First of all, in the interest of safety you should leave this repair to a professional. In fact, your local codes may require that this work be done by a licensed electrician. In most cases a permit will also be required for this work. While not difficult, it requires you to open the interior of your circuit breaker panel and work around live current. The purpose of this article is to describe in general terms some of the steps and considerations an electrician will take when replacing or installing a new circuit breaker.
Located inside or outside of your home is a circuit breaker box or panel (sometimes called a fuse box) that contains circuit breakers for each of the circuits in your home. Some homes have more than one circuit breaker panel, there may be a main panel plus one or more sub panels in other locations.
A circuit breaker provides protection for each of your electrical circuits by stopping the flow of current if an overload or fault occurs. When an electrical fault occurs or the load on your circuit becomes too great, the breaker on that circuit trips and ceases the flow of current to that circuit. A tripped circuit breaker is still sometimes referred to as a "blown fuse" in reference to the older technology that circuit breakers replaced. If your home uses an actual fuse and not a circuit breaker, click here for information on fuse boxes.