Are there cable trays above the low-voltage electrical shaft How are they installed

Cable trays are commonly installed above low-voltage electrical shafts, with high-voltage or power trays positioned on top and low-voltage or instrumentation trays below to minimize interference.

Typical Placement

In industrial and commercial installations, high-voltage or power cable trays are usually installed above low-voltage or control cable trays. This layered arrangement reduces electromagnetic interference (EMI) from power cables affecting sensitive low-voltage instrumentation or communication lines . A minimum vertical separation of 300 mm (12 inches) is recommended between power and control trays, and metal dividers can be used if space is limited . Low-voltage cables, such as data, signaling, or control circuits, are therefore typically routed in trays below the main electrical shaft.

Installation Practices

Support and Mounting: Cable trays are supported by brackets, hangers, or threaded rods attached to walls, ceilings, or structural beams. Supports are spaced according to tray type and load, often every 1.5 to 3 meters for ladder or ventilated trays . Tray Types:

• Ladder trays allow air circulation, keeping cables cool, and are preferred for heavy power cables .
• Solid-bottom trays are used where EMI shielding is needed or aesthetics are important .
• Channel or wire-mesh trays are suitable for light instrumentation and control cables . Cable Securing: Cables are fastened to the tray at intervals using listed cable ties or clamps. For non-horizontal runs, cables are secured to transverse members to prevent sagging or stress at entry points . Fill Limits and Separation: Power cables should not exceed 40% of tray cross-section, and control or low-voltage cables should not exceed 50%. Cables of different voltages may share a tray if rated 600V or less; otherwise, a solid barrier or Type MC cables are required . Grounding: All metallic trays must be grounded according to NEC Article 250.96, either via a separate equipment grounding conductor or integrated within multiconductor cables . Routing Considerations: Trays should follow the shortest practical path, avoid unnecessary bends, and prevent crossovers. Multi-level layouts or bridges are used when trays intersect .

Summary

Yes, cable trays are typically installed above low-voltage electrical shafts, with careful attention to vertical separation, EMI mitigation, proper support, and compliance with NEC standards. Using ladder, solid, or wire-mesh trays depending on cable type, securing cables properly, and maintaining fill limits ensures safe, efficient, and maintainable installations .