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Underground Feeder Cable (UF-B)

UF-B is a jacketed cable rated for direct burial and wet locations. Its conductors are molded into a solid jacket, which is the main visible difference from NM-B.

Ref EL-0007NEC 340UL 493

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Type UF-B (underground feeder and branch-circuit cable) is a factory assembly of insulated copper conductors and a bare equipment grounding conductor, all molded into a solid, moisture-resistant PVC jacket. It is listed to UL 493 and installed under NEC Article 340. It is used for runs to outbuildings, landscape lighting, wells, pumps and other outdoor or buried circuits.

How to identify

UF-B jackets are usually gray. The jacket is solid, so the conductors are embedded in it and are hard to separate. NM-B has a paper wrap and loose conductors inside a thin jacket. The print reads "UF-B," the size and conductor count (for example 12/2 with ground), the voltage, and often "sunlight resistant" and "for direct burial."

UF-B compared with NM-B

Feature	NM-B	UF-B
Jacket	Thin PVC over paper-wrapped conductors	Solid PVC molded around conductors
Typical jacket color	White, yellow, orange, black by size	Gray
Wet and damp locations	Not permitted	Permitted
Direct burial	Not permitted	Permitted, at the depths in NEC 300.5
Interior wiring	Permitted under Article 334	Permitted, installed to the NM rules of Article 334
Stripping	Easy	Harder; the jacket must be split away from each conductor
Governing article	NEC 334	NEC 340

Key points

Burial depth depends on the wiring method, location and circuit. The minimum cover table is NEC 300.5. Do not quote depths from memory.
Where the cable comes out of the ground, NEC 300.5 also requires protection from physical damage, typically in conduit up to the box or equipment.
NEC 340.12 lists places UF is not permitted, including as service-entrance cable and embedded in poured concrete except as allowed for heating cables.
Exposure to sunlight is allowed only if the jacket is marked sunlight resistant.
Ampacity is governed by NEC 340.80 and the code tables, not by the jacket rating.

Common mistakes

Using NM-B outdoors or in buried conduit because it was on hand.
Running UF-B out of the ground with no protection.
Damaging conductor insulation while stripping the solid jacket with a knife.
Assuming UF-B can serve as a service entrance. It cannot.

Governing standards: NEC Article 340; NEC 300.5 (underground installations); UL 493 (thermoplastic-insulated underground feeder and branch-circuit cables).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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