When an outlet receptacle falls in the middle of a circuit run rather than at the end, there are generally five wires in the outlet box. Two cables are hot wires—one bringing power in, the other carrying it onward to the next receptacle. Two cables are neutral and serve the same function. And the final cable is a ground wire. (There may also be a third cable if the circuit is branching in two directions at this point.) There are two basic options for wiring the receptacle to these wires.
First, the circuit can be direct-wired through the receptacle—that is, the entry wires can be attached to one pair of hot and neutral screw terminals on the receptacle, while the exit wires can be attached to the other set of screws. In this configuration, the circuit flows through the receptacle at all times, using the connecting tabs on the receptacle to establish the continuous circuit path.
The second method of wiring a mid-run receptacle is to connect the receptacle to the circuit wires with pigtails that allow the circuit to flow both to the receptacle and to any "downstream" receptacles without being dependent on flowing through the receptacle's connecting tab.
Depending on your situation, one or the other method might work better, although pigtailing is generally preferred.
Why Pigtailing Is Preferred
One drawback to direct wiring through a receptacle is that the receptacle is in the middle of the circuit and any trouble in the receptacle spells trouble devices downstream. Any problem with the receptacle, or even a loose wire under one of the screw terminals, could cause you to lose power to the downstream circuit receptacles, as well. Even diagnosing the problem can be difficult, because if all receptacles lose power, it's hard to determine which one is causing the issue.
Direct wiring also complicates repair or replacement because, if you have to take one receptacle out of the circuit, you interrupt the remaining downstream receptacles. The receptacle must be reconnected before the circuit downstream can function again, leaving it out of commission in the meantime.
With pigtail wiring, these drawbacks are eliminated. A problem or loose connection within one receptacle will not affect the receptacles downstream. You can also remove a receptacle in the middle of the circuit without affecting the others.
One situation in which pigtailing may not be advised is if the wall box is very shallow or is otherwise not big enough to handle the volume of extra wire nuts and pigtail wires. If the box is too small to comfortably handle all the pigtails and connectors, then the solution may be to install a larger wall box—or to make do with direct wiring through the receptacle.
More Than Two Cables in the Box
Sometimes you may open a receptacle box and discover that there are three main cables, each containing multiple wires. In this case, one cable is the line (incoming power) and the other two are load cables (feeding downstream devices). The only appropriate way to wire a receptacle in a box with three cables is to use pigtails to connect the receptacles. Never connect more than one wire under a single screw terminal. It's also not a good idea to direct-wire all three cables to the receptacle by utilizing both the screw terminals and the push-in terminals on the back of the device.
Before You Begin
Before beginning, you should have a basic understanding of how a receptacle works.
On a standard 120-volt receptacle, there are three types of screw terminals: brass-colored screws that accept black hot circuit wires, silver-colored screw terminals that accept white neutral wires, and a green screw terminal that accepts the bare copper (or green) grounding wire.
Just be aware that, in old wiring, you may not see the familiar black and white jackets on the circuit wires—the important thing to remember is that brass screws accept hot wires, and silver screws accept neutral wires. It's also possible that, in some configurations, a hot wire may be indicated by red insulation on the wire jacket.
There are always risks inherent in working with electricity. Before you start this project, you must make sure that you have turned power off to the receptacle you are replacing at your electrical box. If you can't find the proper circuit breaker to turn off, you will have to turn off the main breaker, which will kill power to the entire house.
Equipment / Tools
- Wire stripper
- Phillips head screwdriver
- Needle-nose pliers
- Utility knife
- Replacement receptacle
- NM electrical cable
- Large wire nuts
Watch Now: 2 Ways to Wire an Outlet in the Middle of a Circuit
Direct-Wiring Through the Receptacle
Turn off the Power
If you know the circuit breaker that controls the flow of power to the outlet you will be working on, flip it to the off position. If not, turn off the main breaker.
Remove the Old Receptacle
Remove the faceplate belonging to the outlet on which you'll be working.
Unscrew the two screws holding the old receptacle in the electrical box and pull it forward out of the box. Use a non-contact voltage tester to make sure there is no current in any of the wires connected to the receptacle.
Disconnect all of the wires attached to the receptacle by unscrewing the connectors and throw the old receptacle away.
Connect New Receptacle
Connect one of the black hot circuit wires to one of the brass-colored terminals on the new receptacle, and connect the other black wire to the other brass terminal (it doesn't matter which goes where). Similarly, each white neutral wire gets connected to a silver neutral terminal. That leaves the ground wire, which is green or bare copper and connects to the green screw on the receptacle.
Before attaching the wires, it will help if you make a "J"-shaped hook at the tip of each wire using a pair of needle-nose pliers.
Insert New Receptacle
Place the new receptacle back in the electrical box and attach it with two screws. Cover with the faceplate. Turn the power back on and check for proper function.
Some receptacles also have holes in the back of the receptacle body, used for "back-wiring." Use these only if they are the type that can be clamped down with a screw. The push-in type of connector is unreliable and can lead to loose wires and other hazards. Professionals almost never use push-in connectors on devices.
Wiring With Pigtails
Turn Off Power, Remove Old Receptacle and Test
Follow the steps above to turn off the power to the receptacle, pull it out from the electrical box, and test to make sure it has no current passing through it. Remove all wires attached and discard the old receptacle.
Cut and Strip Cable
Cut a 12-inch length of NM cable that matches the cable already present in the box. Use a utility knife to strip the outer sheath off of the cable, exposing the three wires it contains (usually one black, one white, and one bare). Use a wire stripper to take off about three inches of the sheathing around the black and white wires.
Line up the two black hot wires from the electrical box with the black wire from the NM cable so that the ends are even. Twist them together with a wire nut. Do the same for the white neutral wires. The ground wire does not need a pigtail, as it can be connected directly to the new receptacle.
This configuration will leave you with both wires from the box and one end of the wire from the new NM cable sealed in a wire nut—for both the black and white wires. There will also be one white and one black wire coming from the wire nut.
Once your pigtails are made, push them inside the box. Then, trim about 3 inches of insulation off the ends of the white and black wires. Use a needle-nose plier to bend the wires into hooks. Then, connect the black wire to one of the brass-colored screws, connect a white wire to one of the silver screws, and connect the green or bare ground wire to the green screw.
Push the newly wired receptacle into the box and secure with two screws. Put the faceplate on the receptacle. Turn the power back on and check for proper function.
When to Call a Professional
If you've taken the steps above and your outlet isn't working, the best course of action is to turn the power back off at the main electrical panel and call an electrician. The issue could be more complicated than a bad receptacle and a professional will be best to investigate.