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.
Terminology
Here is the distinction between plugs,
receptacles, inlets and connectors.
| |
Flange or Box Mounted |
Cord Mounted |
Connected to live
source of electricity
(female) |
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
(male) |
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. |
NEMA Configurations
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. |
|
NEMA Nomenclature
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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