Explanation of Cable Tray Support Distance

Cable tray supports should generally be spaced 4 to 6 feet apart for standard runs, with long or extra-long spans requiring 14 to 20 feet or more depending on tray type and load.

Standard Support Spacing

For most horizontal cable tray installations, the National Electrical Code (NEC) recommends that supports be installed at intervals not exceeding 5 feet, while the ideal spacing is typically 4 to 6 feet to ensure proper load distribution and minimize deflection . Ladder-type trays should have rungs spaced no more than 9 inches apart to support heavy power cables effectively . Perforated and wire mesh trays follow similar spacing rules, with attention to cable weight and ventilation requirements .

Long and Extra-Long Spans

For long-span trays, which are often used in industrial or outdoor applications, supports can be spaced 14 to 20 feet apart, with 20 feet being common . Extra-long spans may exceed 20 feet, sometimes reaching 20 to 40 feet for outdoor crossings or to reduce the number of expensive supports . In these cases, the tray strength and splice plate placement become critical to maintain structural integrity .

Solid-Bottom Trays

Solid-bottom trays, often used for instrumentation or EMI/RFI shielding, may require closer support spacing due to their tendency to collect moisture and carry heavier loads. Proper support ensures minimal deflection and prevents water accumulation, which can be mitigated with weep holes every 3 feet in outdoor or humid installations .

Best Practices

• 1/4 span rule: For optimal performance, support locations are recommended at one-quarter of the span, especially near splice plates, to reduce stress and deflection .
• Tray length vs. support span: Ensure the tray length is equal to or longer than the support span to control splice locations and maintain structural integrity .
• Compliance with standards: Follow NEMA VE-1/VE-2, NEC, and IEC 61537 guidelines for load ratings, deflection limits, and environmental considerations .
• Outdoor installations: Consider wind, snow, and other environmental loads when determining support spacing, and use extra-long spans judiciously to reduce the number of supports . By adhering to these guidelines, cable tray systems can safely support electrical and communication cables while minimizing deflection, stress, and maintenance issues.