NEMA Standards.

NEMA is an abreviation for the The National Electrical Manufacturers Association , who
developed a standard range of electronic equipment enclosures. Here is a brief overview
of the standards and comparison between the European equivalent.

NEMA 4.
The Type 4 enclosures are intended for indoor or outdoor use, to provide a degree of
protection against wind borne dust and rain, splashing water and hose-directed water
and to be undamaged by the formation of ice on the enclosure. They are not intended
to provide protection against conditions such as internal condensation or internal icing.

NEMA 4X.
The Type 4X enclosures are intended for indoor and outdoor use. Providing a degree
of protection against corrosion, wind borne dust and rain, splashing water, and hose-
directed water; and to be undamaged by the formation of ice on the enclosure. they are
not intended to provide protection against conditions such as internal condensation or
internal icing.
 

USA NEMA Standard                                  European IP rating

Type 4                                      =                        IP54

Type 4X                                    =                      IP65/66