No bridging in the cable tray section

The absence of bridging in a cable tray section can compromise both mechanical support and electrical grounding, potentially leading to sagging, cable displacement, and safety hazards.

Mechanical Implications

Cable trays function like bridges for electrical conductors, supporting cables across open spans. Without proper bridging or connection between tray sections, the system may experience sagging, bending, or misalignment, especially over long spans or under heavy cable loads. This can place excessive tension on cable terminations, reduce airflow, and increase the risk of mechanical damage to cables.

Ladder-type trays, in particular, require intermediate supports and secure connections to maintain structural integrity.

Electrical Grounding Concerns

Metallic cable trays often serve as equipment grounding conductors (EGC). Bridging or bonding between tray sections ensures a continuous electrical path, which is critical for fault current dissipation. Without bridging, the tray may not provide a reliable grounding path, increasing the risk of electrical shock, arcing, or fire hazards.

NE

C Article 392 allows metallic trays to act as EGCs if they meet minimum cross-sectional area requirements, but proper bonding between sections is recommended to maintain safety.

Best Practices

Use Grounding Clamps or Bonding Jumpers: Even if not strictly required by NEC, bonding each or alternate tray section with a grounding clamp ensures both electrical continuity and mechanical anchoring of the EGC. Insulated Conductors for Aluminum Trays: To prevent electrolytic corrosion, use insulated conductors with exposed ends at bonding points when connecting to aluminum trays. Proper Tray Supports and Accessories: Employ cable tray spacers, clamps, and trapeze brackets to maintain alignment, prevent sagging, and secure cables in place.

Regular Inspection: Check for loose connections, misaligned sections, or missing bridging during installation and maintenance to ensure compliance and safety.

Conclusion

No bridging in a cable tray section can lead to mechanical instability and compromised grounding, increasing the risk of cable damage and electrical hazards. Implementing proper bonding, using appropriate accessories, and following NEC guidelines ensures both structural integrity and electrical safety in cable tray installations.