How to Connect Electrical Cables

If you need to connect two lengths of electrical cable together for a home improvement project, you shouldn't just splice them together as you would a rope. They need to be secured into a junction box with a blank face-plate over it, so the connection will be safe from movement and accessible if there's ever a problem with the connection. This is far easier to do with open walls during new construction or a remodeling project than it is with closed walls, but it's possible either way.

Things You'll Need

• Plastic junction box with two cable clamps installed in it, top and bottom.
• Face plate for the junction box
• Studfinder
• Jigsaw
• 1-inch drywall screws
• Drill with long screwdriver bit
• Two lengths of the same kind of electrical cable (generally, 12-gauge, with a white, black and copper ground wire)
• Razor knife
• Wire cutter
• Wire caps
• Electrical tape

Instructions

1. Cut off all power.

2. If you're working with open walls, install your plastic junction box against a stud and screw it in place with the front edge of the box a half-inch out from the stud so it will be even with the wall after you drywall. Generally it will go near the floor, a few inches above the floor trim. Proceed to Step 4.

3. If the walls aren't opened, find your stud with the electronic studfinder and cut into the drywall with your jigsaw next to the stud--to the shape of the box--but don't screw the box to the stud yet. Proceed to Step 4.

4. Run then ends of your two cables into the electrical box from the holes at the top and bottom of the box, with about 6 inches of cable hanging out the front of the box from each cable. Secure them by tightening the screws on the cable clamps. (If the walls are closed, run the cable out through the hole in the wall and proceed to clamp them into the box as it sits loosely outside the wall.)

5. Use your razor knife to slice open the insulation from the dangling ends of both cables that are going to be connected. Separate out the wires. Generally, there will be a white insulated wire, a black insulated wire, and a bare copper grounding wire in each cable.

6. Use your wire cutters to strip a half-inch of insulation off the white and black wires.

7. Hold the bare ends of the two black wires next to each other side by side. Twist a wire cap over both of them to connect them. Do the same for the two white wires and the two bare copper wires.

8. Wrap electrical tape around the cap and upper parts of the black and white wire connections to secure them and ensure that no bare wire is showing. Wrap it several times. Don't wrap the connected copper wires. NOTE: Leave some of the base of both white wires untaped, so anyone who sees it later will know that they are white wires.

9. If the walls are closed and you've run the wires out through the hole in the wall to the loose box, secure the box to the stud by screwing it in through the holes on one inside wall of the box. Make the front edge of the box even with the wall.

10. Tuck all the wires back into the junction box. Secure the plate on the front of the junction box using the provided screws.

Tips & Warnings

• Always turn off power before working with electrical cables.

References

• Junction box.