Service-Entrance Cable (Types SE & USE)

Type SE cable brings power from the meter into the service equipment, and it's also widely used for feeders and large appliance circuits like ranges and dryers. USE (underground service entrance) is the direct-burial version with moisture-resistant insulation for the run from a transformer or pole.

A key caution lives in the interior use of SE cable: when used as an interior branch circuit or feeder in an unprotected space, its conductor ampacity must be figured on the 60-degree column, because the cable can be run through thermal insulation where it can't shed heat. USE alone lacks the flame rating to come indoors as premises wiring.

When it applies

Service-entrance cable, Type SE, carries the heavy conductors from the meter to the main panel and sometimes feeds subpanels. Its underground relative, Type USE, is rated for direct burial. You will see SE on the outside of a house running from the weatherhead down to the meter and into the service equipment.

Common mistakes

• Using indoor SE where the run is exposed to conditions calling for the underground-rated USE.
• Relying on the uninsulated bare conductor as a neutral in an interior feeder application where that is no longer permitted.
• Failing to protect the cable from physical damage where it comes down a wall within reach.

In the field

On feeder runs inside a dwelling I treat that concentric bare conductor carefully. Rules tightened on using it as a neutral downstream, and I size and run a proper four-wire feeder rather than lean on old habits.