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Direct burial cable is a special type of electrical wiring, or cable, that is designed to be run in a trench underground. The electrical wires in the cable are encased in a thermoplastic sheath that seals out moisture and protects the wires within. While direct burial cable can be run inside conduit for additional protection, the cable is designed to withstand direct exposure to soil and moisture and is rated for wet, dry, and damp environments.
Types of Direct Burial Cables The most common types of direct burial cable used in residential projects are underground service entrance (USE) and underground feeder (UF). Type USE cable is usually black and is most often used for buried lines that bring power from the utility's transformer to individual houses. Type UF cable is usually gray and comes in rolls that look like standard non-metallic (NM) sheathed cable (often referred to by the brand name Romex). While standard NM cable is rated only for dry, interior applications, UF cable can be used outdoor as well as indoors. If you want to install a cable between the house and an outdoor lamppost or to run power out to a garden shed or detached garage, UF cable is the standard choice.
The primary difference between standard NM and underground feeder (UF) cable is in the cable construction. Standard NM cable contains wires that are wrapped with paper and a relatively loose plastic sheath. UF cable has wires that are completely encased in a solid plastic sheath. This encasement protects each wire from the others and does not allow moisture or other external elements to travel inside the cable.
The Rise of Buried Cable Most homes in older neighborhoods in America have overhead service entrances, the power connections to the utility grid. The disadvantages of running wires overhead include having poles in your yard and the dangers of having an exposed power line that can be run into by ladders or damaged by tree branches or other natural elements. Running power lines underground means they’re not susceptible to storm damage, and there are no exposed cables to worry about. Of course, there is one big concern with buried cable: digging (see tips below for how to dig safely).
