Tray Cable Ratings on Cordsets

I want to talk about something that has been quietly creeping onto more spec sheets and into our daily discussions lately. A somewhat mysterious cable rating that almost nobody can fully explain when you put them on the spot: Tray Cable Ratings. You have probably seen the letters floating around: PLTC, TC, and maybe even a little "-ER" hanging off the end.

For most folks, "tray rated" was a phrase reserved for bulk cable on a giant spool, the stuff an electrician cuts to length, terminates by hand, and lays into a cable tray. The industrial pre-molded cordsets (like M12 & 7/8ths) we all love for their plug-and-playability lived in a different world. If you wanted the convenience of a molded connector AND you wanted to run it in a tray or out in the open, well, you couldn't. Not to code, anyway. That has changed.

First, what is the "tray cable" rating even solving?

In a lot of industrial plants, cable doesn't run in conduit. It runs in an open cable tray, which is faster to install, easier to modify, and a whole lot cheaper than bending and pulling conduit all over a facility. But the NEC (National Electrical Code) doesn't let just any cable flop into a tray. It has to be listed and rated for it. Two ratings matter most:

PLTC, Power Limited Tray Cable (NEC Article 725).
Your low-power signal and sensor circuits, the Class 2 / Class 3 world. Rated to 300V and built to survive life in a tray. Think of the cordset running back from a sensor.

TC-ER, Tray Cable Exposed Run (NEC Article 336).
Your power circuits, the cordsets feeding motors, valve banks, IO-Link master blocks, and the like. This is where traditional 7/8" power connectors live, along with newer types like M12 L-Coded, S-Coded, and K-coded.

(You may also see ITC, Instrumentation Tray Cable, which sits between the two for process instrumentation. And don't be thrown by a jacket printed with several marks in a row, like TC-ER, PLTC-ER, ITC-ER, MTW, AWM, FT4. That's just one cable listed against several standards at once. The trick is knowing which mark matters for your install. For us, that's PLTC on the signal side and TC-ER on the power side.)

What actually goes into a tray rating?

Those letters aren't just a label somebody slapped on the jacket. They're shorthand for a whole battery of tests the cable had to pass. The headliner is flame propagation. A loaded tray is essentially a long horizontal stack of fuel, so the cable has to prove it won't carry a fire down the line. The benchmark is the vertical-tray flame test (UL 1685 / IEEE 1202): a 70,000 BTU/hour flame for 20 minutes without letting the char travel too far. On the CSA side this shows up as an FT rating, and FT4 is the vertical-tray test you actually want for tray cable (FT1 and FT2 are basic single-conductor tests; FT6 is plenum-level). On top of that, a proper tray cable carries a defined voltage and temperature rating and is typically marked sunlight (UV) and oil resistant, since tray cables can often run outdoors or through wash-down and machining areas. So a "tray rated" cordset is really a cable that has already proven it can take the heat, the sun, the oil, and the abuse.

Now the magic letters: "-ER"

ER stands for "Exposed Run."

A standard tray cable has to stay in the tray. The second it leaves to reach a device, the code says it has to be protected, either in conduit or as armored (MC) cable. The "-ER" rating changes that. To earn it, the cable survives some genuinely brutal testing, including a 1,000-lb crush test and a 10-lb impact drop without shorting out or biting into the insulation. Because it's that rugged, the code lets an ER-rated cable leave the tray and run exposed, up to 6 feet unsupported and up to 50 feet with proper support, with no conduit required. An ER-rated cordset can make the jump from the tray to your motor, valve bank, or I/O block without a single stick of conduit.

So why does this matter to YOU?

Cost and labor. Plain and simple. Every foot of conduit you don't have to bend, mount, and pull is real money and real hours saved. Tray-rated cordsets let you keep the plug-and-play speed of a molded connector while staying code-compliant in tray applications. You get the convenience AND you pass inspection. That used to be an either/or. It isn't anymore.

A quick selection guide

Reach for a PLTC-rated cordset when:

• You're running sensor or signal cable (power-limited, Class 2/3) in or through cable tray

• You want a clean, code-compliant path from the sensor back to your I/O without hardwiring

Reach for a TC-ER rated cordset when:

• You're running power to motors, drives, valve manifolds, or distribution blocks (7/8", or M12 L/S/K-coded)

• The cordset has to leave the tray and run exposed, and you want to skip the conduit or armored cable on that final run

Stick with a standard cordset (or conduit) when:

• You're not in tray at all and already protected in conduit or an enclosure

• Your local AHJ (Authority Having Jurisdiction) enforces stricter rules. Always confirm locally before you spec.

Final thoughts

Tray ratings sound like alphabet soup, but the payoff is simple: the convenience of a connector with the code-compliance of tray cable.