Cable trays containing conductors rated over 600 volts must be labelled with “DANGER — HIGH VOLTAGE — KEEP AWAY” at intervals not exceeding 10 feet, following NEC and ANSI guidelines.

Key Labelling Requirements

Voltage Thresholds: Cable trays that carry conductors rated over 600 volts require hazard markings. Trays with conductors rated 600 volts or less do not require this specific danger label . Label Wording and Visibility: The label must read “DANGER — HIGH VOLTAGE — KEEP AWAY” and be permanent, legible, and placed in a readily visible position on all applicable cable trays . Labels cannot be handwritten except for variable information that changes over time. Spacing: Warning labels must be placed at intervals not exceeding 3 meters (10 feet) along the cable tray . Design Compliance: Labels must comply with NEC 110.21(B) and follow ANSI Z535.4-2011 standards for product safety signs and labels. This includes specifications for font type and size, color, capitalization, symbols, and the order of information . Exceptions: In industrial establishments, if the cable tray is inaccessible and maintenance conditions ensure that only qualified personnel service the installation, labels may be placed where necessary to ensure safe operation and maintenance .

Additional Considerations

• Material and Environment: While labelling is primarily a safety requirement, cable tray materials (metallic or nonmetallic) and environmental conditions may influence label durability and placement. Labels should withstand environmental factors such as heat, moisture, and chemical exposure .
• International Standards: IEC 61537 provides guidance on cable tray systems, including installation and safety considerations, which may complement NEC requirements in international projects .
• Maintenance and Inspection: Labels should be checked periodically to ensure they remain legible and intact, especially in high-traffic or industrial environments . By following these requirements, electrical installations maintain compliance with safety codes, reduce the risk of electrical hazards, and ensure that personnel are adequately warned of high-voltage conductors within cable trays.