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What happens when you press the TEST button on a circuit breaker in an electric panel?
Thursday, July 12, 2018
All circuit breakers provide “overcurrent protection.” This means that, if current in excess of the breaker’s rating in amps is flowing through the circuit, the breaker will trip and disconnect the circuit to avoid overheating the wiring or equipment it serves, which could potentially start a fire.
Breakers with a small colored button marked “TEST”—it could be white, yellow, green, or red—have a dual protective function. And older GFCI breaker from the 1980s with a red test button is shown below.
There are two primary types: GFCI (Ground Fault Circuit Interrupter) and AFCI (Arc Fault Circuit Interrupter). When the test button is pushed the device simulates the defect that it s designed to protect against, and trips the breaker to the middle position if functioning properly. To reset, you push the breaker switch all the way to “OFF” and and then back to “ON.” If nothing happens when the test button is pushed, that means the device is not functional and therefore not protecting the circuit in the way it was designed.
The GFCI-breakers protect against ground faults, which is essentially current that is traveling off the intended circuit and may be shocking you. These breakers protect circuits for pools and spa tubs, along with receptacles in wet areas like bathrooms, kitchens, garages, and exterior. Because GFCI-protection can also be provided by GFCI-receptacles with “TEST” and “RESET” buttons in the center, GFCI-breakers are used less often in panels today, with GFCI-receptacles placed around the home in the wet areas instead.
AFCI-breakers protect against arc faults, which is when a frayed or damaged wire sparks across a gap in the wire, either along one wire or between two adjacent wires. Because arcing of wiring is known to be a leading cause of house fires, AFCI breakers have been required for bedroom circuits since early in this century, and more recently they are must be installed to protect virtually all the 120-volt receptacles in a home. A newer version, called a Combination AFCI (CAFCI) has been required since approximately 2008.
Also, see our blog post Where are GFCI receptacle outlets required? and What electrical hazards does a Ground Fault Circuit Interrupter (GFCI) NOT protect against? and When did arc fault circuit interrupter (AFCI) breakers first become required? and Are Ground Fault Circuit Interrupters (GFCIs) really necessary and worth the trouble
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