An electrical receptacle, or outlet, is a ubiquitous electrical device in any home. It is designed to receive an electrical plug for lamps and other appliances. In home wiring systems, outlet receptacles are typically either standard 120-volt models or special 240-volt models, such as those for window air conditioners and other large appliances. Standard 120-volt receptacles are typically designed to receive a three-prong grounded plug, each with different sized blades. The rounded hole receives the ground blade of the plug, the narrow slot receives the hot blade, and the long slot receives the neutral blade.
There are two types of 120-volt outlets: 15-amp and 20-amp. They have a similar appearance, but if you look closely, you'll see that 20-amp outlets have a sideways T-shaped slot designed to accept certain plugs on appliances that draw higher amperage. It is important to install the correct type of outlet for the circuit's amperage rating. Most important, while 15-amp outlets can be installed on 20-amp circuits, 20-amp outlets cannot be installed on 15-amp circuits.
In older homes where there may be no circuit ground wire, the original receptacles may be only two-slot models, without the grounding slot. When updating these receptacles, it's a good idea to use a GFCI receptacle, which improves the safety of the outlet in a situation where there is no ground wire.
Start at the Service Panel
Before you begin installing an outlet, it is critical that you first find the branch circuit breaker or fuse in your electrical service panel that feeds the receptacle you will be working on. Then, you must turn off the power to the circuit wiring and test the wires for voltage before you touch them. The circuit breaker you turn off (or the fuse you remove) will be rated for the proper amperage rating of the circuit. The markings on the circuit breaker or fuse will tell you if it is a 15-amp or 20-amp circuit, and therefore whether to install a 15-amp or 20-amp 120-volt outlet receptacle. (15-amp circuits require the use of 14-gauge conductor wires, while 20-amp circuits require 12-gauge conductor wires.)
Never install a 20-amp receptacle on a 15-amp circuit. This can create a serious fire hazard.
Equipment / Tools
- Non-contact voltage tester
- Flat-blade and Phillips screwdrivers
- Needle-nose pliers
- 15-amp or 20-amp outlet receptacle
- Outlet cover plate
Turn off the Power
Turn off the power to the receptacle's circuit by switching off the appropriate breaker in your home's service panel (breaker box). If the box has fuses, unscrew the appropriate fuse and remove it completely from the panel.
Test each wire in the electrical box where the new outlet is going, using a non-contact voltage tester. Touch the tester probe to each wire. If the tester detects any voltage, return to the panel and turn off the correct breaker, then test the wires again to confirm the power is off.
Connect the Ground Wire to the Receptacle
Bend the last 3/4 inch of the bare copper ground wire into a "J" or "U" shape, and place the wire under the head of the green ground terminal screw on the receptacle, so that the wire end is looped clockwise around the screw.
Squeeze the loop closed with needle-nose pliers so it's a little snug over the screw. Tighten the terminal screw by turning clockwise with a Phillips screwdriver, making sure the ground wire is firmly tightened under the screw head.
To maximize safety, electricians connect the wires in a specific sequence: first the ground wire, then the neutral wire, and finally the hot wire. When disconnecting an outlet, reverse the order, removing the hot wire first and the ground wire last.
Connect the Neutral Wire
Bend the end of the white neutral wire, as with the ground wire. Hook the wire onto one of the silver-colored terminal screws, squeeze the loop closed, and tighten the screw firmly.
Standard "duplex" receptacles have a pair of terminals on each side. The silver screws are for neutral wires only. The brass screws are for hot wires only. The neutral wire can connect to either silver screw. The hot wire can connect to either brass screw.
Connect the Hot Wire
Fasten the last wire—the black "hot" wire—to one of the brass terminal screws in the same manner as the previous wires.
Secure the Outlet to the Electrical Box
Gently bend the wires and tuck them into the back of the box, deeply enough so there is room for the receptacle to fit.
Gently push the receptacle into the box, holding the metal mounting strap.
Fasten the outlet to the box by threading the long fine-thread screws that came with the outlet into the screw openings on the box. This will usually require a Phillips screwdriver.
Install the Cover Plate
Fit the cover plate over the outlet and secure it with its center screw.
Turn on the power to the circuit at the electrical service panel by switching on the breaker or screwing in the fuse. Test the outlet with a lamp or appliance to make sure it is working properly.