NEC Article 336 Explained: What Every Electrical Distributor Needs to Know About Tray Cable Installation Rules
Written By: Craig Keller
Posted March 25, 2026
You have a lot on your plate. Between lighting, switchgear, conduit, and the hundred other line items that make up a typical project BOM, tray cable is probably not the product category keeping you up at night. And it shouldn’t be that’s what your master distributor is for.
But here is where tray cable does demand a few minutes of your attention: NEC Article 336 is the code section that governs every tray cable installation in the country, and its rules directly affect what you should be quoting. Order the wrong cable type for an exposed run, and your contractor gets flagged on inspection. Ship standard TC when the job calls for TC-ER, and you’re processing a return. Miss a hazardous location requirement, and the whole project stalls.
These aren’t "wire and cable" problems. They’re "unhappy customer" problems. And they’re avoidable if you understand a handful of key provisions in Article 336. DWC is here to help you with that!
This guide isn’t a code class. It’s a translation of the NEC sections that actually matter for your quoting and selling process for tray cable, written so you can answer the most common tray cable questions without needing to crack open a code book.
What NEC Article 336 Covers (and Why You Should Care)
NEC Article 336 is titled "Power and Control Tray Cable: Type TC." It defines what tray cable is, where it can be installed, where it cannot be installed, how it must be constructed, and how its ampacity is determined. Every Type TC and TC-ER cable in DWC’s product line is manufactured and listed to comply with Article 336 and its referenced standard, UL 1277.
For your purposes as a distributor, Article 336 breaks down into three sections that directly affect your business:
Section 336.10 (Permitted uses)
Section 336.12 (Prohibited use)
Section 336.80 (Ampacity calculations)
NEC 336.10: Where Tray Cable Can Be Installed
Section 336.10 is the heart of Article 336. It lists specific permitted uses for Type TC cable. Here are the ones that come up most often when you’re filling out orders:
Tray Cable in Cable Trays, Raceways, and Conduit
The baseline rule is straightforward: Type TC cable can be used for power, lighting, control, and signal circuits in cable trays (including trays with mechanically discontinuous segments up to one foot), raceways, and conduit. If the entire run stays inside a tray or raceway, standard Type TC cable is all your contractor needs.
The TC-ER Exposed Run Rule (NEC 336.10(7))
This is the provision that matters most for your quoting process. It determines whether your contractor can drop cable from the tray to the equipment without conduit.
NEC Section 336.10(7) permits Type TC-ER cable to be installed between a cable tray and utilization equipment, provided it is marked TC-ER (meaning it passed the crush and impact requirements of UL 1569). The cable must be continuously supported and secured at intervals not exceeding six feet.
The six-foot exception: Where the cable is not subject to physical damage, TC-ER can transition between cable trays, or between a cable tray and equipment, for up to six feet without continuous support.
What this means for your quote: If the project has any cable transitions to motors, VFDs, or control panels, your contractor almost certainly needs TC-ER, not standard TC.
2026 NEC Update: Expanded TC-ER Transition Points
The 2026 NEC cycle introduced a meaningful revision to Section 336.10(7). While the 2023 code was often interpreted narrowly, the 2026 revision explicitly permits TC-ER transitions between a cable tray, raceway, enclosure, or equipment and the utilization equipment. This means the TC-ER cable can now exit a tray, run unsupported for up to six feet, and enter a nearby conduit stub or terminal box without violating the code.
Tray Cable in Hazardous Locations
Type TC and TC-ER cable is permitted in Class I Division 2, Class II Division 2, and Class III Division 1 and 2 hazardous locations.
The proactive move: If the project is Division 1, the tray cable is not compliant. Your contractor will need MC-HL cable or rigid conduit. Catching this during the quote stage saves everyone time.
Tray Cable for Direct Burial (NEC 336.10(10))
Type TC cable is permitted for direct burial only where identified for such use. This means the cable must carry a specific "direct burial" marking on its jacket.
NEC 336.12: Where Tray Cable Cannot Be Installed
Section 336.12 is where inspection failures happen. There are three primary prohibited conditions:
Exposed to physical damage: Tray cable, including TC-ER, cannot be installed where it will be subject to physical damage. It is not armor.
Outside a raceway or cable tray system: Standard Type TC cable must remain inside a tray or conduit. It cannot run between the tray and the equipment; that is the specific job of TC-ER.
Exposed to direct sunlight unless rated: If the cable runs outdoors, it must carry a sunlight-resistant marking. DWC’s VNTC products are sunlight resistant as standard, but always verify this for outdoor orders.
NEC 336.80: How Tray Cable Ampacity Is Determined
Ampacity connects to the actual sizing decisions your contractor is making:
Inside cable tray: Ampacity is determined per NEC Article 392.
Outside cable tray: For TC-ER exposed runs, ampacity follows NEC 310.14.
The Insulation Factor: DWC’s VNTC (THWN-2) products are rated 90°C dry and 75°C wet. XLP (XHHW-2) products are rated 90°C in both wet and dry conditions. In wet locations, the 90°C wet rating on XLP allows for higher ampacity than VNTC, which is a major distinction for contractors sizing cable for damp environments.
Practical Tray Cable Spec Framework: Your Day-to-Day Checklist
Three Questions That Prevent Returns:
"Will the cable transition from the tray to equipment?" (If yes: Quote TC-ER).
"Are there any hazardous area classifications?" (If Division 1: Quote MC-HL).
"Does the spec restrict PVC?" (If yes: Quote FR-EP tray cable).
Why TC-ER Should Be Your Default Stock Position
Standard TC cable has significant installation limitations. In contrast, TC-ER does everything standard TC can do, plus it’s permitted for exposed transitions. Because the cost difference is negligible, stocking TC-ER as your default eliminates the risk of shipping non-compliant cable.
Frequently Asked Questions About NEC Article 336
What is the difference between TC and TC-ER? TC-ER has passed the enhanced crash and impact testing of UL 1569. This allows it to be installed as an "Exposed Run" between the tray and equipment for up to six feet without conduit (per NEC 336.10(7)).
Does NEC 336 allow tray cable in hazardous locations? Yes, for Division 2 locations. It is not permitted in Class I, Division 1 locations, where MC-HL or rigid conduit is required.
What NEC Article covers the tray itself? NEC Article 336 covers the cable. NEC Article 392 covers the cable tray system (sizing, fill, and grounding).
Ready to quote tray cable? Log in to the fastQuote portal or call your DWC Account Manager to get your project moving today.
