Tray cable: TC and TC-ER in plant tray systems

TC, TC-ER and the exposed-run allowance

Tray cable is a factory assembly of insulated conductors, with or without a ground, under an overall jacket, listed for use in cable tray. The standard product is a 600-volt cable, and a 2 kV version exists for small motors and feeder branches. Conductors inside are usually THHN or XHHW, and the jacket is PVC or a nylon-covered PVC, printed sunlight resistant and often marked for direct burial.

TC-ER adds an exposed run rating. It permits the cable to leave the tray and run unsupported for a limited distance to the equipment it serves, which is what most plants actually need, because tray stops at the edge of the aisle and the motor does not. A reel printed TC without the ER marking will not satisfy that run, and an electrician will notice before the invoice does.

What a tray system does to cable

Cable in tray is supported but not protected. It sits in the open above a process line, so it takes heat radiating from the equipment below, dust, oil mist and washdown spray. The jacket on the top face chalks and the print fades first, which is why the underside of a coil is usually the readable side.

Fill and weight matter as well. A tray loaded to its permitted fill with a heavy multiconductor bundle sags between rungs, and the jacket takes a set at every rung. That set is a series of flat spots. A used coil with pronounced rung marks is still electrically sound, but it will not lay straight in a new tray, and that belongs in the description.

Panel changeouts and the cut lengths they leave

The reliable generator of tray cable surplus is a controls or drive upgrade. A line is retooled, the old MCC is replaced and the tray to it is re-routed, and the cable that fed the previous arrangement is cut loose. Some of it goes back on a reel. Most of it is a pile of twenty- and forty-foot lengths that were cut to reach a specific terminal.

Toledo's glass and automotive supplier plants produce this in cycles, and so does any process plant with a tray system running above the floor. A changeout lot is reviewed on the lengths and the conductor count far more than on total footage, because a hundred feet in three pieces is a different proposition from a hundred feet in one.

Reviewing a tray cable lot

Ask for the print at the jacket, the conductor count and the length. Then ask how it was stored, because tray cable is often the cable that sat on the loading dock.

• Whether the print reads TC or TC-ER
• Conductor count, size and whether a ground is included
• Voltage class, 600 V or 2 kV
• Length of each cut piece, listed separately
• Jacket condition: rung marks, chalking, cuts at the ends