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 that connect to the outlet. Two wires are hot wires—one brings power in, and the other carries it onward to the next receptacle. Two wires are neutral—one brings in the neutral, and the other carries it on to the next outlet. The final cable is a ground wire, which is actually two wires twisted together and crimped, leaving a single lead (called a pigtail) to connect to the outlet.
If you're looking to add an electrical outlet in the middle of a run—for the ease of plugging in a nearby electrical appliance, or if you need to power more items than you have outlets for—there are two basic options for wiring: direct run or pigtailing. Depending on your situation, one method might work better, although pigtailing is generally preferred.
Direct Run vs. Pigtailing
When adding an electrical outlet between two existing outlets, the circuit can be direct-wired through the receptacle. Using this method, the entry wires are attached to one pair of hot and neutral screw terminals on the receptacle, while the exit wires are 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 adding an electrical outlet in the middle of a run is to connect the receptacle to the circuit wires with pigtails, which allow the circuit to flow both to the receptacle and to any "downstream" receptacles, without being dependent on the receptacle's connecting tab.
Pigtailing is not advised if the wall box is shallow and can't handle the volume of extra wire nuts and pigtail wires. If the box is too small, you can either install a larger wall box, or make do with direct wiring through the receptacle.
Why Pigtailing Is Preferred
One of the drawbacks to direct wiring through a receptacle is if the receptacle in the middle of the circuit falters, it affects the devices downstream. Even a loose wire under one of the screw terminals could cause you to lose power to the downstream circuit receptacles. Also, any loose wires on a direct-wired receptacle can heat up and cause a fire hazard, since all of the current for the circuit is flowing through this path. Even diagnosing a problem can be difficult. If all receptacles lose power, it's hard to determine which one is causing the issue.
With pigtail wiring, these drawbacks are eliminated. A problem, or a loose connection, will not affect the receptacles downstream. You can also remove a receptacle in the middle of the circuit without affecting the others.
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 when adding an electrical outlet to an existing line. 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.
You'll also need to know how many receptacles you can run on your circuit.
A circuit breaker can only handle about 80 percent of its rated amps. So, if you have a 20-amp breaker, it can really only handle 16 amps before it trips. That said, you should only run 10 receptacles on a 20-amp circuit, as each receptacle draws roughly 1.5 amps. This is helpful knowledge should you want to install a double outlet (or any more than one) in the middle of a run.
There are always risks inherent in working with electricity. Before you start this project, you must make sure that you have turned the 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 throwing 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 by folding the wires, pushing the receptacle back in place, and attaching 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 should only be used for lightly loaded circuits. 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 3/4 inch 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 3/4 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 by folding the wires, pushing the receptacle back in place, 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.
What is a middle-of-run electrical outlet?
Can you add an outlet in the middle of a run?
How hard is it to add an outlet to a room?
With a little know-how and an understanding of circuits and amps, you can add an electrical outlet to a room. This task is not recommended for beginner DIYers, but it can be accomplished on your own without ripping a hole in your wall.