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What is the difference between what trips a GFCI (ground fault) receptacle and a circuit breaker?

Friday, June 15, 2018

Shock vs. Overcurrent Protection

Both devices provide electrical safety protection for a home, but in different ways. A circuit breaker is designed to cut off the electricity to a circuit when the current flow (amperage) exceeds the rating for the wires it serves. High current flow through wires that don’t have a large enough cross-section to handle it will overheat and can start a fire. The breaker trips when the amps exceed the number printed on the switch. So breakers are primarily for fire protection. 

    Ground-Fault-Circuit-Interrupter receptacles provide shock protection for the occupants of a home and are required in the wet areas, such as kitchen, bathrooms, garage, and exterior locations. They measure the amount of current leaving the receptacle and compare it with the current flow returning. If some of the electricity is leaking out of the circuit (a ground fault), the GFCI device in the receptacle trips within 25 milli-seconds.

    Although the current might leave the circuit through multiple different routes, it is also possible that it is flowing through a human body to the ground. Because water is an electrical conductor, and wet areas of the home have the highest likelihood of providing a connection to ground for someone in contact with an electrically “live” surface, they are where GFCIs are required.

    There is also a device that looks like a GFCI receptacle, but without the slots to plug in a  cord. One is shown at the left side of the photo at the top of the page. It’s called a “dead front GFCI.” 

    Also see What is the difference between GFCI and AFCI circuit breakers? and Where are GFCI receptacle outlets required? and When were GFCI receptacle outlets first required?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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