How to wire up an electrical receptacle:
Here we illustrate basic connections seen in the field for the black, white neutral or grounded conductor), and ground wire when hooking up an electrical receptacle (wall plug or "outlet").
We describe how to wire an electrical receptacle by making the right connections between individual electrical wires and the proper screw or clamp connectors on the electrical receptacle device itself.
We also describe connecting the ground wire between the circuit grounding conductor, receptacle ground screw, and the electrical box (if metal boxes are used).
Watch out: mis-wired electrical receptacles are dangerous. Electrical wiring should be performed by a licensed, trained electrician and should comply with the National Electrical Code and local regulations. This article series describes how to choose, locate, and wire an electrical receptacle in a home.
Green links show where you are. © Copyright 2017 InspectApedia.com, All Rights Reserved.
[Click to enlarge any image]
The illustration shows the typical wiring of an electrical outlet or "receptacle", courtesy of Carson Dunlop Associates. Our photo at page top is not an example of a proper electrical outlet installation.
Watch out: Electrical components in a building can easily cause an electrical shock, burn, or even death. Even when a hot line switch is off, one terminal on the switch is still connected to the power source. Before doing any work on the switch, the power source must be turned off by setting a circuit breaker to OFF or removing a fuse.
If you are wiring a 2-wire electrical circuit that has no ground wire, also see CONNECTION for 2-WIRE RECEPTACLE CIRCUITS for proper wiring details.
So where do the wires go: to which screws on the electrical receptacle (shown just above) do we connect the black wire, white wire, and ground wire? And what if there is no ground wire?
On a conventional 120-volt "two pronged" electrical outlet that accepts grounded plugs (two prongs plus the rounded center ground connector prong), your circuit will have three wires:
You will see the hot black wire connected to the bronze or darker-colored screw on the receptacle shown at below right. The receptacle we used for these photos happens to be a 20-A rated device that permits the wire to be inserted straight into a clamp that is tightened against the wire by the screw.
Watch out: for the safest, most reliable electrical connections use either the screw clamp connector shown here, or use a wire connected directly to a binding head screw. We don't recommend using the push-in type backwire method that relies on a simple spring-clip connector inside the device.
See BACKWIRED ELECTRICAL RECEPTACLES for details.
I have a 3 wire (Black, White, Red and ground) feeding a outlet and I want to add another receptacle to run further down the line. The line out is 14/2. What do I do with the Hot Red wire? Can i attach it to the ground. - Rick
NEVER connect a hot (red or black) wire to ground (nor to the white neutral wire) - doing so would form a dead short, should trip a breaker, or if not, could cause a fire or could cause a dangerous shock.
If there is a hot wire that is not used in a junction box, SOP would be to cap it off with a twist-on connector.
It sounds as if you'd be best served by hiring a licensed electrician.
After capping off the red wire, can I extend the line to the next plug by following the diagram above and adding the black and white wires to the respective second screw connections?
You see, the wiring has already been installed by the builders and they left the boxes without receptacles so all I have to do is connect them to the. I don't know why the extra red wire is there. It was done over a year ago. I want to finish the connections. It runs 14/3 and then 14/2. That's why I have the extra red.
Rick often electricians run a 3-wire system into a building area using two hot wires and a shared neutral, to permit providing two circuits in an area while having to pull just one wire to the area. But to sort out how your wires were connected and are being used requires some expertise, visual inspection, and testing using a VOM.
Take a look at multi-wire branch circuit wiring information and hook-up details at MULTI-WIRE CIRCUITS.
Reader Question: What are the "Line" and "Load" marks on recetpacles and switches and which wires go to "LINE" and which wires connect to "LOAD" terminals?
What is the difference between the load and line terminal screws on a 15 or a 20 amp receptacle? How do i wire 4 more recepticles to an existing receptacle in a room? - Anon
Anon: the line and load electrical wire connections are important to get right on certain electrical devices such as GFCIs and AFCIs. Our photograph (left) illustrates the line and load markings on the back of a GFCI electrical receptacle.
Looking at the side or back of the molded case of this and other electrical devices such as AFCIs, you will see that one pair of terminals will be marked "line" and the other "load".
The Line terminals (green arrows in photo at left) on an electrical receptacle are for the incoming hot wire - the terminal marked LINE is connected to the incoming power source or the "hot" wire (typically black or red in insulation color) that connects to the brass colored screw (marked "Black" or "Noir) at the lower left " in our photo.
And the incoming neutral (white) wire from the electrical panel connects to the "Line" and "White" or "Blanc" terminal marked at the lower right in our photo
The Load terminals (red arrows near the top of our photo at left) on an electrical receptacle are for the outgoing wires. These wires feed electrical receptacles that are located "downstream"(farther from the electrical panel) from the device. The outgoing hot or black wire (red arrow, above left in our photo) connects to the terminal marked "Load" or "Charge" and "Black" or "Noir". The outgoing white, neutral wire, connects to the terminal marked "Load" or "Charge" and "White" or "Blanc" in our photograph.
Re-stating, terminals marked LOAD on a GFCI or AFCI are intended to be used to feed other devices (such as receptacle) that are wired "downstream" from the one being worked-on. In a string of electrical receptacles wired in series, incoming electrical power flows in to the first GFCI/AFCI receptacle and is connected to the LINE terminal. The LOAD terminals of that device are connected to hot and neutral wires that subsequently are connected to the next electrical receptacle in the series.
To hook up a quad of electrical receptacles you'll need a larger junction box. And often we wire two separate electrical circuits to the box, placing one pair of receptacles on one circuit and the other on the second circuit - that approach allows us to plug more devices into the wall at that location with less chance of overloading a single electrical circuit in the building.
Watch out: while a conventional receptacle may work with the line and load terminals reversed, a GFCI or AFCI will be unsafe if wired with that mistake, and those devices will not work properly nor test properly in all circumstances. For example, if you connect the incoming "hot" wire and neutral wire to the "load" terminals on a GFCI, and if you connect wires leading to downstream electrical receptacles to the "line" terminals (these are the incorrect connections), then pushing the test button on the GFCI will not activate that device's internal trip mechanism.
Are receptacles wired after GFI receptacles OK? - Denny 11/25/12
Yes, and if wired correctly the downstream receptacles will also be GFCI protected.
Watch out: When wiring a GFCI the incoming leads are connected to the LINE terminals and the downstream receptacles are connected to the LOAD terminals marked on the back of the receptacle. If the devices is not wired correctly it is unsafe and does not provide the intended safety protection from ground faults.
[Click to enlarge any image]
There are two approaches to physically connecting electrical wires to an electrical receptacle ("Outlet") or to an electrical switch ("light switch" or "wall switch"). Back-wiring means connecting the wire through an opening or into a clamp accessed on the back of the receptalce or switch. Our photo above illustrates using a screw-clamp back-wire connector on an electrical receptacle.
Alternatively a wire may be connected directly to a screw on the receptacle or switch as we show in the photo below.
Most literature refers to these as "binding head" screws or "binding head screw connector" because the head of the screw on modern receptacles and switches is designed to grip the electrical wire to hold it securly in place. Some old switch or receptacle screws were rounded or tapered a bit on their underside or at their outer circumference so that if you were not careful the wire would pop out of place when tightening the screw.
At WIRE-TO-CONNECTOR PERFORMANCE SUMMARY you will see that the most-reliable electrical connections are made using either binding-head screw shown in the photo above (first choice) or the screw-clamp connector (shown at the start of this section) on receptalces and switches. We do not recommend using the push-in back-wire connection that relies on a simple spring-clip device inside the receptacle or switch because that connection has both less contact area and less clamping force on the wire.
Below our photo illustrates using the (not-recommended) push-in back-wire connection that relies only on a spring clip connector. You can see that this receptacle also offers side-mounnted binding head screws (recommended).
We have seen field reports of receptacle burn-ups that all involved spring-clip push-in type backwire connections.
See BACKWIRED RECEPTACLE FAILURE PHOTOS for details.
The steps in connecting a wire to a binding head screw are simple but require a bit more labor than connecting an electrical wire in a screw-clamp type connector. Both of those approaches make good connections, and you'll find that on some receptacles and switches you have only two choices: push-in spring-clip back-wiring, or using the side-mounted binding-head screw. For those devices we recommend using the binding head screw connector.
The proper wire size (for 15A or 20A circuit) and type and number of connectors have already been selected. And you've already determined which wires go to which terminal. And you already know which wires go where, as we discussed
at WHICH SCREWS GET the BLACK, WHITE & GROUND WIRES ?
at WHICH WIRES GO to LINE or LOAD CONNECTIONS?
at GROUND WIRE CONNECTIONS
Watch out: electrical wiring involves fire, shock, death and other safety hazards. In many jurisdictions electrical wiring can be performed only by licensed electricians. We recommend hiring a qualified, licensed electrican for electrical work. Even where home-owner electrical work is permitted, permits and electrical code and safety inspections are usually required. Check with your local building department.
Above I'm showing the wire strip-back gauge area marked on the back of a 15A electrical receptacle. This gauge shows the amount of insulation that should be removed presumably for either of the types of connectors provided on this particular device. For the device shown above we are to remove from 1/2" to 5/8" of insulation, or about 16mm.
Below is a rather shorter wire stripping gauge telling us that for the device where this gauge appears - in this case a screw-clamp type wire connector, somewhat less insulation is to be removed. For the device shown below we are to remove 9mm of insulation - about 0.35" - quite a bit less insulation than for the device above.
Watch out: don't strip off too little insulation or the wire will not make a safe, reliable electrical connection: either the wire won't push far enough into the screw-clamp connector or the insluation may prevent the binding head screw from pinching the wire - it'll pinch onto the insulation instead, making a loose, poor electrical contact.
And don't strip off too much wire insulation or the extra length of bare wire may cause a short circuit when you push the device back into its electrical box. That's more than embarrassing, it's dangerous. Trust me.
Most light switches and receptacles include this indicator that tells you how much insluation the manufacturer recommends stripping off when wiring this device. Typically we're removing from 1/2" to about 5/8" of insulation, taking care not to damage or notch the wire. It makes sense, then, to actually look at these instructions given by the manufacturer, as not all strip gauges show the same strip-back quantity.
Also see ELECTRICAL WIRE STRIPPING TIPS
If the wire is being inserted straight into the connector, push the stripped end into the connector skip our illustrations of making a hook or loop at the wire end, just insert the wire into the connector straight, as shown below, and go on to Tighten the Screw below.
In the photo above I've inserted the stripped copper wire into the opening between the pressure plate and the backing plate of a screw clamp type connector on a 20A electrical receptalce.
Bend the wire into a hook for use with a binding head screw if you are using that connector.
I bend the wire into a loop using pliers. I like rounded needle-nose pliers for making a nice smooth hook.
Tip: If I'm going to use the factory-provided bending lug to close this loop around the binding head screw stem then I make the open end of the hook a bit longer than shown in the photo above. That makes it easier to bend the loop shut against the lug as we will illustrate below.
The hook is placed around the shaft of the binding head screw. With the back of the receptacle facing you, place the wire on the left side of the screw so that when you tighten the screw by turning it clockwise the screw tends to pull the wire into the connection rather than pushing it out.
Below is the result of this step. Don't foreget that we're connecting the black or "line" or "hot" wire to the brass or darker or "LINE"-marked screw connector on the receptacle.
In the photo above you can see that the open end of the hooked copper wire pushes against a factory-designed raised lug or protrusion on the side of the receptacle. This feature gives a pushing surface against which the hooked wire can be pushed to close the loop.
Option: close the wire loop around the binding head screw shaft. he electrician can use one of two approaches to maximize the wire-to-screw contact area, making use either of a factory-included detail that helps close the wire loop around the screw (demonstrated below), or by pinching the wire closed with needle-nose pliers. The second of these approaches takes more time and appears to do no better than using the factory-included bending feature. To use the factory-provided wire loop closing feature present on some electrical receptacles we first strip the wire insulation, removing the amount of insulation indicated by the strip gauge on the back of the receptacle - typically about 1/2" to 9/16" of insulation is removed.
Below I'm closing the wire hook by pushing the wire towards the raised lug while the end of the wire hook remains pressing against the lug (white arrow). The photo shows the result of this simple step.
Below is this closed wire hook after I've tightened the binding head screw. Notice that before tightening the screw I returned the wire to a neat 6-O'Clock position .
In the photo below I'm using needle-nosed pliers to close the wire hook around the stem of the binding head screw. You'd use this technique if the receptacle you are wiring does not include the factory-included pressure lug demonstrated above.
As you may agree when seeing the photo below, I don't see that the pliers do any better of a job in closing the loop around the screw stem. But closing this wire hook or loop around the screw improves both the security of the electrical connection and increases the total contact area between the screw connector and the wire. I don't see any difference, however in the contact area between using pliers or using the factory-provided bending stud available on some receptacles and switches.
Use the lug, Luke! or if there is no bending lug against which to push the wire loop or hook's open end, Use the Pliers Luke!
Electricians I've worked with or watched either make the screw hand tight (which turns out to be between 8 and 15 inch pounds of torque in my view), or they use a power driver which most assume applies very high torque. In all events unless your electrical device is being held in a vise the screw tightening-torque you can apply will be limited by the fact that you're usually holding the receptacle or switch in your other hand.
I have never once seen an electrician use a torque wrench at electrical devices like receptales and screws except for forensic engineers and other experts examining electrical connectors, but there are industry specifications for screw tightness or torque. And for using some special connectors such as the aluminum wiring pigtail device, these torque specifications are critical to avoid failure.
See ELECTRICAL SCREW CONNECTOR TORQUE-FORCE for details and for torquin
or for torquing an AlumiConn copper pigtail connector
See AlumiConn TORQUE TESTS
Watch out: it may be possible to damage the screw connector in any electrical device if you over-tighten it, particularly if using a power tool or if like me you enclosed your receptacle in a vise.
See ELECTRICAL SCREW CONNECTOR TORQUE DAMAGE for details.
Proper grounding connections for an electrical receptacle
The electrical receptacle must be properly connected to the building grounding system - not shown in our sketch.
That connection is made from the ground screw on the receptacle to the grounding conductor (usually bare copper) in the wire leading back to the electrical panel where in that location it is connected to a grounding bus and from that bus to the building grounding system, one or more earth-driven electrodes or their equivalent.
The incoming ground wire is connected to the ground terminal on the electrical receptacle (usually a green screw such as shown in our photo at left).
Details of ground wire connections for electrical receptacles are given
at GROUND WIRE CONNECTIONS.
If you are wiring a 2-wire electrical circuit that has no ground wire, also
see CONNECTION for 2-WIRE RECEPTACLE CIRCUITS for proper wiring details.
This information is now at NUMBER of WIRES NEEDED: 2-WIRE, 3-WIRE, 2 or 3 WITH GROUND?
This information has been moved to ELECTRICAL DUPLEX RECEPTACLE WIRING
This topic has moved to ELECTRICAL SPLIT RECEPTACLE WIRING
I recently moved into a 3 1/4 story home, and I have a basement that I am trying to finish with drywall. The room is down to the studs and the electrical receptacles are about 4' up the wall.
The Romex wiring is stapled, and there isn't enough wire to lower them. It is way to much work for me to replace all of the downstairs wiring right to the breaker box, so I'm wondering if it is possible to add onto the existing wires and attach wire screws or marrets within the walls before I start adding drywall, or whether I should add some kind of junction box to contain the marreted wires in between.
My building code stipulations would differ in some cases because I live in Canada, but I just want to do the job right, and I do not want to take the chance of having any fire hazards, as I also have small children. - Dave 2/10/12
Dave,. you are correct to be careful about moving outlets or any other device when the existing wires are too short. The temptation is to just splice on an extension and bury that in the wall or ceiling: an illegal, improper, unsafe as well as really aggravating approach.
The proper approach is to add a junction box at each splice - we never splice 120/240V wires without including them in a box. You can reduce the wiring work a little by using plastic boxes instead of steel - avoiding having to also connect the box to the ground wire.
The proper approach also means that you don't then bury any of these splice-boxes in the walls either. Each box has to be brought to the surface and covered.
The result is a lot of work and expense and an ugly wall with an extra junction box and blind cover all along the wall over each of the now moved or lowered electrical receptacles.
Frankly I figure that especially as you've already got the wall open to the studs, if there are more than one or two receptacles to be moved you'll probably find it is actually much less total work to re-wire the entire circuit, allowing proper lengths of wires for each box. You might carefully remove and re-route the existing wire lower in the wall or you might buy all new electrical wire - depending on the age and condition of the existing materials.
Watch out: when removing wire that appears to be in good condition, if you nick the insulation you've created a new hazard.
Continue reading at GROUND WIRE CONNECTIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see ELECTRICAL OUTLET, HOW TO ADD & WIRE - home - for general wiring procedures, connections & advice for connecting electrical receptacles.
Or see ELECTRICAL RECEPTACLE CONNECTION FAQs - questions & answers about wiring electrical outlets
Or see CONNECTION for 2-WIRE RECEPTACLE CIRCUITS - no ground
Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Recently-posted questions & answers about electrical receptacle wiring connections are at ELECTRICAL RECEPTACLE CONNECTION FAQs
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website