URD vs USE-2: cabled or single conductors for underground runs
Published Sep 30, 2026
URD wins for an aluminum circuit laid straight into a trench, and USE-2 wins when you need copper, conduit, or a run that carries on inside a building. Both are made for direct burial, and most 600 V URD is itself listed as Type USE-2, so the real difference is packaging. URD comes as two, three or four conductors twisted together on one reel. USE-2 is sold as single conductors, and in many builds it also carries the RHH and RHW-2 ratings that let it continue indoors.
What each one is
USE-2 is a single conductor with cross-linked insulation, rated 90 °C in wet and dry locations. It appears in NEC Table 310.4(1) (Table 310.104(A) in the 2017 edition) and is covered as a cable type in Article 338. Most USE-2 on the market is triple rated USE-2/RHH/RHW-2, in copper and in aluminum.
URD (underground residential distribution) is a trade name, not an NEC type. It is aluminum conductors with cross-linked insulation, cabled together as duplex, triplex or quadruplex. The jacket legend on 600 V URD usually shows a USE-2 listing, which is what the inspector goes by. The neutral is often a smaller size than the phase conductors and is marked with a yellow stripe or raised ridges.
Side by side
| URD | USE-2 | |
|---|---|---|
| Form | Two to four conductors cabled together | Single conductor |
| Metal | Aluminum | Copper or aluminum |
| Direct burial | Yes | Yes |
| In underground conduit | Yes | Yes |
| Inside a building | Only if the legend also shows a building wire rating | Yes, when also marked RHH/RHW-2 |
| Neutral marking | Yellow stripe or ridges, by convention | Usually black; mark it yourself |
| Typical job | Service laterals, feeders to a detached building | Service conductors and feeders in conduit, copper runs |
Cabled or single
A cabled URD assembly keeps every conductor of the circuit together, which is what 300.5(I) and 300.3(B) require: all conductors of a circuit, including the neutral and the equipment grounding conductor, in the same raceway, cable or trench, close together. You pay one reel off into the trench and the job is done.
Single USE-2 conductors work too, but you have to keep them together yourself. Bury them in the same trench, laid close, or pull them all into the same conduit. Separate trenches for each conductor are not allowed. Singles make sense when the run needs copper, when the sizes you want are not made up as URD, or when the conductors will go into conduit at some point anyway.
Service laterals
A service lateral is the utility's underground run up to the service point. The utility picks that cable, often URD, and the NEC does not govern it. Underground service conductors on the customer side of the service point fall under Article 230 Part III, and both URD and USE-2 are common there. Check with the utility first: many publish their own rules for depth, conduit, and who supplies the cable.
Burial depth
NEC Table 300.5 sets the minimum cover for circuits up to 1,000 V. For direct-buried cable or conductors under the general condition, column 1, that is 24 in. Other rows of the table change that number, and under streets, highways and roads every method needs 24 in. Service conductors buried 18 in. or deeper need a warning ribbon at least 12 in. above them (300.5(D)(3)), and conductors that come up out of the ground need protection from the required depth to at least 8 ft above grade (300.5(D)(1)). The full table is in our underground wire burial depth guide.
Identifying the neutral and ground
The yellow stripe on a URD neutral is an industry convention, not an NEC identification. 200.6 sets how a grounded conductor has to be identified, and for 4 AWG and larger it allows white or gray marking at each termination. 250.119 allows an equipment grounding conductor 4 AWG and larger to be identified with green marking at each end. Smaller conductors have tighter rules, so check 200.6(A) before you use a 6 AWG conductor as a neutral.
Common mistakes
- Running USE-2 alone (not also RHH or RHW-2) inside a building. 338.12(B) does not permit USE for interior wiring.
- Carrying URD past the service equipment into the building when its legend shows only USE-2.
- Trenching single conductors in separate trenches.
- Leaving the neutral unmarked at the panel.
- Skipping anti-oxidant compound or the lug torque on aluminum.
Shop underground conductors
- 4/0-4/0-4/0 URD, 2/0-2/0-2/0 URD and 2-2-2-4 URD
- 4/0 USE-2/RHH/RHW-2 aluminum and 2 AWG
- 2 AWG USE-2/RHH/RHW-2 copper and 2/0 copper
- Everything else in aluminum building wire and copper building wire
Verify with your local code. Burial depth, service lateral rules and conductor identification vary by NEC edition, local amendment and utility. Call 811 before you dig and ask your inspector before you backfill.