Installing Electric
Service-Entrance Systems

[lesson title]

The ground-cover requirements for underground conductors or conduit vary according to the site. In nontraffic areas, SE cable should be buried at least 18 inches and covered with a 2-inch-thick concrete pad (Figure 2-1). If rigid or intermediate conduit is installed, the depth can be reduced to 6 inches.

Figure 2-1. Buried SE cable (nontraffic area).

When SE cable is subject to vehicle traffic, at least 24-inces of ground cover is required (Figure2-2). The 24-inch-depth requirement will allow the service to withstand the weight of vehicles passing over it. The depth requirement is the same when conduit is used.

Figure 2-2. Buired SE cable (traffic area).

SE cable buried in solid-rock areas can be installed down to the surface of the rock if the cable is covered with at least 2 inches of concrete that extends to the rock surface (Figure 2-3). The same requirement exists for conduit.

Figure 2-3. Buried cable in solid rock area.

Conductors coming out of the ground should be protected by enclosures, raceways, or conduit from below grade to 8 feet above the ground (Figure 2-4).

Figure 2-4. Conductor protection.

When backfilling a trench where there are cables or conductors, do not backfill with-

• Large rocks.
• Paving materials.
• Cinders.
• Sharp substances.
• Corrosive materials.

Placement of SEs. Underground services can be installed using either underground service entrance (USE) cable, direct-burial conductors, or conduit (Figure 2-5). Conductors should not be spliced unless they are placed in a properly installed splice box.

Figure 2-5. Types of installation.

When direct-burial conductors or USE cables are above grade they must be protected in the plastic or metallic conduit at both ends (Figure 2-6).

Figure 2-6. Protection at ends of SE cable.

The installation of a USE to the power panel varies according to the site and the equipment. (Figure 2-7) shows a typical setup that is subject to change to fit the installation.

NOTE: A ¼-inch air space is required when mounting a power panel to a damp wall or surface.

Figure 2-7. Typical USE power-panel setup.

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