2-2-2 ALUMINUM SEU CABLE

SEU cable is a flat, 600V service entrance cable. It has two insulated conductors and a bare neutral wrapped around them, under a sunlight-resistant jacket. It carries power from the utility's service drop or meter to a building's main electrical panel.

The U stands for unarmored. SE means service entrance, and the NEC and UL list the cable as Type SE, Style U. The name sets it apart from older armored service entrance cable and from SER, where the R stands for round.

Both are 600V Type SE service entrance cables, but they are built differently. SEU (Style U) has two insulated conductors wrapped by a bare concentric neutral, which gives it a flat profile. It is mainly used between the utility meter and the main panel. SER (Style R) is round, with its conductors cabled together, and its 4-wire versions carry an insulated neutral plus a separate bare ground. That makes SER the usual choice for feeders to subpanels.

A concentric neutral is a layer of bare wire strands wrapped in a spiral around the cable's insulated conductors. In SEU cable, it serves as the neutral at the service and gives the cable its flat shape. Its size is given as an equivalent AWG; in 2-2-2 SEU, the neutral is equivalent to 2 AWG.

For a 100A dwelling service, 2-2-4 aluminum SEU is the standard choice, or 2-2-2 where a full-size neutral is required. On long meter-to-panel runs, many installers step up to 1-1-1 to limit voltage drop. These sizes apply to 120/240V dwelling services, and your utility or inspector has the final say.

This size comes in two versions: 2-2-4 with a reduced neutral and 2-2-2 with a full-size neutral. On a typical 120/240V residential service, the neutral carries only the difference in current between the two legs, which is why a reduced neutral is common. Choose the full-size neutral when your utility, local code, or inspector requires it, or when a large share of the load is 120V and likely to be unbalanced.

Yes. The XHHW-2 insulation is rated for wet locations and the PVC jacket is sunlight resistant, so SEU is commonly run down exterior walls from the weatherhead to the meter and from the meter to the panel. Secure it within 12 inches of the service head, meter base, or panel and at intervals of no more than 30 inches (NEC 230.51). Where it could be hit, such as along a driveway, protect it with conduit or another approved guard.

Yes, with limits. Indoors, SEU must follow the same support and protection rules as NM (Romex) cable (NEC 338.10(B)(4)). When it carries service conductors from the meter to the main panel, the panel must sit as close as practical to where the cable enters the building (NEC 230.70). Many local codes also set a maximum length for that indoor run.

Yes. Use a service head made for SE cable and sized to fit it. A conduit-type weatherhead is made for individual wires in a mast and won't seal around a flat cable. The NEC also allows the cable itself to be formed into a gooseneck instead (NEC 230.54). Either way, leave a drip loop so water runs off before it reaches the connection.

Yes, above ground. Conduit is often used for short sections where the cable needs protection, such as near grade or along a driveway. Because SEU is flat, size the conduit on the cable's widest dimension (NEC Chapter 9, Note 9). SEU is not permitted in underground conduit.

No. The NEC does not permit Type SE cable underground, with or without conduit. For underground service laterals and feeders, use aluminum URD or USE-2 cable.

Not for a subpanel that serves 120V circuits. Downstream of the main service disconnect, the NEC requires the neutral and the equipment ground to be kept separate. SEU has only one bare conductor to do both jobs, so a subpanel feeder normally calls for 4-wire SER.

Not for a new installation. A feeder to a detached building that serves 120V circuits needs four wires: two hots, an insulated neutral, and a separate ground (NEC 250.32). SEU has only three. Use 4-wire SER for above-ground runs or aluminum URD quadruplex for underground runs. The exception is a detached building with its own utility meter, where SEU can serve as that building's service entrance cable.

Yes, when the lugs are rated for aluminum. Look for an AL/CU or AL9CU marking; most meter bases and main breakers carry one. Before connecting, clean the conductor ends, apply an oxide-inhibiting compound where the lug manufacturer calls for it, and torque each termination to the value marked on the equipment.