How to Select Cable Tray

Image Credit: Rittal Corporation | Legrand

Cable trays are used typically as raceways for cables and wires. A cable tray system supports and protects both power and signal cables and allows cabling networks to be upgraded, reconfigured, or relocated. Use of a cable tray roller can reduce pulling stress on cables, shear load on cable trays, and overall installation time. The amount of cable tray wire that can be installed in a cable tray varies with the type of cable (e.g., twisted pair, coaxial, and fiber optic).

Cable Tray Designs

Cable tray systems can have several designs, including ladder, solid bottom, channel, trough, wire mesh, and single rail. A metallic cable tray is made of steel or aluminum.

Cable Tray Material

A non-metallic cable tray can be made of polyvinyl chloride (PVC) or fiberglass. PVC cable trays are an aluminum cable tray or a steel cable tray with PVC coating. A wire mesh cable tray provides a field-adaptable system for low voltage, telecommunication and fiber optic cables.

Selection Criteria

Considerations for cable trays include environmental conditions (ice, wind, snow,), corrosion requirements, and weight of the installed cable. Other considerations for cable trays include the type and number of cables to support, the bending radius of the cable, able entry / exit freedom, installation design, expandability, heat generated, and length of support spans.

Regulation Standards

• The National Electrical Manufacturers Association (NEMA) publishes several documents regarding cable trays.
  • NEMA VE1 covers general cable tray definitions, manufacturing standards, performance standards, test standards, and application information.
  • NEMA VE2 is a cable tray installation guideline.
  • NEMA FG1 covers fiberglass cable tray systems.
• Articles 250, 318, 392, and 800 of the National Electrical Code (NEC) also cover various aspects of cable trays.
• An electrical cable tray can be UL-classified if it is used as an equipment grounding conductor. Underwriters Laboratory (UL) and American National Standards Institute (ANSI) maintain ANSI/UL 568 for nonmetallic cable tray systems. A fiberglass cable tray can meet ASTM D-635 (flame rating and self-extinguishing requirements) and ASTM E-84 (smoke density rating).

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