Arc-fault circuit interrupt (AFCI) breakers, ground-fault circuit interrupt (GFCI) breakers, and variations of them (CAFCI, AFI, GFI, dual-function, etc.) have a "test" button just like their wall ...

The circuit breaker is one of the most important but least understood parts of your home electrical system, keeping you safe from electrical fires. Appliance Science looks at how they work.

The circuit breaker should trip if, say, a wire comes loose and touches the metal housing of your toaster. Or a squirrel gets into your attic and chomps through an electrical conductor (RIP, buddy).

If you routinely trip circuit breakers, or string extension cords to keep them from tripping, upgrading is essential. Homes even 20 years old can be short on circuits and outlets.