All homes have a main electrical service panel, also known as the circuit breaker panel or fuse box. The panel receives the incoming power from the electrical utility and distributes it to the various branch circuits of the house. Turning off the power at the electrical service panel is the safest way to shut down a circuit before working on it. The service panel also allows you to shut off the power to all of the circuits at once, using the main circuit breaker or the main disconnect fuse block.
Before You Begin: Circuit Breakers vs. Fuses
Unless your home's electrical service is quite old, it probably has a service panel that uses circuit breakers for overload protection. Each individual circuit breaker automatically shuts off if there is a problem with the circuit, such as a short circuit, or an overload—where the circuit is overloaded and draws too much power to safely handle. Breakers and the circuits they protect can also be turned off manually by switching a toggle lever to the OFF position.
It's a good idea to spend some time becoming familiar with the circuit breaker panel and its components. Begin by opening the door on the service panel's cover. Inside, you will see the main circuit breaker rated for 100, 150, or 200 amps—or possibly even more, in a very large modern house. The number printed on the main breaker's toggle switch is the amperage rating and indicates how much power is available to distribute among the various individual circuits. Flipping the toggle on this main breaker will shut off the power to all the individual circuits at once—but it does not eliminate all power present inside the panel itself.
Below the main breaker, you will see multiple branch circuit breakers, each of which controls power to an individual circuit in your home. These breakers are usually rated for 15-amps or 20-amps if they are 120-volt circuits. If they are 240-volt circuits, they are controlled by a double-pole circuit breaker, which usually occupies the same space as two 120-volt breakers, with toggle levers that are joined together. The double-pole breakers usually provide power to dedicated appliance circuits, such as clothes dryers, electric ranges, water heaters, or air conditioners. Flipping the toggle lever on any one of these 120-volt or 240-volt circuit breakers stops the current flow to individual branch circuits. This makes it possible to shut off any circuit in the house in order to make repairs or alterations.
While most service panels have an index or labels taped or glued to the inside surface of the panel door, it's best not to automatically trust this index, as it is very common for the circuits to be mislabeled. Once you think you've shut off the circuit, always test the wires with a circuit tester to ensure the power is indeed off.
A home with older electrical service may have a fuse panel rather than a circuit breaker panel. Here, too, the panel can be used to shut off power to the entire house, or to individual branch circuits. When you open the door of the panel, you will see several screw-in fuses with small glass windows. These are the fuses that control the individual 120-volt branch circuits.
You will also probably see one or more 240-volt fuse blocks, each of which contains a pair of cylindrical cartridge fuses. A small metal handle allows these fuse blocks to be extracted when necessary. One of these blocks serves as the main fuse (main disconnect) for the entire service panel. If there are other fuse blocks, they likely serve 240-volt appliances, such as an electric range or a clothes dryer.
Unlike circuit breakers, fuses must be replaced when they "blow" due to an overload or short circuit. While there are instances where you'll be removing the main disconnect fuse block to shut off power to the entire home, it's more likely that you'll do this in order to replace a blown cartridge fuse.
Any work in the main service panel comes with inherent risks since there is the potential for touching parts that carry the full amperage delivered by the utility company. Professional electricians are taught to be extremely cautious around the main service panel—for example, taking particular care not to touch the panel if the flooring around the panel is damp.
It's very important to know that the main breaker or main fuse does not shut off the power to the incoming service lines from the utility or the connections where those lines join the service panel. These main service wires lines remain live unless the utility company shuts them off. Thus, you should be extremely careful not to accidentally touch these wires or the lugs where they connect to the service panel.
The danger is minimal if all you're doing is shutting off a circuit breaker, since you won't be removing the entire panel cover to expose the service wire connections or the hot bus bars inside. Still, it's wise to be alert whenever you approach the main service panel for any reason—even if it's just to shut off a circuit breaker or reset a tripped breaker.
But if you understand the inner workings of the service panel, any homeowner can safely shut off the power to a circuit or to the entire house.
Watch Now: Everything You Need to Know About Your Breaker Box
Equipment / Tools
- Non-contact circuit tester
- Replacement fuse (optional)
How to Turn off the Main Breaker
Turning off the main breaker and stopping power to the entire house is sometimes necessary if you find it hard to identify the correct branch circuit breaker to make a specific repair. It's also necessary whenever a new circuit breaker is being installed in the service panel. However, circuit breaker installation is almost always done by a professional electrician, since such work requires the removal of the entire cover of the breaker panel, exposing the main service wires.
Open the Panel Door
Locate the main circuit breaker panel and check to make sure the floor around the panel is dry. Open the metal door on the cover of the panel. If your main circuit breaker panel is located in a basement or other interior room without windows, make sure to have a flashlight on hand, as the next steps will cause all lights in the home to go dark.
Identify the Main Circuit Breaker
Inspect the circuit breakers inside the panel and identify the main breaker. It is usually a large 240-volt breaker labeled 100 amps or more, located at the top (or sometimes the bottom) of two vertical columns of branch circuit breakers. In some instances, the panel may be installed sideways, so that the main breaker is located at one end of two horizontal rows of branch circuit breakers.
Shut off the Main Circuit Breaker
Carefully push the toggle lever on the main breaker to the OFF position. This should shut off all power flowing to the individual branch circuit breakers, and you'll notice all lights and appliances in the home going dark at the same time.
Test for Power
Using a non-contact circuit tester, test several outlets in the home to make sure all power in the home has been shut off. It's not uncommon for homeowners to misidentify the main circuit breaker, so it's critical to test for power to make sure.
You can now proceed with whatever circuit work or repairs you need to do.
Restoring the Power
After completing circuit work, turning the power back on is a matter of flipping the main circuit breaker's toggle lever back to the ON position. Because this action can send a considerable power surge to all the circuits at the same time, professional electricians usually do this by first turning all branch circuit breakers to the OFF position, then turning the main circuit breaker back on, then turning each individual circuit back on, one at a time.
With some breakers, turning a breaker back on requires that you first push the toggle lever fully past the OFF position to engage its spring action, back to the ON position.
How to Turn off a Branch Circuit Breaker
Before working on any circuit, such as when replacing a switch or upgrading an old outlet to a GFCI outlet, you must turn off the power to the circuit. This is a better choice than shutting off the main circuit breaker since it allows other circuits to remain active.
Locate the Service Panel and Branch Circuit Breaker
Open the metal door on the main circuit breaker panel and identify the circuit breaker controlling the circuit you want to turn off. The circuits may be identified by an index taped or glued to the inside of the panel door, or by labels attached next to each breaker, but don't assume the index is correct until you test for power.
Turn off the Circuit
Turn off the circuit by flipping the toggle lever on the breaker to the OFF position. In most cases, there will be an audible click as the breaker snaps off, and with many breakers, a red or orange tab appears in a small window to indicate the breaker has tripped.
Test for Power
Use a non-contact circuit tester at several outlets along the circuit to make sure the power to the circuit was shut off by the breaker. If the circuit tester indicates the presence of power, then return to the panel and look for the correct branch circuit breaker.
When you've verified that the power is off, you can proceed with whatever circuit work or repairs you need to do.
When your circuit work is completed, restoring power is a simple matter of switching the toggle lever on the branch circuit breaker back to the ON position. Some breakers may require that you first push the lever fully past the OFF position to load the internal spring before pushing it back to the ON position.
How to Shut off the Main Disconnect in a Fuse Panel
Identify the Main Disconnect Fuse
The main disconnect will be the fuse block with the highest amperage rating, or the one marked "MAIN" on the face of the block. Depending on the age of your home, the amperage of this fuse block may be as high as 100 amps, though it is more common for older electrical services to provide only 60 amps, or sometimes as little as 30 amps.
Extract the Main Fuse Block
To shut off power to the entire house—or to replace a blown main—carefully grip the handle on the main fuse block with one hand only and pull outward with steady pressure. (Using one hand is a safety precaution to prevent electrical current from passing easily through your body in the event of a short circuit).
The fuse block will pop free of the service panel. Inside the fuse block, you should see two cylindrical cartridge fuses, which can be replaced with exact duplicates if one has blown due to an overload.
Turning the power back in is a fairly simple matter of pushing the main disconnect fuse block—containing functional cartridge fuses— back into its slot in the panel. Again, use one hand to push the fuse block back into place, and take care not to touch any other parts in the panel.
Test lights and outlets in the home to make sure power has been restored.
How to Remove Branch Circuit Fuses
Identify the Correct Fuse
If you are removing the fuse in order to do circuit work, read the panel index to identify which fuse to remove. If you are merely replacing a blown fuse, the bad fuses should be evident from scorch marks or cloudiness in the small window on the face of the fuse. You may be able to see that the metal filament within the fuse has melted through.
Unscrew the Fuse
Unscrew the branch circuit fuse while touching only the ceramic rim, or face, of the fuse. Unscrew it all the way and remove it completely from the socket. Make sure not to touch the metal threaded base of the fuse while removing it from its socket.
Test for Power
If you have removed the fuse in order to shut off a circuit for work, test the circuit using a non-contact circuit tester to make sure the power is off. If the tester still detects power, return to the fuse panel and look for the correct fuse.
Once your circuit work is complete, restore power to the circuit by carefully screwing the fuse back into its socket, using one hand only.
If you are replacing a bad fuse, make sure to use an exact replacement. Screw-in fuses come in two main types: Edison fuses have large threaded sockets that look just like light bulb sockets. Type-S, or "Rejection," fuses are similar to Edison fuses but have smaller threaded bases. In an old fuse panel, there may be Edison-type sockets containing adapters that accept Type-S fuses. These prevent users from installing the wrong type of fuse and creating a potential fire hazard.