NEC 340 UF Cable for the Journeyman Exam: Where Underground Feeder Cable Can Go, the 11 Places It Cannot and Its 60°C Ampacity

Tsai Electro is an independent learning site. Not affiliated with TDLR, PSI or NFPA. We explain the ideas in our own words and do not reproduce NEC text. Check every rule and table value in your own 2026 NEC, and follow your supervisor and the local inspector.

UF next to NM and USE

On the job, UF looks like gray NM cable with a solid jacket molded around the conductors. On the exam, the questions are about where it may go. NM and MC cable are covered on NEC 334, 330 and 400 cables and cords; this page is only about what makes UF different.

Question	UF (Article 340)	NM (Article 334)
Direct burial	Yes, at the required depth	No
Wet locations	Yes	No
Use indoors like NM	Yes, multiconductor UF under the NM rules	Yes
Service-entrance cable	No	No
Ampacity column	60°C	60°C

Where UF is allowed

• Underground, including direct burial in the earth, at the depths set by the underground installation rules (NEC 340.10).
• As single-conductor cable, with all conductors of the circuit installed together, including the grounded conductor and the equipment grounding conductor where present (NEC 340.10).
• In wet, dry or corrosive locations, with the cable and its fittings suitable for the condition (NEC 340.10).
• As nonmetallic-sheathed cable inside a building, when it is multiconductor UF installed under the NM cable rules (NEC 340.10).
• In cable trays, as multiconductor UF cable (NEC 340.10).

The eleven uses not permitted

Article 340 lists eleven places UF cannot go (NEC 340.12(1)). Group them so you can find them under time pressure:

• Building types: commercial garages, theaters and similar locations, and motion picture studios.
• Special rooms and shafts: storage battery rooms and hoistways or on elevators and escalators.
• Hazardous locations, except where another article permits UF.
• Installation conditions: embedded in poured cement, concrete or aggregate (except nonheating leads embedded in plaster where the heating rules allow it), exposed to direct sunlight unless identified as sunlight resistant, and where subject to physical damage.
• As service-entrance cable.
• As overhead cable, except where installed as messenger-supported wiring.

A typical trap: a question proposes UF as the service-entrance wiring between the meter and the service disconnect. UF cannot be used as service-entrance cable. Do not classify a cable only by where it runs, because a feeder on the load side of the service disconnect is a different use. UF exposed to direct sunlight must also be identified as sunlight resistant.

Ampacity: the 60°C column

The ampacity of UF cable is the 60°C value for its conductors. Look up the conductor size in the 60°C column of the ampacity table, then apply any correction and adjustment factors.

Copper UF size	60°C ampacity
14 AWG	15 A
12 AWG	20 A
10 AWG	30 A
8 AWG	40 A
6 AWG	55 A

Worked example: feeding a detached shop

A detached shop needs a 240-volt load of 38 A, not continuous. The run is direct-buried copper UF, and correction factors do not apply.

1. Use the 60°C column. 10 AWG copper is 30 A, too small. 8 AWG copper is 40 A.
2. Check. 40 A ≥ 38 A, so 8 AWG copper UF meets the ampacity for this noncontinuous load under the stated assumptions. Ampacity is one check, not the whole feeder design.
3. Other rules. The burial depth and the disconnect at the second building come from other articles. Check them before you call the job done.

Check yourself

1. Can UF cable be used as service-entrance cable? No.
2. Can UF be buried directly in the earth? Yes, at the required depth.
3. What temperature column sets UF ampacity? 60°C.
4. Can UF be embedded in a concrete slab for a general branch circuit? No.

FAQ

Sources checked October 2026

• PSI Candidate Information Bulletin, Texas electrician examinations (updated September 15, 2026): https://test-takers.psiexams.com/api/content/bulletin/1682
• NFPA 70, National Electrical Code, 2026 Edition, Articles 310, 334 and 340