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EMF RF FIELD & FREQUENCY DEFINITIONS
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FIRE SAFETY Checklist, CPSC
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KNOB & TUBE WIRING
LIGHTING, EXTERIOR GUIDE
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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
How & where to route electrical wires when hooking up an electrical receptacle or wall plug or electrical outlet.
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.
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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.
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. Our photo (left) illustrates a 6-inch NS-2 Nail Stop produced by Simpson Strong-Tie. Simpson Strong-Tie describes these as Protecting Shield Plate Nail Stoppers.
We are showing the side of the nail-stop that will be in contact with the stud surface when it it tapped into place, providing 5 3/8" of 16-gauge steel that will protect electrical wiring (or plumbing pipes) from punctures by nails or screws driven into the wall when this nail stop has been placed on a wall stud over the point through which an electrical wire (or pipe - see CONDENSATE DRAINS) has been passed.
Nail stops by Simpson Strong-Tie are made of 16-gauge steel, include sharpened protrusions that allow the plate to be tapped into place on stud surfaces, and are sold in 1 1/2" or 5-inch widths and in lengths ranging from 2 1'2" to 16 5/16". The most commonly-seen nail stop we encounter is the NS1 3-inch model.
Simpson Strong-Tie provides a Code Compliant Repair and Protection Guide that describes the company's range of protective and reinforcing steel devices to comply with the various building code requirements to protect wiring and plumbing from nail and screw fastener damage.
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.
The illustration at left shows the typical wiring of an electrical outlet or "receptacle", courtesy of Carson Dunlop Associates.
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.
Unsafe Electrical Wire Material & Routing
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.
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Frequently Asked Questions (FAQs)
Question: how to wire up a pair of receptacles in one electrical box
Channing, re Hooking up a Pair of Receptacles in One Electrical Box:
That's a perfectly acceptable use of the second pair of screw terminals you see on the receptacles.
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
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?
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: When wiring an electrical receptacle, what do I do with the r
Question: how do I install multiple electrical outlets (receptacles) along a wall?
putting in more than outlet on along a 12ft wall - Mike Tucker
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: 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: 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. Details about back-wired electrical devices (receptacles & switches) are at BACK-WIRED ELECTRICAL DEVICES.
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: electrical outlet height requirements
I was looking at some height requirements on electrical outlets this is a very informational site.
Jerm, in the article above at HEIGHT above FLOOR for OUTLETS we give the data you want. Let me know if anything is unclear.
Question: how do I wire a switched electrical receptacle?
I have double receptacle that has 3 wires coming in: one being the main power wire; one is incoming which feeds another receptacle, and the 3rd wire will feed a single pole switch. How do I wire the receptacle and then, how do I wire the single pole switch with 2 incoming wires? - JMS 6/3/12
JMS I don't have a perfectly clear idea of what you are wiring, but it may help to simplify: using a twist on connector and additional short wire lengths, the incoming hot and neutral can then be connected to receptacles in the same box, and any outgoing hot and neutral join the same twist on connectors.
Question: can I add an electrical outlet on the wall where there is already a light switch?
I would like to wire in an outlet on the same wall where there is currently a light switch. Can I run wires from the light switch to power the outlet?The light switch is a 2 way switch. thank you. - Marv Walker 7/10/12
Well yes, maybe, sort-of.
Because a light switch is indeed switching a hot wire to the light, you've got power at the switch location. But depending on how the building is wired, you may not have an acceptable neutral wire, and in some still older circuits you may not have a safe ground wire.
Provided that you know how to work on electrical wiring without getting killed by electrocution, you (or your electrician) will open the switch box, carefully pull the switch assembly out enough to inspect for additional wires that may be present, and then use a VOM or DMM or even a simple neon tester to determine what wires are present.
To add a receptacle you need a proper hot, neutral and ground wire.
Watch out: if the "hot" wire in your light switch is on a 3-way circuit you may not always have power at your add-on receptacle.
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: are receptacles wired "downstream", that is, after a GFCI receptacle OK?
Are receptacles wired after GFI receptacles OK? - Denny 11/25/12
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.
Question: how do I wire multi-way light switches so that all switches can be "down" or "up" when the lights are all off.
How should multiple way light switches be wired so that when all switches are down/up the light is off? Only some of the two-way switches in the house are working that way. With the 3-way and 4-way there's always one switch that has to be opposite the others.
Jim this is one of my favorite questions - thanks. Because a circuit with two or more "three-way" switches installed can be turned on or off from any of the switches on the circuit, it is impossible to wire the circuit so that when the circuit is "OFF" all of the switches are in a predictable position, say "down" (which we like to use to mean "off").
Imagine that all the switches are "down" and the lights are off (which is a possible case). Someone turns the lights ON at switch #1.
When someone wants to turn that light OFF, IF and ONLY IF that very same switch (now in the "up" position) is used, then by definition they are going to be using some other switch (now in the "down" position). When that "other" switch is used to turn lights off, it was "down" and is now switched "up".
You can't get there from here on a conventional 120V 3 or 4 or n-way lighting circuit.
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 needed 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.
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 permitted 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 screw and is marked LINE or HOT or BLACKI).
Questions & answers or comments about how to install and wire electrical outlets or receptacles in buildings.
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