Cable trays must be grounded to provide a low-impedance path for fault currents, ensuring safety, equipment protection, and compliance with NEC standards.

Purpose of Grounding

Grounding a cable tray ensures that any stray electrical currents or fault currents are safely directed to the earth, reducing the risk of electric shock, fire, or equipment damage. It also helps protect against lightning strikes, minimizes electromagnetic interference (EMI), and improves overall system reliability by stabilizing voltage levels in the facility .

Methods of Grounding

1. Using the Cable Tray as an Equipment Grounding Conductor (EGC)
   • Metallic cable trays can serve as the EGC if they meet minimum cross-sectional area requirements specified in NEC Table 392.60(A) .
   • Steel trays should not be used as the sole EGC for circuits with ground-fault protection above 600 A, and aluminum trays above 2000 A .
   • All metallic trays must be grounded regardless of whether they are used as the EGC .
2. Bonding Cable Tray Sections
   • Each section of the tray should be electrically continuous, bonded using clamps, splice plates, or bonding jumpers to maintain a continuous path to ground .
   • Side rails of ladder or trough trays should be bonded together to ensure continuity .
   • If an EGC cable is installed in the tray, it should be mechanically anchored and bonded to each or alternate tray sections to prevent displacement under fault conditions .
3. Connecting to the Facility Ground
   • The cable tray system must be bonded back to the main power source or grounding electrode system .
   • Grounding conductors should be sized according to NEC requirements to safely carry fault currents .
   • For aluminum trays, use insulated conductors with tin or zinc-plated connectors to prevent electrolytic corrosion .

Best Practices

• Maintain low grounding resistance, ideally 4 ohms or less, to ensure effective fault current dissipation .
• Keep grounding wires clear of flammable or corrosive environments to prevent degradation .
• For non-metallic trays, a separate EGC or the EGC within the cable can be used to bond sections together .
• Ensure compliance with NEC Article 392 and other relevant standards for safety and inspection purposes . Proper grounding of cable trays is critical for electrical safety, system reliability, and regulatory compliance, and should always be performed by qualified personnel following NEC guidelines and industry best practices.