Classification and Use of Cable Trays in Low Voltage Wiring Shafts

Low-voltage cable trays should be organized with proper separation, spacing, and routing to ensure safety, minimize interference, and facilitate maintenance.

Separation and Layering

In low-voltage shafts, it is critical to separate power and low-voltage/instrumentation cables. Typically, power cables are installed on top, while low-voltage and instrumentation cables are routed below. This layered arrangement reduces electromagnetic interference (EMI) and preserves signal integrity for sensitive control and communication systems . Where space is limited, metal dividers or partitions can be used to maintain separation and prevent interference .

Spacing and Segregation

Industry standards recommend a minimum vertical and horizontal spacing of 300 mm (12 inches) between power and low-voltage trays . This spacing helps reduce EMI and allows for easier maintenance. In dense installations, segregated trays or separate channels for different cable types are preferred to avoid cross-talk and overheating .

Tray Types and Materials

Cable trays come in various types suitable for low-voltage applications, including ladder, ventilated trough, wire mesh, and solid-bottom trays . Material selection depends on the environment:

• Galvanized or stainless steel for corrosion resistance
• Aluminum for lightweight and moderate corrosion environments
• Fiberglass for chemical or highly corrosive areas

Routing and Layout

Cable trays should follow straightforward, shortest practical paths between equipment to minimize bends and junctions, reducing material costs and voltage drop . Rung spacing of 150–230 mm (6–9 inches) is recommended for low-voltage and instrumentation cables to provide adequate support without excessive bending . Avoid sharp bends and maintain the minimum bend radius for each cable type to prevent damage .

Installation Orientation

While horizontal tray orientation is standard, edge-wise or vertical rung orientation is permissible if supported by manufacturer guidelines and local electrical inspectors . This orientation can reduce dust accumulation and may be advantageous in certain industrial environments.

Compliance and Standards

Cable tray installations should comply with NEC Articles 318, 250, and 800, as well as NEMA VE1, VE2, and FG1 for fiberglass systems . Proper earthing, electrical continuity, and fire resistance must be ensured according to manufacturer specifications and local regulations .

Best Practices

• Maintain consistent labeling and color coding for low-voltage cables.
• Use covers or enclosed trays in areas with high dust or mechanical risk.
• Plan for future expansion by leaving extra tray capacity.
• Ensure adequate support spans (typically 12–30 feet) to prevent sagging . By following these principles, low-voltage cable trays in shafts can achieve safe, organized, and interference-free installations that are easy to maintain and compliant with industry standards.