Cables from the cable trays in the enclosure

Cable trays in enclosures provide organized, safe, and accessible routing for electrical, control, and communication cables while supporting grounding and protection requirements.

Purpose and Function

Cable trays are used inside enclosures to support insulated electrical cables for power distribution, control, and communication, offering an alternative to conduits or open wiring systems. They allow for easy installation, maintenance, and future expansion, as new cables can be laid in the tray without dismantling the enclosure. Inside enclosures, cable trays help maintain spacing, prevent cable damage, and manage heat buildup, especially when equipped with solid or ventilated covers.

Types of Cable TraysSolid-bottom trays: Provide maximum protection against dust, debris, and mechanical damage but require fittings or cutouts for cable entry/exit. Ventilated trays: Feature slots or holes for air circulation, water drainage, and dust fall-through, suitable for heat-sensitive environments. Ladder trays: Support cables on rungs at regular intervals (100–300 mm), ideal for heavy or large bundles of power cables.

Channel trays: Economical for small cable runs or branch connections, often used where conduit is undesirable. Wire mesh or basket trays: Lightweight and flexible, suitable for numerous small cables like data or instrumentation lines.

Installation Considerations

Mounting: Cable trays are supported using brackets, suspended supports, or center suspensions attached to walls, ceilings, floors, or structural beams. Fittings: Horizontal/vertical bends, T-pieces, crossovers, and end closures allow routing changes and proper cable entry/exit. Spacing: Maintain proper rung spacing (150–230 mm) to support cables and prevent sagging.

Covers: Solid or ventilated covers protect cables from dust, debris, and mechanical impact; peaked covers are recommended outdoors or in dusty environments.

Material Selection

Cable trays can be made from steel, stainless steel, aluminum, or pultruded fiberglass, chosen based on mechanical strength, corrosion resistance, and environmental conditions. Aluminum offers excellent corrosion resistance due to its natural oxide layer, while stainless steel (AISI 316L) provides high resistance to corrosion and stress cracking.

Grounding and Bonding

Metallic cable trays can serve as the Equipment Grounding Conductor (EGC) if installed by qualified personnel. Key practices include: Bonding each or alternate tray sections using grounding clamps to maintain electrical continuity. Avoid placing bare copper conductors in aluminum trays to prevent electrolytic corrosion; insulated conductors with proper bonding connections are preferred.

Ensure compliance with local electrical codes (e.g., NEC Article 250. 96 in the U. S.) for grounding and bonding.

Summary

Using cable trays in enclosures ensures organized cable management, mechanical protection, heat dissipation, and compliance with safety standards. Selection of tray type, material, mounting, and grounding practices should be based on cable type, environmental conditions, and regulatory requirements, providing a safe and maintainable electrical system.