NEMA connector: Difference between revisions

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{{main|AC power plugs and sockets}}

 

NEMA 1-15P (two-pole, no ground) and NEMA 5-15P (two-pole with ground pin) plugs are used on common domestic electrical equipment, and NEMA 5-15R is the standard 15-ampere electric receptacle (outlet) found in the United States, and under relevant national standards, in Canada (''CSA C22.2 No. 42<ref name="CSA C22.2 No. 42-10">{{cite book |author=<!--staff writer(s); no by-line--> |title=CSA Standard C22.2 No. 42-10: General use receptacles, attachment plugs, and similar wiring devices |publisher=Canadian Standards Association |location=Mississauga, Ontario |date=2010 |page=1}}</ref>''), Mexico (''NMX-J-163-ANCE'') and Japan (''JIS C 8303'').

== Precedents ==

{{Main|History of AC power plugs and sockets}}

 

=== Harvey Hubbell's inventions ===

 

In 1910, Hubbel worked on improving his popular flat blade design, filled {{US patent|1064833}} in 1912. The new design had parallel blades, a more compact design and was easier to manufacture. This design was improved once again in 1915, introducing a polarized plug under the {{US patent|1180648}}. The flat blade plug which in subsequent years evolved to become NEMA 1-15 was born.

 

==== Other American manufacturers ====

 

=== NEMA ===

 

==Nomenclature==

[[File:NEMA simplified pins.svg|thumb|350px|alt="Row and column table of NEMA receptacles."|NEMA receptacles, with their common US uses listed (in purple text)]]

 

 

 

As an example, the 5-15R is the common 125&nbsp;V two-pole, three-wire receptacle rated for 15&nbsp;A. The L5-15R, while sharing the same electrical rating, is a locking design that is not physically compatible with the straight-blade 5-15 design. The 5-30R has the same two-pole, three-wire configuration and 125&nbsp;V rating, but is rated for 30&nbsp;A.

Other types of NEMA connectors that do not follow this nomenclature include: the ML series (so-called "Midget Locking" connectors named for their diminutive size), TT (for connecting [[travel trailers]] and other [[recreational vehicles]] to external power sources), SS series ("ship-to-shore" connectors for connecting boats to [[shore power]]) and the FSL series (used in military and aircraft applications).

 

 

The blades of a NEMA connector are identified within the dimensional standard as follows: 'G' identifies the grounding conductor, 'W' identifies the (grounded) neutral conductor, and 'X', 'Y', and 'Z' are the "hot" line conductors. Single-phase connectors have only a single terminal identified as 'X' or two terminals, 'X' and 'Y'. Three-phase connectors will use 'X', 'Y' and 'Z'.<ref name="WD6"/>

 

Criticism has been aimed{{By whom|date=October 2021}} at the design leaving a gap with exposed prongs. This safety flaw has been exploited by a January 2020 [[Internet phenomenon]] known as the ''[[Outlet challenge]]'', where conductive materials, usually coins or paper clips were dropped into the gap, causing [[electric spark]]s, which once led to a building [[Emergency evacuation|evacuation]] in [[Westford Academy]].<ref>{{cite web |last1=Lee |first1=Bruce Y. |title=What Is The 'Outlet Challenge'? How It Can Electrocute Or Burn You |url=https://www.forbes.com/sites/brucelee/2020/02/23/what-is-the-outlet-challenge-how-it-can-electrocute-or-burn-you/ |website=Forbes |language=en |date=2020-02-23}}</ref><ref>{{cite web |title=Dangerous TikTok Challenge Sparks Warning From Firefighters |url=https://www.nbcboston.com/news/local/fire-officials-warn-parents-about-outlet-challenge/2065446/ |website=NBC Boston |date=2020-01-21}}</ref><ref>{{cite news |title=Authorities warn about dangerous TikTok 'outlet' challenge |url=https://abcnews.go.com/US/authorities-warn-dangerous-tiktok-outlet-challenge/story?id=68531391 |access-date=5 November 2020 |work=ABC News |date=2020-01-25 |language=en}}</ref>

{| class="wikitable" style="text-align: center;"

! rowspan="2" |[[Volt|'''V''']]

! rowspan="2" |NE

MA

|-

!Socket

!125 V

!1

|''5-20R''

|''5-30R''

| colspan="2" | -

| colspan="2" | -

!2

|''6-15R''

| colspan="2" | -

| colspan="2" | -

!125 V

!5

| colspan="2" | -

| colspan="2" | -

!250 V

!6

| colspan="2" | -

| colspan="2" | -

!277 V

!7

| colspan="2" | -

| colspan="2" | -

!10

| colspan="2" | -

| colspan="2" | -

| colspan="2" | -

|-

!3Φ

!11

| colspan="2" | -

| colspan="2" | -

!125/ 250 V

!14

| colspan="2" | -

| colspan="2" | -

250 V

!15

| colspan="2" | -

| colspan="2" | -

120/ 208 V

!18

| colspan="2" | -

| colspan="2" | -

! no !! yes !! no !! yes !! no !! yes !! no !! yes

|-

| 120&nbsp;V || [[#NEMA_1|1]]; [[#ML|ML1]] || [[#NEMA_5|5]]; [[#NEMA_TT-30|TT]];

[[#SS|SS1]]; [[#ML|ML2]]

| 240&nbsp;V || - || 25

|-

| 240&nbsp;V (split-phase)<br />208&nbsp;V (wye) || [[#NEMA_2|2]] || [[#NEMA_6|6]]

| 480&nbsp;V || - || [[#NEMA_8|8]]

| 415&nbsp;V || - || -

|-

| 120/240&nbsp;V (split-

phase)<br />120/208&nbsp;V (wye)

| 240/415&nbsp;V || - || -

|-

| 240&nbsp;V (delta)<br />208&nbsp;V (wye) || [[#NEMA_11|11]] || [[#NEMA_15|15]]

| 480&nbsp;V || [[#NEMA_12|12]] || [[#NEMA_16|16]]

| 415&nbsp;V || - || -

|-

| 120/208&nbsp;V || [[#NEMA_18|18]] || [[#NEMA_21|21]]

| 277/480&nbsp;V || [[#NEMA_19|19]] || [[#NEMA_22|22]]

In older plug designs both blades were the same width, so the plug could be inserted into the receptacle either way around. Many plugs manufactured since 1948 are [[Polarized plug|polarized]]; the neutral blade is {{convert|5/16|in|mm|1|abbr=on|disp=or}} wide, {{convert|1/16|in|mm|1|abbr=on|disp=or}} wider than the line blade, so the plug can be inserted only one way. Polarized 1-15P plugs will not fit into unpolarized receptacles, which possess only narrow slots. Polarized 1-15P plugs will fit 5-15R grounded receptacles, which have the same wider slot for the neutral blade. Some devices that do not distinguish between neutral and line, such as internally isolated [[AC adapter]]s, are still produced with unpolarized narrow blades. [[Cheater plug]] adapters allow a "3-prong" grounded 5-15P plug to be mated to a non-grounded 1-15R receptacle. The adapters include a [[spade lug]] to allow connecting to ground, often via the cover screw used to attach the outlet faceplate. These adapters are illegal in some jurisdictions, in particular throughout Canada.<ref>[https://novascotia.ca/lae/electricalsafety/esbadapterplugs.asp Electrical Safety | Novascotia.ca<!-- Bot generated title -->]</ref>

 

 

The Japanese plug and socket with narrow insulating faces appear and work physically identical to NEMA&nbsp;1-15, and such non-grounded receptacles are still common in Japan (though grounded 5-15R and 5-20R receptacles are slowly becoming more common). The Japanese system incorporates stricter dimensional requirements for the plug housing, different marking requirements, and mandatory testing and approval by [[Ministry of Economy, Trade and Industry|METI]] or [[Japanese Industrial Standard|JIS]].<ref name = JIS>{{Citation | title = JIS C 8303-1993, Plugs and Receptacles for Domestic and Similar General Use | publisher = Japanese Standards Association | year = 1993}}</ref>

In [[stage lighting]] for film and theater, this connector is sometimes informally known as ''PBG'' (''Parallel Blade with Ground''), ''U-ground'', ''Edison'' or ''Hubbell'', the name of a common manufacturer.<ref>Drew Campbell ''Technical Film and Tv for Nontechnical People'', Skyhorse Publishing Inc., 2002 {{ISBN|1581159986}} Chapter 9</ref> (The name "Hubbell" can be confusing as several different connectors share this name depending on the company, industry, and use.) In the motion picture and TV production industries, an extension cord that uses this type of connector (usually with 12 AWG or 10 AWG wire)<ref name="tftv">{{cite book|last=Campbell|first=Drew|title=Technical Film and TV for Nontechnical People|publisher=Allworth|year=2002|page=133|isbn=1-58115-229-9|url=https://books.google.com/books?id=CARrSo742ycC|access-date=2010-02-16}}</ref> is called a "stinger".{{citation needed|date=November 2013}} Generally, [[lighting technician]]s use these extension cords to deliver power to lights rated at 2,000&nbsp;watts or less.<ref name="slth">{{cite book|last=Box|first=Harry C.|title=Set Lighting Technician's Handbook: Film Lighting Equipment, Practice, and Electrical Distribution|publisher=Focal|year=2003|edition=3rd|page=20|isbn=0-240-80495-3|url=https://books.google.com/books?id=EfUlyxSlBYMC|access-date=2010-02-16}}</ref>

 

 

===NEMA 6===

NEMA 6 devices, while specified as 250&nbsp;V, may be used for either 208 or 240&nbsp;V circuits, generally depending on whether the building has a [[three-phase electric power|three-phase]] or [[split-phase electric power|split-phase]] power supply, respectively. The NEMA 6-20R or 6-30R found in many hotel and motel rooms is typically supplied with either split-phase or two phases of three-phase 208&nbsp;V.

 

 

|File:Nema 6-15.svg|NEMA 6-15 (Green "U"-shaped contact is ground.)

|File:Silo - 50A power socket for silo unloader.jpg|NEMA 6-50 with dustproof flexible shroud, used on a farm [[silo]] unloader

 

===NEMA 11===

 

===NEMA 12===

 

===NEMA 13===

 

===NEMA 14===

 

All NEMA 14 devices offer two hots, a neutral, and a ground, allowing for both 120 and 240&nbsp;V when supplied by [[Split-phase electric power|split-phase power]], or 120 and 208&nbsp;V if the supply is [[three-phase electric power|three-phase]]. The 14-30 has a rating of 30&nbsp;A, and an L-shaped neutral blade. The 14-50 has a rating of 50&nbsp;A, and a straight neutral blade sized so that it does not mate with 14-30 connectors.

 

 

|File:220sb.svg|NEMA 14-30 and 14-50 receptacles

|File:NEMA 14-30 Dryer Receptacle.jpg|NEMA 14-30 clothes dryer receptacle and plug

 

===NEMA 15===

 

===NEMA 20===

 

===NEMA 21===

 

===NEMA 22===

 

===NEMA 23===

 

===NEMA TT-30===

[[File:NEMA TT-30.png|thumb|upright|NEMA TT-30 plug and receptacle. (The center hole on the receptacle is not a contact.)]]

 

The appearance of this plug is sometimes confused with a NEMA 10 connector, rated for 240&nbsp;V, but the NEMA TT-30 is a 120&nbsp;V device. The hot and neutral blades are angled at 45° from vertical and 90° to each other, unlike NEMA 10 devices (where the angles are 30° and 60° respectively), also the plug is slightly smaller than a NEMA 10 and larger than ordinary 5-15P plugs. The ground pin is round, like those on straight-blade NEMA grounding devices. Referring to the picture, the orientation is the same as the NEMA 5 plug and receptacle, with the neutral blade on the lower right.

 

 

==Twist-locking connectors==

===ML===

ML-series "Midget Locking" connectors are for 15&nbsp;A applications where a larger locking connector would not fit.

 

* ML-1 connectors are two-pole, no ground, rated for 125&nbsp;V.

 

===NEMA L1===

 

===NEMA L2===

 

===NEMA L3 and L4===

 

===NEMA L5===

NEMA L6 connectors are rated for a maximum of 250 volts. They are intended for two-pole, three wire, line-line-earth (or hot-hot-ground) circuits with a nominal supply voltage of 208 or 240 volts, depending on phase configuration. The L6 connector does not provide a neutral connection.

 

 

 

===NEMA L7===

 

===NEMA L11===

 

===NEMA L12===

 

===NEMA L13===

 

===NEMA L14===

 

===NEMA L19===

 

===NEMA L20===

 

===NEMA L21===

Like most current interrupting devices, a GFCI receptacle can optionally be wired to feed additional "downstream" outlets; correctly installing one GFCI receptacle in a circuit can protect all the plugs, lights, switches, and wiring which receive power from it. This allows for cost-effective retrofits on older installations where branch circuits were often [[Daisy chain (electrical engineering)|daisy-chained]] between wet and dry locations. A GFCI receptacle may be installed indoors where it is sheltered from dampness and corrosion, while still protecting an outdoors receptacle wired downstream.

 

 

===Tamper-resistant receptacles===

 

===Leak-current detection and interruption (LCDI) cordsets===

 

==Color code==

 

However, although colors are not standardized by NEMA, some industries utilize colors for certain applications, following [[de facto standard]]s:

*Per UL Standard ANSI/UL 498, a receptacle (any color) with an orange triangle, is an [[isolated ground]] (IG) device, where the grounding pin of the receptacle is connected to ground independently of the frame of the receptacle and wiring outlet box. This is also a requirement of the National Electrical Code (NFPA 70), Article 406. While neither UL nor the CSA require the face of the receptacle to be a specific color, most IG receptacles are orange.<ref>{{cite web|url=https://www.nema.org/Standards/Pages/Application-Guide-for-Isolated-Ground-Wiring-Devices.aspx|title=Application Guide for Isolated Ground Wiring Devices|last=NEMA|website=www.nema.org|access-date=2016-03-26}}</ref>

*A red receptacle may indicate a special-service outlet such as one connected to an [[Emergency power system|emergency standby power source]]. The ''Canadian Electrical Code'' requires that "essential" receptacles in hospitals, connected to emergency power systems, must be red.<ref>{{cite book |date=2015 |title=C22.1-15—Canadian Electrical Code, Part I: Safety Standard for Electrical Installations |publisher=Canadian Standards Association |edition=23rd |isbn=978-1-77139-718-6 |page=Rule 24–106(6) |no-pp=y}}</ref>

 

==Break-away tabs==