What are Circuit Breakers

How Electrical Circuit Breakers Protect Your Home and Family

By Mark J. Donovan

Circuit breakers are located in your home’s circuit panel box. The circuit panel box is often found in a basement, attached garage, a closet, or in a hallway. Circuit breakers are designed to protect your home and family from electrical fires and deadly shock. There are several types of circuit breakers including standard, ground fault, and arc fault circuit breakers. Moreover circuit breakers are rated based upon current draw and voltage levels. There’s also a main circuit breaker in the circuit panel box that enables the flow of electricity to all of the other individual circuit breakers within the box.

Circuit breakers monitor the amount of current that flows from the main circuit panel bus bar to the electrical outlets, lights, and appliances that are connected to the circuit breaker.

When a circuit breaker senses that there’s more current flowing through the circuit than what the circuit breaker and wiring are rated for, the circuit breaker trips and stops the flow of electrical current.

One of the biggest advantages of circuit breakers over fuses is that circuit breakers can be reset with a simple flick of a switch when they are tripped. When a fuse blows, on the other hand, a new replacement fuse has to be installed.

Typically there is an electrical circuit breaker for each room of a house. In some cases, such as with bathrooms, there may be just one circuit breaker feeding two bathrooms. In kitchens there are often three or four circuit breakers. One for the oven, one for the microwave/refrigerator, and one or two for all of the other electrical outlets and appliances in the kitchen.

Electrical circuit breakers operate by effectively either measuring the amount of heat that is produced by the flow of current through it, or by the strength of a small magnetic field produced by a small coil inside the circuit breaker.

Here are circuit breakers in a main circuit panel box.

With magnetic field sensing types, as the current flows through the coil it produces a magnetic field. The more current that flows through the coil the stronger the field. When the magnetic field gets too high the circuit breaker trips.

A heat sensing based circuit breaker works similarly. When a temperature sensor inside the circuit breaker senses a certain temperature point it trips the circuit breaker stop the flow of electrical current.

Electrical circuit breakers are also helpful for controlling the flow of electricity in the home. For example you can shut off electricity to a portion of the home to either fix or work on an electrical outlet or switch, or to install a new light fixture or electrical appliance.

Most commonly used circuit breakers in the home are rated for 15 amp or 20 amp (120VAC). Ovens and driers are typically rated for 30 amps (240VAC). It’s important to install a circuit breaker that is rated for the particular wire rating on a circuit.

For example a 15 amp circuit breaker should be used with 15 amp rated wire (e.g. 14-2 or 14-3 Romex wire). If you installed a 20 amp circuit breaker with 15 amp rated wire, the wire could overheat and cause a fire in the home.

In bathrooms, kitchens, basements, garages and other wet areas ground fault circuit breakers should be used. These types of circuit breakers protect your family from experiencing a deadly shock. In bedrooms and other living areas arc fault circuit breakers should be used. They sense small arcing caused by appliances that could cause a fire. When an arc is sensed they trip.

When installing circuit breakers always label the circuit breaker to indicate what portions of the home are powered by it.

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