Cable tray supports must be grounded
Yes, all metallic cable tray supports must be grounded to ensure electrical safety and compliance with NEC standards.
NEC Requirements
According to the National Electrical Code (NEC) Article 250.96 and Article 392, all metallic cable trays must be grounded, regardless of whether the tray itself is used as an equipment grounding conductor (EGC) or not . Grounding provides a safe path for fault currents, reducing the risk of electric shock, fire, or equipment damage .
Methods of Grounding
- Separate Grounding Conductor: A dedicated EGC (minimum size #4 AWG) can be installed inside or attached to the tray to bond all sections together .
- Cable Tray as EGC: In qualifying installations, the tray itself can serve as the EGC if it meets minimum cross-sectional area requirements for steel or aluminum trays . Steel trays are limited to circuits with ground-fault protection up to 600 amperes, while aluminum trays can handle up to 2,000 amperes .
- Bonding Clamps and Jumpers: Grounding clamps or bonding jumpers are used at tray joints, splices, and where the tray connects to equipment to ensure electrical continuity .
Safety Considerations
- Material Compatibility: Avoid using bare copper conductors in aluminum trays to prevent electrolytic corrosion; insulated conductors with exposed bonding points are preferred .
- Electrical Continuity: All tray sections must be electrically continuous, even if mechanical continuity is not required .
- Low Resistance: Grounding systems should maintain low resistance (ideally 4 ohms or less) to ensure effective fault current diversion .
Additional Notes
- Metallic trays carrying only low-energy signal or communication circuits may not require power grounding, but grounding is still recommended for lightning protection, EMI reduction, and noise control .
- Proper grounding improves system stability and ensures compliance with safety regulations, protecting both personnel and equipment . In summary, grounding cable tray supports is mandatory for metallic trays, either through a separate EGC, the tray itself, or bonding jumpers, following NEC guidelines and best practices for electrical safety.
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