Cable tray connection with mechanical equipment

Cable trays should be mechanically and electrically bonded to equipment using proper grounding, bonding clamps, and secure supports to ensure safety and compliance.

Mechanical Connection

When connecting a cable tray to mechanical equipment, the tray must be physically supported and anchored to prevent movement or stress on cables. Typical methods include:

• Direct attachment to equipment enclosures using brackets, threaded rods, or trapeze supports, ensuring the tray is level and stable .
• Use of factory fittings or splices to extend or transition trays to equipment while maintaining structural integrity .
• Material considerations: Aluminum trays should avoid direct contact with bare copper conductors to prevent electrolytic corrosion; insulated conductors or tin/zinc-plated connectors are recommended .

Electrical Bonding and Grounding

Cable trays often serve as the Equipment Grounding Conductor (EGC), but proper bonding is essential:

• Bonding clamps or mechanical connectors should be used to connect the tray to the equipment enclosure, ensuring low-resistance electrical continuity .
• Grounding practices: All metallic trays must be grounded according to NEC Article 250.96, regardless of whether the tray itself is used as the EGC .
• Insulated conductors may be required in aluminum trays to prevent corrosion, with insulation removed only at bonding points .
• Tray cross-sectional area must meet minimum requirements for the intended fault current rating to safely carry fault currents .

Compliance and Safety Considerations

• Ensure that UL classification is maintained; cutting or modifying trays may affect UL listing if the tray is intended as an EGC .
• Follow NEC and UL guidelines for bonding and grounding, particularly for high fault-current circuits or sensitive equipment .
• Maintain continuous electrical continuity along the tray path to reduce shock hazards and electromagnetic interference .

Best Practices

• Use mechanical connectors or bonding jumpers provided by the manufacturer for reliable connections .
• Verify that the tray and equipment connection does not introduce mechanical stress on cables.
• Ensure segregation of power and data cables when connecting trays to equipment to maintain EMC compliance .
• Regularly inspect connections for corrosion, loose fittings, or compromised grounding. By following these mechanical and electrical connection practices, cable trays can safely interface with mechanical equipment while maintaining compliance with NEC, UL, and EMC standards.