Installing a junction box
MATERIALS: Junction box with cover, wire nuts, screws
TOOLS: Combination tool, lineman's pliers, screwdriver, drill, voltage tester
Install a junction box wherever wires must be spliced. Keep the box accessible—never bury it in a wall or ceiling. Junction boxes are usually flush-mounted to walls or attached to attic, basement, or crawlspace framing. But you can set one inside a wall as you would a switch box. Cover the junction box with a blank plastic cover plate. Code requires that all splices be accessible for Inspection and repair. Trying to take shortcuts here can be costly and dangerous.
1 ATTACH THE BOX. Shut off power to the wires that you will be splicing. Anchor the box with screws. To attach the box to a masonry surface, drill holes with a masonry bit. Drive masonry screws.
2 WIRE THE BOX. Strip cable sheathing and clamp the cable, or connect conduit. Strip wires and splice them with wire nuts. If the box is metal, make a grounding pigtail and connect it to the green grounding screw.
3 COVER THE BOX. Fold the wires into the box and attach the cover plate. To do so, loosen the screws at two opposite corners of the box, hook the cover plate on one screw first and then the other; tighten the screws.
USE A METAL COVER PLATE IN UTILITY AREAS - If a receptacle or switch is in an exposed box, use a metal rather than a plastic cover plate. You may need to break off the device's metal ears. Attach the device to the cover plate first and then attach the cover plate to the box.
Installing NM cable in new walls
MATERIALS: NM or armored cable, electrical boxes, protective nailing plates, cable staples
TOOLS: Drill with 5/8 inch or 3/4 inch bit, hammer, tape measure, level, long-nose pliers, utility knife, safety goggles
Nonmetallic (NM) cable is easy to cut and quick to install. Just be careful when you remove the sheathing so you don’t accidentally slit the wire insulation. If you do, cut off the damage and start again; otherwise you will get a short or a shock. Whenever possible, strip sheathing before cutting the cable to length. That way, if you make a mistake you can try again.
A TYPICAL CABLE ROUGH-IN. Run cable in a straight horizontal line, 1 foot above the receptacles (areas under windows are an exception) or according to local code. To keep cable out of the reach of nails, drill all holes in the center of studs and at least 1 1/4 inches up from the bottom of joists. Nail on protective nailing plates for extra safety. Even if you will only hang a light, installs ceiling fan box in case you choose to add a ceiling fan later.
1 DRILL THE HOLES. Wherever possible, use a tape measure and level to mark studs and joists. Mark so holes will be in a straight horizontal line. Drill 5/8 inch holes for most NM cable and 3/4 inch holes for three-wire cable or armored cable. A 3/8 inch drill works fine for small jobs, but give it a rest if it overheats. PULL THE CABLE. To avoid kinks, keep the cable straight and untwisted as you work. When possible, pull the cable first and then cut it to length. If you must cut it first, allow plenty of extra length. Pull the cable fairly tight, but loose enough to have an inch or so of play.
2 PROTECT THE CABLE WITH NAILING PLATES, which are inexpensive and quick to install. Be sure to nail one wherever the cable is within 1 1/4 inches of the front edge of the framing member. For added safety (and to satisfy some local codes), install nailing plates over every hole. STAPLE THE CABLE AND RUN IT INTO THE BOXES. Staple cable tightly wherever it runs along a joist so it is out of the reach of nails. Staple within 8 inches of a plastic box and within 12 inches of a metal box for clamping methods.
Working with NM cable
MATERIALS: Nonmetallic (NM) cable
TOOLS: Knife, lineman's pliers, side-cutting pliers, cable ripper
USING A CABLE RIPPER - Use this tool to strip cable that is already installed in a box. Practice on scrap cable first so you know how to make sure the ripper doesn't cut too deeply and damage wire insulation.
1 SLIT THE CABLE WITH A KNIFE. One side of the cable has a slight valley. Insert the blade into the middle of the valley about 3 inches from the end so the blade just pierces the sheathing. Slit to the end of the cable. Be careful not to damage the ground or pierce the sheathing on the hot and neutral wires. PULL THE GROUND WIRE. Cut or pull back the sheathing so you can grab the green or bare ground wire with lineman's pliers. Hold the cable end in the other hand and pull back the ground wire until you have a 12-inch slit in the sheathing. Pull carefully so you don't break the ground wire.
2 REMOVE THE WRAPPING. Pull back the plastic sheathing. Peel back any protective paper wrapping or thin strips of plastic, and cut them off. SNIP THE SHEATHING. Use side-cutting pliers, a combination stripper, or the cutting portion of lineman's pliers to cut the sheathing.
3 PULL THE CABLE INTO THE BOX. Push the wires through the clip or clamp on the box. Pull the cable into the box so at least 1/4 inch of sheathing is inside. Clamp the cable to the box.
NEVER NOTCH - In a tight spot like this, you may be tempted to whip out the hammer and chisel and chop notches in the face of the studs so the cable runs easier. But the cable would then be dangerously exposed and severely bent at the corner. Instead, drill slightly larger holes, bend the cable before poking it in, and grab it with long-nose pliers.