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Why do some breakers in my electric panel have a TEST button on them?
Thursday, October 18, 2018
Every breaker in an electric panel provides “over-current protection,” meaning that if too much electricity is flowing through the circuit it protects--which may cause the wiring to overheat and start a fire--the breaker trips, shutting off the electricity. The breaker switch moves to the middle position between “ON” and “OFF” when it trips, and must be toggled to “OFF,” and then back to “ON” to re-energize the circuit.
Breakers with a button marked “TEST,” like the green ones in the photos above, are either “GFCI” or “AFCI” type and serve a dual protective purpose. Manufacturers recommend that you press the test button on a regular basis (typically monthly) to confirm that the secondary protective mechanism is still functional.
GFCI is an acronym for Ground Fault Circuit Interrupter, meaning simply that when a “ground fault” occurs it interrupts (trips) the circuit. It is intended to provide shock protection to occupants of a home in wet areas, such as the bathroom and kitchen, where it is possible for electricity to flow through your body to a wet area connected to the ground or grounded material. Most GFCI-protection in a home is provided by wall receptacles with two buttons marked “TEST” AND “RESET” on them. But for an appliance such as a jacuzzi tub, where the receptacle that it’s plugged into is deep in a compartment under the tub, placing the GFCI-protection in the panel provides an easier way to test and/or reset the GFCI-protection. Also, older pre-1980 homes often have GFCI-breakers in the panel because the wall GFCI’s were not readily available when the home was built.
The AFCI circuit breaker is an Arc Fault Circuit Interrupter. It trips the circuit when arcing, commonly called sparking, is detected anywhere in the wiring. The arcing can occur in series (between one side of a frayed/broken piece of wire and the other) or parallel (between one frayed/broken piece of wire and an adjacent one).
Building codes began requiring an AFCI-breaker for circuits that serve wall receptacles in bedrooms in 2000, in response to research by the CPSC (Consumer Products Safety Commission) indicating that 40,000 fires each year result from home electrical wiring, and arcing faults are one of the major causes. When arcing occurs, it generates high temperatures that can ignite nearby combustibles such as wood, paper, and carpet.
The requirement was upgraded in 2008 to include breakers for most wall receptacles in new home construction and a new type of AFCI-breaker is now the standard. It is called a combination-AFCI or CAFCI, and recognizes both series and parallel arcing, whereas the older AFCIs only tripped for series arcs.
Because the markings that indicate whether a breaker with a test button is GFCI or AFCI are often on a part of the breaker that is concealed by the cover plate (called a “deadfront” by electricians), sometimes it’s difficult to determine which type breaker you are looking at without removing the cover plate. But if it is serving bathroom, kitchen, garage, laundry room, or exterior receptacles—essentially any wet area—then it will be a GFCI.
Also, see our blog posts What happens when you press the "TEST" button on a circuit breaker in an electric panel? and What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?
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