Allied Encyclopedia – The -ER Rating: Exposed Run Tray Cable

Allied EncyclopediaYou may have seen the -ER rating on the jacket of your tray cable, but do you know what it means? ER stands for “exposed run.” It is a rating that sometimes follows the UL Type TC (Tray Cable), ITC (Instrumentation Tray Cable), or PLTC (Power-Limited Tray Cable) classification.

On tray cable jackets, these ratings appear as TC-ER, ITC-ER, or PLTC-ER. These are marked for the benefit of inspectors, who must check that all wiring is done properly. For tray cables made prior to 2005, -ER rated cables may be marked as “open wiring.”

So what gets a cable an -ER rating? Well, to be approved for this rating, tray cables must pass additional crush and impact tests. Once a tray cable is marked with this rating it is deemed durable enough to be used as exposed wiring. This means that the cable does not require armoring and that it may be installed outside of conduit or another raceway.

Now, what does this mean for you, the consumer? Fortunately, it means you may be able to save money on your cable installation! While standard tray cables can not extend more than six feet outside a tray without requiring the protection of armor or a raceway, -ER rated cables can go for more than fifty feet if given sufficient protection and support. Because -ER rated cables do not require armoring, the cable itself may be less expensive. Exposed run tray cabling also saves on the cost of conduit and raceway for the same reason.

Remember, there are a few rules to follow when installing exposed run tray cables, but they are very straightforward:

  • First, exposed runs can only be utilized in industrial establishments which provide qualified people to maintain, supervise, and service the installation. The exposed run must also be located between a cable tray and some sort of equipment or electrical device.
  • Second, the cable must be adequately protected by struts, angles, or channels. It must also be secured once every six feet, at minimum.
  • Finally, there are a few regulations that apply to specific tray cable types. Type TC-ER cables are required by the National Electric Code (NEC) to include an equipment grounding conductor within the cable, while it is not mandatory for ITC-ER and PLTC-ER cable to include an equipment grounding conductor. However, ITC-ER cables are limited to an exposed run of fifty feet between a cable tray and connected equipment, while PLTC-ER and TC-ER cables have no set length limitations.

Despite the additional NEC requirements, exposed run cables remain very straightforward to use and simple to install. If you are working in an industrial environment, they just may be the answer to your budget-saving needs.

About awcwire
Allied Wire & Cable is a value-added manufacturer and distributor of electrical wire and cable, tubing, and more. We are a family owned and operated company, serving a wide range of industries, including the military, automotive, aerospace, and telecommunications markets. Allied is headquartered in Collegeville, PA. Additional locations can be found across the US, in Merrimack, NH, Tampa, FL, Pewaukee, WI, and Las Vegas, NV. For more information on Allied, visit our main website at

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