Tray cables are the assembly of two or more insulated conductors for installation in cable trays. Generally, the cables which are used in cable tray systems are the quality products that have been tested to stand against the severity of extreme environments.
The cables can be used for various locations as rated by the manufacturers. It includes indoors, outdoors, corrosive areas, for rather dangerous sites, or areas with high electrical noise. The article is intended to understand the different kinds of tray cables permitted in cable trays, as mentioned under the guidelines of National Electrical Code (NEC) NFPA 70.
Here is the list of frequently used tray cables.
Tray Cable (Type TC)
It is a factory setup of two or more insulated conductors which can be used with or without associated bare or covered grounding conductors. The cables are covered under non-metallic jackets. These are most commonly used in industrial power or control circuits. It is rated for 600 volts and best suited in conditions with extreme heats.
Power Limited Tray Cable (PLTC)
PLTC cables are best suited for hazardous locations, including sunlight exposure. It is rated for 300 volts and used in computer interconnects, burglar alarms, intercom systems, cash registers, Power Limited Circuits, and a lot more.
Instrumentation Tray Cable (Type ITC)
ITC cables are most commonly used in industrial structures. It can be installed in various establishments, including raceways, hazardous locations, direct burial, under raised floors in rooms containing industrial equipment and others. It is available in different variants like shielded & unshielded construction with multiple conductors, twisted pairs, and others. They have a 300-volt insulation rating and specially designed for use with power limiting structures.
Metal Clad Cables (Type MC)
MC cables are the assembly of one or more insulated circuit conductors, which are wrapped in a shield of interlocking metal tape. They are rated for 600 volts power transmission and widely used in MV power, lighting, and control applications. It may be installed indoors or outdoors, both wet and dry locations, cable tray, direct burial, and other conditions.
Mineral Insulated (Type MI)
MI cables are the factory assembly of one or more conductors insulated with a highly compressed mineral insulation, which is typically made up of magnesium oxide. It is commonly used in high-temperature environments such as alarm circuits, fire pumps, and smoke control systems. These are suitable for both 300 volt and 600-volt applications.
Optical Fiber Cables (Type OFC, OPC)
OFC uses the technology related to the transmission of information as light impulses along a glass fiber. It is more efficient in passing information in comparison to copper wires as it is far less subject to electromagnetic interference. It works best in long distances and provides high-speed data communication.
Communication Cables (Type CMP)
Just like optical fiber, communication cables are also used to send information signals. It is done with the help of coaxial conductors, copper conductors, or twisted wire pairs. These are widely used in recording studios, data transmission, intercoms, copper conductors, or twisted wire pairs.
Fire Alarm Cables (Type NPLF)
Fire alarm cables are classified into two categories, namely power-limited or non-power limited. If the cables are rated as CI from the manufacturers, it indicates that they have met the requirements and ensures the continuous operation of circuits under fire conditions.
Tray cable plays a vital role in understanding the cable distribution and management in any significant establishment or structure. The basic knowledge of different kinds of tray cables eventually helps in understanding the proper use and installation of cable tray systems.