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536
Technical annexes
Classification of electrical
equipment enclosures
according to NEMA and UL
NEMA and UL are standardisation bodies, commonly recognised in North America,
which have issued classifications of enclosures according to the protection offered
in various environments.
These classifications are similar.
The 1
st
table below summarises this classification, which does not include potentially
explosive areas. The detailed recommendations of this classification are given on
the next page.
The 2
nd
table indicates the classification of our enclosures.
These classifications appear in our UL certifications (see Certification technical
annex on page 532).
Certification according to the UL classification guarantees the corresponding NEMA
classification by equivalence.
Environment and protection
Classification
1 2 3 3R 3S 4 4X 5 6 6P 12 12K 13
Indoor use
Outdoor use
Incidental contact with the equipment
Dirt
Drips and gentle splashes of non-corrosive liquids
Rain, frost* and snow
Frost**
Dust, fibres and particles in suspension
Built-up dust, fibres and particles in suspension
Clouds of dust
Splashes and jets of water
Gentle splashes and leaks of oil or non-corrosive coolants
Drips, splashing and spraying of oil or non-corrosive coolants
Corrosive agents
Occasional temporary immersion
Occasional prolonged immersion
* The operation of the external mechanisms is not required when the enclosure is covered with frost.
** The operation of the external mechanisms is required when the enclosure is covered with frost.
Enclosures
Type of protection (1)
Name
Range
1 2 3 3R 3S 4 4X 5 6 6P 12 12K 13
Steel wall-mounting enclosures
S3D (1)
(3)
(3)
(3)
(3)
(3)
(4)
S3HF
Stainless-steel wall-mounting enclosures
S3X (2)
(3)
(3)
(3)
(3)
(3)
(3)
(4)
(3)
Steel floor-standing enclosures
SM
(3)
(3)
(3)
(3)
(3)
Steel suitable enclosures
SF
Stainless-steel floor-standing enclosures
SMX
(3)
(3)
(3)
(3)
(3)
(3)
Stainless-steel suitable enclosures
SFX
Thermoplastic boxes
TBP
Polyester modular boxes
PLS
Polyester wall-mounting enclosures
PLM
Polyester floor-standing enclosures
PLA
(3)
(3)
(3)
(3)
(3)
(3)
(1) Also S3DM, S3DEX, S57 and S3DC.
(2) Also S3XEX.
(3) 1 door.
(4) 2 doors.
Components
Type of protection (4)
Name
Range
1 2 3 3R 3S 4 4X 5 6 6P 12 12K 13
Ventilation system
CV
Thermal regulation system
CC
(4) In some ranges the classification depends on the model and version. The detailed protection types are indicated in the UL certifications.