Load centers are used for the protection and distribution of power in a building or residence. They are also called circuit breaker boxes. Typically, load centers mount on a wall. Power from the mains enters the breaker box and is connected to circuit breakers that distribute power to the building. In this way, load centers are used both for holding the circuit breakers and for electrical distribution. Products are available for commercial, residential, and industrial applications at both small installations and large facilities. Load centers for three-phase power are also available, but residential breaker boxes are single-phase devices. Typically, load center are rated in amperage. In the United States, a typical home has a 200-amp service load center. Load centers are not universal. Rather, they are designed for a particular manufacturer’s circuit breakers. By definition, these circuit breakers are switching devices that are capable of making, carrying, and breaking current under normal circuit conditions. For a specified time, circuit breakers can also make, carry and break current under abnormal conditions (such as a short circuit). Low-voltage circuit breakers have voltage ratings from 250 to 600 VAC and 250 to 700 VDC. Medium voltage circuit breakers are rated up to 72.5 kV. Load centers for miniature circuit breakers must to accommodate devices with features such as a supplementary protector, a shunt trip, and a ground fault circuit interrupter (GFCI). GFCI devices are designed to protect people from severe or fatal electric shocks. There are many different types of load centers. Some products are designed for single-family or multi-family residential construction. Others are designed for commercial buildings and industrial construction. Specifications for load centers include amperes or amps, number of supported circuits, and suitability for indoor or outdoor use. Products for flush and surface installation are available as either main breakers or main lugs. There are several types of mains, including straight-in and convertible. Straight-in mains are designed to eliminate waste and save installation time because they do not require bends. Convertible mains permit the field-conversion of main breaker load centers to main lugs, or vice versa. Load centers with backed-out neutral screws can also help electricians, home builders, and other personnel to reduce labor costs and installation time.