Cable tray systems serve as the backbone of modern electrical infrastructure, providing essential support, organization, and protection for cables in commercial and industrial applications. While high-quality tray systems are fundamental, selecting appropriate cable types and ensuring proper installation are equally critical for system reliability and safety. This article examines common cable types used in tray systems, with reference to relevant National Electrical Code (NEC) NFPA 70 requirements.
Imagine the electrical network of a skyscraper without cable trays - a chaotic tangle of wires compromising both aesthetics and safety. Cable trays function as the structural framework that organizes and protects cables, ensuring stable power transmission and signal integrity. Proper cable selection and code-compliant installation form the foundation of safe and reliable electrical systems.
Cables designed for tray systems undergo rigorous testing to ensure performance in demanding environments. These cables typically feature plastic jackets or metal armor protecting insulated conductors, with characteristics including weather resistance, corrosion protection, explosion-proofing, or electromagnetic interference shielding. All tray system cables must carry UL certification, verifying compliance with standards for flame resistance, mechanical strength, and temperature limitations.
Many tray-rated cables also pass crush and impact testing, qualifying for "Exposed Run" (ER) ratings that permit limited external routing (up to six feet) from trays when properly supported. Selection criteria should consider specific application requirements - for 600V motor power applications, either Tray Cable (TC) or Metal-Clad (MC) cable may be appropriate, provided they carry UL listing for tray use.
NEC Article 392.10(A) enumerates permitted cable types for tray systems and corresponding wiring methods, with cross-references to other NEC sections addressing specific cable applications. Article 392 additionally covers tray fill capacity, ampacity derating, splicing, and support requirements. Design professionals must consult both NEC provisions and manufacturer specifications to ensure full compliance.
While less common, NEC 392.10(A) also permits tray installation of Type AC, CATV, NM, and other specialty cables. As with primary cable types, installers must consult relevant NEC articles for proper implementation methods. The section additionally allows certain raceway types (EMT, RMC, PVC conduit) in trays, though these are typically more economically installed using conventional support methods.
