PARTS OF ELECTRIC SERVICE ENTRANCE BASICS

How to install service entrance? You will only know it if you know its parts. The details of how the service lateral or triplex cable provided by the electrical utility is fastened and spliced to the customer’s service point are illustrated in Fig. 5-3.

The bare neutral/grounding cable that supports the triplex is fastened at one end to the utility pole and the other end is fastened at the service point with a combination insulator and anchor bolt crimped onto the cable. This attachment method leaves the end of the neutral/grounding cable and the bare ends of the two insulated “hot” conductors available for splicing.

Electrical utility employees splice these three ends to corresponding ends of the customer’s service entrance (SE) cable, which is installed by the electrical contractor. The three ends of the customer’s SE cable are pulled through the bushings in a protective metal hood called the weatherhead or service head with enough slack to permit an adequate drip loop to be formed when the three conductors are spliced.

The drip loop, which must be at least 36 in. long, prevents water from entering the weatherhead. Without a drip loop, water could drain down the conduit to the cable connections inside the meter base to the bus bars that power the watthour meter, corroding them and causing a short circuit.

The details of two different aerial feed service entrances are illustrated in Fig. 5-4. A 200-A service entrance made with three-wire service entrance (SE) cable is shown in Fig. 5-4a. The cable from the weatherhead is brought down to the meter base, where the busbar connections to the meter are made. Another length of SE cable goes from the meter bus bars to the loadcenter.

A second version of a 200-A service entrance has the SE cable protected by metal or nonmetallic conduit between the weatherhead and the meter base, as shown in Fig. 5-4b. The service entrances for 175- and 100-A service are identical except that the SE cable has either a 175- or a 100-A rating. The limits of the meter height dimensions above grade level are approved by NEC 2002.

A 200-A service with the triplex cable terminating on a metal conduit mast is shown in Fig. 5-5. The mast projects high enough to comply with NEC 2002 for the minimum distances of the triplex termination above the ground. The hollow pipe functions as both a mast and a conduit for SE cable from the weatherhead to the meter base. As in Fig. 5-4, the service entrances for 100- to 175-A service are identical except for the lower SE cable ratings. All of the dimensional limits shown are those approved by NEC 2002.