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

Nomenclature
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.

 

NEMA 5-15R

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

NEMA 1-15P

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

NEMA 5-15 plug and connector


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.
Manufacturer:  Pass & Seymour (part of Legrand Group); socket has been made in China by W.E. (full name is unknown).   {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.
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 hot and neutral (W) blade changes an essentially non-polarized NEMA 1-15 plug into a polarized type. Neutral (W) blades might be nickel plated rather than standard brass (see left plug).

The plug at right is unusual, but certified* type; blades do not have circular holes. Most sockets have some type of bump on the contacts which match up with the holes in the plug blades to help increase the plug retention force.
• plug has been made in China and has a very small Underwriters Laboratories Inc. certification mark.  
{DH}
7 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. Manufacturer: Pass & Seymour; plug has been made in China by W.E.   {DH}
8 Industrial grade NEMA 5-15P plug and connector. Manufacturer: Leviton.

 

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 system.
Click here for 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

 


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

Type A swivel multi-plug

US flat blade, grounded 3-way multi-plug

US flat blade, grounded 6-way multi-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}
12 Multi-plugs for two blade 15 A plugs (125V). The lower example is a swivel type device, which can be tilted over 180 degrees. Both plugs are protected against attempts to insert plugs with ground pins.
13 Multi-plug for three, grounded 15 A plugs (125V). Manufacturer: Eagle.
14 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.

US flat bald adapter plug-in switch tap

Lamp holder with US flat blade two-pole outlets

US lampholder adapters

Flat blade power strip and adapter with indicator light


Examples of very simple plugs TAP-A-LINE outlet with plugs NEMA 1-15R

15 NEMA 1-15 plug-in switch tap.
16 Pull chain medium size* light bulb socket with two non-grounded outlets. Only the lamp is switched on/off by the pull chain; outlets are continuously active. Read also the historical note about classic material on the classic plugs and sockets page.
* medium refers to the diameter of the Edison screw base; medium = 26 mm (U.S.), or 27 mm (Europe). Size are also indicated as E26 and E27.
17 Two medium size light bulb adapters. Left: screw base to 2-pole outlet. Right: non-grounded 15A, 125V plug to medium light bulb socket. Manufacturer: Leviton.
18 Duplex 15A - 125V grounded power strip with a lighted adapter plug, 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. Manufacturer: Leviton.
19 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. Top: 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}
20 Tap-A-Line outlet with elongated slots to receive the prongs of multiple appliance plugs. Details are given on a separate page.
21 Not earthed 15A-125V NEMA 1-15R socket; a nearly 'classic' model. Since 1974 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}

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



22, 23 Leviton Wetguard 5-15R (15A-125V) connector (image no. 22) and 6-15P (15A-250V)* plug (image no. 23). 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 page on dual Amp / Volt page.

 


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