Should cable trays and supports be grounded

Yes, all metallic cable trays and their supports must be grounded to ensure electrical safety and compliance with NEC standards.

NEC Requirements and Safety Rationale

Metallic cable trays are required to be grounded according to NEC Article 250. 96 and Article 392, regardless of whether the tray is used as an equipment grounding conductor (EGC) itself. Grounding ensures that any fault current or electrical leakage is safely directed to the earth, reducing the risk of electric shock, equipment damage, and fire hazards.

Proper grounding also minimizes electrical noise and interference, which is critical in environments with sensitive electronic equipment.

Methods of Grounding

Tray as EGC: In some installations, the metallic tray itself can serve as the EGC if it meets cross-sectional area requirements and is electrically continuous across sections. Steel trays are limited to circuits with ground-fault protection up to 600 amperes, while aluminum trays can handle up to 2,000 amperes. Separate Grounding Conductor: A separate EGC (minimum #4 AWG) can be installed inside or attached to the tray.

This conductor is bonded to each tray section using grounding clamps or bonding jumpers to maintain electrical continuity. Bonding Jumpers: Where mechanical connections alone do not ensure continuity, flexible bonding jumpers are used to connect tray sections, supports, and conduit drops back to the main grounding system. Both side rails of ladder or trough trays should be bonded together to the next section to maintain a reliable path for fault currents.

Supports and Non-

Metallic Trays

Supports: Metallic supports for cable trays must also be bonded to the grounding system to ensure the entire tray assembly is electrically continuous.

Non-

Metallic Trays: Non-metallic trays cannot serve as grounding conductors. In such cases, a separate EGC must be provided within or alongside the tray.

Best Practices

Use insulated conductors when bonding to aluminum trays to prevent electrolytic corrosion. Ensure all tray sections are mechanically tight and electrically continuous. Verify grounding conductor sizing according to NEC tables to handle potential fault currents.

For installations with sensitive electronics or telecommunications circuits, additional grounding for EMI and lightning protection may be required. In summary, grounding metallic cable trays and their supports is mandatory for safety, regulatory compliance, and system reliability. Proper bonding, conductor sizing, and continuity checks are essential to maintain an effective grounding system.