NEMA Chart: Know Your Plug And Receptacle

Whether at home or in the workplace, few things are as confusing as electric cords and the plugs, receptacles, and connectors that come with them. Meanwhile, you need the right plug and socket to get any electric device to work correctly and safely.

So what are you to do? Fortunately, the National Electrical Manufacturers Association (NEMA) took matters into its own hands to standardize the manufacture and use of different electrical configurations. Hence, you only need to know the NEMA’s general approach to understand how your plugs and receptacles match each other. In short, you have to learn the NEMA chart.

What is The NEMA Chart?

The NEMA organization represents the manufacturers of electrical and imaging products in North America. It comprises over 400 companies, with notable members such as Philips and General Motors.

As part of the NEMA’s efforts to standardize electrical configurations, the NEMA chart was introduced.

This chart is a tabular representation of the different plugs and receptacles according to the NEMA standards, as illustrated below.

The chart above displays the variety of plugs and receptacles for 125ac and 250Vac single-phase locking systems used in countries like the US, Mexico, and Canada. It’s the typical system used in most residential settings.

Apart from these, some of the receptacles in the chart feature twist locks. These products allow you to lock in once they are in the mating position. This locking system is vital in situations where connections will be subject to vibrations or pressure. It’s also used to prevent cords in unnatural positions from accidental unplugging.

The chart below features non-locking plugs and receptacles. Other electrical configurations use the ANSI/NEMA WD 6 standard.

Such standards apply to the higher voltage, 3 phase applications, and they typically serve specific uses like ship-to-shore connections.

Distinguishing The Connectors, Plugs, and Receptacles

Much of the confusion around electrical products are centered around the four elements listed below.

• Receptacle - This is a female wiring device, usually flange-mounted, used to supply electricity, and serves as an outlet. It has an insulated outer surface and backward placed conducting elements. When it has nothing plugged into it, the receptacle usually is live, which means that they are directly wired to the power source.
• Plug - This is a male wiring device mostly mounted on a cord. Unlike the receptacle, the conductive pins of the plug are outward pointing and protruded. Hence, it must never be live or connected to a power source while not in use. That explains why plugs are always dead until plugged into a power outlet.
• Connector - It’s a female wiring device mounted on a cord. Like the receptacle, the conducting parts of the connector are also out of sight. It is also wired to a power source and is live even when it is idle.
• Inlet - It's a box-mounted wiring device that’s conductive surfaces are extended and exposed. It is dead when the mating device is out of use and should never be live wired.

Understanding NEMA Nomenclature

The NEMA nomenclature is the code of alphabets and numbers used to denote the configuration of a specific electric product. It applies to receptacles, represented by R, and plugs by P, ranging from 1-15 to 18-60.

As you might have guessed, the lower numbers NEMA 1-15P are domestic sizes, whereas higher numbers like NEMA 18-60R are high-voltage industrial sizes.

Also, the first number indicates the voltage, while the second shows the amperage. Some products like NEMA L1-15R have L in front of the first voltage indicating the number to show whether the product is locking or non-locking. In this case, NEMA L1-15 is a locking 125V and 15A, two-prong receptacle.

The NEMA connector’s blades are recognized within the dimensional standard like this:

“G” - indicates the grounding conductor

“W” - indicates the (grounded) neutral conductor

“X, Y, Z” - indicates the “hot” line conductors

Connectors with single-phase connectors have only one terminal denoted as 'X" or two terminals,' X" and 'Y." Whereas three-phase connectors usually employ 'X,' 'Y,' and 'Z.'

Color Codes

Aside from these, some electrical products also have color codes. However, these colors do not represent the voltage class or power system of the device. That’s because the NEMA standards do not determine these colors.

Instead, the color-coding of a receptacle may be determined by a manufacturer or customer. In which case, colors like ivory, black, grey, or brown may help blend the cords and wiring of a building with the decor.

Nevertheless, some industries rely on color to identify certain applications, not according to standards or rules.

Conclusion

The NEMA chart and ratings were designed to enable electrical enclosures to operate safely while ensuring optimal functioning and compatibility of electrical products. Assuming you can understand the naming and what each number and letter means, you can know the best way to use your electrical products.

This applies to any place you go and use electrical products. But bear in mind that knowing isn't enough. It would be best to exercise the necessary precautions when dealing with electricity, especially when traveling abroad. When in doubt, ask questions and avoid making assumptions to prevent damage to life and properties.