The NEMA Numbering System

NEMA (National Electrical Manufacturers Association) has a variety of standards for electrical manufacturers. This is so that consistency and safety can be achieved. A numbering system has been created to standardize the description and rating of NEMA plug and socket patterns.

The NEMA pattern and numbering system consists of four main identifiers.

First Identifier

The first identifier can be blank or have the letter “L.” This determines whether the device will use straight or locking blades.

Second Identifier

The second identifier is a number which determines the voltage rating. For example:

• “1” identifies that the configuration is rated for 125VAC, Class II
• “5” identifies that the configuration is rated for 125VAC, Class I
• “6” identifies that the configuration is rated for 250VAC, Class I

The rating given is the highest voltage allowed for use with the device by the standard, ANSI/NEMA WD-6. In a Class I application, the component must have the ability to provide grounding. In a Class II application, no grounding is required.

Third Identifier

The third identifier is also a number. This specifies the amperage rating. The amperage rating, like the voltage rating, is the highest amperage allowed for use with the device by the standard.

Fourth Identifier

The fourth identifier is a letter. “P” stands for a plug and “R” stands for a receptacle (also referred to as an outlet or a socket).

Examples

1-15R is a 125V, Class II, 15-amp receptacle
L5-20P is a locking, 125V, Class I, 20-amp plug
6-15P is a 250V, Class I, 15-amp plug

NEMA Plug Patterns

NEMA Nomenclature Chart

For a detailed listing of the NEMA numbering system, please see the NEMA Nomenclature chart below.

Other resources to consult include the North American Non-Locking NEMA Configurations and Connect to North America.

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Source:
ANSI/NEMA WD-6