Guide to types of electrical receptacles (wall "outlets" or "wall plugs"):

How to choose the right type of electrical receptacle when adding or replacing a wall outlet in a building. Here we describe matching 15-Amp receptacles to 15-Amp circuits, 20-Amp receptacles to 20-Amp circuits, two-wire receptacles where no ground is present, GFCI and AFCI electrical receptacles, and the proper electrical box to hold and mount these devices.

This article series 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.

Choose the Proper Electrical Junction Box When Adding a Receptacle

These questions and answers about choosing the right electrical box size were posted originally at ELECTRICAL JUNCTION BOX TYPES - be sure to review the specifications given there.

The proper sized and type of junction box must be used to house the electrical receptacle, must be properly secured in the wall, and must be located at the proper height from the floor.

The National Electrical Code Article 314 contains complete details and tables of electrical box sizes in dimensions and cubic inches and should be consulted for complete accuracy because the actual size of the box required, in cubic inches, depends on the number of wires that will be within that enclosure.

On 2018-08-31 by (mod) - depends on the cubic inches that the Box provides

The answer to your perfectly good question depends on the cubic inches that the Box provides matched against the table of cubic inches required for the number of wires and connectors by wire size in the circuit that you are wiring

On 2018-08-31 by Mike

Can I use an old-work plastic box for a 50 amp outlet?

On 2018-06-08 by (mod) -

You can cut a hole just slightly larger than the physical dimensions of the electrical box you are installing, then use an OLD WORK electrical box that provides clips to secure the box in the wall.

At our ARTICLE INDEX see OLD WORK ELECTRICAL BOXES for RETROFIT where I describe using old - work electrical boxes.

Below my comment is a steel Raco old work box that I've used.

When the screws are tightened the clip expands to secure the box in place.

Similar products are available in plastic electrical boxes.

An "ear" swings out and tightens against the cavity side of the drywall or cabinet back.

On 2018-06-08 by bob

I need to install a receptacle inside a kitchen cabinet. I will have to cut out a hole for the junction box. What size hole should I cut? There is a stud with a receptacle and junction box in the wall below the hanging cabinet.

I plan to cut into the cabinet and wall directly above that box to intercept wiring. I'm concerned that I will not be able to hammer or screw the junction box into the stud if the hole for the junction box is limited to the size that can be covered by the receptacle outlet plate. Is there a special box for this situation?

On 2018-02-11 by (mod) -

Yes, among others RACO 1-1/2 in. Deep, Gangable Switch Boxes are available. These are 7.5 cu.in. in capacity and are available with plaster ears for old work.
Watch out for overcrowding and thus code and safety violations in small capacity boxes.

On 2018-02-11 by Dean

Is there a single hang plastic cut in box that is 1 and a half inch deep with holding ears

On 2018-01-18 by (mod) - are plastic electrical boxes permitted everywhere?

Mike

Most US jurisdictions will permit plastic electrical boxes provided you're using NMC (plastic) wire as well.

Some such as New York City may require use of armored cable and thus metal electrical boxes.

So you need to check with your local building code or electrical code inspector.

On 2018-01-18 by Mike

I would like to add a second GFI outlet in an unfinished portion of a basement bathroom. Does it matter if I use a plastic or metal box. I am located in Milwaukee WI.

On 2017-12-01 by (mod) -

Glad to help, your question is helpful to me as well as it tells me where I need to explain things better

On 2017-12-01 by Anonymous

Thank you so much for the help once I read your answer it completely clicked in my head. Really appreciate it!!!!

On 2017-11-30 by (mod) - Relationship of watts / volts / amps

Matt,

Yes indeed. Put most basically: Watts = Volts x Amps

Details
Relationship of watts / volts / amps:

Voltage = Current x Resistance where Current = Amps and Voltage = Volts

Current = Voltage / Resistance

Resistance = Voltage / Current

Watts = Volts x Amps and of course using simple algebra we can rearrange this formula to give any of those three measurements.

Volts = Watts / Amps

Amps = Watts / Volts

example: 4 100 W bulbs = 400 W. 400W / 120Volts = 3.3 Amps that's just for the 4 100W bulbs. Now we can add the 3 75W bulbs but I can't add the fan because we don't have a watts usage rating number. Just knowing the volts doesn't tell us that. At typical ceiling fan at high speed uses 55 Watts. So let's use that figure and guess:

400W (4 100W bulbs) + 150W (3 75W bulbs when at full brightness) + 55W (typical ceiling fan at high speed) = 605 Watts

605 / 120 = 5.042 Amps. total usage for the items you listed.

At DEFINITIONS of ELECTRICAL TERMS inspectapedia.com/electric/Electrical_Definitions.php we give definitions and formulas for all of these terms.

On 2017-11-30 by Matt - mathematical formula that can help me understand watts / volts / amps.

Is there any mathematical formula that can help me understand watts / volts / amps.

For example I have 4 100 w. Bulbs that I will run 14/3 wiring from to a new gang box.

That runs to a 15 a. Breaker. That breaker is already feeding a 120 v fan, and a three-way light switch of 3 75 w bulbs. So how many amps will I be using?

On 2017-11-27 by (mod) - Is there a combination box for the TV cable and the receptacle?

You should not ever run a TV co-ax cable in the same electrical box as 120VAC electrical wiring. Doing-so could electrocute someone.

However there are listed box combinations that will permit the construction of power and cable connections for a TV in one location in a wall, such as the

PASS & SEYMOUR TV3W-TVSSW : RECESSED TV BOX 3 GANG TVSS WHITE 3G RCSD TV BOX

Widely available from electrical suppliers. Here is an image of the installed product clipped from sales material at Gordon Electric Supply:

On 2017-11-27 by vincent

I am hanging a TV on a bedroom wall. Is there a combination box for the TV cable and the receptacle?

On 2017-11-26 by (mod) -

Exton

I don't think that you will find a height restriction for the case that you described.

On 2017-11-26 by Exton

I’m installing a junction box in the bathroom. How much high it should be above the floor?

On 2017-04-06 by (mod) -

Paul

The best and maybe only workable fix is to install a newer larger box in the same location. I'd look for a 4" box that is also one of the deeper units - once you're going to the bother to install a new box there's no cost and some gain in using a larger deeper one.

Set the box deep enough in the wall that the adapter/cover that you'll install to accept the switch brings its front surface just flush with the front surface of the wall (drywall?). That way your switch will mount at the proper depth.

Then there are 2 options: a 4" plastic electrical box cover to present one switch in its center is easiest.

Alternatively one might fill in joint compound to reduce the wall opening to the smaller opening afforded by the 4" to single-switch-or-receptacle adapter plate.

The name of the adapter plate you want for your 4" box is a
4 in. Square Single Device Mud Ring, Raised 1/2 in. (for 1/2" drywall).

Flush plates are also available for boxes whose edges are already flush with the drywall face.

The cover plate is ab out $1.00 U.S.
A 4" metal electrical box is about $2.25 U.S.

I prefer to connect the side of the box directly to a wall stud for secure mounting, but other forms and mounting systems to secure a box to a drywall opening are also available.

On 2017-04-06 by Paul

I am replacing a switch which is larger than the existing one, I dont have the room for the wires. what do I need?

On 2017-02-28 by (mod) - box extensions

John

I like using box extensions - of which 1/4" thick is a standard dimension - along with screws of sufficient length, because it
- gives a stronger mount for the device and the face plate
and
- for deeper-recessed boxes I'm confident that the box is totally enclosed - no openings into the wall cavity around the box.

On 2017-02-28 by john

all the switch and outlet boxes in the home we are having built are 1/4"+ recessed into the drywall. will box extensions be necessary or will they be ok using longer screws. great website

On 2017-02-28 y (mod) - using box extensions for recessed boxes

John

I like using box extensions - of which 1/4" thick is a standard dimension - along with screws of sufficient length, because it
- gives a stronger mount for the device and the face plate
and
- for deeper-recessed boxes I'm confident that the box is totally enclosed - no openings into the wall cavity around the box.

On 2017-02-28 00:16:41.047952 by john

all the switch and outlet boxes in the home we are having built are 1/4"+ recessed into the drywall. will box extensions be necessary or will they be ok using longer screws. great website

On 2017-02-09 00:42:41.862827 by steve carver

should have added to be mounted in attic with blank, also they are allied boxs moulded...best there is i think

On 2017-02-09 by steve carver

can you use 3 and 4 gang device boxes as junction boxes..purpose is for more volumn

On 2017-01-02 by Anonymous

How to install a standard electrical box in a six inch diameter hole

On 2016-12-08 by (mod) - receptacle mounting covers that will fit on a round electrical box, b

Convert

There are receptacle mounting covers that will fit on a round electrical box, but before you go that route you need to look at the box size (diameter and depth and cubic inches) to be sure that there is adequate and code-complying wiring space.

In a companion article https://inspectapedia.com/electric/Plastic_Electrical_Box_Repair.php you'll see an example of a fairly deep round electrical box being reinserted into a ceiling and secured to support the weight of the light fixture. That could have been a receptacle instead.

If the receptacle ears that mount to the box don't fit the existing screw receives on the round ceiling box you 'll need to purchase an adaptor plate that mounts to the existing box screws and contains additional screw fittings and a cutout to which the receptacle is mounted.

Then there are some nice round receptacle covers such as the brass ones from Raco, Carlon, Gampak and Reddot also make a round box cover for exterior fixtures that could work. Look at your electrical supplier or at a building supplier like Lowes or Home Depot or your local hardware store.

On 2016-12-08 by Convert ceiling light receptacle

I would like to install a electrical single gang outlet in my ceiling where we currently have an empty plastic round electrical box that has all the wires available.

Do they sell kits that have the outlet and outlet cover that will fit into the round box or will I need to purchase a single receptacle and then try to find a single receptacle outlet cover (which is not easy to find).

On 2016-11-19 by (mod)

Sorry, Birge I don't know what black box you are asking about.

On 2016-11-19 by Birge

Can an open back box be used for 120 V circuit?

On 2016-11-10 by (mod) - Does the ceiling box need to be metal?

Gabriel I think the answer is ... it depends. E.g. in NYC wiring is armored cable and thus of course metal junction boxes.

On 2016-11-09 by Gabriel

In commercial applications. Does the ceiling box need to be metal? what is the minimum size required? 3"? or 4"?

On 2016-10-17 by Michael

Is there a weight requirement for ceiling boxes in commercial buildings. An is there a difference between a metal box an a plastic box for the ceiling

On 2016-09-29 by (mod)

SS covers are unsafe. Relying on a ground plug prong to avoid sparks isn 't avoiding somebody getting fried. I'd suggest a better grade of receptacle and a heavier plastic cover.

On 2016-09-29 by Anonymous

We install outlets with the ground plug up. We use the outlets heavily and have SS covers. When they get loose they sometimes fall onto the hot and neutral causing a show. Ground plug on top solves the issue.

On 2016-05-30 by (mod)

Paul, I agree that some old boxes are waay too small to jam in a new GFCI receptacle. Even taping the sides to avoid electrical contact is unsafe, improper, and doesn't solve the over-crowded box problem.

Yes the best solution is to install a larger box and wall plate.

On 2016-05-30 by (mod)

Al

REplace the box

On 2016-05-21 by Paul

I tried to install a g f i in a standard wall box but the side clearance is almost against the box. Can I get a wall box about 1/4 in. id.wider so that the cover plate will fit

On 2016-05-19 by Al

I have a 3 1/2" round outlet box in the ceiling of my garage. How do I make a standard outlet fit into it?

On 2016-04-03 by (mod)

Hank,

This common problem can be easily fixed, Hank.

Stop by your local electrical supplier, or building suppliers such as Home Depot, and look through the plastic electrical box extenders.

These are plastic rectangles sold in various thicknesses that serve essentially as a rectangular but structural washer to bring the face of the electrical box out flush with the surface of the wall.

Typically you can buy an electrical box extender of sufficient thickness to do the job, or you might need to buy a pair of them depending on the thickness of your drywall.

Plastic electrical box extenders are also discussed at this website.

On 2016-04-03 by hank

Kitchen remodel electrician used metal clad cable and metal boxes -- at our request -- but installed the boxes flush with the studs. Now they're more than half an inch below 5/8 sheetrock. They're licensed electricians, but young.

Am I being fuddyduddy about wanting the boxes brought forward with metal extenders here? Hell, I always installed the temporarys with screws so I could back the screws out and pull the box forward as needed.

So what if there's "nothing in the electrical box that can burn" -- which I don't believe anyhow. I can't see leaving a gap between the front of the metal box and the back of the sheetrock as being safe.

Someone point me to a code cite for the exact rule?

And that was with a manual screwdriver, uphill both ways in the wintertime.

They got power screwdrivers.

On 2016-02-08 by (mod)

Wayne,
Floor receptacles, if permitted by your local electrical inspector, require a special cover designed for floor-use and intended to protect the receptacle from dirt, water, damage. Typically they're brass or stainless steel, flush with the floor surface. The box can be plastic or steel as permitted locally.

On 2016-02-08 by Wayne Hadley

Hello! I am thinking of putting a plug in the floor, under my kitchen table. The floor is ceramic tile. Could you please tell me what codes I need to know about. On the box, plastic and steel ?? Thank You

On 2015-11-05 by (mod)

Robert we've provided a detailed reply along with a repeat of your question in a companion article at

ROMEX SPLICE CONNECTORS inspectapedia.com/electric/Electrical_Wiring_Splices.php#Tyco

On 2015-11-05 by ROBERT WEISBERG

IS IT SAFE TO USE ROMEX SPLICE KITS SOLD AT HOME DEPOT, SO THAT 6 RECEPTACLES IN A KITCHEN BACK SPLASH CAN BE LOWERED ABOUT 4" AND REALIGNED FROM VERTICAL TO HORIZONTAL?

On 2015-09-10 by (mod)

Mark there are quite shallow steel electrical boxes - about 3/4" deep - available at electrical supply houses.

On 2015-09-10 by Mark

Does any company make a smaller (depth) interior electrical box, that houses the plugs and switches behind the drywall. We are installing on the outside of a cabinet and are pressed for depth space.

Thanks

On 2015-07-21 y Robert

can a single ground wire be added to a two wire system

On 2015-04-10 by (mod)

I may be missing something Anon but certainly 3-way switches are widely available from electrical suppliers and home supply stores; to go to mroe than 3-way one uses the same switch type.

On 2015-03-28 by Anonymous

I seem to have a 3 inch box for two toggle switches, a 3 way and a 4 way. Would like to replace them with more up to date switches but am unable to locate any.

On 2014-08-06 by Dick N - Is it legal to use a plastic outlet box with AC or MC cable when there is only one cable entry

Followup:

What I meant was: Is it legal to use a plastic outlet box with AC or MC cable when there is only one cable entry and therefore no issue of bonding the cladding of multiple cables together?
How about when there is a second cable entry but that one is non-metalic? Is it legal to use a plastic box with AC or MC cable?

Question: I'm installing a box extension but the top screw won't hold - it's stripped

I started installing a box-extender on a receptacle in my kitchen because I'm tiling my backsplash and need to raise the outlet above the tile. However, the top screw connecting the outlet and box wouldn't hold. I spent way too much time bent double under my cabinets trying to get it to bite, but when I finally gave up and pulled it out it was stripped at the tip (which was as far as it'd go in). I'm sorry to bother you with triviality, but I'm new to home renovations and don't know what to do. Advice? - Julia 1/29/13

Reply: step by step tips for replacing a stripped electrical receptacle or switch box mounting screw or screw opening

Julia,

If the problem is the screw itself is stripped, simply purchase a replacement screw or a hand full of them from your electrical supplier. These screws are a standard thread and length, but longer versions are available at any hardware store.

For the case you describe, if the stripped problem is the mounting hole you'll need to either enlarge and tap the hole for tine next size larger screw, or purchase a clip-on adapter that slips over the stripped ear through which the original hole passed.

Taking care to move electrical wires out of the way of your drill bit, in a metal electrical box you can drill out the 6/32 screw opening to tap and accept an 8/32 screw.

For photos and step by step details on how to repair stripped electrical outlet mounting screws, see OUTLET BOX SCREW REPAIR.

Article Series Contents

• ELECTRICAL JUNCTION BOX TYPES
  • ELECTRICAL BOX SIZING TABLE
  • GANG BOXES for MULTIPLE SWITCHES or RECEPTACLES
  • GANG BOX EXTENDERS for WIRING SPACE
  • OLD WORK ELECTRICAL BOXES for RETROFIT
  • ELECTRICAL BOX TYPE FAQs

...

Continue reading  at ELECTRICAL JUNCTION BOX TYPES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Electrical Box Articles

• ELECTRICAL BOX TYPES
  • CEILING LIGHT FIXTURE INSTALLATION
  • ELECTRICAL BOX SCREW REPAIR
  • ELECTRICAL BOX SCREW REPAIR, METAL BOX MENDER
  • EXTERIOR ELECTRICAL BOX REPAIR
  • METAL ELECTRICAL BOX SCREW REPAIR
  • OLD WORK ELECTRICAL BOXES for RETROFIT
  • PLASTIC ELECTRICAL BOX REPAIR
• ELECTRICAL BOX GROUND WIRING
• ELECTRICAL RECEPTACLE LOCATIONS
• ELECTRICAL RECEPTACLE TYPES
• SIZE of WIRE REQUIRED for ELECTRICAL RECEPTACLES for receptacle circuits and similar wiring situations

Suggested citation for this web page

ELECTRICAL BOX TYPE FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

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