When a circuit breaker trips repeatedly, it is usually because of a problem in the wiring, such as a short circuit or ground fault problem—or because the circuit is overloaded for the amperage rating it carries. But from time to time, a circuit breaker may simply wear out and get weak, or fail entirely.
Sometimes breaker failure occurs because a circuit problem has caused a circuit breaker to trip too often, wearing out the internal switch linkage. Or, failure may occur if you have used the breaker switch to turn the power on and off too many times. This is a bad practice and should be avoided. Use the circuit breaker switches only to turn off the power when servicing the circuit, not to routinely shut a circuit on and off. There are also instances where power spikes and lightning hits have damaged circuit breakers. Water damage due to leaks or flooding can also cause failure.
Replacing Circuit Breakers
Whatever the reason, when a breaker fails, removing the old one and installing a replacement is the cure. Circuit breakers are fairly inexpensive and are very easy to replace—provided you have a bit of understanding about electrical issues. This is not a project everyone is comfortable performing since it involves working at the main service panel with the safety cover removed. Although the process is not difficult—in fact, it's considerably easier than many routine wiring projects—the main power bus bars will be exposed as you replace a circuit breaker and there is a danger of serious shock if you're not careful.
Since 1999, the National Electrical Code (NEC) has gradually expanded the requirements for residential circuits to have AFCI (arc-fault circuit interrupter) protection. Today, virtually all circuits for living spaces must have AFCI protection, and this is normally done by installing special AFCI circuit breakers. When professional electricians replace an old standard circuit breaker, they are required by law to install an AFCI circuit breaker if the circuit requires it. If you want to be fully in compliance with code, this means you, too, should replace a standard circuit breaker with a AFCI receptacle for circuits that require it. AFCI circuit breakers and GFCI circuit breakers have slightly different installation procedures, since they also are connected to the white neutral circuit wires, and have a coiled white wire that is connected to the neutral bus bar in the panel.
Equipment / Tools
- Safety glasses
- New circuit breaker
Identify Breaker Brand, Type, and Size
Before you can begin replacement, you’ll need to identify the brand, type, and size breaker you’ll be replacing. Circuit breakers are proprietary to the manufacturer of the particular circuit breaker panel you have. Square D and Homeline, for example, are two of the major manufacturers of breaker panels, and each accepts only breakers designed for its panels.
Breakers come in many different shapes and sizes. You should never replace a breaker with one from a different breaker manufacturer. Even if they look identical, there are differences in tension, the way they connect in the holder, and how deeply they mount to the bus bars. Look carefully at the front of the circuit breaker. A small label near the reset lever contains the identification numbers you need. Note these specifications, and buy a replacement that matches.
Turn the Main Power Off
Professional electricians sometimes replace individual circuit breakers without shutting the main power supply off, but for an amateur doing this work, it is best to shut off the entire power supply, which interrupts the power to the two hot bus bars running down through the service panel.
Careful electricians always stand to the side of the service panel when turning a circuit breaker on or off, and they turn their eyes away from the panel until the power is on. Although the possibility is remote, there is a chance of explosion in a circuit breaker panel, and standing to the side and looking away is a safety measure designed to protect vision. Some electricians wear safety glasses whenever working with electrical components and devices.
Locate the main circuit breaker and flip it to the OFF position. This may now put you in the dark, so make sure you have a flashlight handy, if necessary. All branch circuits in the panel will now be shut off.
The main breaker shuts off power to the branch circuit breakers, but it does not affect the incoming power service lines or the terminals they connect to (called service lugs) in the service panel. These components remain live—carrying deadly voltage—unless the power company shuts off your service. Do not touch the service lugs or the bare wire of the incoming service lines at any time.
Remove the Breaker Panel Cover Plate
Remove the screws holding the panel cover plate on. It's best to leave the middle two screws in place until last, removing the corner screws first. Loosen the two remaining screws while holding the cover from falling to the ground. Be very careful not to let the cover tip into the panel as you remove it and set it aside.
Remove the Old Circuit Breaker
Now that the cover is off, locate the breaker to be replaced. Turn off the breaker by flipping its reset lever to the OFF position.
If the black insulated circuit wire connected to the breaker is folded tightly along the sides of the panel, carefully extend it out from the panel, being careful not to touch any other wires or the panel itself.
Now, carefully grasp the edge of the old breaker at the inner center part of the panel and pivot it out towards the outer side of the panel. The breaker should snap free and pull out from the panel. Be very careful not to touch the metal bus bar to which the breaker was attached. Once pulled free of the panel, the breaker is guaranteed to be inactive because it is no longer in physical contact with either of the hot bus bars in the panel.
Remove the black circuit wire attached to the breaker by unscrewing the screw terminal gripping the wire. (If replacing a 240-volt breaker, it will have two hot wires, usually red and black.)
If you are replacing a AFCI or GFCI circuit breaker, it will also have a neutral circuit wire connection on the circuit breaker, as well as a coiled white pigtail wire that runs to the neutral bus bar in the panel. Also disconnect these wires. The bus bar wire is easily disconnected by loosening the set screw and extracting the wire from its lug on the bus bar.
Attach Wires to New Circuit Breaker
Attach the black circuit wire to the new circuit breaker by inserting the bare end of the wire under the screw terminal on the breaker and tightening the screw. On some breakers, this terminal may be labeled LOAD or LOAD POWER.
If you are replacing an AFCI or GFCI (or AFCI/GFCI combination breaker), connect the white neutral circuit wire to the corresponding screw terminal on the breaker. This terminal may be marked NEUTRAL or LOAD NEUTRAL. Also connect the coiled white wire attached to the circuit breaker to a screw terminal on the neutral bus bar in the panel.
Set the breaker reset lever on the new breaker to the OFF position before installing it.
Insert the Breaker
Hook the back of the new breaker into the back holder clip on the breaker panel, and push the breaker forward into place. In some cases, this will require a bit of force. Make sure the breaker lines up with the bus bar as you install it. You should feel a click as the breaker snaps into place onto the hot bus bar.
Tuck the excess wire into the panel, neatly folding it into the empty space along the side of the panel. Again, be careful not to touch other wires or metal parts on the panel.
Turn the Power On
First, replace the service panel cover and its screws. Then, flip the toggle levers on all individual branch circuit breakers to the OFF position before turning the main breaker on. This will prevent a sudden high power demand on the electrical service when the main circuit breaker is activated.
With all branch circuits off, flip the lever on the main circuit breaker to the ON position. Now, flip each individual branch circuit breaker to the ON position, one at a time.
Make sure the circuit fed by the new circuit breaker is operating correctly by testing fixtures and outlets powered by the circuit.
When to Call a Professional
Replacing a circuit breaker is not inherently difficult, but it can cause nervousness, even for DIYers with advanced skills, since it involves working inside the main circuit breaker panel, where the potential for fatal shock always is present. If you are not fully confident of your skills, or if the circuit breaker panel seems old or unusual, it is best to call a professional electrician to make this repair. A professional will also understand all AFCI and GFCI requirements, and will ensure that your installation meets code requirements.