Burying a line to a shed, lamp post, or well pump means picking a cable that survives wet soil for decades — and 10/3 UF-B is the one most supply counters hand you. The “10” is the wire gauge, the “3” counts the current-carrying conductors, and UF-B is the designation that makes burial legal in permitted applications.
The details below cover what the cable actually contains, where it belongs, and the mistakes that trip up first-time buyers.
What Is Inside A 10/3 UF-B Cable?
10/3 UF-B holds three insulated conductors — black, red, and white — plus a bare copper ground, all wrapped in a gray PVC jacket built for wet locations.
One caveat worth checking before you buy: some listings describe solid conductors, others show stranded copper. Construction varies by brand and listing, so confirm the spec sheet on the exact spool you’re handed.
If you’re comparing brands before ordering, this roundup of 10/3 direct burial wire options lines up the tested picks side by side.
Where Does 10/3 Direct Burial Wire Belong?
UF-B goes underground — feeder circuits for detached structures, lamp posts, pumps, and other outdoor loads where the cable meets earth directly.
Home Depot’s listing for the 100 ft. 10/3 UF-B names lamp posts and pumps as typical loads, and describes the jacket as resistant to moisture and light. That combination — wet-rated, sunlight-tolerant, direct-burial-listed — is what separates UF-B from indoor cable.
The three insulated conductors plus ground also support 240 V and multi-wire feeder use, which is why 10/3 shows up on subpanel runs and well circuits rather than simple single-load drops.
| Spec | Listed Value | What It Means For You |
|---|---|---|
| Gauge | 10 AWG | Handles 30 A circuits, not 40 A or 50 A |
| Conductors | 3 plus bare ground | Supports 240 V and multi-wire feeders |
| Voltage rating | 600 V | Exceeds any residential circuit need |
| Ampacity | 30 A at 86 °F | Breaker and load must stay at or under this |
| Jacket | Gray PVC, 30 mil | Wet-location and sunlight resistant |
| Insulation | 24 mil | Rated for direct soil contact |
| Outer dimensions | ~0.215 x 0.727 in | Sizing for conduit fill and trench width |
| Standards | UL Listed, UL 493 | Meets the underground feeder standard |
| Common lengths | 10, 25, 50, 100, 250, 500 ft | Measure your run before ordering |
What Size Breaker And Load Can It Carry?
That 30 A ceiling is the fact most people get wrong. A 10/3 run is often bought for a subpanel feeding a garage or shop, and it’s easy to assume the cable carries whatever the panel’s main breaker allows. It doesn’t — the cable sets the limit, and the breaker protects the cable.
Voltage rating is a separate question from ampacity. Every listing here shows 600 V, but that figure describes insulation capability, not how much current the copper can move. Breaker sizing and burial depth follow your local electrical code, which product pages don’t cover.
If you need more than 30 A at the far end, step up to a larger gauge rather than pushing this cable past its rating.
Common Mistakes With 10/3 Direct Burial Cable
The most expensive error is grabbing 10/3 NM-B instead of UF-B — indoor cable isn’t rated for soil contact and fails inspection.
- Treating all 10/3 as identical. Strand count, outside diameter, and weight differ by brand; verify the spool, not the shelf tag.
- Counting the bare ground as a current carrier. It’s an uninsulated ground wire, not a fourth conductor for your load.
- Assuming the listing covers code. Burial depth, conduit rules, and GFCI requirements come from local code, not the product page.
- Ignoring the temperature note.
FAQs
Can 10/3 UF-B be run inside a house?
UF-B is rated for wet and underground locations, so it can be used indoors where code permits, but NM-B is usually cheaper and easier to strip for interior runs. Check your local code before deciding, since some jurisdictions restrict UF-B indoors for specific applications.
Does 10/3 direct burial wire need to be in conduit?
Not always. Direct burial cable is designed to sit in soil without conduit in allowed applications, though many installers still sleeve it in conduit where it emerges from the ground or crosses a driveway for physical protection. Your local code sets the exact requirement.
What is the difference between 10/2 and 10/3 UF-B?
10/2 has two insulated conductors plus ground; 10/3 has three plus ground. The extra conductor is what allows 240 V multi-wire circuits or a shared neutral, which is why 10/3 is common for subpanels and 10/2 for simple single-load runs.
References & Sources
- Southwire. “10-3 CU UF-B With Ground, 50 ft.” Confirms gauge, conductor count, ground size, and outer dimensions.
- Southwire. “Underground Feeder Copper Cable.” Supports the 600 V rating and 30 A ampacity figures.
- Home Depot. “Southwire 100 ft. 10/3 Gray Solid CU UF-B W/G Wire.” Lists lamp posts and pumps as typical underground feeder loads.
