How much spacing should be used between trapezoidal cable trays

Trapezoidal cable trays should generally be supported every 4 to 6 feet for standard spans, with longer spans requiring engineered support intervals based on load and tray type.

General Guidelines

For trapezoidal cable trays, support spacing depends on the tray span, load, and installation environment. According to NEC and industry best practices, horizontal runs should not exceed 5 feet between supports for standard installations, though a range of 4 to 6 feet is typical to ensure uniform load distribution and prevent sagging or mechanical stress on the tray and cables .

Span Categories

Cable trays are often categorized by span type, which affects support spacing:

• Short Span Trays: Typically supported every 6 to 8 feet, suitable for non-industrial indoor installations .
• Intermediate Span Trays: Supported every 10 to 12 feet, used for moderate loads and longer runs .
• Long Span Trays: Supported every 14 to 20 feet, often used outdoors or for heavy-duty applications .
• Extra-Long Span Trays: Exceed 20 feet between supports, used for road crossings or to minimize expensive outdoor supports .

Installation Considerations

• Load Capacity: The tray's support spacing must account for the weight of cables, environmental loads (wind, snow), and any additional mechanical stress .
• Splice Plates: Only one splice plate should be placed between supports to maintain structural integrity .
• Tray Length: The tray length should be equal to or longer than the support span to avoid unsupported sections .
• Bends and Transitions: Supports should be placed near bends, tees, or changes in elevation to prevent cable damage and maintain stability .

Safety and Compliance

• Supports must be designed to prevent undue mechanical strain on cables and terminations .
• Fire-resistant materials are recommended for supports to ensure system integrity in case of fire .
• Regular inspections and maintenance are essential to identify corrosion, wear, or loose fasteners .

Summary

For most trapezoidal cable tray installations, a support spacing of 4 to 6 feet is standard for indoor applications, while longer spans require careful engineering based on load and environmental conditions. Always follow manufacturer specifications and applicable codes (NEC, BS 7671) to ensure safety and reliability .