High-voltage and low-voltage cable trays should be installed with adequate horizontal and vertical spacing to ensure safety, minimize EMI, and allow maintenance access.

Horizontal Spacing

• Between parallel trays at the same height: Maintain a minimum distance of 0.6 meters to allow proper airflow, heat dissipation, and maintenance access .
• Between power (high-voltage) and signal/control (low-voltage) trays: A minimum separation of 0.5 meters is recommended to reduce electromagnetic interference (EMI) and maintain signal integrity .
• If trays are shielded: The separation can be reduced to 0.3 meters or less, as shielding contains EMI .

Vertical Spacing

• Floor-mounted or stacked trays: Maintain a minimum vertical clearance of 150 millimeters (6 inches) between trays to prevent obstruction, facilitate ventilation, and allow future cable additions .
• Above trays for installation and maintenance: NEC 392 recommends at least 12 inches (300 mm) of vertical clearance above the tray .

Support Spacing

• Standard trays: Supports (brackets or hangers) should be installed every 6 to 10 feet (1.8–3 meters) depending on the tray type and load .
• Heavy-duty or long-span trays: Can span up to 20 feet (6 meters) between supports, but always verify against the manufacturer's load capacity chart .
• Unsupported transitions: When moving cables from a tray to equipment or another raceway, the unsupported span should not exceed 6 feet (1.8 meters); otherwise, additional supports are required .

Additional Considerations

• Tray fill limits: Power cables should not exceed 40% of the tray cross-sectional area, while control cables can fill up to 50% .
• Cable fastening: Use listed cable ties or fasteners to secure cables without damaging insulation; avoid overtightening .
• Environmental factors: Material selection (aluminum, steel, FRP) should consider corrosion, moisture, and mechanical loads . By following these spacing and support guidelines, installations will maintain safety, proper heat dissipation, EMI reduction, and ease of maintenance, ensuring compliance with NEC and industry best practices.