Electrical connections of the cable tray

Proper electrical connections of cable trays involve secure mechanical joins, grounding, and bonding to ensure safety, system stability, and code compliance.

Mechanical Connections

Cable tray sections must be joined securely to maintain structural integrity and prevent sagging or misalignment. Common connection methods include splice plates, bolted connections, quick-connect systems, fish plates, clamps, and welding. Splice plates are flat metal plates with holes that are bolted to the ends of two tray sections, providing a straight, stable join. Bolted connections are widely used for their strength and reliability, while quick-connect systems allow faster installation with moderate load capacity. Proper mechanical connections ensure the tray can support the weight of cables without bending or shifting, which is critical for safety and durability .

Grounding and Bonding

Metallic cable trays can serve as the Equipment Grounding Conductor (EGC) if installed according to NEC Article 392 and Article 250.96. All metallic trays must be grounded, whether or not they are used as the EGC. When using the tray as an EGC, grounding clamps are recommended to bond each or alternate tray sections to the EGC, providing both electrical continuity and mechanical anchoring to prevent displacement under fault currents. For aluminum trays, a bare copper conductor should be avoided due to the risk of electrolytic corrosion; insulated conductors with removed insulation at bonding points are preferred, using tin or zinc-plated connectors .

Material Considerations

The choice of tray material affects electrical connections. Steel trays are suitable for most grounding applications but should not be used as EGCs for circuits with ground-fault protection above 600 A. Aluminum trays are limited to 2000 A for similar applications. Non-conductive materials like fiberglass-reinforced plastic (FRP) provide corrosion resistance and electrical isolation, which may be preferred in moist or chemically aggressive environments .

Best Practices

• Ensure continuous electrical continuity across all tray sections.
• Use properly rated connectors and clamps for bonding.
• Avoid mixing incompatible metals to prevent corrosion.
• Verify that the tray's cross-sectional area meets the minimum requirements for EGC use based on the circuit's fault current rating.
• Maintain clearances and proper support spans to prevent mechanical stress on connections . By following these practices, cable tray systems remain safe, stable, and compliant, while facilitating future maintenance and cable additions.