Installing a Circuit Breaker in an Existing Panel
When adding a new circuit or replacing a faulty breaker, here is what you need to know to work safely in the panel.
Synopsis: Even when the main breaker is turned off, live conductors are still feeding into the box. Follow our steps to keep this installation safe and simple. Learn the right order to work in, the right tools to use, and the right mentality you’ll need when working with electricity. We include a detailed diagram to help you identify every wire and component beneath the panel, and we highlight five types of breakers to help you choose which one is right for your job. This article will guide you step-by-step through the installation, from the moment you shutoff the breaker, to the moment you label your new, working circuit.
If you’ve made it this far, chances are the hard work is done. You’ve built an addition, remodeled your kitchen, or set up a home office, and you’re ready to hook up new electrical circuits to the juice. Not so fast. While this part of installing a new circuit is the easiest, it’s also the most dangerous. Even when the main breaker is turned off, live conductors still are coming into the box. Any time I work in an electrical panel, I treat it as if it were live. Safety is my No. 1 concern.
When in doubt, test the draw
Most likely, a modern house with 200-amp electrical service and room for a new breaker is capable of carrying a larger load. But never assume your service can handle more draw. If you have a smaller or crowded panel, you should test the panel with a voltage meter to determine the available capacity.
Turn on every electric device that you can, and read the amperage being drawn on each main feeder. The incoming feeder on the left side of the panel feeds phase A. The one on…