How to Run a New Line to a Circuit Breaker Box

Consult the local city building department for the correct gauge of electrical cable required for the circuit it will serve. The size of gauge, as well as number of wires in the cable, will depend on whether the circuit is for outlets, lights, a stove or air conditioning unit.

Place a rubber mat on dry ground below the circuit breaker box. Stand on the rubber mat at all times while working on the box. Open the box's front cover. Turn off the main breaker, as well as all individual breakers.

Remove the screws from the box's inner cover, using a screwdriver. Take out the inner cover. Do not touch any bare metal inside the breaker box at any time with any part of your body. Place the tip of a screwdriver against the center of a cable access cover located either on the side, or back, of the breaker box. Push on the screwdriver to remove the cover.

Unscrew the nut from the end of 3/4 inch cable clamp, by hand. Push the clamp through the access hole from the inside of the breaker box. Screw the nut onto the clamp from outside the box, by hand. Tighten the nut to the clamp with pump pliers.

Push three feet of electrical cable into the breaker box through the center of the cable clamp. Tighten the screws on the cable clamp with a screwdriver, to secure the cable in place.

Run the tip of a utility knife blade along the cable's outside sheathing inside the breaker box, to within two inches of where it is secured to the cable clamp. Pull the sheathing from the cable's interior wires, and cut off the loose sheathing with the knife. Strip off 3/8 inch of plastic coating from the ends of the cable's interior wires, using wire strippers. The ground wire will be bare.

Run the cable from the breaker box to the appliance's electrical wall box, an outlet box or switch box. This will generally entail drilling holes through wall studs or ceiling joists, for the cable to pass through. If this is needed, use a 1/2 inch wood drill bit and power drill to make the holes in the studs/joists for the cable's access. Install cable staples around the cable and into the studs/joists every two feet, using a hammer.

Knock out a cable access cover on the side or back of the electrical box that the cable is running to. Install a 3/4 inch cable clamp into the access hole, as before. Push the cable into the box, and tighten the cable clamp screws to the cable. Use wire cutters to cut off the spare cable, leaving 12 inches of cable in the box. Strip off the cable's outer sheathing, as well as 3/8 inch of plastic coating from each of the cable's wires.