Cable tray support for ground installation

Ground-mounted cable trays require stable support structures, proper spacing, corrosion-resistant materials, and compliance with NEC Article 392 for safe and reliable installations.

Types of Cable Trays Suitable for Ground Installation

For ground installations, ladder trays, ventilated troughs, and wire mesh trays are commonly used. Ladder trays are ideal for power cables due to excellent ventilation and easy cable anchoring, while ventilated troughs provide continuous support for smaller control or instrumentation cables, preventing sagging between rungs. Wire mesh trays are lightweight and flexible, suitable for light-duty or complex routing scenarios .

Support Structures

Ground-mounted trays require mechanical support elements such as:

• Pedestals or stanchions: Vertical supports anchored to concrete pads or footings.
• Support brackets: Adjustable brackets to secure trays at the correct height.
• Cross beams or rails: For wider trays, horizontal beams distribute the load evenly. Supports must withstand mechanical loads, environmental conditions, and potential external forces like wind or snow . Spacing between supports depends on tray type and load; for ladder trays, typical spans range from 1.5 to 3 meters (5–10 feet), while solid-bottom trays may require closer spacing to prevent sagging .

Material Selection and Corrosion Protection

For outdoor or ground-level installations, aluminum, galvanized steel, stainless steel, or FRP (fiberglass-reinforced plastic) are recommended. Aluminum and stainless steel resist corrosion, while FRP is non-conductive and ideal for chemically aggressive environments . Galvanized steel is cost-effective but may require periodic inspection for rust.

Grounding and Bonding

Metallic trays must be bonded and grounded according to NEC Article 392. Grounding ensures the tray can act as an equipment grounding conductor (EGC), providing safety against electrical faults . Non-metallic trays like FRP do not require grounding but may need additional measures for static discharge in sensitive environments.

Installation Considerations

• Maintain minimum clearances for maintenance access, typically 12 inches above the tray .
• Ensure proper tray fill: power cables ≤40% of cross-sectional area, control cables ≤50% .
• Use sunlight-resistant cables and expansion joints for outdoor trays to accommodate thermal expansion .
• Avoid placing trays in hoistways or enclosed spaces; they must remain accessible for inspection and maintenance .
• Secure cables with fire-rated ties if installed in plenum or high-risk areas .

Summary

Ground-mounted cable trays require careful planning of support spacing, material selection, grounding, and NEC compliance. Using pedestals, brackets, and corrosion-resistant materials ensures mechanical stability and long-term reliability. Proper installation not only protects cables but also facilitates maintenance and future expansion .