Instrument Tray Cable

Sept. 2, 2014
Why you have to know what you’re doing when specifying ITC cable

Article 727 of the National Electrical Code (NEC) addresses instrument tray cable (ITC) and its permitted uses. In industrial locations, ITC cable is commonly used for instrumentation circuits in association with distributed control systems (DCSs). ITC cable is a perfect wiring method for these low-voltage, low-power installations. The typical DCS system will have I/O at a max of 24V. The I/O cards within the DCS system usually limits the power to the parameters set forth in Sec. 727.5.

The insulation level on ITC cable is rated for 300V, although the voltage level won’t be indicated on the cable jacket (Sec. 727.7). The voltage rating isn’t marked on the cable jacket because it could be confusing —some users might have a cable marked 300V and think it’s okay to apply 240V or 277V, which isn’t allowed.

There are several advantages to using ITC cable. Because the insulation rating is 300V, the outer diameter (O.D.) of the cable is much smaller than that of 600V rated cable. This becomes important, for instance, in cable tray fill and under raised floors of control rooms when crossing from the DCS cabinets to the marshalling cabinets.

Be careful when specifying ITC cable. ITC-ER (exposed run) cable must be used wherever the cable is exposed for any length. Using ITC cable without the “–ER” rating is a common issue right now in industrial facilities and probably will continue to be until all ITC cable is “–ER” rated — just like the transformation that occurred with 600V-rated tray cable (type TC) several years ago.

© 2014 Fluor Corporation. All Rights Reserved.

About the Author

Eddie Guidry | Senior Fellow

Eddie Guidry is a senior fellow with Fluor Enterprises, Inc., Sugar Land, Texas. He is highly skilled in electrical and control systems for industrial construction, design, and engineering (both domestic and abroad). The majority of Eddie’s 38 years of experience includes upstream and downstream portions of petrochemical plants and refineries. He is also heavily experienced in water and wastewater treatment facilities. Eddie is very active in the development of U.S. national (ANSI) and international codes and standards, and has been a principal member of the National Fire Protection Association (NFPA) National Electrical Code (NEC) committee since 1999 and NFPA’s National Advisory Committee on Electrical Safety Research since 2008. Eddie, who has also developed and conducted many electrical courses and seminars over the years, currently holds the corporate Master Electrician license for Fluor Corporation in the State of Texas and is also an ICC/IAEI certified electrical inspector.

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