Construction of enclosed cable trays

Enclosed cable trays are constructed by selecting the appropriate tray type, preparing structural supports, assembling the tray sections, and securely routing and protecting cables according to code requirements.

Material Selection and Tray Type

Enclosed cable trays are typically made from steel, aluminum, or stainless steel, chosen based on environmental conditions, mechanical strength, and corrosion resistance . They can have solid or ventilated bottoms, with solid covers providing protection against dust, moisture, and electromagnetic interference, making them suitable for sensitive instrumentation and control applications . The choice of tray type depends on cable types, load, and aesthetic or safety requirements.

Structural Support and Layout

Before installation, a support system is designed to maintain proper spacing and alignment. Supports may include brackets, hangers, or threaded rods, and must account for tray weight, cable load, and bending radii . Typical rung spacing for enclosed trays ranges from 150 to 230 mm (6–9 inches) to ensure cables remain in place and avoid sagging . Accurate measurements and layout planning are critical, especially in areas with uneven ceilings or obstacles.

Assembly and Installation

1. Cutting and Preparing Sections: Tray sections are measured and cut to fit the planned route, including bends, tees, and transitions .
2. Joining Sections: Sections are connected using bolts, clamps, or welding, ensuring a continuous, rigid structure .
3. Securing to Supports: The tray is mounted to the pre-installed supports, maintaining level alignment and proper spacing from walls or ceilings .
4. Cover Installation: Solid or ventilated covers are attached to protect cables from environmental hazards and maintain safety compliance .

Cable Routing and Fill

Cables are carefully routed through the tray to prevent abrasion, overheating, or interference. Proper cable fill calculations are performed according to NEC 392.22 to ensure the tray is not overfilled, which could reduce ampacity or damage conductors . Cables are tied or secured at intervals to maintain organization and prevent movement.

Grounding and Bonding

Enclosed cable trays must be bonded and grounded to prevent electrical hazards. Connections between tray sections and to the building grounding system are made using approved bonding conductors and hardware . This ensures safety and compliance with electrical codes.

Final Inspection

After installation, the system is inspected for alignment, secure fastening, proper fill, and grounding continuity. Any adjustments are made to ensure compliance with safety standards and manufacturer specifications . By following these steps, enclosed cable trays provide a safe, organized, and durable pathway for electrical and instrumentation cables in commercial and industrial installations.