Anytime you are working with electricity you need to shut off the power to the circuit feeding the outlet or fixture. Never work on a “hot” circuit.
Find the panel
Grab a flashlight and find the electric panel, which is typically in the basement or a back room, and open the panel by sliding the latch on the right side and opening the cover like a door. Inside you will see switches for breaking the circuits, which are cleverly named “circuit breakers.”
Breaker, breaker, good buddy
Each circuit breaker is rectangular and has a switch with a number on it that you can flip back and forth to turn the circuit on and off.
There will be two columns of circuit breakers in each electric panel. When the switch is pointed to the center of the panel the power is on. When the switch is pointed toward the outside of the panel the power is off to that circuit.
Looking at the photo, we know all four circuits are on because the breakers are in the right column and the switches are pointed left.
In the next photo, the switch of the top breaker is pointed to the right (the outside), which means the circuit is turned off.
Getting tripped up
There is a third possibility for the switch position. If it is in the middle (pointing straight at you), the breaker has “tripped,” which means that it detected a large current in the circuit. Usually this means a short circuit, i.e. the electricity can flow directly from the hot wire to the neutral wire without encountering any resistance like a light bulb or a toaster.
If there is nothing to resist the flow of current the wires will catch on fire and might burn down the house, which to my way of thinking is suboptimal. This is one of the main reasons for circuit breakers. They break the circuit if the wires could overheat.
The numbers on the switches indicate how much current (in amps) the circuit breaker will allow through before tripping. The top breaker in the photo is labelled “15,” which means it will allow up to 15 amps of current to flow through the circuit. Above that it will shut off the electricity by tripping.
The middle two breakers in the photos are “20,” i.e. 20 amps.
When a 12 is better than a 14
The wires in your walls are typically either 14 gauge or 12 gauge. In this case, 14 is smaller than 12. A 14 ga. wire must be paired with a 15-amp (or less) circuit breaker. A 12 ga. wire must be paired with a 20-amp (or less) circuit breaker.
Let’s say you have a 15-amp circuit breaker that keeps tripping. Should you replace it with a 20-amp breaker? NEVER. Remember that the purpose of a circuit breaker is to protect the wires in the walls–not whatever is plugged in. If you replace a 15-amp breaker with a 20-amp you can overload those 14 ga. wires and start a fire. You need to find the short or unplug some appliances from that circuit to reduce the amount of electricity going through those wires.
After you have corrected the problem, turn the switch on the circuit breaker from the middle position to the off position and then to the on position. If it trips again you’ll have to keep looking for a bad appliance that might have shorted out.
Labels are good
A labelled panel door is very helpful when you want to work on a particular circuit. For example, you might be replacing a bad (or dated) light fixture or a broken outlet in the dining room.
You want to turn off the power to the circuit that feeds the outlets or fixtures you are working on. The labels will give you a good idea which breaker you need to turn off. But NEVER TRUST THEM. Always have something plugged into that circuit that makes a noise or shines a light so that you can see if the breaker really shuts off that circuit.
Some of the labels might be a little cryptic. “AH” means air handler, “WH” means water heater, etc.
A circle with two vertical lines through it is the symbol for outlet. So “LR” followed by that symbol would mean “living room outlets.”
Here’s another thing you have to watch out for. Sometimes more than one circuit will go into the same outlet box or light switch box! I hate it when they do that. Make sure all of the circuits are off.
The large breaker at the top is the main shut off for the whole panel. And, if this is the only panel or the main panel for the house, shutting off that breaker will shut off electricity to the whole house.
If you need to shut off the power quickly and not spend time figuring out which circuit breaker controls the affected area, just flip the main breaker off.