Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

• HOME
• AIR CONDITIONING
• ELECTRICAL
• EXTERIORS
• HEATING
• HOME INSPECTION
• INTERIORS
• PLUMBING
• ROOFING
• SEPTIC SYSTEMS
• STRUCTURE
• WATER SUPPLY

• ENERGY SAVINGS
• ENVIRONMENT
• INDOOR AIR IAQ
• INSULATION
• MOLD INSPECT TEST REMOVE
• NOISE
• ODORS
• SOLAR ENERGY
• VENTILATION
• EXPERTS DIRECTORY
• CONTACT US

This article describes how to choose, locate, and wire an electrical receptacle in a home. Electrical receptacles (also called electrical outlets or "plugs" or "sockets") are simple devices that are easy to install, but there are details to get right if you want to be safe. This article explains receptacle types, receptacle grounding, connecting wires to the right receptacle terminal screws, electrical wire size, electrical wire color codes, and special receptacles for un-grounded circuits. If you don't see information you want, ask us for it using the comments box at the end of this article.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

Electrical Outlet Wiring Instructions for Homeowners & DIY Repairs

Readers of this article should also see Electrical Code Basics, ELECTRICAL DEFINITIONS and also SAFETY FOR ELECTRICAL INSPECTORS. Our photo at page top is not an example of a proper electrical outlet installation.

This website provides information about a variety of electrical hazards in buildings, with articles focused on the inspection, detection, and reporting of electrical hazards and on proper electrical repair methods for unsafe electrical conditions. Critique and content suggestions are invited. Credit is given to content editors and contributors.

How to add an electrical outlet in a home - i.e. an electrical receptacle

We use the proper term electrical receptacle to describe the "wall plug" or "wall outlet" into which you will insert a two-prong or three prong plug to connect an appliance, lamp, etc. Technically in the electrical code, an "outlet" is any place in where you provide a junction box and electrical wires to which something can be connected: a light fixture or an electrical receptacle, for example.

With a few simple tools, electrical wiring of an electrical receptacle is not difficult, but there are a few details to get right in order for the electrical receptacle to be safely installed.

Why might we need to add an electrical receptacle in a building?

• Convenience: we'd like to be able to plug in more electrical devices at some spot, say at a home office;
• Safety: we need to plug in more devices at some location and we don't want to risk tripping someone or starting a fire by using extension cords;
• Function: we need to plug in more devices at some location in a building, or we need to plug in a new high-current using device in a building, and we find we keep blowing fuses or tripping a circuit breaker; in this case we want to add a whole new circuit, from electrical panel to the location where we need the outlet, so that we can deliver adequate electrical power without blowing fuses or tripping circuit breakers.

Wiring Details for Installing a 15-Amp or 20-Amp Electrical Receptacle

Where do the Black, White, & Bare Ground Wires Go on an Electrical "Outlet" or Receptacle?

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:

• The white "neutral" wire - this wire is connected to the silver screw on the electrical receptacle, often labeled "neutral" . You can see our white neutral wire connected to a silver screw on the receptacle in our photo, below-left.
• The black "hot" wire - this wire is fed from the circuit breaker to deliver power to the receptacle, and it connects to the brass or bronze-colored screw on the receptacle, often labeled "hot" or "live".
  
  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.
  

The bare ground wire - this wire connects to the green ground screw usually found on the bottom of the electrical receptacle (photo at left). You can also see our ground wire connected at the left side of our previous photo, above-left.

What is Reversed Polarity at an Electrical Receptacle and Why Is It Unsafe?

The hot and neutral wires must be connected to the proper terminals on the electrical receptacle. The "hot" or "live" black wire (or red wire) is connected to the brass-colored screw terminal on the electrical receptacle, and the "neutral" white wire is connected to the silver-colored screw terminal on the electrical receptacle. Carson Dunlop Associates' sketch points out that the white wire, i.e. the neutral wire, will be connected through the receptacle's internal parts to the wide slot on the receptacle face in order to assure that the neutral wire side of an appliance being plugged-in there is properly connected. Watch out: Reversed polarity on an electrical outlet is dangerous. If you accidentally reverse these wires the device you plug in to the receptacle may "work" but it is unsafe and risks a short circuit, shock, or fire. Some appliances and some electronic equipment may be damaged if left connected to a reversed-polarity electrical circuit.

How Much Insulation to Strip Off of the Electrical Wire?

If the wire insulation is stripped the perfect amount then after it has been inserted into the clamp or wrapped around the screw you'll see that no wire insulation is under the connector itself, but little or no bare wire is exposed past the edges of the connector. Above our white wire was stripped correctly - the stripped end was pushed into the clamp until it stopped, and the screw was tightened against bare copper, but just about 1/16" or less of bare copper shows above the screw (photo shown above left). Our black wire was stripped too much (photo above-right) and some unnecessary bare copper remains exposed after the screw was tightened. If you going to wrap the electrical wire around the terminal screw on the electrical receptacle (or a light switch terminal) you need to strip back a bit more than 1/2-inch in order to have enough copper to go around the screw leaving no insulation under the screw head when it is tightened. Our photo (left) shows the strip gauge marked on the edge of our receptacle - those two parallel lines cast into the black plastic housing just below our stripped-back white wire.

What Size Electrical Wire Should I Use When Wiring an Electrical Outlet (Receptacle)?

The electrical wire used for the receptacle circuit must be the proper type in size (thickness or gauge) and number of conductors for the ampacity of the electrical circuit

How Many Conductors Should be in the Receptacle Circuit? 2-Wire? 3-Wire? 2-Wire with Ground?

The electrical wire must have the proper number of conductors. In modern electrical circuits used to wire receptacles (electrical outlets).

Typically an electrical receptacle is wired with two insulated wires and a bare ground wire, all three of which are encased in a plastic (NMC) or metal (BX) jacket.

You'll see this wire labeled as 14/2 Type NM B with ground (photo at left) or 14/2 Type NM C with ground.

These wires are color coded black, white, and bare (photo below right). Sketch at left showing the number of conductors in types of electrical wire is provided by of Carson Dunlop Associates.

Nicks in Stripped Electrical Wires Make a Bad Connection

Choose the Proper Electrical Receptacle Type

It's generally ok to plug a 15-A appliance into a 20-A circuit since that appliance is not going to overload the circuit in normal use. But the opposite is not true. If you plug a 20-Amp appliance into a 15-Amp circuit you are risking overloading the circuit and tripping the circuit breaker, blowing the fuse, or worse, overheating the circuit and risking a fire.

Below our photographs illustrate a 15-Amp grounded electrical (below left) and a 20-Amp grounded electrical receptacle (below right). You'll notice that the heavier-duty 20-Amp electrical receptacle has that T-slot at it's wider connection opening - an easy way to identify a wall receptacle rated for 20-Amps - provided that the receptacle was properly matched to the wire size and the circuit breaker or fuse size.

Wiring Older Two-Wire Electrical Receptacle Circuits

Older two-wire electrical circuits, such as the two circuits depicted at the right of our sketch above may provide only the hot and neutral wires and no ground wire. If no ground wire or ground path is provided, it is improper and unsafe to install a grounding (3-prong) electrical receptacle on that circuit. Our photo (left) shows a conventional grounded three-prong electrical receptacle - the round hole is the ground connection - at the left end of the picture closest to my thumb. At right in the photo is an ungrounded electrical receptacle. This is the right device to install if no ground is present on the electrical circuit. You don't want to "fool" a building occupant into thinking that a ground is present when there is not one, so you don't install a receptacle that has that third ground opening in its face. Some older two-wire circuits which are covered with a flexible metal jacket ("BX" or "armored cable" wire) may provide a ground path by means of the cable jacket itself. We don't rely on it, and in event of certain short circuits it's unsafe: the exposed metal sheathing of the wire becomes live, risking a shock.

Connecting the Ground Wire at the Electrical Box

If there is more than one feeder wire entering the electrical junction box then all of the grounds are connected together as well as being connected to the ground screw on the receptacle itself. If the junction box is plastic, you're done. If the junction box is metal, a ground wire is also connected to the metal box using an approved grounding screw or clamp device to tie the wire end to the box. Most metal electrical boxes have a threaded hole intended for use as a connection point for the ground wire connecting screw, as illustrated in our photograph (left).

Grounding: the junction box and electrical receptacle must be properly connected to the building grounding system - not shown in our sketch.

The incoming ground wire is connected to both the ground terminal on the electrical receptacle (usually a green screw), and if the junction box is metal (not plastic) the ground wire is also connected to the metal junction box itself, usually by a special green screw that connects to a tapped threaded hole on the junction box back side, or by a grounding clip that secures the ground wire to the edge of the metal box.

Don't rely on the connection between the electrical outlet's steel mounting strap and the steel screw openings of the junction box to provide the ground connection. That's not a legal ground and it's unreliable. Use the a ground wire and ground screw on the receptacle itself to be sure that this important safety feature is correctly installed. See ELECTRICAL GROUND SYSTEM INSPECTION and Definition of Electrical Ground Terms.

Routing and Securing Electrical Wires for a New Receptacle

The electrical circuit wire must be properly routed and secured between the electrical panel and the receptacle location, and must be properly secured at the junction box that is to hold the electrical receptacle.

We secure wires at intervals specified by the electrical code so that it doesn't sag, hang, pull on itself, and become damaged or unsafe. The two sketches below, courtesy of Carson Dunlop, show examples of routing electrical circuit wires through a wood stud wall and through a wall supported by metal studs.

The electrical circuit wire must be protected from damage. We don't route electrical wires where they can be punctured by someone driving a nail into a wall to hang a picture.

Wires running in walls anywhere from floor level to seven feet above the floor (U.S.) or five feet above the floor (Canada) must be protected from nails driven through walls. We also don't route wires too close to places where the wires can be damaged by heat from a heating appliance or chimney, flooded, etc. as you'll see depicted in the two Carson Dunlop sketches below. Thanks to Steve for pointing out erroneous illustration link details, now fixed.

Electrical Wire Splices When Adding a Receptacle

Some if not all newer electrical outlets with push-in terminals have been modified to use only the smaller #14 sized wire opening to prevent this failure. But we still prefer the increased contact area and increased contact security that comes from being able to tighten a screw.

A screw-terminal (upper left in the sketch) is a more reliable connection for wiring at an electrical outlet. Some newer electrical outlets have a back-wire push-in type terminal which uses a screw to securely pinch the wire in the receptacle - these are fine. The splice at lower left in the sketch depicts using a twist-on connector - the right way to make a wire splice inside of an electrical junction box.

See more electrical wiring splice instruction details at Electrical Splices, how to make

Choose the Proper Electrical Junction Box When Adding a Receptacle

It's likely to be permitted and safe to install a larger sized junction box than you need for an outlet or switch or wire splice, but you may need to purchase a special adapter-cover for the box in order to properly secure an electrical outlet therein. Installing a junction box that is too small is illegal and unsafe.

Below-left we show a typical 4-inch metal junction box, and below-right a common and deeper plastic junction box.

Specification of Proper Wall Location for Electrical Receptacles (Outlets)

An electrical outlet must be properly located on the wall, according to local electrical codes and the National Electrical Code. Examples of proper electrical outlet locations are shown in our two sketches below, courtesy of Carson Dunlop and in the following list of electrical outlet location requirements:

Tub-Shower clearance: Keep electrical receptacles at least three feet (one meter) away from a tub or shower.

Electric baseboard clearance: Keep electrical outlets offset above and to the side of vanity sinks, not right over the sink (left hand sketch below)

Electric baseboard clearance: Keep electrical receptacles off to one side, not right over electric heating baseboards to avoid overheating and possibly melting electrical cords draped over the heater (a fire risk) - see photo at below right, courtesy of Timothy Hemm.

Outlets in floors, countertops: Generally we do not mount electrical outlets flush in countertops or floors, though in some codes and jurisdictions the inspector may require that special (protected) floor-mount electrical receptacles be installed in order to meet the requirement that electrical outlets are available within six feet in any direction along a wall, and where no "wall" is available to install such receptacles (such as along a sleeping loft).

Garage electrical outlet location: In the garage electrical outlets should be 18" or more above floor level.

Electrical Outlet Height Above the Finished Floor

Question: Can I put an electrical receptacle up five feet from the finished floor level?

Before I contact an electrical contractor, I would like to know whether there are any Michigan electrical codes that apply to the "HEIGHT" above floor level - when adding a new (GFCI) A/C outlet to an existing residential home?

Specifically: I very much need to add a dedicated outlet in my bathroom to feed a nice quartz (1,500 W) wall space heater. And - to avoid a messy cord situation, I want to locate the outlet "up" (about 5 feet) off the floor - with a 60 min. wall timer in series.)

Is this OK? (The outlet will be more than 4 feet from the bathtub).

Thanks for your great website! (I read through - but couldn't find the answer to this.) - T.V.M., Grand Rapids MI

Reply:

Because local building code jurisdictions may have their own local requirements, I'd give a call to your local building department and ask (please let me know what happens).

Most of the sources we have reviewed for details about the required height of electrical receptacles above the floor (see Mike Holt's Forum for example) assert that there is no National Electrical Code (NEC) specification of the height of wall-mounted electrical receptacles in homes. [After all, we regularly install a ceiling-mounted receptacle to power garage door operators.] One electrician cited 5'6" maximum above floor level for receptacles meeting the 6' horizontal spacing rule (NEC 210-52) [4]. So you'd be OK with your high receptacle.

Just be sure it's a GFCI-protected receptacle as you're installing in a bathroom, and that the circuit amperage is high enough to operate the electric heater safely.

But there are some ADA requirements that might make you want to put the receptacle a bit lower on the wall.

If your bathroom might need to meet Americans with Disabilities Act standards, you'd want to respect those heights - the ADA (Section 4.2.5 and 4.2.6) requires that outlets be at least 15" above the floor and switches and outlets should not be more than 48-54" (the variation is due to other conditions).

Our photo (left) shows an electrical receptacle mounted just about 2" above the finished floor - which is ok except for the ADA requirements, but that zip cord wiring that is run into the wall is improper, unsafe, and a fire hazard.

Here are some general guides: (heights pertain to electrical receptacles mounted in walls except where we note switches or other devices)

• 0 min receptacle height above floors indoors
• Min 6-1/2" above grade outdoors
• 9" low side reach minimum height above floor for ADA
• 14" to center of receptacle, above floor, in Canada, higher allowed.
• 15" minimum receptacle height to bottom of outlet box - California
• 15" minimum receptacle height above floor for ADA
• 16" to top of box - common install height above floor but see 18" below
• 18" (max?) above countertops
• 18" above floor to top of outlet box - standard practice among many electricians
• 40" maximum height above finished floor to switch for HUD Section 8 housing
• 42" floor to bottom of light switch box - some installers use 48" to the top of the box,
• 44" to top of box for bath vanity receptacles
• 44" to 46" - most electrical switches above floor to bottom of box
• 48" floor to center of light switch (max per NFPA)
• 48" maximum high forward reach for ADA (Americans with Disabilities Act)
• 48" maximum height to top of outlet box - California
• 54" maximum high side reach (ADA)
• 5'6" maximum above floor level for receptacles meeting the 6' horizontal spacing rule (NEC 210-52) [4]

Example CA code on layout and heights http://www.sanjoseca.gov/building/PDFHandouts/5-7CommercialReceptacle.pdf

Mounting Electrical Receptacles in the Box & Installing Cover Plates

The electrical receptacle must be properly screwed to or mounted in the junction box, and the extra length connecting wires carefully pushed back into the junction box so as to avoid crimping, damage, etc.

An electrical receptacle cover plate must be installed over the finished receptacle. We like plastic cover plates better than metal as they reduce the chances of a cover plate becoming electrically "live" and thus unsafe.

Choosing GFCI and AFCI Receptacles

Ground fault protection - GFCI's: The NEC also requires that only special ground fault circuit interrupter (GFCI) protected outlets can be installed in certain hazardous locations like kitchens, baths, garages, outdoors. A GFCI-protected electrical receptacle includes circuitry that turns the electric power off at the outlet quickly should a ground-fault (electricity flowing to earth, such as through your hand and down a water pipe) be detected. [4] Arc fault protection - AFCI's: Beginning in 2002 the NEC also required arc fault protection for electrical outlets for bedrooms. [4] AFCI's are similar to GFCI's discussed above, but they include an additional level of protection against fire by detecting small electrical arcing at a connection - a condition that can lead to overheating and fire. As you can see from this US CPSC photo, you can add Arc fault protection to a home circuit by installing a special circuit breaker in the electrical panel. By this means you can provide arc fault protection and thus improved fire safety for all electrical outlets on the circuit - for example in the building's bedrooms In the FAQs (below) we discuss the importance of wiring the Line and Load terminals of GFCIs and AFCIs correctly. .See GFCI PROTECTION,Testing GFCIs AFCIs and AFCIs ARC FAULT CIRCUIT INTERRUPTERS for details about these devices.

Frequently Asked Questions (FAQs) about how to install and wire electrical outlets or receptacles in buildings.

Question: how to wire up a pair of receptacles in one electrical box

I would like to wire 2 single plugins to one live wire..how do i do that? - Channing

Reply:

Channing, re Hooking up a Pair of Receptacles in One Electrical Box:

If your two plugins (two electrical receptacles) are located in the same electrical box (we call this a "quad" electrical receptacle installation since each individual receptacle provides connections for two wall plugs), you'll want to wire the hot and neutral to one pair of screws on the first receptacle, and use short black and white jumper wires to connect the the proper terminals on the first receptacle to the second one in the same box.

That's a perfectly acceptable use of the second pair of screw terminals you see on the receptacles.

The ground wire can be continuous, tying the two ground screws on the receptacles together and onwards to the circuit ground.

However a better practice when wiring up a quad-plex of electrical receptacles is to place left and right or upper and lower receptacles on separate electrical circuits - thus reducing the chances of overloading the circuit when many things are connected simultaneously. There are two approaches: you can wire the left and right duplex receptacles each to different individual electrical circuits, or you can wire the upper and lower half of the pair of duplex receptacles to different electrical circuits.

Wiring a Split Receptacle to Two Different Electrical Circuits

If you choose to wire the upper and lower duplex receptacle openings to different circuits, we call this the "split receptacle" wiring method, because we are splitting the individual duplex receptacle upper and lower connectors onto two different circuits.

Our photo (left) shows an electrical receptacle that is being wired to a single circuit. The white neutral wire is connected to the silver screw (left side of our photo).

If we were wiring this electrical "outlet" as a split receptacle, we'd want to feed the upper and lower halves of the device from two different electrical circuits.

To do so we'd have to break away the "breakaway" connecting tab pointed to by our orange arrow.

Daisy Chaining Receptacles in Separate Electrical Boxes

If your two receptacles are in different locations and thus in different electrical boxes, your circuit that wires the second or "downstream" receptacle can be powered by those same extra terminal screws on the first or "upstream" receptacle. You'll need to run a wire from the first receptacle through the wall into the second electrical box of course.

Wiring Electrical Receptacles on a Single Circuit In Parallel

In some jurisdictions electricians to not "daisy chain" receptacles in the same box together by using the second pair of screws on each one. Rather the circuit enters the box and using twist-on connectors, short pig-tail wires are connected to each receptacle at the proper screws. This approach requires a larger electrical box as it will contain more connections, connectors, and so needs more room.

Question: what is the minimum height that indoor house wiring must be above the ground or floor level?

When running wire for a basement, is there a min height the wires must be off the ground? Not the outlet box, but the wire running through the joists. Justin Sheppard

Reply:

No, Justin. But if there is the slightest danger that wires will be nicked by someone driving a nail into a stud though which the wires are run be sure to use steel plates to protect the wire where it passes through the studs. Simple nail plates are available at any building supplier.

Question: are electrical junction boxes required for wall plugs?

Do I really need an electrical box to put a new wall plug in ? - Thomas

Reply:

Yes, Thomas, electrical devices such as switches and receptacles (wall plugs) need to be mounted in a code-approved plastic or metal receptacle (box) for fire safety as well as to assure that the device is mechanically secure. In fact when you purchase a "wall plug" you'll see that its metal mounting ears and screws are spaced and designed to connect to an electrical box.

Watch out: while it's physically possible to install a wall receptacle or "plug" without using an enclosure, doing so is dangerous, risking fire and shock, and of course, it's also illegal in virtually every building code jurisdiction.

Take a look at our photograph at left - a fire was contained within this electrical junction box. Had the box been omitted there is a good chance the fire would have spread to the building itself.

When we hear a question like this it makes me very afraid for you and for future building occupants - as amateur electrical wiring is dangerous.

Question: how do I get rid of a four-way switch

Wanting to get rid of a four way switch not sure what wires to remove in order to remove the switch. I have three switches to control one light in my kitchen is this what they call a four way switch? Any help would be very helpful - Jim

Reply:

Jim, once you've got more than one electrical switch installed to control a single device - such as a kitchen light - all of the switches and wiring can be installed using three-way switches. The wiring details are right on the package.

Question: When wiring an electrical receptacle, what do I do with the red wire? Can I ground it?

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

Reply: NO!!

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.

Reader follow-up:

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.

Reply: how three-wire circuits or multiwire branch circuits with a common neutral (and ground) are used and wired

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.

Question: how do I install multiple electrical outlets (receptacles) along a wall?

putting in more than outlet on along a 12ft wall - Mike Tucker

Reply:

Mike, if your comment is a question of how to put in more than one outlet along a 12 foot wall, yes it's perfectly permitted to exceed the minimum number of receptacles along a wall.

The wiring system is unchanged except that in some cases I recommend installing two different circuits and alternating which outlet is served by which circuit. That avoids overloading one circuit if you are plugging in lots of devices in one area.

Question: what's the difference between "line" and "load" terminal screws on electrical receptacles? How do I hook up a quad of four receptacles to an existing circuit?

What is the difference between the load and line terminal screws on a 15 or a 20 amp receptical? How do i wire 4 more recepticles to an existing receptical in a room? - Anon

Reply: how to wire line and load terminals on receptacles (outlets)

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".

Which wires connect to the "Line" terminals:

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

Which wires connect to the "Load" terminals"

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.

Question: Which end of electrical outlets go "up"? The ground hole should be up, down, or sideways?

Can the outlet be installed any way? For example ground hole facing up, down, or sideways? thanks, - Anon

Reply:

Anon, the position of installation of an electrical outlet won't affect its operation and should not normally affect its approval by the electrical inspector.

In some areas I see the outlet installed with the ground connector always "up" as in our photo at left, though to me that's less attractive than the position shown in our electrical outlet photo at far left.

I've also seen arguments expressing the OPINION that the position of the grounding pin connector might help resist the tendency of a plug to fall out of its connection. That's nonsense. If a plug is falling out of a receptacle, one of the two objects is worn or damaged and should be replaced to assure a safe, mechanically secure connection.

Question: Is 14/3 wire ok to use to wire between the light switch and the light? What about an electrical outlet on the same circuit as the ceiling light fixture?

is it okay to use 14/3 wire for power to light to switch to receptacle?

Reply:

Anon:

If you are asking about using a shared neutral wire on a lighting circuit combined with an electrical receptacle circuit, see (search InspectAPedia.com for) our article on "multi wire branch circuits" or "shared neutral electrical wiring".

In general we'd use 14-2 wire on a 15 amp circuit to power electrical receptacles and a SEPARATE circuit to power the lighting fixtures. If we lose power on one circuit we want the other still working so that there is safe lighting in the area.

For a light fixture such as a ceiling light, in addition to bringing power to the junction box where the light fixture is to be mounted (using 14-2 copper wire) we'd use a separate length of 14-2 wire to run from the light switch to the junction box to control the light. Tape the white wire at both ends of the switch circuit with black tape so that the next worker knows that this is a switch circuit and that the white wire is not a neutral wire.

Watch out: we do not wire fixed lighting fixtures such as ceiling lights on the same circuit as electrical receptacles ("wall plugs"). If one of the two circuits should be switched off by a circuit breaker (perhaps detecting a fault or overcurrent) we want the other circuit to remain on so that room occupants are less likely to be left in darkness.

Question: how is an electrical outlet wired to the electrical panel?

how do wire the outlet plug to the electrical panel - Anon

Reply:

Anon, the electrical circuit that powers an "outlet plug" or receptacle is connected, usually through building walls, ceilings, or floors, from the first receptacle in the particular series back to a fuse or circuit breaker connection in the electrical panel. The fuse or circuit breaker, by its connecting mount in the electrical panel, receives electrical power from the income electrical service.

Question: When adding an electrical outlet in a garage, what's code: metal or plastic junction box?

I am putting outlet in garage wall that has kitchen on the other side. What is code, plastic or metal? I would think in a garage fire that a plastic box would melt and fire would go through the wall faster? - Steve Smith

Reply:

Steve both plastic and metal receptacle boxes are code-approved and neither, properly installed and wired, should violate the fire-rating of the wall.

Question: can I connect a pigtail from multiple hot, neutral, or ground wires over to a receptacle

I have 2 receptacles that are both side and back wired, 3 hot and 3 neutral wires. I eliminated one receptacle (capping the 3 wires together) but want to keep the other. Is it safe to just run a pigtail from the 3 wires to the receptacle? - Greg

When wiring multiple boxes in series, how do you connect both incoming and outgoing ground wires to the back of the receptacle? With 12 ga. wire, only one wire will fit under the green screw (and not very tightly, at that - there's no washer or clamp.) - Bob M.

Reply:

Yes, Greg, that's a common practice. Be sure that your junction box is big enough to contain all of the wires and twist-on connectors.

Bob, similar to Greg's question, I see two approaches to hooking up the ground wire in junction boxes and at electrical receptacles.

1. If the incoming ground wire from the feed circuit was left long enough, it can be run continuously, connected to a grounding screw that connects the wire to the metal junction box (skip this step if plastic junction boxes are in use), on to the ground screw terminal at each electrical receptacle, and ending with a ground clamp crimp connector that ties the incoming ground to the ground wire of the outgoing wire that continues to the next junction box.
2. If the incoming ground wire is not long enough to run as above, then an additional length of ground wire is pigtailed to the incoming ground and makes the other connections I've described above.

Question: connecting 14-3 to 14-2 wires & to the junction box

How do you connect 14-3 to 14-2 to a junction box - Moe.

Reply:

Moe, twist on connectors are used to connect the incoming and outgoing hot, neutral, and ground wires, and a single pigtail length in that same twist-on connector can connect the ground to the local junction box.

Watch out: when mixing 14-3 and 14-2 wires on an electrical circuit.

If the 14-3 wires are the hot wires entering the box, and if only 14-2 is leaving the junction box, cap off the unused (typically the red) hot lead.

Do not just bond it together with the outgoing hot wire in the 14-2 group. Making that mistake would short two hot leads together, would be improper, unsafe, and a fire or shock risk.

Question: how many electrical receptacles are allowed on a 20-amp circuit? How many receptacles on a 15-amp circuit?

How many receptacles can be wired To one 20 amp circuit No. 12. Wire - John K.

Reply:

John K:

In general, the Electrical Code [NEC] allows

• 10 electrical receptacles to be wired on a 15-Amp (#14 copper) wire circuit, and the Electrical Code [NEC] allows
• 13 receptacles on a 20-amp (#12 copper) wire circuit.
  
  Watch out: When purchasing the receptacles to use on a 20A circuit, be sure to also buy receptacles that are themselves rated for 20Amp use. You'll see that those least-costly receptacles found in a big pile at building supply stores are more likely intended only for 15-Amp use.

Our photo (left) illustrates an electrical receptacle intended for use on a 20-Amp circuit. Notice that extra horizontal slot? You won't see that on a 15-Amp electrical receptacle.

Question: how to fix loose electrical receptacles in a ceramic tile wall

Is there a way to repair electrical outlets on finished (glass and ceramic tile) walls that were not installed properly without damaging the tile? The outlets and the covers pull away from the wall when the electrical cord plug in removed?
Also, what does it mean when an electrical switch with multiple switches which control recessed lights, the ceiling fan and light on the ceiling fan gets hot; what is happening? Is this a fire hazard? - Mrs. Spencer

Reply:

Mrs. Spencer:

It sounds as if you need a licensed electrician to check and secure your loose electrical outlets - I agree that a loose electrical receptacle is unsafe. But an inspection is needed to understand the underlying problem. It could be simply tightening screws, or it could be that the electrical box itself is not adequately secured in the wall. Luckily there are retrofit parts that can be used and inserted along the box to make it secure, usually without disturbing the surrounding ceramic tile.

Some dimmer switches use a resistor to dim the light and it is common for them to get warm. Very hot - a subjective judgment for homeowners - may indeed be a fire hazard and should be investigated.

Questions & Answers regarding this article

Questions & answers about how to install and wire electrical outlets or receptacles in buildings..

Recommend / Share this Article            

...

Technical Reviewers & References

InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.

InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also list books on the specific article topic as well as other references, and information sources.

Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.

Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

  Electrical Outlet-how to add

• Timothy Hemm has provided photographs of various electrical defects used at the InspectAPedia ^TM Website. Mr. Hemm is a professional electrical inspector in Yucala, CA.
• Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• [3] NFPA - the National Fire Protection Association can be found online at www.nfpa.org
• [4] The 2008 NEC National Electrical Code (ISBN 978-0877657903) Online Access LINK (you'll need to sign in as a professional or as a visitor)
• Special thanks to our reader Steve who pointed out prior errors in our illustrations.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
• * Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
• Aluminum Wiring Information Website Aluminum Electrical Wiring Hazards and Repairs: in-depth authoritative info, photos, documents including selection of proper vs. ineffective repair methods. E.g.: Ideal 65 "Twister" purple connector fails in field and lab testing with aluminum wire.
• Ampacity of an Electrical Service: How to determine the electrical service size or ampacity entering a building
• Circuit Breaker, a bad one fails to trip failure at aluminum bus-to-circuit breaker connection - field report and photographs
• Electrical Panels, How to Inspect in buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
• Federal Pacific Electric (FPE) Stab-Lok Circuit Breaker Panel Hazards Website - Latent fire hazards, in-depth authoritative research, documents, advice on Stab-Lok electric panel and circuit breaker failures and what to do when this equipment is found in buildings.
• Lightning Strike Risk Assessment, Protection Systems & Services
• Multi-wire branch circuit inspection and defects
• Rust and Corrosion in Electrical Panels, A Study and Report on Frequency and Cause for Electrical and Home Inspectors at Residential Electric Panels
• "Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
• Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
• "Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
• "How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
• "Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
• "Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
• "How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
• "Home Wiring Inspection," Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
• "Evaluating Wiring in Older Minnesota Homes," Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
• "Electrical Systems," A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
• "Basic Housing Inspection," US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.
• Electrical System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page
• ...