Page last updated Jul 16, 2011 @ 12:18am
Confused about the multitudes of plug, connector and receptacle combinations? This page will help. The National Electrical Manufacturers Association (NEMA) has assigned designations to the various configurations. The purpose of so many different types is to prevent the wrong combinations of electrical systems from being plugged together, thereby avoiding potentially dangerous conditions.
Here is the distinction between plugs, receptacles, inlets and connectors.
Flange or Box Mounted
Connected to live source of electricity
receptacle - A female flange mounted wiring device with the conducting elements recessed behind the mating surface. Often referred to as an outlet. This type of device is normally wired to be live when nothing is plugged in to it. Therefore, receptacles are wired to the source of power. connector - A female cord mounted wiring device with the conducting elements recessed behind the mating surface. This type of device is normally wired to be live when nothing is plugged in to it. Therefore, connectors are wired to the source of power. Connected to load
inlet - A male flange mounted wiring device with the conducting pins protruding and exposed. This type device should never be wired to make the exposed pins live while the mating device is unplugged. plug - A male cord mounted wiring device with the conducting pins protruding and exposed. This type device should never be wired to make the exposed pins live while unplugged. Therefore, plugs are always dead until they are plugged into a power source such as a wall outlet or generator outlet.
This chart shows the most common NEMA configurations in use in North America for 125ac and 250Vac single phase systems. This covers most residential applications.
Twist-lock devices have the advantage of locking in the mating position. This is useful in applications where the connection experiences vibration or the associated cord is hanging or subject to accidental unplugging.
Additional configurations are defined in the ANSI/NEMA WD 6 standard which cover higher voltages, 3 phase applications, and specific purposes such as travel trailers, marine ship-to-shore and more.
The NEMA nomenclature for the code numbers follows this table.
If you have a NEMA code number for a device, use this table to determine the device ratings.
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