Electrical: Installing Outlets & Switches
Most switches and outlets are installed after mechanical rough-ins, drywall and paint are completed. When you shop for devices like switches and outlets, there are several different types to wade through. Make sure to get the device that works properly with the circuit. The type of switch you install is determined by the circuit's wiring scheme. Outlets are pretty standard, but GFCIs are required in some rooms and box size is another thing to consider.
Sizing Junction Boxes
All switches and outlets (receptacles) need a properly-sized junction (electrical) box. For example, a 2" x 3" box with 3 wires (14 gauge) should be 2 1/2" deep. The same box with 5 wires must be 3 1/2" deep. Installing an undersized box is probably the most common wiring mistake for do-it-yourselfers. When in doubt, it's usually best to use a larger box. If you're not sure about box size requirements, remember to ask your electrical inspector when submitting diagrams. Here's one way to calculate minimum box size:
1. Count the number of wires for the box. Don't count outlet/switch pigtails and count all ground wires as one.
2. Take that number, add one for each cable clamp, and two for each device (like a switch or outlet).
3. If the box contains only 14-gauge wires, multiply the total by 2 cubic inches. Or, for 12-gauge wires, multiply the total by 2.25 cubic inches. The result is the minimum allowable volume the box should be. Volumes are usually stamped into the back of the box on the inside.
GFCI Outlets
A GFCI (Ground Fault Circuit Interrupter, also GFI) is an outlet designed to prevent electrical shock. It's a little bigger than a normal outlet and has two buttons on the front. These buttons allow you to check the GFCI monthly to see if it's still working properly. Push in the black "Test" button to kill power to that circuit. Restore power by pushing the red "Reset" button. A GFCI also monitors the current being used by anything plugged into it. Normally, a balance of current passes through the GFCI. If a misdirection of current, called a "fault to ground," the GFCI senses it and shuts down almost instantly -- which can prevent potentially hazardous shocks. On the back side of a standard GFCI are four (two sets) terminal screws -- two brass "hot" screws and two silver "neutral" screws. The bottom brass and silver set -- marked "Line" -- is for incoming wires. The top set -- marked "Load" -- is for wires going to other protected outlets. The GFCI also has a green "ground" screw on the bottom. That's where the bare copper ground wire connects and provides a path for dangerous current to be safely diverted.
Single-Pole Switches
A single-pole switch has two brass screw terminals. Both are hot leads for one incoming and one outgoing line. Those are all the wires that connect to the switch. The neutral wires tie together separately and the ground wires tie together separately in the box. Many new switches include a ground screw; others may not have one. If you have the choice, get a switch with a ground screw terminal. That's where the bare copper or green wire connects. When a switch is at the end of a circuit (one incoming cable), the neutral also becomes a hot lead and connects to a terminal. This type of wiring scheme is often called a switch loop. NOTE: Install the switch so flipping it UP turns the light ON. This is very important if using a silent, "mercury" switch, because they won't operate properly unless they're installed correctly.
Three-way Switches
Three-way switches can control one light from two different places. Like switches that operate a light from both the top and bottom of a staircase. A three-way switch has three screws. One screw is colored darker than the other two. It's called the "Common" terminal. The other two screws are called "Traveler" terminals. You can wire two three-way switches and a light in a few different ways. It all depends where the light is located: before, between or after the switches. What we describe is not how all three-way switches are wired. But the following will give you an idea of how they're connected. For simplicity, let's say the light is after both switches. The first box has two cables: one 14-2 incoming from a power source, and one 14-3 outbound to the second box. The second box has that incoming 14-3 cable and an outbound 14-2 cable to the light. In each box, twist all the ground wires together (add a pigtail in each metal box). Screw on a wire nut (and fasten the pigtail to the back of the metal box). Connect the two neutral leads in each box with wire nuts. In the first box, connect the incoming (14-2) hot lead to the switch's "Common" terminal. Connect the outbound (14-3) leads to the two "Traveler" screws. In this case, the traveler leads can be hooked to either terminal. In the second box, hook up the incoming (14-3) hot leads to the switch's travelers screws. Finally, hook up the outbound (14-2) hot lead going to the light to the "Common" screw. That completes wiring the switches. Complete the circuit by hooking up the light to the neutral, hot and ground leads.
Electrical: Installing Light Fixtures
There are no hard-and-fast steps for installing light fixtures. Most new lights have diagrams and instructions which you should read over at least once before you get started. In an add-on situation, you can run a new circuit. Or, you can draw power from an existing circuit. But too many devices can constantly trip a breaker so figure the circuit's load capacity before adding a light. A big installation battle is just getting fixtures mounted properly. Normally, an extra cross brace is nailed up during the framing process. If you're retro-fitting, you may have to tear out some wallboard to add extra bracing, or settle for locating the fixture's box on the nearest stud or joist.
Retro-fitting Recessed Lights
Usually recessed lights are installed after framing and before drywall. Sometimes that step is forgotten or you may want to retro-fit a recessed light to enhance a room's lighting scheme. For this project, we purchased a recessed fixture with a mounting bracket designed to fit through the hole. Use the light's housing as a guide to mark the hole. Then use a keyhole saw to cut the hole. NOTE: Remember, your circuits and some of these steps will probably be different. Keep insulation at least 3" away from recessed lights, unless light is marked "I.C." (Insulated Ceiling) to avoid overheating and fire. Mark the location of the fixture. We ran incoming power directly to the light fixture then ran cable down to the switch to make a loop. To mount the light, slip the frame brackets up into the opening. Position the fixture to set flush with the bottom of the wood framing. Fasten the frame to the joists by pounding in the metal teeth on its supporting arms. Use small mounting clips included with the light to fasten it slightly recessed from the surface of the drywall. Paint the area before putting in the reflector shield and bulb if you can. Then snap the shield into place.
Hanging Ceiling Fans
How a ceiling fan is mounted depends on the model. Always follow the manufacturer's instructions. We'll describe a few ways to mount a fan, but almost all of them need a special ceiling fan-rated junction box anchored to a ceiling joist. Determine the location of the fan, usually in the center of the room. If you can't alter the location to be next to a joist, nail up a cross brace between the joists. Nail up a junction box so it will set flush with the ceiling drywall. Then run the incoming power cable, leaving about 1' of extra cable for connections. Hang drywall if needed at this point. Careful of the electrical cable, cut out around the outside edges of the box then finish anchoring the drywall. Use a step ladder to rest the fan on and fasten the mounting bracket to the junction box. Connect the respective cable and fan wires together, securing each pair with a wire nut. Lift the fan into position (make sure the decorative cover is on), fasten it to the mounting bracket, and slide on the decorative cover.
Electrical: Common Electrical Codes
Before you do any kind of electrical work, you should know what codes pertain to your project because they determine how electrical work should be done. Electricians follow the National Electric Code (NEC) to figure circuit wiring and capacity necessary for each situation. It's a fairly complex guide, so you may want to consult your local inspector for more help in clarifying codes. As you plan out circuits, keep in mind that it's generally better and safer to have more available circuits and extra capacity, than too few. Figure in any future updates and a maximum load demand each circuit may have when making a diagram. For terms and definitions see [2]Electrical Glossary.
General Guidelines
Here are a few typical guidelines that do-it-yourselfers should know about when doing electrical work. These are NOT legal interpretations of the National Electrical Code, so check with your local authority before starting work: Kitchens * All the kitchen, breakfast room, pantry, and dining room outlets must be supplied by at least two 20-amp small appliance circuits. * Outlets above the kitchen counter normally are fed by both circuits -- they all cannot be wired to just one circuit. The circuits should not supply any lights or other outlets in the house. Appliances * Separate circuits are needed for built-in appliances (i.e. oven, range, disposer, dishwasher, central air conditioner, furnace). * One 20-amp circuit is needed for the laundry outlet within 6' of the machines. An electric dryer requires an additional 240-volt circuit. Outlets * One lighting/convenience outlet circuit for every 575 square feet of floor space in a house. * Any bathroom or garage outlet within 6' of a sink must be GFCI protected. A new code requires all kitchen outlets for countertop use to be GFCI protected. * At least one GFCI outlet is required in an unfinished basement and for most outdoor outlets (exceptions include inaccessible outlets like at a garage ceiling or behind a refrigerator. * Any point along the bottom of a wall (which is 2' or wider) must be within 6' of an outlet. The 6' distance cannot be measured across a doorway or fireplace. And the outlet must be within 5 1/2' of the floor. This code cuts down on extension cord use, especially across doorways, fireplaces and similar openings. Switches * A light switch must control lighting in every habitable room, hallway, stairway, or garage. The switch can control either a light fixture or a receptacle into which a lamp is plugged. * In kitchens and bathrooms, the light switch must control a permanently installed light fixture.
Electrical: Troubleshooting
This section explains how to repair some common household electrical problems. Remember, always make sure the circuit you'll be working on is shut off. When you shut off a breaker or pull a fuse, post a message at the service panel (or fuse box) notifying others so they don't try to restore power while you're working. Also, replace any device (i.e. switch, outlet) with one having the same number of terminals and power rating -- unless you know the original device was wrong for the job.
Changing Outlets
Outlets (receptacles) have to withstand the wear and tear of yanking cords out of the sockets. If an outlet is loose, or anything that's plugged into it flickers on and off, it's time to be replaced. On its back side, an outlet is rated for voltage and amperage (125 volts and 15 amps is most common). Make sure to get a replacement with the same ratings. Turn off the circuit breaker that controls the outlet. Test that the power is off by sticking both circuit tester probes in the outlet slots of each socket. No light means the power is off. Take off the cover plate. Just to be safe, test the circuit again. This time, touch the probe to the screw terminals on both sides where the wires are attached. Start with the top set of screws, and then test the bottom set. No light means no power, so the outlet is safe to work on. Next, unscrew the outlet and pull it out of the wall box by the mounting tabs. The wires should unfold and stretch out so you can access them. A grounded outlet has a round hole on the face in addition to the two slots. If there are three holes in the outlet face, there should be three wires attached to the outlet. The black (hot) and white (neutral) wires carry the current, and the copper wire is the ground. Note that the outlet's screw terminals are certain colors. The white wire goes on the silver screw. The bare copper or green wire goes on the green screw. And the black wire gets attached to the brass screw. If the terminals aren't easy to identify by color, the ground terminal may be marked with a "GR." Also, the white wire goes to the side with the longer slot on the face. And the black wire always goes to the short slot side. Make a note of how the wires are arranged and unscrew them. Bend each wire in a clockwise direction. Hook them around the new outlet's terminals so when the screws tighten, the wire pulls inward for a better connection Screw the wires onto the new terminals, carefully push the outlet back into the box so the wires don't kink and tighten down the mounting screws and cover plate.
Replacing Three-Way Switches
Electricians get many repair calls when a homeowner has wired a three-way switch incorrectly. Or, an old three-way switch has been accidentally replaced with a single-pole switch, which won't operate the light correctly. It's not necessary to understand the whole theory of how a three-way switch system is wired. But it's important to remember which wire was connected to the common screw of the old switch. Before doing any electrical work, turn off the circuit. Double-check it with a circuit tester to make sure that it's dead. Put one test lead on the ground (copper or green color) wire or box if it's metal, and the other test lead on the hot wire, then the neutral wire. If the light stays off, the circuit is dead. Take off the cover plate and unscrew the switch from the box. It's easy to identify a three-way switch because it has three screws (two brass and one dark). Pull the switch out and label the wire hooked to the dark "common" screw. Unhook the old switch and hook up the new one: ground wire pigtailed to the box, travelers to the light-colored screws (interchangeable), and most important, the labeled wire to the darker "common" screw. Fold the wires back in the box, attach the switch to the box, and put on the cover plate.
Repairing Lamps
A common problem for lamps is a bad connection with the bulb and contact tab in the bottom of the socket. Make sure the lamp is unplugged. Use a screwdriver tip to scrape off any corrosion, and then prying it up a little. If the problem remains, take apart the socket. Most sockets have a "PRESS" mark stamped into the upper cover. Squeeze the cover there, and work it off. Remove the insulating cardboard sleeve. Check the wire connections. If they look good, the next thing to troubleshoot is the cord. Remove the wires from the screw terminals, noting how they're connected. If there's a silver wire and a copper wire, the copper goes on the brass screw. If both leads are copper, the lead with the ridge on the side of the insulation goes to the brass screw. Use a continuity tester to check the cord. If there's a switch somewhere on the lamp or cord, make sure it's "ON" when you test. If there's continuity in the cord, replace the inner socket. Be sure to get a replacement that matches the original. We also add an "underwriters" knot that protects the new leads from being yanked off the terminals. Then connect the wires to the new socket. Twist the bare ends of the wire, hook them clockwise around the terminals and screw them down. Put the socket inside the sleeve, and the sleeve inside the cover. Push the cover back down on the base and orient the switch in the desired direction. If the lamp still doesn't work, it's a good idea to have a professional take a look at it.
Fixing Cord Plugs
The plug end of a lamp or appliance cord may pull lose of it's cord connection. Replacement is fairly easy, however. For basic flat cords, you can use a "quick-connect" plug. The plug pulls apart by squeezing the prongs together. Feed the end of the plug through the back of the cover. Spread the prongs apart and insert the wire into the back of the core. Squeeze the prongs together. They have small metal spikes that penetrate the cord's insulation to make contact with the copper wires inside. Slide the cover down onto the core to complete the job. For a little stronger connection, use a plug with screw terminals. Start with a clean end on the cord -- sometimes called "zip cord" because the two side pull apart easily. Strip about 3/4" off the end of the two wires and twist the lead strands together tightly. Hook each lead to fit around the screw terminals and attach the lead that has a ridge on the insulation to the brass terminal. If the screws aren't color-coded, this lead goes to the thinner plug prong. Work the cover back down over the core.
Fixing Grounded Cord Plugs
Most cords with grounding plugs are molded right onto the cord end. However, they can fray and work loose. If this happens, it's best to replace the plug. Cut off the old plug and strip the ends of the wire. Many cords have an outer sheathing of insulation. Strip it back about 1 1/2" with a utility knife and cut off the excess. Strip about 3/4" off the end of each lead. Feed the cord through the plug's back cover and connect the wires. The plug terminals are located in the back. NOTE: Terminals on the face of replacement plugs covered by a removable cardboard disk are illegal and not a safe choice. The green (ground) lead goes to the green screw. The white (neutral) lead goes on the silver terminal. The black lead goes around the brass screw. Finally, put the cover over the plug and screw down the cord clamp.