Different Types of Circuit Breakers
All will protect you from overload or other dangers
By Kimbra Cutlip
Circuit breakers are devices incorporated into electrical wiring to protect people from electrical shock and fire caused by faulty or overloaded circuits. When the breaker senses an irregular current or the buildup of heat because of an overload, it trips and breaks the electrical connection. It's like a switch turning off the power to whatever is on that circuit. Five different types of circuit breakers are common in residential construction in the United States. Each is specific to a different use.
Main Circuit Breaker
A main circuit breaker de-energizes the entire 240-volt electric feed that serves the house or individual unit within a commercial building. They are the largest breakers on a panel and are generally rated at 200 amps. This means they will trip when the current exceeds 200 amps.
A double-pole (also called a two-pole) breaker controls the electricity supply to equipment that uses 240 volts. These include appliances such as certain power tools, electric ranges, water heaters, air conditioners and hot tubs. They are rated to trip when the amperage exceeds 30 amps.
Single-pole breakers are the most common in a panel. They provide 120 volts to small electrical equipment such as lights and receptacles. They are generally rated to 15 or 20 amps.
Mini breakers can be single- or two-pole breakers. They are about half the size of standard breakers, though they are rated for the same voltage and amperage. People often use mini breakers when they are adding circuits to a full electrical panel. They are UL approved, but they are not preferred because they are for lighter duty. Think of the difference between particleboard shelves and solid hardwood for a comparison.
Ground fault current interrupters (GFCIs) are used in dedicated circuits that supply energy to wet places such as bathrooms, kitchens, outdoor fixtures, pool decks and basements. With a GCFI installed at the panel, you do not need individual ground fault interrupter outlets (outlets with a test and reset button) in these locations. A properly installed GFCI is very sensitive to ground fault conditions and should protect against electrocution if a hair dryer falls into the tub or a wet child grabs a broken extension cord plugged in on your pool deck.
Arc fault circuit interrupters (AFCIs) are required by the National Electric Code for new construction on all circuits that run to sleeping areas. They are more sensitive than standard breakers and will trip before a short circuit happens, thus adding more protection against fire hazards. They can sense the fluctuations in current caused by wires nicked with a staple or screw (such as when you're hanging a picture).
About the Author
A former science writer for the Smithsonian Institution, Kimbra Cutlip is also the co-owner of a remodeling company specializing in energy efficient sustainable building and solar hot water systems.
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