Double T Slot Receptacle

On a polarized receptacle, or a grounded receptacle, the larger slot is neutral (white wire) and the smaller slot is hot (black wire). While you're there, make sure any other connections in the box are tight, including wire nuts holding all wires securely, tucked out of the way, and any clips or screws are tight. Types of electrical receptacles: how to select the right type of electrical receptacle (outlet): it's important to use 20-A rated receptacles if the electrical circuit is a 20-amp circuit. Don't install a grounded electrical receptacle plug on a circuit that has no electrical ground. Remember to install AFCI or GFCI devices where they are required.

• Double T Slot Receptacle Adapter
• Double T Slot Receptacle Holder

True or false? The NEC requires receptacles to be mounted with the neutral slot on the left. Keep your answer in mind as we take a closer look at Art. 406 requirements. Art. 406 covers the rating, type, and installation of receptacles, cord connectors, and attachment plugs (cord caps). One important requirement of Art. 406 is that you must ground (bond) the grounding terminal of a receptacle to a low-impedance fault current path [250.146, 250.148, and 406.3(C)]. You don't need to do this, however, if you're replacing a receptacle and if you comply with the applicable portions of 406.3(D).

1. Old-fashioned two-prong receptacles, also known as outlets, connected to two-wire cables don't have the ground wires that protect people and electrical devices in case of a fault. Yet it is possible to retrofit a new three-prong or GFCI receptacle into the same outlet box without any rewiring, as long as the box itself is grounded.
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The NEC specifies what that low-impedance path is by requiring you to connect the receptacle-grounding terminal to the branch-circuit equipment-grounding conductor (250.146). If you install an isolated ground receptacle, though, follow the requirements of 250.146(D).

Receptacle replacement requirements. If you have a grounding means in the enclosure, use a grounding-type receptacle — even if you're replacing a nongrounding-type receptacle [406.3(D)]. Make sure you ground (bond) the grounding terminal of that receptacle.

If the enclosure doesn't have a grounding means — for example, if the box contains old 2-wire NM cable without a ground — you can use a nongrounding type receptacle (Fig. 1). You have two other options as well. You can use a GFCI receptacle if you make sure it's marked “No Equipment Ground,” or you can use a grounding-type receptacle if it's GFCI-protected and marked “GFCI Protected” and “No Equipment Ground.”

When you replace a receptacle in a location where GFCI protection is required, the replacement must be GFCI-protected. See 210.8 for GFCI protection requirements.

Test your understanding of this concept with this pop quiz. A relative asks you to replace a failed GFCI receptacle at his home, but you notice the home has a 2-wire system without a ground wire. Will that GFCI provide ground-fault protection?

The answer is yes. GFCI protection functions properly on a 2-wire circuit without an equipment-grounding conductor. The equipment-grounding conductor serves no purpose in the operation of the GFCI protection device (Fig. 2). The GFCI uses a small CT on the neutral and the hot but not on the ground. This information is probably in the instructions that come with the new GFCIs.

Does this mean that if you extend a circuit from an ungrounded box you can install a GFCI? No. Permission to replace nongrounding type receptacles with GFCI-protected grounding-type receptacles doesn't apply to new outlets that extend from an existing ungrounded outlet box. Once you add a receptacle outlet (branch-circuit extension), the receptacle must be of the grounding type and be grounded per 250.130(C) (Fig. 3).

This requirement may seem inconsistent, but it's not. Here's the logic. Your existing two-wire system was installed per the Code that existed at the time. Today's NEC doesn't mandate ripping out existing 2-wire systems and replacing them just so you can add a GFCI. Nor does it allow you to add on to the 2-wire system and just throw in a GFCI. A 3-wire system is safer than a 2-wire system. So if you add to an existing system, what you add must be of the 3-wire configuration — not the 2-wire configuration.

Mounting. Have you ever wondered if you can mount a receptacle in a hobby box you just happen to have lying around or in a cutout in the side of a panel where there's plenty of room and the receptacle is obviously protected? Stop wondering — you can mount a receptacle only in a box designed for the purpose (406.4). Fasten that box securely in place (314.23).

If you mount a receptacle in a box that's set back from the wall surface, install it so the mounting yoke of the receptacle is held rigidly to the wall surface. If the receptacle sits back too far, break off the “ears” on the yoke and use them as shim washers on the receptacle mounting screws.

In walls or ceilings of noncombustible material, boxes can't be set back more than 0.25 inches from the finished surface. In walls or ceilings of combustible material, boxes must be flush with the finished surface (314.20). You can't have gaps greater than 0.125 inches at the edge of the box (314.21).

If you mount a receptacle in a box that's flush, install it so the mounting yoke of the receptacle is held rigidly against the box or raised box cover. If the receptacle mounts to the cover, it must be secured to the cover with two screws [406.4(C)] (Fig. 4).

Receptacle faceplates must completely cover the outlet opening and seat firmly against the mounting surface (406.5). If a metal faceplate is used, make sure it's grounded (bonded) by securing it to the receptacle.

Receptacles in damp or wet locations. You can install a receptacle next to, but not within, a bathtub or shower space. Receptacles must be located at least 5 feet from spas or hot tubs [680.21(A)(1) and 680.43(A)(1)].

Receptacles that are installed outdoors under roofed open porches, canopies, marquees, and similar areas but not subjected to beating rain or water runoff require enclosures that are weatherproof only when the attachment plug cap isn't inserted and receptacle covers are closed [406.8(A)]. Receptacles installed as such are considered to be in damp locations.

Those are the requirements for a damp location, but what if you think you have a wet location? Look up “location, wet” in Art. 100 to find the definition. If your location meets this definition, 406.8(B) applies. All 15A and 20A, 125V and 250V receptacles installed outdoors in a wet location must be within an enclosure and cover that's weatherproof at all times — even when an attachment plug is inserted.

Any other receptacle in a wet location must comply with one of the two following rules:

• If the equipment plugged into it isn't attended while in use, the receptacle must have an enclosure that's weatherproof with the attachment plug cap inserted or removed.

• If the equipment plugged into it is attended while in use, the receptacle must have an enclosure that's weatherproof when the attachment plug is removed.

Suppose you flush-mount an outlet box on a wall surface in a wet location. In such a case, you must make the enclosure weatherproof by using a weatherproof faceplate assembly that provides a watertight connection between the plate and the wall surface.

Overlooked requirements. Familiarity with receptacles can cause you to overlook certain requirements. For example, what kind of receptacle can you use with aluminum wire, and how can you wire it? First, look for the marking CO/AL on the terminal screws. These markings are required for all receptacles rated 20A or less and designed for direct connection with aluminum conductors. If the receptacle is rated higher than 20A, see the manufacturer's instructions or contact the manufacturer to ensure you're not violating the UL Listing for that receptacle.

Here's another fact regarding UL. Per UL requirements, aluminum conductors can't terminate onto screwless (push-in) terminals of a receptacle. More than one installation has been rejected for this practice.

Suppose you wire a receptacle for isolated ground. Do you know how to identify the right kind of receptacle for such an application? It must have an orange triangle marking on its face [250.146(D)].

The requirements for isolated ground receptacles (IGRs) are also commonly forgotten. Keep these in mind:

• You can use IGRs only with an insulated grounding conductor installed with the circuit conductors.

• If you install an IGR in a nonmetallic box, you must cover it with a nonmetallic faceplate because you can't ground (bond) a metal faceplate in such an installation.

What about that question that opened this discussion? The answer is “false.” The NEC doesn't specify which way to orient a receptacle. The ground terminal can be up, down, or to the side. In the last few Code cycles, proposals to specify the mounting orientation were all rejected.

However, there's one exception to this non-specification. If you install a receptacle in a countertop or similar work surface in a dwelling unit, you can't install it in a face-up position.

No matter how much you think you know about Art. 406, you still might find a surprise or two in it, and that's a good reason to become familiar with it now rather than at inspection time. You'd hate to be cited for something as “simple” as a receptacle requirement, wouldn't you?

• POST a QUESTION or COMMENT about how to install and wire electrical outlets or receptacles in buildings.

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Types of electrical receptacles: how to select the right type of electrical receptacle (outlet):

It's important to use 20-A rated receptacles if the electrical circuit is a 20-amp circuit. Don't install a grounded electrical receptacle plug on a circuit that has no electrical ground. Remember to install AFCI or GFCI devices where they are required.

This article explains how to match the receptacle type to the circuit type and use. We describe both 120V receptacles and 240V receptacles.

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.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Choose the Proper Electrical Receptacle Type

The proper type of electrical receptacle must be selected: some receptacles are rated only for 15-Amp circuits and must not be installed on a 20-Amp circuit.

20-Amp electrical receptacles may be designed to only accept plugs for 20-Amp appliances (which may have a different plug-spade configuration in which one of the plug terminals is twisted to be at 90 degrees to the other).

[Click to enlarge any image]

Some 20-Amp electrical receptacles are designed to accept either conventional plugs used by a 15-A appliance as well as 20-A plugs used by a 20-A appliance.

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.

Details about how to wire up an electrical receptacle are at ELECTRICAL RECEPTACLE CONNECTION DETAILS - where to connect black, white, red, green, ground wires .

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 (above 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.

Details about how to wire up an un-grounded receptacle are at 2-WIRE RECEPTACLE CONNECTIONS - no ground

The illustration at above-left shows the typical wiring of an electrical outlet or 'receptacle', courtesy of Carson Dunlop Associates.

Click any image to see an enlarged, detailed view of electrical wiring details for 'plugs' or electrical receptacles.

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 AFCI GFCI WIRING, TESTING & SAFETY

and AFCIs ARC FAULT CIRCUIT INTERRUPTERS for details about these devices.

Readers of this article should also see SAFETY for ELECTRICAL INSPECTORS.

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.

Question: Is it safe to plug a 10-Amp A/C into an outlet that is back wired?

is it safe to plug in an ac unit that runs 10 amps , into outlet that is backed wired, i had read that you don't like this method, the outlet is on third floor and is on a 15 amp breaker - Johnny B 5/2/12

Reply: Comparing Three Types of Backwired Receptacles: 20-A Clamp Type & 15-ASpring Type & Clamp Type Backwiring Devices

Johnny, that's an interesting question and one I'm scared to answer - by online posting one cannot assure the electrical safety of your building.

Details about back-wired electrical devices (receptacles & switches) are at BACK-WIRED ELECTRICAL DEVICES.

Here we will illustrate three different types of electrical receptacles that can be wired from their back-side.

Our photo (left) illustrates a spec-grade 20-Amp, 125V rated electrical receptacle that looks as if it is 'back-wired' - in fact while a wire can be wrapped around the terminal screws on this device.

The screw is intended to be used to tighten a rectangular brass plate against a square metal nut (silver in color) that makes a very strong and positive connection over a good area of wire surface.

This receptacle is marked on its back surface as CU Wire Only - copper only. [Click images to see enlarged details.]
That said, I agree that older, spring-type back-wired electrical connections (shown at below left) are not as reliable as connections made under a screw or clamp, as the total contact area between the back-wire spring edge and the wire surface is minimal.

Nevertheless, on a 15-A circuit using 15-A devices such as receptacles, the circuit and its devices are rated and intended to be able to support the 10-amp load you describe, so long as the sum of all of the items plugged into that electrical circuit don't overload it.

Contractor-grade 15-A spring-type-connector back-wired electrical receptacles (below left) provide a single opening at each of the four terminals (two neutral wires, two hot wires) on the back of the receptacle (red arrow).

The yellow arrow points to a release spring that will allow removal of the wire, but we prefer not to re-use this type of back-wired receptacle. Tightening the screw at the main wire terminal (blue arrow) has nothing to do with the spring-clamp that is securing the back-wired terminal wire.

Some newer heavy-duty 15-A back-wired electrical receptacles (above right) o not rely on a simple spring-edge to contact the electrical wire, as we illustrate in our second photo (above right).

Rather, when the wire is inserted into a receiving hole on the back of the receptacle (either of the two red arrows).

When the terminal screw is tightened (blue arrow) that actually snugs up a clamp that contacts a much larger surface area of the back-wired wire.

That's a more secure connection mechanically. On this receptacle, instead on a single back terminal accepting a single wire, there are a pair of back terminal openings at each of the four terminal screws.

Follow-up:

Thank you for responding, my town home was built in 1999, not sure if that is considered newer or older, lights do dim though when i use 10 amp vacuum . - Johnny B.

Reply:

Backwiring electrical receptacles is a permitted installation and might be found in a 1999 home - but as we show above, there are two different approaches, the second of which is a better quality installation and is in our opinion more reliable.

Older & Antique Electrical Receptacles or 'Outlets'

At above and below are photos of an un-grounded electrical receptacle found in many older homes where the electrical circuit wiring did not include a grounding conductor.

These receptacles can still be purchased and are the only receptacle type that should be installed on an un-grounded electrical receptacle circuit as the absence of a third ground-prong opening makes clear to the user that no ground is present.

See FALSE GROUND at RECEPTACLES for a discussion of how this particular receptacle enjoyed giving the author a shock.

Above at right is an antique surface-mount plastic or bakelite wall receptacle or 'wall plug' or 'wall outlet' in common parlance. This installation is not just obsolete but improper and unsafe as you can see exposed wires poking through the wall trim below the receptacle. Property inspector Steve Smallman, Raleigh NC, who contributed this receptacle points out that

• We expect the receptacle to have been designed for a 20A circuit based on the Tee-shaped slot
• The receptacle has been heavily painted over, interfering with its use
• The wiring exposed below the receptacle is stripped-back armored cable ('BX') without proper strain relief or protection.
• If the actual circuit is powered by a 15A circuit breaker or fuse, the fact that it pretends to offer 20A is mitigated by proper fusing but could also cause trouble for the homeowner as it invites overloading.

Thanks to frequent InspectApedia contributor also cited at ABOUT InspectApedia.com

• Steve Smallman, Raleigh, NC, Email: steve@stevesmallman.com, Website: http://stevesmallman.com/ Tel: 919-669-3639 - Quoting: Steve Smallman Property Inspections (SSPI) inspectors have performed or supervised over 25,000 inspections since we introduced home inspections to the Triangle area in 1980. Mr. Smallman, located in Raleigh N.C., is a contributor to InspectApedia.com and has commented on or provided information on plumbing traps, electrical wiring, commercial FPE electrical panels and DIY Tests of FPE equipment, roofing underlayment, and building exteriors.

Below are two versions of another antiquated and complex electrical receptacle.

I think that these electrical receptacles provide either 120V or 240V connections depending on the receptacle and slots used and on the actual wiring present. Comments are invited.

Below: an older Harvey Hubbell (1857-1927) design electrical receptacle designed to accept 120VAC wall plugs sporting either the 'modern' 15A standard parallel blade design OR the older tandem design.

Hubbell, a prolific inventor of electrical receptacles, plugs, and also bulb sockets and controls, designed and patented a number of key electrical receptacles that are cited below.

• Bossert, William F. 'Outlet-box for interior conduits.' U.S. Patent 754,414, issued March 15, 1904.
• Hubbell Inc. HUBBELL CORPORATE HISTORY [PDF] Hubbell Inc., 584 Derby Milford Road Orange, CT 06477-4024 USA, Tel: (203) 799-4100 Website:
• Hubbell Inc. HUBBELL ELECTRIC CO CATALOG 1906 [PDF] Western Electric Company, Eleventh & York Sts, Philadelphia PA USA, retrieved 2018/12/20, original source https://ia600607.us.archive.org/14/items/ElectricalSpecialitiesCatalogueAndPriceListNo.9August1906/Cca49543WesternElectricCo..pdf

Below: illustration from Harvey Hubbell's Separable Attachment Plug patent from 1904.

[Click to enlarge any image]

• Hubbell, Harvey. 'Separable attachment-plug.' U.S. Patent 774,250, issued November 8, 1904.
  Excerpt:
  I have devised the simple and novel separable attachment-plug which I will now describe, referring to the accompanying drawings forming part of this specification
• Hubbell, Harvey. 'Separable attachment-plug.' U.S. Patent 774,251, issued November 8, 1904.
  Excerpt:
  Be it known that I, HARVEY HUBBELL, acitizen of the United States, residing at Bridgeport, county of Fairfield, State of Connecticut, have invented a new and useful Separable Attachment-Plug, of which the following is a specification.
  My invention has for its general object to produce a practical, durable, and inexpensive direct-acting separable attachment-plug that will avoid the objections raised by the underwriters to attachment-plugs of this type now upon the market and shall have for its special objects to produce a direct-acting attachment-plug in which ample current-carrying capacity shall be provided independently of locking-springs, which may or may not be used, and in which the possibility of arcing or sparkingin making the contact shall be wholly done away with.
  With these and other objects in view I have devised a novel attachment-plug in which a base is provided with insulating-chambers to receive contact-plates and locking-springs, if used, and with contracted insulating-passages leading to said chambers, in which the end block is made independent of the base and is secured thereto, covering the chambers, and in which an insulating-cap is provided with knife-blade contacts which engage the contact plates after they have been passed through the contracted insulating-passages.
  It should be noted that the object in making the base and end block independent is to permit the formation of the insulating-chambers in the base, which receive the contact-plates and the locking-springs, if usechsaid chambers being covered by the end block, and, furthermore, that by providing contact-plates of ample current-carrying capacity in the chambers independent of the locking-springs it becomes immaterial, so far as the currentcarrying is concerned, whether or not locking-springs are used.
  My present construction therefore enables me to avoid certain of the most serious objections raised by the underwriters to attachment-plugs heretofore placed upon the market.
• Hubbell, Harvey. 'Cartridge-fuse and fuse-block.' U.S. Patent 819,657, issued May 1, 1906.

Photo above: a round pin receptacle, possibly with ground and missing one mounting screw, possibly an early Hubbell-design round two-pin floor receptacle, courtesy of Bay State Home Inspections and discussed originally

This receptacle is also similar to George Thomas' receptacle and plug design from 1910 and cited below.

at OLD ELECTRICAL WIRING TYPES

Below: an excerpt from the patent illustration for Harvey Hubbell's multiple attachment plug patent issued in 1904.

Knife blade (flat) plug and receptacle connectors designed by Hubbell were produced as early as 1904 and became the dominant connector design used in the U.S. and Canada.

• Hubbell, Harvey. 'Multiple attachment-plug.' U.S. Patent 776,326, issued November 29, 1904.
  Excerpt:
  I Harvey Hubbell, a citizen of the United States, residing at Bridgeport, county of Fairfield, State of Connecticut, have invented a new and useful Multiple Attachment-Plug, of which the following is a specification.
  My invention has for its object to provide a multiple attachment-plug which shall comprise a body adapted to engage floor, wall, or ceiling receptacles or other fixtures and a plurality of separable caps which shall be adapted to engage the body, so that a plurality of lights, groups of lights, fans, motors, heating, soldering, surgical, or other appliances may be placed in the circuit simultaneously or independently.
• Hubbell, Harvey. 'Separable attachment-plug.' U.S. Patent 774,250, issued November 8, 1904.
• Hubbell, Harry C., 'Portable Electrical Lamp', U.S. Patent 753,138, issued February 23, 1904
  Excerpt:
  I, HARRY C. HUBBELL, a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New a portable electric lamp for miners use or for other purposes which will be safe, efficient, and durable.
• Hubbell, Harvey. 'Attachment-plug.' U.S. Patent 783,275, issued February 21, 1905.
• Hubbell, Harvey. 'Flush attachment-plug.' U.S. Patent 857,176, issued June 18, 1907.
• Hubbell, Harvey. 'Self-closing flush-receptacle plate.' U.S. Patent 961,720, issued June 14, 1910.
• Hubbell, Harvey. 'Pull-socket.' U.S. Patent 1,053,176, issued February 18, 1913.
• Krantz, Hubert. 'Electrical outlet-box.' U.S. Patent 740,663, issued October 6, 1903.
  Excerpt:
  Be it known that I, HUBERT KRANTZ, a citizen of the United States of America, residing in the borough of Brooklyn, county of Kings, State of New York, have invented Improved Electrical Outlet-Boxes, of which the following is a specification.
  The main object of my invention is to provide a simple and eificient electrical outletbox the face of which can be readily adjusted toward or from the body of the box as the particular place of use may require, and this without interfering with the wires in the interior of the box.

• Thomas, George B. 'Electrical plug-receptacle.' U.S. Patent 952,961, issued March 22, 1910. - illustrated above.
  Excerpt:
  Be it known that I, GEORGE B. THoMAs, a citizen of the United States of America, and residing at Bridgeport, in the county of Fairfield and State of Connecticut, have invented a certain new and useful Improvement in Electrical Plug-Receptacles, of which the following is a specification.
  My invention relates to plug receptacles and particularly to flush receptacles of the type described in Goodridge 7 54,863 the object of my -invention being to improve in several features the construction shown therein.

240VAC Electrical Receptacles

There are several common appliances or tools that require a 240-Volt-AC electrical receptacle and a number of 240VAC (or 220 VAC or 204VAC depending on where you live) electrical receptacle designs.

When wiring a 240V receptacle the circuit wires used will include

• A black 'hot' wire (120V)
• A red 'hot' wire (120V) normally from separate circuit that is on the opposite side or different elecrical phase in the electrical panel from the black wire
• A grounding conductor wire

No neutral wire is typically connected to this device. The 240V power is achieved across the two individual 120V 'hot' circuits.

Examples are listed below.

Double T Slot Receptacle Adapter

Our photo of a 240V electrical receptacle shown here is a 20-Amp 240-volt electrical outlet that would be installed on a 20-Amp wall or window air conditioner circuit in a building.

This particular recetpacle, a Leviton product, is UL-listed for 20 Amp, 250 Volt, NEMA 6-20R, 2-pole, 3-wire circutis; it's further described as a narrow-body single receptacle, straight blade, commercial grade, grounding, side-wired, steel strap; available in ivory, white, brown. Similar products are sold in North America by Cooper, Eagle Wiring, and Pass & Seymour.

240-Volt window or through-wall room air conditioner

240-Volt equipment such as small welders

Double T Slot Receptacle Holder

Below are two additional configurations and types of 240 VAC electrical receptacles.

The white three-bladed 240-V receptacle below is a 20-Amp Leviton product that is a non-grounding type electrical receptacle. This is a 20A, 125/250 V, NEMA 10-20R, 2P, 3W, narrow-body single receptacle, straight bladeed, non-grounding, side-wired, steel strap device.

The orange 240 V receptacle below is a also a Leviton product, a flush-mounting twistlock single 20-Amp receptacle wired to provide an isolated ground and is described as a 20-A, 250V, NEMA L6-20R, 2P, 3W, flush mount locking receptacle, industrial grade with locking ground.

...

Continue reading at BACK-WIRED ELECTRICAL DEVICES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

HOW TO ADD an ELECTRICAL OUTLET - home

GFCI PROTECTION, GFCI CODES - ground-fault-circuit-interruptor receptacles (and circuit breakers)

Suggested citation for this web page

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

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Technical Reviewers & References

• [1] ...

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.
• 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.
• Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
• John Cranor [Website: /www.house-whisperer.com ] is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-873-8534 or by Email: johncranor@verizon.net
• [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)
• [5] Special thanks to our reader Steve who pointed out prior errors in our illustrations.
• [6] Simpson Strong-Tie, 'Code Compliant Repair and Protection Guide for the Installation of Utilities in Wood Frame Construction', web search 5/21/12, original source strongtie.com/ftp/fliers/F-REPRPROTECT09.pdf, [copy on file as /Structures/Framing/Simpson_Framing_Protectors.pdf ]. 'The information in this guide is a summary of requirementsfrom the 2003, 2006 and 2009 International Residential Code(IRC), International Building Code (IBC), International PlumbingCode (IPC), International Mechanical Code (IMC), 2006 UniformPlumbing Code (UPC) and the 2005 National Electrical Code.'
• '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.
• 'Simplified Electrical Wiring,' Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
• '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.

• ...

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