Cables installed in cable trays can be exposed if they are rated for open-air use and protected from mechanical damage, with additional precautions required for outdoor or high-risk environments.

General Guidelines

Cables in cable trays are designed to be exposed and accessible for maintenance and inspection, as per NEC recommendations (Article 392 and 318-6) and industry standards . Only conductors rated for open-air environments, such as Tray Rated (Type TC) or Metal-Clad (Type MC) cables, should be used in exposed trays . Exposed installation allows for proper ventilation, heat dissipation, and easy access for inspection or modifications.

Protection Requirements

Even when exposed, cables must be secured and protected from mechanical damage. In areas with potential impacts, such as near forklifts, vehicles, or heavy equipment, additional protection like conduit or covers may be necessary . OSHA guidance recommends that exposed trays in high-risk areas be installed at a minimum height of 8 feet above grade and may include ventilated covers to prevent physical damage while allowing cooling .

Outdoor and Sunlight Exposure

For outdoor installations or areas exposed to sunlight, cables must be rated for UV resistance and manufactured with materials suitable for prolonged exposure . Using non-UV-resistant cables outdoors can lead to brittle insulation, electrical failures, and reduced lifespan. Proper installation, including expansion splice plates for thermal movement, helps maintain performance and safety .

Additional Considerations

• Separation of cables: High-power and low-power cables should be separated to prevent electromagnetic interference .
• Fill limits: Power cables should not exceed 40% of the tray's cross-sectional area, and control cables should not exceed 50% .
• Prohibited areas: Cable trays should not be installed in hoistways or enclosed spaces and must remain accessible .
• Conduit requirements: Conduit may be required for tray cables in underground, hazardous, or high-risk locations, or for runs longer than 6 feet outside the tray .

Summary

Exposed cable tray installations are permissible and common, provided that the cables are properly rated, secured, and protected from mechanical and environmental hazards. Compliance with NEC, OSHA, and manufacturer guidelines ensures safety, longevity, and reliable operation of the electrical system .