Cable tray supports in shafts should generally be spaced according to manufacturer specifications, typically every 6 to 10 feet for standard trays, with closer spacing for vertical runs or heavy loads.

General Guidelines

For standard cable trays, supports are usually installed every 6 to 10 feet along the tray length, while heavy-duty or long-span trays can extend up to 20 feet between supports, depending on the tray's load capacity and material strength (NEC 392.30(A)), . The exact spacing must be determined by consulting the manufacturer's load chart, which accounts for the total weight of the cables and the tray type .

Vertical and Shaft Installations

In vertical shafts, cable trays are subject to additional mechanical stress due to gravity. Cables should be fastened to the tray's transverse members to prevent sagging and maintain proper alignment . Unsupported vertical spans should generally not exceed 6 feet; if longer, additional supports are required to prevent undue stress on the conductors . This ensures both safety and compliance with electrical codes.

Rung and Tray Considerations

• Ladder trays: For small-diameter control and instrumentation cables, rung spacing of 6 to 12 inches is recommended to prevent drooping, while larger power cables may require 9 inches or more .
• Solid-bottom trays: May require weep holes every 3 feet if installed in humid or outdoor environments to prevent water accumulation .
• Cable bending radius: Ensure that rung spacing does not violate the minimum bending radius of the cables; sometimes rungs may need to be removed or repositioned to accommodate proper cable routing .

Additional Considerations

• Clearance: NEC 2026 requires at least 12 inches of vertical clearance above the tray for installation and maintenance access .
• Cable ties: Use listed and approved ties to secure cables, especially in plenum spaces, to maintain spacing and improve heat dissipation .
• Transitions: At points where cables exit the tray or enter equipment, provide strain relief and additional support to prevent mechanical stress .
• Thermal expansion: For long outdoor runs, expansion splice plates should be installed to accommodate temperature-induced expansion and contraction . By following these guidelines, cable trays in shafts can be installed safely, maintain proper cable support, and comply with NEC and manufacturer requirements.