What's a main circuit breaker?
A circuit breaker is the central component to your home's electrical system. It's an important safety device that limits the amount of power moving through the circuits. In modern homes, the breaker is located inside, usually in a basement, garage, or utility closet. It prevents overloads that could cause damage to your electrical system or start a fire. Knowing what your circuit breaker does and where to find it are two things every homeowner should know, especially in an emergency after severe weather damage.
You may be familiar with your circuit breaker because you've had a tripped fuse. From time to time, everyone experiences a sudden outage of an electrical outlet when the current carried exceeds the rated value. This happens when there are too many lights or plug-in appliances drawing power from the circuit, and it overloads the fuse. Appliances that heat (such as toasters or hair dryers) or those with motors (such as vacuum cleaners) are especially prone to causing overloads when they first startup because of their large power draw. Your fuse trips before the circuit wires can heat to a dangerous level; you have to reset that switch and use a different outlet.
A short circuit can also cause a tripped fuse from an internal wiring problem in an appliance. You can usually slowly eliminate each appliance one-by-one to find the culprit. A continually-tripping circuit breaker is a sign that there is an electrical problem in your home that is consistently causing too much power to flow through a circuit. This could be a serious fire hazard. If you can't determine what's causing the trips or the switch continues to trip no matter how many times you reset it, you should call an electrician.
Finding your circuit breaker
Locate your main circuit breaker by looking for a matte gray metal box. If you live in an apartment, your circuit breaker may be in a hallway or laundry area and painted to match the wall. Check next to the meter box for your house. If you still can't find it, ask a neighbor where theirs is. There's a good chance yours might have a similar location.
In older homes, power mains are outside the home and may be a fuse box rather than a circuit breaker box. A fuse box has sockets and fuses that look like small light bulbs, and a circuit breaker box has rows of switches. You may even have a combination of both.
How to turn off your circuit breaker
It's wise to wear gloves and rubber-soled shoes when working in the fuse box. Newer boxes have a handle to open the door while older models can have screws, or you may need to pry the cover off with a crowbar. You should see the main power switch in the box to toggle On/Off.
In older boxes, there will be a fuse block rather than a switch, usually in the top center. Pull it out and check to see if it is labeled “on” and one side and “off” on the other. If so, reinsert it with the “off” side facing up. If not, leave it out.
WARNING: The main breaker or main fuse does NOT shut off the power to the service lines coming in from the utility or the connections where those lines meet the main breaker or fuse inside the service panel. These lines carry deadly levels of electrical current unless your utility company shuts them off.