DDB NEMA 4 Enclosures
“NEMA TYPE 4” has become a confusing term in the industry at large. The term “NEMA” amongst code writers, enforcers, AHJ’s and electrical inspectors is synonymous, colloquially, with “Listed” Type 4. When a code inspector calls for a “NEMA” Type 4 enclosure, then also requires that this be “Listed” by an NRTL, while this is technically conflicting and inaccurate, the code is clear that it must be a listed enclosure. The NEMA 250 Standard is never used by an NRTL as it is a set of guidelines; instead, UL 50/50E and UL 508 are the standards used to declare a Type rating. Building and Safety Inspectors often have little to no training as to what NEMA or UL 50 is or states; they merely look for the “Type 4” designation on a Listed Label during inspection. When in doubt about what they are looking at, they call for a field inspection by the NRTL to provide verification that the enclosure they are looking at is in fact a Listed enclosure per the lab report. The consumer sees that enclosure manufacturers market and sell enclosures as NEMA Rated Type XX, but are unaware that this enclosure, will not pass an AHJ inspection, if the code calls for the enclosure to be listed by an NRTL.
What is the standard for NEMA 4 ratings
Indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); and that will be undamaged by the external formation of ice on the enclosure.
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NEMA 4 and 4X Ratings
|Protection Against the Following Conditions
|Access to hazardous parts
|Ingress of solid foreign objects
|Circulating dust, lint, fibers, and flyings **
|Setting airborne dust, lint, fibers, and flyings **
|Windblow dust, lint, fibers, and flyings
|Ingress of water
|Dripping and light splashing
|Hosedown and splashing water
|Rain, snow, and sleet ***
|Occasional temporary submersion
|Occasional prolonged submersion
|Oil & Corrosion resistance
|Oil and coolant seepage
|Oil or coolant spraying and splashing
When in doubt, purchase a Listed enclosure
Enclosure manufacturers are responding to the requirement for Listed enclosures as many local, regulatory codes, continue to increase the types of enclosures being installed in certain applications, especially those that house police and firefighter radio equipment. It can be extremely frustrating and costly for the consumer to purchase an enclosure marketed as “NEMA Type 4”, only to find out that it will not pass an inspection after integration, install, permits etc., have been completed and obtained, because it is lacking the necessary marking. Costs for enclosure returns, reintegration, deadlines missed, can far outweigh the extra cost for the initial purchase of a listed enclosure.