Museum of Plugs and Sockets logo, small NEMA standards
North American plugs and sockets
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NEMA* standards are used in the US, Canada and Mexico. Comparable flat blade plugs are used in Japan, various Caribbean islands, parts of South America and some Southeast Asian countries
* National Electrical Manufacturers Association (U.S.A.)
Profile types A/B Related galleries:
locking devices
dual Amp / Volt types
classic types
heavy duty types

Receptacle is used in American English
rather than socket, but for the sake of unambiguity socket is preferred here.
In North America different names and abbreviations are used. Neutral (N) is indicated as W which corresponds to the white wire; the black wire is 'Hot' (L)*. Equipment earth is indicated as Ground. Three phase L1, L2, L3 is in North America indicated as: X, Y, Z.
* Occasionally a single phase hot connection is indicated as X.

The following pages give additional information about US plugs:
(1) History of US flat blade plugs, with emphasis on the role of Harvey Hubbell.
(2) Logos and notes on history of manufacturers of material shown on North American pages.


NEMA 5-15R

NEMA 5-15TR, detail of shutters
NEMA 5-15R with GFCI

NEMA 1-15P

NEMA 1-15P, polarized plug
NEMA 5-15P with cord side entry

NEMA 5-15P with rotatable pin base plate

1 Duplex, grounded socket rated at 15A - 125V. The model corresponds to NEMA 5-15R (NEMA codes are explained below). Slots for flat blades may have a different width. See plug no. 6 for explanation. Manufacturer: Cooper Electric Supply, New Jersey U.S.
2, 3
Tamper Resistant NEMA 5-15 socket. Hot and W slots have shutters. From November 2013 new and renovated residential housings in the U.S. and Canada have to be equipped with tamper resistant sockets. Simultaneous plugging in both power blades pushes the shutter aside. Manufacturer: Pass & Seymour (part of Legrand Group).   {DH}
4 15A - 125V grounded duplex socket (NEMA 5-15R), with ground fault circuit interrupter (GFCI). This feature evaluates the current difference between line and neutral and interrupts the flow of electricity when a sudden difference is measured.
Manufacturer: Leviton.
5 15A - 125V (NEMA 1-15P) plug (top) and connector (bottom). For safety reasons, extensions (indicated by green arrows) prevent the insertion of a grounded, 3 pole plug in an non-grounded connector. The plug has brass blades of equal width. Manufacturer: Eagle Electric (plug).
6 A difference in width between line (hot) and neutral (W) blade changes an essentially non-polarized NEMA 1-15 plug into a polarized type. Manufacturer: Leviton.   {DH}.
7, 8

Grounded 15A - 125V plug (NEMA 5-15P). The position of the U-shaped earth pin results in a polarized plug; hot and neutral are irreversible. The earth pin is 4 mm longer than the W and X (hot) blades. This safety measure ensures that grounding is already effective before power pins make contact.
The round base plate with pins can be fixed in eight positions with 45 rotational steps. Image nos 7 and 8 show five of eight positions. The plug has a side cord entry (downwards in plug no. 7). Without the possibility to adapt cord entry orientation it would be impossible to use two of these plugs in a dual socket (socket nos 1, 2 and 4). Orientations 8b and 8d are also useful when a socket has been mounted horizontally rather than vertically.   {DH}

The plug has a WE logo, indicating that it has been made in China by Weico (Asia) Industries Ltd.

Very similar industrial grade 15A-125V (NEMA 5-15P) and 20A-250V (NEMA 6-20P) angle straight blade plugs, and 15A-125V (NEMA L5-15P) angle locking plugs are made also by Leviton Manufacturing Co. Inc. Plugs have the same eight different cord orientations. See respectively  5266-CA, 5466-CA and 4720-CA in Leviton catalog for details. Source of information: Cornell Wright.

NEMA 5-15R with isolated ground
NEMA 5-15R with isolated ground NEMA 5-15P Hospital Grade

Leviton Wetguard 5-15R connector
Leviton Wetguard 6-15P plug

9, 10 NEMA 5-15R socket with isolated ground, also known as clean earth. It has two, separate earth connections – one is connected to the earth pin contacts of the outlets (green wire), and the other connects socket fixing screws to the general building earth. The green wire is connected to an earth reference bar.  Read more about clean earth at the page on uncommon British sockets. The green dot indicated that it is a hospital grade socket (see no. 11 for details). Manufacturer: Leviton.   {DH}
11 Hospital grade NEMA 5-15 plug, which means that (i) blades are usually solid instead of folded metal, (ii) the blades are normally nickel-plated, and (iii) the plug includes a cable retention device or strain relief to prevent any stress to the plug's internal connections. Many hospitals prefer that the plugs be clear so that internal connections can be inspected visually, but this not an obligation. Hospital grade devices are marked with a green dot (see inset top right).   {DH}
Manufacturer: Ching Cheng Wire Materials, Taiwan.
12, 13 Leviton Wetguard 5-15R (15A-125V) connector (image no. 12) and 6-15P (15A-250V)* plug (image no. 13). Wetguard watertight straight blade devices are engineered to IP66 and IP67 standards. Manufacturer: Leviton in Melville NY, USA.   {FSE}
* Find more U.S. 250 Volt device at the dual Amp / Volt page.

Flat blade power strip and adapter with indicator light

US flat blade, grounded 3-way multi-plug

US flat blade, grounded 6-way multi-plug

14 Duplex 15A - 125V grounded power strip and an adapter plug with light, indicating when power is on. The top of the adapter has a single grounded outlet. The indicator light can also be used as a night light. Manufacturers: Leviton (power strip) and Woods Industries (adapter plug with indicator light) .
15 Multi-plug for three, grounded 15A - 125V plugs. Manufacturer: Eagle.
16 Multi-plug for six, grounded 15A plugs. This device has to be used in a duplex socket (the 'standard' configuration, see no. 1) for providing sufficient stability. No brand name; made in China.

NEMA 1-15R US flat bald adapter plug-in switch tap Type A swivel multi-plug Examples of very simple plugs

17 Not earthed 15A-125V (NEMA 1-15R) socket; a nearly 'classic' model. From November 1973 all new outlets must have an earth contact (NEMA 5-15R). NEMA 1-15R is still available, but for repair use only. Manufacturer: Pass & Seymour / Legrand.   {DH}
18 NEMA 1-15 plug-in switch tap. Manufacturer: General Electric (USA).
19 Multi-plug for two blade 15 A plugs (125V). The lower example is a swivel type device, that can be tilted over 180 degrees. Both plugs are protected against attempts to insert plugs with a ground pin; see image no. 5 for comparable protection system.
20 Besides US, Canada and Japan flat blade plugs are also used in many other countries. The reliability of plugs in some Latin American and Asian countries is occasionally doubtful. The image shows two examples.
Chinese made 15A molded flat blade plug. Bottom: Peruvian 15A "mini" connector. The Chinese plug is the only plug in the museum that fits in the mini-connector. The blades of standard US plugs are too wide and too thick. Unlikely that plug and connector comply with the U.S. safety standards.
Note that plug and connector were (and still are?) used in countries that have a 220 Volt network.   {PO}

The variety in plug and socket standards is unsurpassed

The National Electrical Manufacturers Association (NEMA, USA) has set standards for configurations that differ depending on current rating (15, 20, 30, 50 or 60 A) and electrical potential (nominal 125, 208, 250, 277, 480 or 600 V)*. This has resulted in more than 35 different straight blade configurations (various grounding systems included). The system rules out accidental intermating of devices and related risks.

* 480 and 600 V are three-phase only. The page on three-phase transformers explains the source of the other voltages.

NEMA codes
Codes consist of two numbers followed by R (receptacle) or P (plug).  The first number indicates a class, second number refers to current.
Class defines voltage, single, split- or three-phase, and grounded or non-grounded. Locking devices have a code preceded by an L
For example NEMA 5-15R stands for a class 5 (125 Volt, grounded) socket.

Plugs and sockets in Japan
Also Japan uses flat blade plugs and sockets, in part comparable to NEMA types; they are shown on a separate page.


US locking plug, small Locking devices
Besides flat blade plugs and sockets NEMA
has also defined locking devices. Japan has developed a deviant locking system.
Click here for US locking devices.

Dual Amperage / Voltage types
Series of sockets exist that can be used for more than one type of plug. Plugs can differ
with respect to amperage and/or voltage.
Click here for dual types.
US combination receptacle, small


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