NEMA Configurations for General Purpose Non-Locking Connectors:
NEMA Nomenclature
There are two basic classifications of NEMA device: straight-blade
and locking. The twist-locking type is preferred in many industrial
environments, while the residential and commercial environment is home
to straight-blade devices. (Of course, the straight-blade 5-15 and 5-20
are found nearly everywhere.) Numbers prefixed by L are curved-blade,
twist-locking connectors, others are straight blade non-locking.
The numeral preceding the hyphen in NEMA nomenclature indicates the
configuration type, i.e. number of poles, number of wires, voltage, and
whether single- or three-phase. A grounding type of device will be
described as two-pole, three-wire; or four-pole, five-wire; etc. A
non-grounding device will be two-pole, two wire; or three-pole,
three-wire; etc.
The numeral following the hyphen is the rating of the device in
amperes. The number is followed by the letter R to indicate a
receptacle or the letter P to indicate a plug.
As an example, the 5-15R is the common 125V two-pole, three-wire
receptacle. The L5-15R, while sharing the same rating, is a locking
design which is not physically compatible with the straight-blade 5-15
design. The 5-30 has the same two-pole, three-wire configuration and
125V rating, but is rated 30 amperes.
Although there are several non-grounding device types in the NEMA
standards, only a few of them are in widespread use today. These are
the two-pole 1-15, still in use in millions of buildings built before
1965, and the three-pole 10-30 and 10-50.