How to connect longitudinal and transverse cable trays

Longitudinal and transverse cable trays are connected using splice plates, fittings, and bolts to ensure structural integrity and proper cable support.

Understanding the Tray Structure

Cable trays typically consist of longitudinal side rails connected by transverse members or rungs. Ladder-type trays have open rungs for ventilation, while solid-bottom trays provide full support and protection for cables . Transverse members are perpendicular to the longitudinal rails and are the points where connections are made between sections.

Connection Methods

1. Using Splice Plates
   • Snap-in or bolted splice plates are commonly used to join two longitudinal sections. These plates align the side rails and provide mechanical strength across the joint .
   • For ladder trays, the splice plate is positioned under or over the rungs and secured with bolts to the side rails.
   • Ensure that the splice plate covers both longitudinal rails and overlaps the transverse rungs for stability.
2. Fittings for Directional Changes
   • Horizontal Tees and Crosses allow transverse trays to branch off from a main longitudinal tray at 90° angles .
   • Reducers are used when connecting trays of different widths in the same plane.
   • Elbows enable directional changes, either horizontally or vertically, while maintaining proper support for cables.
3. Bolting and Fastening
   • Use appropriate bolts, nuts, and washers to secure splice plates and fittings. Ensure all fasteners are tightened according to manufacturer specifications to prevent movement or sagging .
   • For aluminum trays, use corrosion-resistant fasteners to prevent galvanic corrosion.
4. Alignment and Support
   • Ensure that the trays are level and aligned before final tightening.
   • Maintain proper span support according to load ratings, typically every 10–24 feet for ladder trays, depending on cable weight and tray type .
   • Check that the transverse tray is properly supported at the junction to prevent sagging or stress on the cables.

Safety and Compliance

• Follow NEC Article 392 for clearances, fill limits, and grounding requirements .
• Maintain at least 12 inches of vertical clearance above trays for maintenance access.
• Separate high-power and low-power cables to prevent electromagnetic interference.
• Ensure that all metallic trays are properly grounded if used as equipment grounding conductors.

Summary

To connect longitudinal and transverse cable trays effectively:

• Use splice plates to join longitudinal rails.
• Employ tees, crosses, elbows, or reducers for transverse connections.
• Secure all connections with bolts and fasteners.
• Align trays and provide adequate support and clearance.
• Follow NEC and manufacturer guidelines for safety and compliance. This approach ensures a rigid, safe, and code-compliant cable tray system that supports cables efficiently while allowing for ventilation and maintenance access.