Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
ACCURACY vs PRECISION of MEASUREMENTS
AFCIs ARC FAULT CIRCUIT INTERRUPTERS
ALUMINUM SECs & WIRING
ALUMINUM WIRING HAZARDS & REPAIRS
AMPS & VOLTS DETERMINATION
AMPACITY - the LIMITING FACTOR
APPLIANCE EFFICIENCY RATINGS
BACKUP ELECTRICAL GENERATORS
BACK-WIRED ELECTRICAL DEVICES
BOOKSTORE - ELECTRICAL
BUILDING SAFETY HAZARDS GUIDE
Cadet & Encore Heater Recall
CIRCUIT BREAKER FAILURE
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
Classified CIRCUIT BREAKER WARNING
CORROSION in ELECTRICAL PANELS
CORROSION & MOISTURE SOURCES in PANELS
CUTLER HAMMER PANEL FIRE
DEFINITIONS of ELECTRICAL TERMS
DIRECTORY OF ELECTRICIANS
DMM Digital Multimeter HOW TO USE
ELECTRIC METERS & METER BASES
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRIC PANEL AMPACITY
ELECTRIC PANEL INSPECTION
ELECTRIC PANEL MOISTURE
Electric Power Frequency Table
ELECTRICAL DISTRIBUTION PANELS
ELECTRICAL GROUND SYSTEM INSPECTION
ELECTRICAL SERVICE DROP
ELECTRICAL SERVICE ENTRY WIRING
EMF RF FIELD & FREQUENCY DEFINITIONS
FEDERAL PACIFIC FPE HAZARDS
FIRE SAFETY Checklist, CPSC
GFCI PROTECTION,Testing GFCIs AFCIs
HEATING COST FUEL & BTU COST TABLES
HEAT TAPE USAGE GUIDE
Hertz - Definitions of KHz MHz GHz THz
KNOB & TUBE WIRING
LIGHTING, EXTERIOR GUIDE
LIGHTING, INTERIOR GUIDE
LIGHTNING PROTECTION SYSTEMS
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
MAIN ELECTRICAL DISCONNECT
MAIN DISCONNECT AMPACITY
MOISTURE SOURCES in PANELS
MURRAY SIEMENS Recall
PHOTOVOLTAIC POWER SYSTEMS
PUSHMATIC - BULLDOG PANELS
REMOTE ELECTRIC POWER, PHOTOVOLTAIC
RUST in ELECTRICAL PANELS
SAFETY for ELECTRICAL INSPECTORS
SE CABLE SIZES vs AMPS
SIEMENS MURRAY Recall
UNDERGROUND SERVICE LATERALS
VOLTS / AMPS MEASUREMENT EQUIP
VOLTAGE MEASUREMENT METHODS
WIND ENERGY SYSTEMS
WIND TURBINES & LIGHTNING
ZINSCO SYLVANIA ELECTRICAL PANELS
What size electrical wire should you use when hooking up an electrical receptacle (wall plug or electrical outlet)? Here we explain the choice of No. 14 or No. 12 copper wire for 15A and 20A electrical circuits where receptacles are being wired.
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.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
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
Note: it's safe and ok to use a smaller fuse or circuit breaker, such as a 15-amp fuse protecting a circuit wired with #12 copper wire.
Electrical Conductors: 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.
Details are at NUMBER of WIRE CONDUCTORS needed
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.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
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?
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
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
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.
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.
Watch out: while the electrical receptacle ground may also be electrically connected to the metal strap that mounts the receptacle to the junction box (photo at left), and while the junction box may be metal, do not rely on the receptacle mounting screws and receptacle strap-to-box contact to serve as the grounding connection.
It's easy for the receptacle mounting screws to be deliberately left loose or to work loose - making that ground connection unreliable. Use a ground wire.
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.
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.
Our photo (left) shows a 20-Amp electrical receptacle - you can recognize it by that horizontal opening that makes the left-hand slot look like the letter "T" on its side.
Our photo (left) illustrates an electrical receptacle intended for use on a 20-Amp circuit.
Question: I don't have enough wire to lower receptacles on the wall
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
Reply: if you have to move an entire string of electrical receptacles complete re-wiring is faster and cheaper than adding a splice box for every device.
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.
Question: armor around wire through concrete?
I am running a new 15A outlet into the back of a bookcase in a 50 year old house with updated electrical. The wire runs out the back of the retrofit box and down through the concrete foundation into the crawlspace to a wire I plan to splice into. Do I need to put armor around the wire run through the foundation? It goes through open air for about 2 feet and there is no way to secure it to anything.
You need to look at the type and rating of the electrical wire to determine if it is permitted to bury it in concrete or not.
Question: Am I allowed to add one more outlet onto an existing string?
I have an existing outlet being used for lamps I wanna run one more outlet shares from the hot on is it okay? - Phantom 113 8/1/12
Usually, yes provided all safe and proper wiring code procedures are followed.
Question: is it legal to convert a split receptacle into two separate receptacles
Is it legal to change a spit receptacle to two separate receptacles? - Gord
Watch out about overloading the circuit however.
Question: I've lost electrical power to the whole room after testing power at the light switch
I've lost elec to the whole room.
I tested the wiring at the light switch.
If I turn the switch off I get elec to the switch,If I turn it on I get no elec.to the switch. I've lost electricity to the whole room - Dave
Dave, your wiring or perhaps the switch itself is unsafe; sounds as if it's shorted. Leave the circuit off until the wiring has been traced, lest you start a fire or zap someone.
Question: I need to add a light, fan, and fan switch to an existing bath - I can't find where to kill the power
very informative article thumbs up . I have a question nevertheless:
When i checked the existing switch there was a black and a white wire on the switch and when i attempted to shut the power off to the light and switch at the panel there is no breaker that kills the power to the light
What is the likely cause of this and how do i fix this problem - Blinden 12/12/12
I have one line with power coming into a box that will have one two way switch, one three way switch and one power line exiting. Is it proper to splice the incoming black wire to make 3 black wires by pig tailing with wire connectors and doing the same for the white wire and ground? - is it ok? 12/13/12
I'm sorry but I'm confused by the question. I think it's safe to say that in general it's common practice to use a twist-on connector to splice pigtails or individual wires at an individual hot or neutral wire where more connections are needfed than fit with the original wire.
Just watch out to avoid violating the space or number of connectors permitted in a junction box of the particular size you're working on.
Electrical wiring are the devices that are used to generate electricity. There are different types of electrical wiring that are usually vary according to three factors - purpose, quantity of electricity to be carried, and location. All the above three factors are really very important while doing electrical wiring. - Bella Cruse, Dublin electrical contractor
Question: which circuit is better to use when adding a closet light
If I want to add light to closet, which circuit is it better to pull from? I have access to 120 plug and switches in outside wall facing away from closet that could be pulled into closet. Also, can you help explain the two different wiring configurations on my non GFI plugs. On two different plugs on different walls the plugs are 8 wire push in style (4 hot and 4 common), but the wiring config is different between the two plugs. One one all white and black are inserted in the bottom 4 connectors with tabs in place. On another same style plug, one set of 4 wires (2 blk and 2 white) are inserted in bottom left row, and other set of 4 wires are inserted in opposite side top row. These plugs are not controlled by switches. Thank you. - Chris 12/30/12
In my OPINION, it's best to connect a closet light to the room lighting circuit if possible.
About your other question, I'm a little confused by the query, but in general, receptacles and switches often have more than one permittted connection point, such as under a screw terminal, on older devices via a back-wiring push-in connector (something we do not recommend using), or on newer devices a side-clamp operated by a screw.
In all events, regardless of which connection point you are using, receptacles and switches have a designated side or screw or connector set for the white (neutral wire) (typically the side that has a silver colored screw and that is marked NEUTRAL on the device) and for the black (hot wire) (typically the side that has a brass-colored screwe and is marked LINE or HOT or BLACKI).
Questions & answers or comments about how to install and wire electrical outlets or receptacles in buildings.
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
HTML Comment Box is loading comments...
Technical Reviewers & References