National cable tray standards like NEMA and UL define material, load, and installation requirements, while non-standard or international standards like IEC 61537 provide globally recognized guidelines with different testing and classification approaches.

National Standards

NEMA (National Electrical Manufacturers Association) provides key standards for cable trays in the U.S.:

• NEMA VE 1: Covers metal cable trays including ladder, ventilated, solid bottom, channel, and wire mesh types. It specifies manufacturing requirements, load/span classifications, and installation guidelines in accordance with the National Electrical Code (NEC) rules .
• NEMA FG 1: Previously covered nonmetallic (fiberglass) cable trays, including ladder, trough, and solid bottom types. It has been rescinded but still serves as a reference for fiberglass tray design .
• UL 568: Focuses on performance and safety requirements for fiberglass cable trays, ensuring compliance with electrical and mechanical standards .
• NEC (NFPA 70): Provides installation requirements, including ampacity considerations for conductors in cable trays (Article 310), .
• CEC (Canadian Electrical Code, C22.1-Part 1): Governs installation and maintenance of electrical equipment in Canada, including cable tray systems . These standards emphasize load testing, material quality, and safe installation practices, but NEMA does not prescribe minimum thickness; instead, trays must pass load tests at specified spans .

Non-Standard / International Standards

IEC 61537 is the international benchmark for cable tray systems:

• Applies to metallic and nonmetallic trays, including wire mesh, ladder, and solid bottom types .
• Specifies construction, mechanical strength, corrosion resistance, electrical continuity, fire resistance, ventilation, and fill ratio .
• Includes testing protocols for load capacity and environmental durability, with recent revisions (2023) adding corrosion classifications and use as protective earth conductors .
• BS EN 61537 aligns with IEC 61537 but includes UK-specific guidance and deviations . Unlike NEMA, IEC standards are more prescriptive, providing thickness tables and detailed classification systems. Compliance ensures global compatibility, safety, and performance consistency across installations.

Key Differences Between National and Non-Standard Standards

• Design Philosophy: NEMA focuses on load-based testing, while IEC/BS uses prescriptive thickness and corrosion classifications .
• Scope: National standards often cover installation and code compliance (NEC, CEC), whereas IEC addresses global performance, testing, and environmental factors .
• Material and Testing: Fiberglass trays may retain more strength at elevated temperatures than older NEMA FG 1 guidelines suggest, highlighting differences in testing protocols .
• Documentation: NEMA and UL provide class designations and load ratings, while IEC/BS emphasizes system-wide compatibility, fittings, and accessories .

Practical Considerations

• Project Location: Use national standards (NEMA, UL, NEC, CEC) for domestic projects; IEC/BS for international or export projects .
• Load and Span: Verify whether the specification is based on rated load (NEMA) or safe working load (IEC/BS) .
• Material Selection: Consider aluminum, steel, stainless steel, or fiberglass based on environmental conditions and corrosion resistance .
• Compliance Verification: Always check manufacturer test data and certifications to ensure adherence to the relevant standard . In summary, national standards provide code-compliant, load-tested guidance for domestic installations, while non-standard or international standards offer prescriptive, globally recognized criteria for performance, safety, and environmental durability. Understanding both is essential for engineers and contractors to ensure safe, reliable, and compliant cable tray installations.