure safety and prevent sagging or mechanical stress on cables (Electrical Trader, 2026 NEC update) . For vertical or angled runs, cables should be fastened to the tray's transverse members to maintain stability. Vertical runs exceeding 32 meters require strain relief sections, often implemented by offsetting the cable by at least two cable diameters per section. For runs over 100 meters, additional tension-relieving measures, such as short horizontal sections of at least 1 meter, are recommended (Prysmian, 2026) .

Rung and Tray Considerations

For ladder-type trays, rung spacing affects cable support and appearance. Small-diameter control and instrumentation cables typically require 6, 9, or 12-inch rung spacing, while large power cables may need 9-inch or wider spacing. Wider trays and rungs reduce overall strength, so load charts should be checked to avoid overloading (Eaton B-Line) .

Clearance and Safety

NEC 392 requires at least 12 inches of vertical clearance above trays for installation and maintenance access. Cables must be supported at transitions to equipment or other raceways, with unsupported spans not exceeding 6 feet without additional supports. Proper cable ties or fasteners should be used to maintain spacing, improve heat dissipation, and prevent mechanical stress (Electrical Trader, 2026 NEC update) .

Best Practices

• Maintain even spacing of bearers along cable bundles to prevent sagging and ensure stability (BEAMA guide) .
• Separate high-power and low-power cables to reduce electromagnetic interference (Apex Tray) .
• Ensure strain relief at bends and transitions to protect cable terminations and maintain system integrity (Prysmian) .
• Use manufacturer-approved supports and follow BS EN 61537 or BS 6946 standards for tray and channel systems (BEAMA) . By following these spacing regulations and best practices, cable tray installations will meet safety standards, maintain structural integrity, and allow for efficient maintenance and heat dissipation.