No, cable trays do not have to be enclosed; they are designed as open support systems, though covers can be used for protection in certain situations.

Open vs Enclosed Cable Trays

Cable trays are support structures for electrical and communication cables and are distinct from raceways, which are fully enclosed conduits. According to NEC Article 392, cable trays are typically open on at least one side, allowing air circulation and easy access for installation and maintenance, and they are not required to be fully enclosed . The open design is intentional to accommodate tray-rated cables that are durable enough for exposure to air and environmental conditions.

Cable Types and Safety

Only tray-rated cables (Type TC) or metal-clad cables (Type MC) are permitted in open cable trays because these cables are designed to withstand heat, mechanical stress, and exposure to air . Using non-rated cables in open trays can lead to safety hazards such as overheating or insulation damage.

When Covers Are Recommended

While not mandatory, covers can be added to cable trays in specific scenarios:

• High-traffic areas where tools or objects might fall onto the cables
• Outdoor installations to protect cables from sunlight or weather
• Areas requiring additional mechanical protection Covers do not make the tray a raceway; they simply provide extra protection while maintaining compliance with NEC standards .

Summary

• Cable trays are not required to be enclosed; they are open by design.
• Only approved tray-rated or metal-clad cables should be used.
• Covers are optional and used for protection in certain environments.
• Open trays allow ventilation, easy maintenance, and compliance with NEC Article 392 . This approach ensures safety, accessibility, and proper cable management without the need for full enclosure.