Regardless of the type of the main disconnect used, the breaker(s) must be in series with both hotlines. In other cases, one or more circuit breakers are housed in the electrical panel that provides the required main disconnect capability.įigure 7: An externally operated (EXO) main disconnect In some cases, the Main Disconnect switch (or breaker) is an Externally Operated (EXO) Switch that is inserted between the service meter and the electrical panel. Main DisconnectĮvery residential service entrance must provide a means of disconnecting the electrical power feed in case of an emergency. The electronic meter is essentially a series-parallel circuit that converts the incoming current and voltage to a signal that indicated the amount of energy used. This meter in Figure 6a is an electromechanical meter, while the one shown in Figure 6b is an electronic meter. However, any problems beyond the service meter are the customer’s responsibility. Any repairs required in the service drop or service meter are made by the utility with no charge to the customer. In most cases, the electrical service meter is the point where the utility’s responsibility ends.
There is an important point to be made at this time. That is the dial on the left rotates counterclockwise (CCW), the next rotates clockwise (CW) and so on. Note that the dials on the analog meter rotate in alternating directions. For example, the value indicated by the meter in Figure 6a is found as: The values indicated by each dial equals the reading times its weight (the value printed above the dial). The weights of the dials (from left to right) are 10000,1000,100,10, and 1. The dials on the meter in Figure 6a are read from left to right. \ġ000 in the denominator of the equation converts the power to kilowatts (kW). A kilowatt-hour is the amount of energy used in one hour, found as: The electrical service measures energy in Kilowatt-hours (kWh). Two electrical services meters are shown in Figure 6, one providing an analog display (rotary dials) and the other providing digital display. Service MeterĪs stated earlier, the service meter measures the amount of energy that is used by the customer. In this case, the transformer is used to lower the voltage from the utility to the 120/240V residential level. Transformers are devices that are used to raise or lower a voltage level. The secondary power lines connect the transformer output to the electrical service meter. The primary power lines pass through the conduit to the pad transformer input. This distinguishes the clevis service drop from the mast service drop.įigure 4: Clevis-Type Service Drop Service LateralĪn underground service connection, or Service Lateral, is illustrated in Figure 5. Note that the weather head and conduit are secured to the side of the residence below the roof line. The term Clevis refers to the connectors that fasten the conductors to the building. Second, they prevent any water (due to rain) from traveling along the lines into the service drop conduit.Ī clevis service drop has fasteners that secure the power lines (or triplex cable) to the side of the residence, as shown in Figure 4. Firstly, they provide slack that reduces any mechanical stresses on the power lines.
The conduct Tails (or drip loops) serve two purposes. The service drop is attached to the mast at the mast knob. The term Mast refers to the conduit and weather head that extend upward from the roof. A mast service drop is illustrated in Figure 3. There are two types of overhead service drops, mast, and clevis. This concept is illustrated in Figure 2.įigure 2: Service Drop Voltages Mast and Clevis Service Drops This is why the service is identified as a 120/240V service. Between the two hotlines, there is a difference of potential 240V.
Each hotline as a potential of 120V to the neutral line. The three conductors comprising the service drop consist of two hotlines and one neutral. The three lines may be independent conductors or housed in a three conductor cable called a triplex cable (As shown in the figure). The service drop illustrated in Figure 1 has two 120V lines and a neutral conductor. An overhead power connection from the utility lines to the service entrance is called the Service Drop.