Home Wiring And Service Panels
Types and How They Work When dealing with home wiring you must know about the service-entrance panel (SEP) and that it is the main house panel. It serves two primary purposes. First, the main panel is the only location in or outside the house where all electrical power can be cut off at once. Every adult member of your household should know the location of this panel and how to cut the power in case of an emergency. Second, the main panel is the distribution point and protection center for all of the circuits. All the branch circuits, ones that go to the receptacles, switches, and appliances throughout your house, originate here. Under the home wiring panel cover, circuit breakers, and wires are two copper or aluminum strips. These are the power buses, called hot buses. Each bus is connected to a hot incoming main cable. The circuit breakers are all plugged into these two buses, which provide the breakers with power. Neutral and grounding wires from each circuit are connected to the aluminum neutral/grounding buses on each side of the hot buses. Dead center in the upper part of the panel is a very large breaker, called the main breaker. This breaker controls all of the house power. Its purpose is to monitor the current being drawn, opening the circuit when there is a short or an overload. It also provides manual control over the house power. Panel Sizes. A typical house panel may provide 100, 150, or 200 amps. Today, 200 amps is most common, although larger all-electric-power homes may use up to 400 amps. Your house's power capacity is noted either on the panel or on the main breaker. Panels rated for the same maximum current capacity, such as 200 amps, are subdivided by the number of breakers they can hold. The maximum number of breakers a residential panel can hold is 40 breakers plus the main breaker. This type of panel is called a 40/40 panel.
The first number refers to the number of full-size breakers the panel can hold, and the second number refers to the maximum number of breakers the panel can hold regardless of breaker type. The next panel size below a 40/40 is a 30/40 panel. It can hold only 30 full-size breakers. To increase the panel while working with home wiring to 40 breakers, half-size breakers must be used. It is preferable to use full-size breakers for safety reasons. Smaller panels may hold a maximum of 20 or 30 breakers. Avoid these panels because they will not provide breaker space for future expansion. Circuit-Breaker Sizes. Individual breakers distribute power from the hot buses to the circuits. A standard-tab hot bus will accept only standard full-size breakers; a split-tab hot bus can accept either twin (dual) or half-size breakers. A twin breaker consists of two breakers installed within the space usually occupied by a single breaker. TO INSTALL AN INDIVIDUAL BREAKER with home wiring, left, first turn off the main power; then hook the notched end onto the hot bus tab, and snap it firmly in place. A circuit's hot wire, right, is secured beneath a circuit breaker screw. Insert the bare wire end in the terminal hole, and tighten the screw over the wire THE SERVICE-ENTRANCE, or main panel is both the entry and distribution point for all the circuits in your home. If the panel cover, breakers, and wires were removed, you would see the two power buses into which all of the circuit breakers are plugged. The main breaker, at the top, controls power entering the hot buses. Turn off the power by moving the handle to the off position on the main disconnect. Breakers trip automatically if the circuit shorts or is overloaded. |