Connection between shaft and cable tray

Cable trays entering or passing through a shaft require proper vertical risers, elbows, tees, and secure support to ensure safe, organized, and code-compliant installation.

Vertical and Horizontal Connections

When connecting a cable tray to a shaft, the main cable tray backbone typically runs vertically through the shaft, with horizontal branches extending to each floor or equipment level. Vertical risers are used to transition from horizontal runs to the shaft, often incorporating elbows or bends to allow cables to sweep smoothly without exceeding minimum bend radii . Horizontal branches can start with a downward bend from the vertical riser to facilitate cable entry. In practice, a tee fitting may be used to split the vertical tray into multiple horizontal runs, though some software or BIM libraries may not have a pre-defined vertical tee, requiring custom solutions or manufacturer-specific BIM content .

Support and Mounting

Cable trays must be mechanically supported using wall brackets, suspended supports, or center suspensions to connect the tray to the building structure, such as the shaft walls or ceiling . Splice plates are recommended at joints to maintain structural integrity and alignment. Proper spacing of supports ensures that the tray can carry the intended cable load without sagging or deformation .

Material and Environmental Considerations

Cable trays are typically made of steel, stainless steel, or aluminum, with galvanization or other coatings to resist corrosion . Aluminum trays should avoid bare copper grounding conductors to prevent electrolytic corrosion; insulated conductors with tin or zinc-plated connectors are preferred .

Grounding and Bonding

All metallic cable trays should be grounded according to NEC Article 250.96, whether or not they serve as the equipment grounding conductor (EGC). Grounding clamps can bond the tray sections and any EGC conductors, providing both electrical continuity and mechanical anchoring to withstand fault currents .

Best Practices

• Maintain minimum bend radius for cables exiting the tray to prevent damage .
• Use elbows and bends to create smooth transitions from vertical to horizontal runs .
• Ensure secure mechanical support at regular intervals and at shaft entry points .
• Select materials and finishes appropriate for the environment to prevent corrosion and maintain structural integrity .
• Consider custom or manufacturer-specific fittings if standard vertical tees are unavailable .

By following these guidelines, cable trays can be safely and efficiently routed through shafts while maintaining compliance with electrical codes and ensuring long-term reliability.