12/2 UF wire is a 12-gauge underground feeder cable with two insulated conductors plus an optional ground, rated 600 volts and built for direct burial to outdoor loads like lamp posts and pumps.
A run out to a backyard lamp post dies fast when the wrong cable goes in the trench — moisture wicks into the sheath, the inspector flags the burial depth, and the whole line gets dug up twice. Southwire’s UF-B listing describes the cable as a 600-volt copper feeder for exactly that job: carrying 120V power from an existing distribution point to a detached load, buried or not. The trade-off is that “UF” gets printed on cable it doesn’t always belong on, and the ground conductor is the detail buyers miss most.
What Do The “12/2” And “UF” Actually Mean?
The “12” is American Wire Gauge — 12 AWG copper, the same gauge used on 20-amp household circuits. The “2” counts insulated conductors: one hot and one neutral, so a 12/2 cable feeds a single 120V load.
UF stands for underground feeder. Southwire rates the cable at 600 volts and lists PVC insulation with a nylon sheath engineered to resist sunlight, moisture, and fungus — the three things that quietly destroy ordinary indoor cable buried in wet soil.
Whether a ground wire rides along depends entirely on the SKU. Southwire’s with-ground version carries a bare 12 AWG ground. Southwire also publishes a 12-2 UF-B WOG listing marked “Ground Size: None.” WOG means “without ground,” and it looks nearly identical on the shelf.
- 12 AWG — conductor size, good for 20-amp circuits when protected properly
- 2 — insulated conductors, hot and neutral
- UF — rated for underground and wet locations, direct burial allowed
- W/G vs. WOG — includes a ground conductor, or doesn’t
What Is 12/2 UF Wire Actually Used For?
Southwire ties the cable to feeder and branch-circuit duty outdoors: post lamps, pumps, and similar loads fed from an existing panel or distribution point. Direct burial in soil is the headline use, and Southwire also permits interior branch-circuit wiring in residential or agricultural buildings under specified conditions.
Conduit is not required in the direct-burial application. That’s the practical appeal — no pipe to buy, glue, or backfill around.
Southwire also notes UF-B may be used in applications permitted for NMC under NEC 334.10(B), a detail that matters if a run starts outdoors and finishes inside a barn or shed.
| Spec | Southwire UF-B Rating |
|---|---|
| Conductor size | 12 AWG copper |
| Insulated conductors | 2 (hot, neutral) |
| Ground (W/G SKUs) | 1 bare 12 AWG |
| Voltage rating | 600 V |
| Insulation thickness | 20 mils |
| Jacket thickness | 30 mils |
| Approx. OD (12-2 W/G) | 0.183 x 0.463 in |
| Ampacity basis | Limited to 60°C column |
Where Do People Get This Cable Wrong?
The 90°C temperature marking is the most expensive misread. It refers to the conductor’s temperature rating, not its ampacity — Southwire states plainly that ampacity is limited to the 60°C conductor column, which is the number an electrician must size the breaker against.
The second mistake is buying by the label instead of the SKU. Two boxes can both read “12/2 UF-B” while only one contains a ground conductor, and a 120V run without a ground path fails inspection in most jurisdictions. Check for “W/G” or “with ground” on the label before checkout.
Treating UF-B as a universal outdoor answer causes the third problem. It handles burial and wet locations in the roles Southwire describes, but it isn’t a blanket replacement for conduit-based wiring in every outdoor scenario — physical protection still matters where the cable is exposed above grade. Most buyers grab a favorite 12 2 UF wire pick from this tested roundup rather than sorting through SKU codes at the counter.
Southwire’s listing describes the product construction in detail, and the UF-B copper cable specification page carries the current ratings shown above.
How Do You Pick The Right Spool And Install It?
Match the gauge to the circuit and the spool to the run length, then verify the ground conductor before the trench gets backfilled.
- Confirm 12 AWG fits the circuit — 20-amp protection at the 60°C ampacity figure.
- Check the SKU for “W/G” or “with ground” if the run needs an equipment ground.
- Measure the total run and add slack for terminations at both ends.
- Buy length in one pull — Southwire sells 25, 50, 100, 250, 2500, and 5000 ft spools.
- Terminate both ends in a listed box, not in open air.
Pricing swings with brand, length, and seller, so compare per-foot cost rather than box price. When the spool arrives, the sheath should read UF-B and the conductors should strip clean — if the jacket tears or the print is missing, the cable isn’t the right product.
FAQs
Does 12/2 UF always include a ground wire?
No. Southwire publishes both versions, including a WOG listing with no ground conductor. “W/G” or “with ground” on the label is the marker that tells you a bare 12 AWG ground is inside. Confirm the SKU before buying, because the packaging looks nearly the same from a few feet away.
Can 12/2 UF wire be buried without conduit?
Yes, in the direct-burial application Southwire describes. That’s what the UF designation covers. Local code still governs burial depth and any physical protection required where the cable rises above grade into a box or fixture. Check with the authority having jurisdiction before the trench goes in.
What size breaker goes with 12/2 UF wire?
A 20-amp breaker is the typical pairing for 12 AWG copper. Southwire limits ampacity to the 60°C conductor column, so size to that figure rather than the 90°C marking on the jacket. Voltage drop over a long buried run can push you to a larger gauge entirely.
References & Sources
- Southwire. “UF-B Copper Cable.” Product listing with construction, ground conductor, and spool length options.
- Southwire. “UF-B Copper Cable Specifications.” Voltage rating, insulation and jacket thickness, OD, and 60°C ampacity limit.
- WireRef. “UF-B Wire.” Reference notes on UF-B wire types and applications.
