Control Panels
Enclosure Type Ratings
What each enclosure type rating protects against, and where each is normally used in controls work.
Source of these values
Summarised from the enclosure type definitions used by NEMA and referenced in NFPA 70 Table 110.28. Consult the standard for the full definitions and test requirements.
| Type | Environment | Protects against | Typical use in controls |
|---|---|---|---|
| Type 1 | Indoor | Incidental contact with enclosed equipment, falling dirt | Clean, dry indoor electrical rooms |
| Type 3R | Outdoor | Rain, sleet, snow, external ice formation | Outdoor equipment where dust ingress is acceptable |
| Type 4 | Indoor or outdoor | Windblown dust, rain, splashing water, hose-directed water | Wash-down areas, outdoor sites |
| Type 4X | Indoor or outdoor | Type 4 plus corrosion | Wastewater, coastal sites, chemical feed areas |
| Type 12 | Indoor | Circulating dust, falling dirt, dripping non-corrosive liquid | Indoor plant floor areas |
| Type 7 | Indoor hazardous | Contains an internal explosion in Class I Division 1 areas | Classified areas, with the applicable group |
| Type 9 | Indoor hazardous | Combustible dust environments, Class II | Classified dust areas |
In short
Enclosure type ratings describe what the enclosure protects against. Type 1 is indoor general purpose, Type 12 adds dust and dripping liquid, Type 3R adds outdoor rain, Type 4 adds hosedown and windblown dust, and Type 4X adds corrosion resistance. Type 4X stainless is the usual choice for wastewater.
Notes and limits
- In wastewater, hydrogen sulfide attacks painted steel. 316 stainless in a Type 4X rating costs more initially and is routinely the cheaper decision over the life of a lift station.
- A type rating is not preserved through an unsealed penetration. Drilling an enclosure without a properly rated fitting invalidates the rating.
- NEMA type ratings and IEC IP codes are not directly interchangeable. A type rating covers corrosion, icing, and oil resistance that an IP code does not.
Direct contact
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