Which type of cable should be used for laying in cable trays

Cable trays are used to support a variety of cables including power, control, instrumentation, telecommunication, and fiber optic cables, all of which must be rated for tray use.

Common Cable Types

1. Tray Cable (TC)
   • Purpose: Power and control circuits in industrial and commercial settings.
   • Construction: Factory-assembled with two or more insulated conductors, optionally including bare or covered grounding conductors, under a non-metallic jacket.
   • Voltage Rating: Typically 600 volts.
   • Special Features: Flame retardant, UL listed, and suitable for Class 1, Division 2 hazardous locations. TC cables can be used in cable trays, raceways, and outdoor locations if supported by a messenger wire. Type TC-ER (exposure-rated) cables can extend up to six feet outside the tray if properly supported and secured .
2. Instrumentation Tray Cable (ITC)
   • Purpose: Instrumentation and control applications.
   • Construction: Multiple single conductors or twisted pairs, available in shielded or unshielded forms, sometimes with metal armor.
   • Applications: Used in control rooms, industrial panels, and areas requiring precise signal transmission .
3. Metal-Clad (MC) Cables
   • Purpose: Power distribution and motor circuits.
   • Construction: Insulated conductors enclosed in a metallic sheath for mechanical protection.
   • Applications: Can be used in cable trays for 600-volt motor power circuits, often alongside TC cables .
4. Fiber Optic and Telecommunication Cables
   • Purpose: Data transmission and communication networks.
   • Considerations: Often installed in solid-bottom or wire mesh trays to protect against electromagnetic interference (EMI) and physical damage .

Installation Considerations

• Code Compliance: All cables must be UL listed and marked as cable tray rated, following NEC Section 392.10 and related articles.
• Support and Securing: Cables should be supported at intervals not exceeding six feet and secured to prevent sagging or damage.
• Environmental Factors: Selection of cable type may depend on exposure to moisture, temperature, or potential mechanical impact. Solid-bottom trays are preferred for sensitive signal cables to prevent EMI, while ladder trays are ideal for heavy power cables due to ventilation and heat dissipation .

Summary

Cable trays provide a structured, safe, and accessible method for routing multiple types of cables. Power, control, instrumentation, telecommunication, and fiber optic cables are commonly laid in trays, with the specific type chosen based on voltage, shielding, environmental exposure, and NEC compliance. Proper selection ensures safety, performance, and ease of maintenance .