Knockouts are the raised circles stamped on the sides, top and bottom of a breaker box, and the thin rectangles on the panel cover. They can be easily removed to bring circuit wires into the box through the round knockouts, and add circuit breakers in place of the rectangular knockouts.
Things You'll Need
- Needle-nose pliers
Turn the main breaker off before removing the knockouts. Unscrew the mounting screws that hold the panel cover on, and pull the cover off. This permits access to the knockouts.
Determine the proper size of the round knockout to remove for a new circuit. The size of the conduit or cable clamp used determines the size of the knockout. Selecting the rectangular knockout is simply deciding which of the two rows to place the circuit breaker in. Remove two of the rectangles side by side, if a 240 volt double-pole breaker switch is used.
Dislodge the knockout by placing the tip of a flat screwdriver against the edge of the knockout, and tap with a hammer, causing a separation. Stick the end of the screwdriver into the separation and pry the knockout up. Grab the bent edge of the knockout with a pair of needle-nose pliers, and wiggle it until it breaks off. Install a conduit connector or cable clamp in a circular knockout to protect the wire from damage.
Replace the panel cover after installing the circuits and breakers, and turn the main breaker back on.
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