UL 758 AWM vs UL 1277 TC-ER: Which Certification Your Cable Needs

01Two certifications, two different legal worlds

The confusion starts because both strings appear on the same reel, printed a few millimetres apart. They are not two grades of the same approval. One is a component recognition that lives inside equipment. The other is a cable type the installation code recognises as a wiring method.

AWM — Appliance Wiring Material — is a recognised component under UL 758. It is evaluated per style number, and the style number, not a trade name, fixes the voltage rating, the temperature class and the insulation wall thickness. Style numbers matter because each one carries its own construction rules: a UL 1015 hook-up wire and a UL 21198 industrial Ethernet cable are both AWM, and they share almost nothing but the standard they are evaluated under. Sorivo's AWM family, for example, covers UL 1007 (300 Vac, 80 °C), UL 1015 (600 Vac / 750 Vdc, 80 / 90 / 105 °C), UL 1569 (300 Vac, 80 / 90 / 105 °C) and UL 10012 (600 or 1000 Vac) — all single-conductor, all to UL 758, with the same wire family available as MTW to UL 1063 for machine-tool wiring at 600 V.

TC and TC-ER are a listed cable type under UL 1277. Type TC is defined in the installation code itself, at Article 336.2, as a factory assembly of two or more insulated conductors, with or without associated bare or covered equipment grounding conductors, under a nonmetallic jacket. Because it is a recognised wiring method, a listed TC cable may be installed in cable trays, in raceways, and in the other locations 336.10 permits. The ER marking is an additional qualification: it says the cable also meets the crush and impact requirements that apply to Type MC cable, which is what allows the exposed-run transitions described in 336.10(7).

One sentence that prevents a lot of argument on site: the standard lists the cable, the code says where it may be installed, and the code does not certify anything. UL 1277 is the product standard. Article 336 is the installation article. A datasheet that says "NEC certified" is mixing the two, and that is a reason to read the rest of the datasheet more carefully.

TC / TC-ER ratings and construction above are the values published on the Sorivo tray cable product page; AWM style ratings are the values published on the hook-up wire product page. Flame-test assignments are construction-dependent and are stated per order, not assumed. The 90 °C dry / 75 °C wet pair is the conductor insulation rating; the current a circuit may actually carry is set by the terminal ratings and the applicable ampacity table, not by the insulation figure on its own.

02What Article 336 actually permits

Article 336 is short, and almost every practical question about tray cable is answered inside it. 336.10 lists the permitted uses: power, lighting, control and signal circuits; cable trays, including trays with mechanically discontinuous segments up to 300 mm (1 ft); raceways; outdoor locations supported by a messenger wire; Class 1 circuits under Article 725; and non-power-limited fire alarm circuits where the conductors comply with 760.49. Direct burial is permitted only where the cable is identified for it, and hazardous (classified) locations only where another article specifically permits it.

336.12 is the other half of the answer, and it is the one that decides most disputes. Type TC shall not be installed where it will be exposed to physical damage, shall not be installed outside a raceway or cable tray system except as permitted in 336.10(4), (7), (9) and (10), and shall not be used where exposed to direct rays of the sun unless it is identified as sunlight resistant. That middle restriction is exactly why the ER marking exists.

The six conditions attached to the exposed-run allowance

336.10(7) permits a run between a cable tray and the utilisation equipment, but only where all of the following apply. Read them as a checklist, because a quotation that mentions only the first one is not describing the installation:

1. The cable is Type TC-ER. The ER marking is a condition, not a nicety.
2. Industrial establishments where maintenance and supervision ensure that only qualified persons service the installation.
3. Continuous support and protection against physical damage using mechanical protection such as struts, angles or channels.
4. The cable complies with the crush and impact requirements of Type MC cable and is identified with the marking "TC–ER".
5. The cable is secured at intervals not exceeding 1.8 m (6 ft).
6. Equipment grounding is provided by a conductor within the cable. For cables containing conductors sized 6 AWG or smaller, the equipment grounding conductor shall be within the cable or, at installation, one or more insulated conductors shall be permanently identified as an equipment grounding conductor in accordance with 250.119(B).

Two of those conditions are the ones buyers discover late. The requirement in item 3 is not satisfied by a cable tie to a strut every few metres — the cable has to be continuously supported and mechanically protected for the whole exposed run. And item 6 means an imported tray cable with no equipment grounding conductor inside it cannot be used for this allowance at all, whatever its print legend says.

The 1.8 m transition exception — and the "50 ft" figure that is not in the code

TC-ER-HL in classified locations

Tray cable also has a hazardous-location variant. 336.130 applies to cable listed and marked Type TC-ER-HL: the overall nonmetallic jacket must be suitable for the environment, the overall construction must be essentially circular in cross-section, and the jacket must be continuous and gas/vapour tight. Hazardous-location use is permitted only where another article of the code specifically allows it — which is a sentence worth keeping in mind when a datasheet advertises "TC-ER-HL" without naming a Class and Division. Our own product page states the Division 2 applicability of a specific construction as confirmed before it is offered, rather than as a blanket claim.

03What the ER suffix actually has to survive

The ER marking is earned by a mechanical qualification, not by marketing. Under 336.10(7)(d) the cable has to comply with the crush and impact requirements that apply to Type MC cable — a cable type built for physical abuse in industrial environments. The logic is straightforward: an exposed cable dropping from a tray to a motor is exposed to being stepped on, hit by a lift truck or leaned on by a ladder, in a way a cable tucked inside a tray never is.

Where a datasheet goes further and names a flame test, the numbers to look for on North American industrial constructions are UL 1685 FT4 and IEEE 1202. Both are vertical-tray flame-propagation tests, and both are reported in Btu/hr; manufacturer literature commonly cites a 70,000 Btu/hr exposure for the IEEE 1202 test applied to 1/0 AWG and larger constructions. They are related but not interchangeable, and a datasheet that lists one should not be read as having passed the other. What matters at specification time is narrower than the argument: the flame rating must be stated for the construction you are buying, at the conductor size you are buying, not for the family as a whole.

For the tray itself — fill ratio, allowable cable area, derating of more than three current-carrying conductors in a tray — the calculation lives in Article 392, and we walk through the fill-ratio arithmetic in how to size a cable tray to NEC 392 fill ratio. TC and TC-ER construction requirements sit in 336.100, which also carries a point buyers miss: a metallic sheath or armour is not permitted either under or over the nonmetallic jacket, though metallic shield(s) are permitted over groups of conductors, under the outer jacket, or both.

04Bending radius: one number that trips experienced installers

336.24 sets the minimum bending radius for Type TC by overall diameter, and it splits on whether the cable has metallic shielding. Cables without metal shielding step through three bands; cables with metallic shielding are held to a single, much larger multiple.

Values as written in 336.24. Note the general provision that opens the section: bends must be made so as not to damage the cable, which governs regardless of the tabulated minimum.

The 4× figure is the one people quote from memory, and it applies only to the smallest, unshielded band. Two practical consequences follow. First, a shielded control construction — including the foil or braid screens used on VFD cable — is a 12× cable, not a 4× cable, and that changes tray layout and radius at every direction change. If your route is built around drive cable, the shield-termination side of the problem is its own topic: we cover glands, 360° bonding and drain-wire practice in EMC cable glands and shield termination for VFD and servo cable. Second, a manufacturer's own catalogue value may be larger than the code minimum, and the catalogue value governs what the cable can actually be installed to without damage — the code figure is a floor, not a target.

05Ampacity: where 336.80 sends you next

336.80 does not contain a table. It routes the reader to other parts of the code, and the route depends on where the cable is installed and how big the conductors are:

• 14 AWG and larger, installed in cable trays: ampacity is determined in accordance with 392.80(A) — the tray article's adjustment provisions, which is where the reduction for more than three current-carrying conductors lives.
• 18 AWG through 16 AWG, installed in cable trays: in accordance with 402.5, the fixture-wire article.
• Installed outside of cable trays, where permitted: in accordance with 310.14.

Two further limits are easy to forget, and both bite on small tray cable. The small-conductor overcurrent limits of 240.4(D) cap 14 AWG at 15 A, 12 AWG at 20 A and 10 AWG at 30 A unless the installation falls within one of that section's exceptions — a 12 AWG conductor rated 90 °C in a table is still a 20 A circuit in most installations. And the conductor temperature has two numbers, not one: for TC the published rating is 90 °C dry and 75 °C in wet locations, with an emergency overload allowance to 105 °C and a short-circuit temperature of 250 °C. Reading the dry figure against a wet-location installation is a common and expensive mistake in buried or washdown areas.

06AWM styles: the machine-side rules, and why there is no ampacity table

On the other side of the enclosure wall the governing document changes. AWM is a component approval, and it is applied to wiring inside equipment or between pieces of listed equipment. That is what machine builders need — and it is also a hard limit, because an AWM-only cable is not a recognised wiring method and cannot be run as permanent plant wiring, in a tray or anywhere else.

What the style number fixes

The style number fixes the voltage grade, the temperature class and the minimum insulation wall. In the four styles we build, that plays out as: UL 1007 at 300 Vac and 80 °C; UL 1015 at 600 Vac / 750 Vdc in 80, 90 or 105 °C; UL 1569 at 300 Vac in 80, 90 or 105 °C; and UL 10012 at 600 or 1000 Vac. Insulation is extruded PVC, with a minimum average wall of 15 mils (0.38 mm) for UL 1007 and 30 mils (0.76 mm) for UL 1015 in the 30–9 AWG range. Conductors are solid or stranded copper, tinned on request.

The voltage grade is where specification errors actually happen. UL 1007 and UL 1569 are 300 Vac styles, and their surface marking may carry the note "600 V Peak – for electronic use only". That is a peak marking for electronic circuits. It is not a 600 V rating, and a drawing that treats it as one is a drawing that will be questioned at inspection. Where a genuine 600 V rating is needed, the style is UL 1015 at 600 Vac / 750 Vdc, or UL 10012.

Why we do not publish an AWM ampacity table

UL 758 style pages do not carry a current table. AWM is a material and construction approval, and the current a wire may carry in service depends on the equipment temperature-rise test and the installation — which is a property of the machine, not of the wire. The exception in principle is MTW to UL 1063, whose ampacity is limited to that for a 75 °C conductor per NFPA 79; MTW is a 600 V machine-tool wire, dry-rated 90 °C and rated 60 °C wet or oil-exposed, and it is the same wire family as our AWM styles. We state the limit rather than publishing a table we cannot reproduce from the standard itself: tell us the current, the ambient and the bundling, and we will confirm the size with you.

07Pick the application first, then the certification

In practice the choice is not a preference. The installation decides which marking is required, and the table below maps the common North American industrial cases.

Table 3 is a mapping aid, not an interpretation. Confirm the final requirement against the code edition your authority having jurisdiction has adopted, and against the project specification.

Most serious industrial cables resolve the dilemma by carrying both worlds on one reel. A construction marked "TC-ER per UL 1277" and carrying an AWM style as well gives you the tray approval and the machine-wiring approval from one drum — which is why buying dual-marked is normal practice rather than a luxury. It also means the print legend, not the marketing description, is what tells you whether you got what you ordered.

08What to verify on an imported TC-ER datasheet

Certification claims on imported industrial cable deserve a five-minute check, and it is the same check every time. Our own tray cable page commits to four of these being confirmed together before an order is released; the fifth is the one only your supplier can answer.

• The print legend says what the datasheet claims. "TC–ER" must appear on the cable. A datasheet promising exposed-run capability with no ER in the legend is describing a capability the cable does not carry.
• The voltage and temperature rows are for the system you are buying. TC / TC-ER is 600 V; PLTC is a separate 300 V product under UL 13, and a quotation that merges them into one row with one temperature is describing a cable that does not exist.
• The equipment grounding conductor is inside the cable if you intend to use 336.10(7). Item 6 of the six conditions is not optional.
• Flame and sunlight identification are stated for your construction. 336.12(3) prohibits sun-exposed use unless the cable is identified as sunlight resistant; direct burial requires identification for that use.
• The listing is verifiable. Ask for the UL file number and check it in UL's public Product iQ database. A listing entry shows the exact construction, sizes and ratings covered. If a supplier cites "meets UL requirements" with no file number, treat the claim as unverified until it is produced.

Two documents should arrive with the order regardless: the drawing that fixes the construction you approved, and the form-type test report. The first settles arguments about what was sold; the second is what answers the inspector, the auditor, or the customer who asks for evidence a year later. If your project is also carrying UL-listed building wire on the same site, the marking conventions overlap and are worth reading together — what a UL 83 THHN marking actually tells you covers the building-wire side of the same print-legend logic, and THHN vs THWN-2 vs XHHW-2 compares the grades that most often appear alongside tray cable in a North American plant.

If your project is running on a newer code cycle, the wiring-method picture has moved too: what changed between the 2023 and 2026 NEC editions for cable and wiring summarises the amendments that reach cable specifications. And for the residential variant of the same family — a dual power-and-control tray cable permitted for branch circuits and feeders under 336.10(9) — see what TC-ER-JP cable is under UL 1277.

09What we publish, and what we will not pretend to publish

This article states what Article 336 and the two product standards say, at the level we can source. It deliberately does not do three things. It does not interpret the code for a specific site: 336.10(7) is conditioned on "industrial establishments" and on conditions of maintenance and supervision, and whether a given plant qualifies is a judgement for the authority having jurisdiction, not for a cable supplier. It does not claim code-level detail from UL 758, UL 1277 or UL 1063 that we cannot quote from the standard text itself — we cite standard numbers, scope and the construction values that appear in manufacturer data, and we mark the boundary there. And it does not treat any third-party figure as a code number: when a number in this article comes from a standard, we say so; when it comes from a manufacturer's datasheet, we say that instead.