National Standard Specifications for Fiberglass Cable Trays

Fiberglass cable trays are governed primarily by NEMA FG-1, UL 568, and the National Electrical Code (NEC), which define manufacturing, performance, and installation requirements. Key StandardsNEMA FG-1 specifies the manufacturing requirements for nonmetallic (fiberglass) cable trays, including ladder, ventilated trough, solid bottom, and channel types, along with associated fittings. It ensures compliance with the National Electrical Code (NEC) for safe electrical installations and provides guidance on load/span designations and material properties.

U

L 568 is the Underwriters Laboratories standard that covers performance requirements for fiberglass cable trays, ensuring they meet safety and durability criteria for electrical installations.

NE

C (NFPA 70) provides installation requirements for cable tray systems, including ampacity calculations, conductor fill, and proper support spacing. Article 318 and Article 310 are particularly relevant for fiberglass cable trays, addressing cable fill and ampacities. Canadian Electrical Code (CEC C22.

1-Part 1) applies in Canada, specifying installation methods, conductor ampacities, and cable tray requirements for nonmetallic systems.

Installation Guidelines

Support Spacing: Each tray section should be supported at intervals equal to or greater than the support span, with splices ideally located at quarter spans. Fastening: Thread rod nuts should be torqued to 3–4 ft.-lbs., and all-thread rods must be fully engaged in clamps for load safety. Cutting and Drilling: Fiberglass can be cut with a circular saw or hack saw and drilled like hardwood.

Any exposed surfaces must be sealed with compatible resin to maintain integrity. Load Safety Factor: A design load safety factor of 3: 1 is recommended for fiberglass cable tray systems.

Material and Performance Considerations

Fiberglass trays are manufactured using pultrusion processes with polyester or vinyl ester resins, providing high strength-to-weight ratios and excellent corrosion resistance. They are suitable for harsh environments where metal trays may corrode. Carbide-tipped tools are recommended for large-scale cutting or drilling operations to prevent chipping.

Summary

For compliance and safe installation of fiberglass cable trays in the U. S., NEMA FG-1 and UL 568 define the manufacturing and performance standards, while the NEC governs installation practices. Proper support, fastening, and handling are critical to maintain structural integrity and electrical safety.

For Canadian installations, the CEC provides equivalent guidance.