Should cable trays be connected to the grounding grid

Yes, metallic cable trays should be connected to the facility's grounding grid to ensure safety, system reliability, and compliance with electrical codes.Importance of Grounding Cable Trays

Connecting cable trays to the grounding grid provides a low-impedance path for fault currents, protecting personnel and equipment from electrical hazards, including electric shock, fire, and equipment damage due to overvoltage or insulation failure . Grounding also helps dissipate lightning energy, reducing the risk of voltage surges, and minimizes electromagnetic interference (EMI), which is critical for sensitive electronic and communication systems . Proper grounding enhances overall system reliability and operational efficiency .

NEC and Industry Requirements

According to the National Electrical Code (NEC) Article 250.96 and Article 392, all metallic cable trays must be grounded, regardless of whether they serve as an equipment grounding conductor (EGC), . Cable trays can be used as the EGC in qualifying installations if they meet minimum cross-sectional area and conductivity requirements, but in most cases, a separate grounding conductor is recommended . All tray sections should be electrically continuous, bonded at splice points, and securely connected to the building's grounding system .

Bonding Methods

Cable trays are bonded together using bolts, clamps, splice plates, or bonding jumpers to maintain electrical continuity across sections . A continuous grounding conductor can run along the tray length, or the tray itself can serve as the grounding path if it meets conductivity and mechanical strength requirements . For aluminum trays, insulated conductors are preferred to prevent electrolytic corrosion when connecting to copper EGCs .

Best Practices

• Ensure mechanical tightness and electrical continuity at all tray connections .
• Use properly sized grounding conductors according to NEC tables to handle fault currents .
• Maintain low grounding resistance (ideally 4 ohms or less) to ensure effective fault current dissipation .
• For trays carrying only signal or low-energy circuits, grounding is still recommended for lightning protection and EMI control . In summary, connecting cable trays to the grounding grid is essential for safety, code compliance, and system performance, and should be implemented using proper bonding techniques and materials to ensure continuous and reliable grounding throughout the installation .