Evaluation of enclosures for Electrical Equipment for environmental rating as per UL 50E Shelesh Tiwari he scope of this article is to briefly discuss the Environmental / type rating requirementsof enclosures for electrical equipment (referred here after as enclosure for sake of simplicity) intended to be installed and used in non-hazardous locations.
T
NEED FOR EVALUATION FOR TYPE RATING Primary function or objective of enclosure is to protect the electrical equipment or assembly it houses, from external environment to which it is subjected after it is in service. Therefore it is important to evaluate the performance of the enclosure against all possible external environmental hazards. UL 50E Standard provides an excellent way to evaluate the enclosure for type rating (environmental rating) since it covers almost all possible external environmental Hazards or their combinations to which an enclosure may be subjected.
ENVIRONMENTAL RATINGS OR TYPE RATINGS Type rating of enclosure is defined based on their suitability to environment where they are intended to be installed i.e. indoor or outdoor. Enclosures are marked with the enclosure type ratings for which they were investigated.Enclosed industrial control panels are marked with an enclosure type rating. The type rating of the industrial control panel may differ from therating of the basic enclosure due to the presence of components or assemblies installed through the enclosure walls by the manufacturer. Table 1 and 2 provides the enclosure types and corresponding type ratings and degree of protection provided by them respectively.
TABLE 1 Enclosure Suitability Indoor location Indoor or Outdoor location
Type rating 1, 2, 5, 12, 12K, and 13 3, 3R, 3S, 4, 4X, 6, and 6P
TABLE 2 Enclosure Type Rating Enclosure Suitability Type 1 Indoor
Degree of protection provided against falling dirt against falling dirt, dripping and light splashing of noncorrosive liquids.
Type 2
Indoor
Type 3
Indoor or outdoor
against falling dirt, rain, sleet, snow, windblown dust and should not be damaged by the external formation of ice on the enclosure.
Type 3R
Indoor or outdoor
against falling dirt, rain, sleet, and snow; and should be undamaged by the external formation of ice on the enclosure.
Type 3S
Indoor or outdoor
Type 4
Indoor or outdoor
Type 4X
Indoor or outdoor
Type 5
Indoor only
Type 6
Indoor or outdoor
Enclosure Type Rating Enclosure Suitability Type 6P
Indoor or outdoor
Type 12**
Indoor only
Type 12 K**
Indoor only
Type 13
Indoor only
**Enclosure is without knockouts.
against falling dirt, rain, sleet, snow, windblown dust and any external mechanism(s) should remain operable when ice laden. against falling dirt, rain, sleet, snow, windblown dust, splashing water, ,hose-directed water it should be undamaged by the external formation of ice on the enclosure. against falling dirt, rain, sleet, snow, windblown dust, splashing water, hose-directed water, corrosion it should be undamaged by the external formation of ice on the enclosure. against falling dirt; against settling airborne dust, lint, fibers, and flyings, dripping and light splashing of noncorrosive liquids. against falling dirt, rain, sleet, snow, hose-directed water, entry of water during occasional temporary submersion at a limited depth, and it should be undamaged by the external formation of ice on the enclosure. Degree of protection provided against falling dirt, rain, sleet, snow, hose-directed water, corrosion, entry of water during prolonged submersion at a limited depth and it should be undamaged by the external formation of ice on the enclosure. against falling dirt, against circulating dust, lint, fibers, flyings, dripping and light splashing of noncorrosive liquids and against light splashing and consequent seepage of oil and non-corrosive coolants. against falling dirt, circulating dust, lint, fibers, flyings, dripping and light splashing of non-corrosive liquids and against light splashing and consequent seepage of oil and non-corrosive coolants. against falling dirt, circulating dust, lint, fibers, flyings and against the spraying, splashing, and seepage of water, oil, and non-corrosive coolants.