Cable tray supports are usually grounded

Metallic cable trays must be properly grounded to ensure electrical safety, either by using the tray itself as an equipment grounding conductor (EGC) or by connecting a dedicated grounding wire along the tray.

NEC Requirements and Standards

According to the National Electrical Code (NEC) Article 392, all metallic cable trays must be grounded, regardless of whether they are used as an EGC . The tray can serve as the EGC if it meets the minimum metal cross-sectional area requirements specified in NEC Table 392.60(A), which depends on the circuit's fuse rating, breaker ampere trip rating, or ground-fault protection setting . Steel trays should not be used as EGCs for circuits with ground-fault protection above 600 A, and aluminum trays should not be used above 2000 A .

Grounding Methods

1. Using the Cable Tray as the EGC: The tray itself can carry fault current if it meets NEC requirements. Sections of the tray should be electrically bonded to maintain continuity .
2. Full-Length Grounding Conductor: A continuous grounding wire, typically copper or stainless steel, runs along the tray and is bonded at each tray section. This provides a reliable path for fault currents and prevents mechanical displacement of the conductor under fault conditions .
3. Bonding at Joints: Grounding wires or the tray itself should be bonded at each connection point using clamps, bolts, or welds to ensure low-resistance continuity .

Material Considerations

• Copper Wire: Excellent conductivity and corrosion resistance, ideal for most installations .
• Hot-Dip Galvanized Steel: Durable and corrosion-resistant, suitable for industrial environments .
• Stainless Steel: Recommended for harsh or corrosive environments .
• Avoid placing bare copper conductors in aluminum trays in moist environments to prevent electrolytic corrosion; insulated conductors with exposed bonding points are preferred .

Safety and Performance

• Grounding Resistance: The system should ideally have a resistance of 4 ohms or less to ensure effective fault current diversion .
• Mechanical Stability: Grounding clamps also help secure the conductor mechanically, preventing displacement during fault conditions .
• Separation and Accessibility: Maintain proper separation from power and data cables to prevent interference, and ensure trays remain accessible for maintenance .

Best Practices

• Bond each or alternate tray sections to the grounding conductor.
• Use tin or zinc-plated connectors for bonding points to prevent corrosion.
• Ensure compliance with NEC Article 392 for tray fill, cable types, and grounding continuity.
• Regularly inspect grounding connections for corrosion, looseness, or damage. Proper grounding of cable tray supports is essential for electrical safety, equipment protection, and regulatory compliance, and following NEC guidelines ensures a reliable and safe installation .