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.
Why Circuit Breakers Fail
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 relatively 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.
WARNING: If you are not confident of your abilities when it comes to working around electrical equipment, do not replace a circuit breaker yourself; call a licensed electrician instead.
Tools and Supplies You Will Need
- New circuit breaker
- Safety glasses
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 panel.
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 is exactly the same.
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 will 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.
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.
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.
Attach the New Circuit Breaker
- Attach this black circuit wire to the new circuit breaker by inserting the bare end of the wire under the screw terminal and tightening the screw. Set the breaker reset lever on the new breaker to the OFF position before installing it.
- 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 black circuit 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.
- Replace the service panel cover and its screws.
Turn the Power On
- First, shut off the toggle levers on all individual branch circuit breakers 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.