The installation of service-entrance cable is covered in NEC Article 338. Service-entrance cable for above ground use is supplied in one of two varieties. A “U” style consists of two insulated conductors with a bare neutral wrapped around the insulated conductors in a spiral configuration.

At terminations, the spiral neutral conductor is unwound and twisted together to form the third or neutral conductor. A 4-wire variety of Type SE cable is manufactured and is suitable for installation where a separate neutral and equipment grounding conductor are required, such as for wiring ranges, dryers, and some panels.

As shown in figure below, fittings are specifically designed to facilitate installation of service-entrance cable outside the building. These fittings include a weatherhead and raintight and non-raintight cable clamps.

Typical hardware used for installation of service entrance cable for services.

Sill plates are available to protect the cable and weatherproof the installation where the cable is routed inside the building. The cable must be protected against physical damage in accordance with NEC 230.50.

Be sure to check with the local electrical inspector, as some jurisdictions limit the length of serviceentrance
cables inside a building. It is considered more fragile than a metal raceway such as EMT, IMC, or rigid steel conduit and requires protection against physical damage in accordance with NEC 300.4.

Verify Which Overhead Clearances Apply
Electricians must abide by the NEC. Utilities must go along with the National Electrical Safety Code. These codes may have different clearance requirements for service-drop conductors and drip loops.

When involved with installing an overhead service, check with your electrical inspector to determine which code is enforced in your area. The installation requirements of the serving electric utility must always be complied with so long as they do not reduce the requirements of the NEC.

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