Making Sense of the Breaker Panel :: How Electrical Works

Built By Chris Long for Building Moxie & Published December 5, 2012.
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If you’ve ever replaced a light switch, installed a new thermostat, or troubleshot the wiring on an appliance, you’ve likely utilized your circuit breaker panel. Typically hidden behind a metal door in some dark corner of our homes, this array of switches serves as a building’s electrical control panel. In addition to a master switch that cuts all power to the home, the panel allows for isolated on-off control of the electrical current running to each room and section of a house.

In a world where do-it-yourselfers are quickly being replaced by ‘do-it-for-mes’, many renters and homeowners never even attempt to understand the array of switches on the circuit breaker panel. Fortunately, it’s pretty easy, but it helps to understand what’s at play and how the switches work. Most importantly, having control of your home’s electricity can help keep your family safe (by helping to prevent electrical fires) and empower you to tackle simple home projects yourself.

How Home Electricity Works

When electricity flows into a building, that raw energy can be measured in voltage (it’s technically ‘electrical pressure’).  Resistance (ohms) is created by wiring within walls and appliances, decreasing that pressure as it flows (current, measured in amps) through your devices, chargers, dishwashers, light bulbs, and everything else plugged into the wall. The total energy being consumed by your home is the ‘power’ being used (and billed).

We wouldn’t want our home’s full potential current flowing through the toaster — that would make for some quickly burnt bagels, and a fire to follow. Resistance keeps our power usage in check. Voltage divided by resistance equals current.

In a circuit breaker, an electromagnet controls whether the power to a particular room is on or off. Think of a fuse: if the current flowing through it becomes too strong, it’s designed to ‘blow,’ stopping the flow of electricity past it. Although some homes still use fuses, most now utilize an electromagnet switch that doesn’t have to be replaced. When the current flowing through the connection grows too strong, the magnet is strengthened enough to attract it to a second magnet, breaking the connection and stopping the flow of electricity.

When you flip a switch at your circuit breaker panel, you’re manually breaking or reconnecting the flow of electricity. And although the magnets are designed to stop the flow when it becomes dangerously high, it’s still possible to overdraw electricity to a wall socket.

Watch out for too many items plugged into one socket, especially when it’s time to string lights around the holidays. At best, you’ll continuously ‘blow the switch’ and have to return to your circuit panel to reestablish the connection. At worst, the flow could heat the connection at the socket to the point of smoking or igniting. This is the sort of incident where it’s most important to be able to localize and identify each switch in your circuit breaker panel.

Conduct an Electrical Scavenger Hunt (How to Label the Circuits in Your Breaker Panel)

Take a look at your circuit breaker panel door. Ideally, each switch is neatly labeled. You’ll probably notice tags like ‘Dining Room,’ ‘Upstairs Bathroom,’ and ‘Water Pump.’ If these labels are worn off and illegible or no longer apply to the names you use for rooms in your house, it’s important to update them. In some cases, your panel may not identify the switches at all.

To accurately label your panel, you’ll want to gather the following:

• White address label stickers
• A pen or permanent marker
• A friend

If some labeling exists, you won’t have to start from scratch, but if your circuit breaker panel switches are completely unidentified, take some solace in the knowledge that your task will get easier as you go through the switches.

Start by turning off the top switch. Send your friend to the room or area that you suspect the first switch corresponds to, armed with a small lamp or easy-to-carry electrical device. If they’re not in shouting distance, stay on the phone or use walky-talkies. Your friend will eventually discover which room, socket, or sockets are not receiving power. And if you don’t have an available friend, just walk back and forth between the breaker panel and the outlets you’re testing on your own.

Once you figure out where a switch controls, put a sticker next to it and label it appropriately. Just remember that some bigger rooms may have two switches, or a wall with sockets on either side may correspond to the same switch, so make sure to check each socket in the vicinity as you go.

With your accurately labeled circuit breaker panel, you’re now in control of your home’s electricity. When you’re ready to install a motion-sensor light switch in the guest room, for example, you’ll know exactly how to turn the power off to that room. Just remember to (double) check the socket with a voltage regulator (a tester), just to be sure, before touching any wires!

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Chris Long is a Home Depot store associate in the Chicago suburbs. He also writes for the Home Depot blog. Chris has interests in household electrical topics ranging from the simple smoke detector to solar panels.