How to mark cable trays

Cable trays should be marked clearly with voltage, hazard warnings, and identification labels at regular intervals to ensure safety and compliance.

Key Marking Requirements

Voltage and Hazard Labels: Cable trays carrying conductors rated over 600 volts must be marked with “DANGER — HIGH VOLTAGE — KEEP AWAY” at intervals no greater than 10 feet. Labels must comply with NEC section 110.21(B) and follow ANSI Z535.4-2011 guidelines for font, color, symbols, and capitalization. Handwritten labels are not permitted except for variable information that may change over time . Identification Labels: Each tray should be labeled to indicate the type of cables it carries, such as power, control, or instrumentation. This helps in maintenance, troubleshooting, and ensures proper segregation of circuits . Material and Environmental Considerations: For outdoor or sun-exposed trays, use UV-resistant cables and mark trays to indicate sunlight resistance. Black or dark jackets are preferred for natural UV protection, and markings should reflect compliance with standards like UL 1277 for sunlight-resistant cables .

Practical Marking Tips

1. Measure and Mark Accurately: Use a tape measure and permanent markers or pre-printed labels to mark tray sections before installation. Ensure markings are visible from multiple angles .
2. Consistent Spacing: Place hazard and identification labels at regular intervals (e.g., every 10 feet for high-voltage trays) to maintain visibility along the entire tray length .
3. Use Durable Labels: Labels should be resistant to heat, moisture, and mechanical wear. Laminated or engraved tags are recommended for long-term durability.
4. Follow Standards: Ensure markings comply with local electrical codes, NEC, and any applicable international standards (e.g., IEC, CSA) for safety and inspection purposes .
5. Color Coding: Consider color-coded labels or tags to differentiate between power, control, and communication cables for easier identification and maintenance.

Summary

Proper marking of cable trays involves high-voltage warnings, cable type identification, and environmental compliance labels. Labels must be durable, standardized, and spaced appropriately to ensure safety, code compliance, and ease of maintenance. Regular inspection of markings is recommended to ensure they remain legible and effective over time.