Yes, electrical wires can be run through cable trays, provided they are properly rated, installed according to NEC Article 392, and separated as required for safety and performance.

Cable Tray Overview

Cable trays are open support systems made of metal or plastic, designed to organize and support electrical conductors in commercial, industrial, and large residential installations . Unlike conduits, cable trays are not fully enclosed, so the wires inside must be rated for open-air exposure.

Approved Cable Types

Only certain types of cables are suitable for cable trays:

• Tray-rated cables (Type TC) or metal-clad cables (Type MC) are required for open-air installations .
• THHN/THWN wires can be used if installed according to their temperature and location ratings, with THWN suitable for wet areas .
• Cables must be durable, heat-resistant, and protected against abrasion, especially in high-traffic or outdoor areas .

Installation Guidelines

• Clearances: Maintain at least 12 inches of vertical clearance above trays for installation and maintenance .
• Fill Limits: Power cables should not exceed 40% of the tray's cross-sectional area; control cables can fill up to 50% .
• Separation: High-power and low-power cables must be separated to prevent electromagnetic interference (EMI), .
• Grounding: Metallic trays can serve as equipment grounding conductors if properly bonded .
• Covers: Optional but recommended in high-traffic areas or outdoor installations to protect cables from physical damage and sunlight .

Restrictions

• Cable trays cannot be used in hoistways or enclosed spaces and must remain accessible for maintenance .
• Mechanical piping, water, or air tubing cannot share the tray with electrical cables .
• Nonmetallic trays are limited to corrosive environments or where voltage isolation is required .

Practical Considerations

• Cable trays can be installed horizontally or vertically without affecting fill limits .
• Outdoor trays require sunlight-resistant cables and expansion splice plates to accommodate thermal expansion .
• Proper installation ensures long-term reliability, reduces fire risk, and facilitates future maintenance . In summary, running electrical wires through cable trays is a standard and safe practice when using approved cables, following NEC Article 392, and adhering to spacing, grounding, and separation requirements. This approach provides organized, accessible, and code-compliant wiring infrastructure.