Requirements for the Dimensions of the Inclined Side of the Cable Tray

The dimensions of the inclined side of a cable tray must ensure proper cable support, maintain fill limits, and comply with NEC 392 and NEMA VE 1 standards.

General Guidelines

Inclined or sloped cable tray sections are used to transition cables between different elevations or to navigate around obstacles.

While NE

C Article 392 does not specify exact slope dimensions, the following principles apply: Slope Angle: Typically, cable trays are inclined at angles between 30° and 45° to maintain cable stability and prevent excessive stress on conductors. Steeper angles may require additional support or barriers to prevent cable slippage. Width and Depth: The tray width must accommodate the maximum cable fill as per NEC 392.

22. For power cables, fill should not exceed 40% of the tray's cross-sectional area, and for control or communication cables, 50% is allowed. The inclined section should maintain the same width and depth as the horizontal sections to ensure consistent support and prevent cable compression or bending.

Barriers and Separation: If single-core cables above 600 volts are installed, barriers must be used to separate them from lower-voltage cables. The barrier height should be comparable to the tray height and fabricated from the same material as the tray to maintain structural integrity and safety. Mechanical Support: Inclined sections must be supported at intervals consistent with the tray type and load.

Ladder trays, for example, require support spans according to NEMA VE 1 load/span tables to prevent sagging or deformation. Material Considerations: The tray material (aluminum, steel, or FRP) must be suitable for the environment and capable of supporting the cable weight along the incline without excessive deflection.

Installation Considerations

Accessibility: NEC 392. 10(A) requires that cable trays remain accessible for maintenance. Inclined sections should not obstruct access or violate clearance requirements.

Cable Handling: Avoid sharp bends at the top or bottom of the incline. Maintain a minimum bend radius for each cable type to prevent insulation damage. Grounding: Metallic inclined trays must be bonded and can serve as an equipment grounding conductor if installed according to NEC 392.

60.

Practical Recommendations

Maintain consistent tray width and depth along the incline. Use gradual slopes (30°–45°) to reduce cable stress. Install barriers for high-voltage single-core cables where required.

Support the tray at intervals specified by NEMA VE 1 for the given load. Ensure all materials and fasteners are UL-listed and compatible with the tray system. By following these guidelines, the inclined side of a cable tray will provide safe, compliant, and mechanically stable support for electrical conductors while maintaining NEC compliance and long-term reliability.