Control panels listed to the standard UL508 are certified with an environmental rating that provides an indication of the degree of protection offered by the enclosure to the controller. These ratings are crucial to the longevity of the controller in the environment it is installed in. Some of the environmental ratings as defined in the standards UL50 and UL50E and their typical applications are listed below:
Type 1
Enclosures constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts and to provide a degree of protection against ingress of solid foreign objects such as falling dirt.
This is best suited for control panels located indoors in a relatively clean environment with low particulates. Protected by general purpose enclosures, it prevents incidental contact with internal components but does not protect against the ingress of particulates or liquids through openings/penetrations.
Type 3R
Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection against ingress of solid foreign objects (falling dirt); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, and snow); and that will be undamaged by the external formation of ice on the enclosure.
This is generally recommended for control panels located indoors or outdoors and offers a higher degree of protection against dripping water and particulates in the air. The internal components are protected by enclosures with knockouts located on the sides or on the bottom, offering some protection against dripping water, snow in addition to the protections offered by Type 1 enclosures. It is not weatherproof and does not prevent the entry of water through these knockouts or openings.
Type 4
Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts ; to provide a degree of protection 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.
This is best suited for control panels located in outdoor locations where corrosion is not a concern, but splashing and dripping water is present in addition to wind-blown particulates in the air. The enclosures for these control panels are weatherproof and prevent the entry of foreign objects and liquids. These protections can be supplemented with air conditioners or heaters to regulate internal temperature and humidity.
Type 4X
Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection 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); that provides an increased level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.
This is best degree of protection offered for panels located outdoors in environments that have adverse climate conditions such as salt sprays, sea water, high heat, humidity and extreme cold. In addition to the protection offered by a Type 4 enclosure, these enclosures are protected against corrosion to an extent by the use of poly carbonate or stainless steel material (304/316).
Type 12
Enclosures constructed (without knockouts) for indoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection against ingress of solid foreign objects (falling dirt and circulating dust, lint, fibers, and flyings); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing); and to provide a degree of protection against light splashing and consequent seepage of oil and non-corrosive coolants.
Typically for indoor applications, these enclosures offer protection similar to Type 3R with an emphasis on corrosion protection and oil seepage. This is best recommended for industrial applications.
Type 13
Enclosures constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection against ingress of solid foreign objects (falling dirt and circulating dust, lint, fibers, and flyings); and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing); and to provide a degree of protection against spraying, splashing, and seepage of oil, and non-corrosive coolants.
Suitable for use in heavy industrial applications, this type of protection is similar to Type 12, still restricted to indoors but offers protection against oil and coolant sprays.
Other ratings are defined and can be found in the standards UL50 and UL50E. It is important to note that to comply with the installation requirements under UL508, conduit, tubing and fittings used for wire entry will need to comply with standard UL514B.