Posted on: 03 Dec, 2021
Types of Cable Typically Used in Cable Tray
The purpose of a cable tray system is to support, route, and protect cable as part of the cable management system. Through NEMA and the Cable Tray Institute numerous articles, standards, and other general guidance can be found regarding the proper use and installation of cable tray systems.
The cable tray system is only one component of the cable management system. Another important component is obviously the cable. Therefore, it is also important to understand how to properly apply and install the cables in a cable tray system. To that end, this Bulletin is intended to discuss the types of cables most frequently used in cable trays and the wiring methods permitted in cable trays under the National Electric Code (NEC) NFPA 70.
In general, tray-rated cables are quality products that have been tested to withstand the rigors of severe environments. They are protected by either a plastic Jacket or metal Armor over individual conductor insulations. They can be rated for outdoor, indoor, corrosive areas, hazardous locations, or high electrical noise areas. They should be UL listed indicating they have been tested for ratings relative to flammability resistance, mechanical resistance, and temperature limitations. Many cable tray-rated cables include a crush and impact test as part of the listing and are rated as exposure rated (ER). ER cable is allowed to leave the cable tray for distances up to six feet, as long as it is supported and secured.
In many cases there is more than one type of cable for a particular application, for instance, both cables rated as tray cable (TC) and cables rated as metal-clad (MC) can be used for 600- volt motor power cables. In all instances, cables utilized within a cable tray system should be UL listed and marked as cable tray rated.
The types of cables, allowed in cable trays, and the wiring methods permitted in cable trays can be found in NEC Section 392.10 (A). This Section also lists various corresponding NEC Articles which describe the conditions of use and installation requirements for a particular class or type of cable. Additional considerations such as fill capacity, allowable ampacity, cable splicing within trays, and securing and supporting cables are addressed in Article 392. Users should be familiar with all these Articles and check the manufacturer’s specifications, to verify selected cables meet all application requirements and NEC requirements.
The most frequently used cable tray are:
Tray Cable – type TC
Power Limited Tray Cable – type PLTC
Instrumentation Tray Cable – type ITC