Damp vs Wet Location Ratings for Lights|
Article - November 30, 2017 By LarsonElectronics.com
Damp vs Wet Location Ratings for Lights
There are numerous elements that could hinder the performance of luminaries, such as harsh impacts and the ingress of water.
The latter factor is a major issue for work sites that are wet or damp, such as cleaning stations, pipelines, restrooms and storage centers that hold wet materials. As a result, lighting manufacturers reinforce their products with protective designs and components, which are regulated by safety standards set forth by the NEC, UL and other large agencies.
Such environments and protective mechanisms are rated by the institutions, based on the following classifications: Wet Locations, Damp Locations and Dry Locations. Read on to understand how these ratings affect lighting performance and reliability.
Wet locations are environments that directly expose lights (and other types of equipment) to water, which could include rain, massive amounts of moisture and snow. When UL ratings are applied to devices designed for wet locations, the units must be tested accordingly. For wet-location lights that allow water to enter the unit during operation, a drain hole must be present. This feature is thoroughly examined during a rain test or a sprinkler test.
Article 410 in the NEC sets forth that lights suitable for installation in wet areas must bear a “Suitable for Wet Locations” marking. Note that language in 410.10(A) of the NEC places the responsibility of proper installations of wet-location equipment on the electrician.
Examples of wet locations include car washes, food prep stations, uncovered steps, wells, landscapes, manufacturing floors that are washed down on a regular basis, sewers and underground basements. The NEC sets forth special requirements for wet-location installations for bathtubs and showers in 410.10(D).
UL guidelines define damp locations as an indoor or outdoor space that is sometimes exposed to watery elements, such as condensation or light moisture. The main difference between damp locations and wet locations is the duration and intensity of exposure to watery conditions. Because damp-rated luminaries are not designed with water-tight seals typically reserved for wet locations, they cannot withstand direct, persistent contact with water. Such options are ideal for areas with protective coverings, including covered porches and decks. Note that porches and decks without protective covers (roof or overhang) need to use wet-location rated lights.
The NEC regulates that equipment designed for damp locations must bear a “Suitable for Damp Locations” marking. Examples of damp locations include freezers/refrigerators, public restrooms, covered walkways, handwashing stations, outdoor gathering areas and more.
Dry-location ratings are self-explanatory; however, there are some points to consider when encountering this standard. As the name of the rating suggests, lights designed for dry areas should not expect to encounter damp or wet elements. The NEC and UL establishes that dry locations can be “temporarily” exposed to dampness or wetness. A building being constructed is the main example provided by both agencies. With this in mind, operators should proactively ensure the area is dry, when using dry-location lighting, due to lack of protective features designed to control the ingress of water. In most cases, proper ventilation is enough to deter the accumulation of moisture in dry locations.
“Suitable for Dry Locations” markings are not required, unless there is a need to make a distinction about the luminary’s features or limitations. In such cases, a marking or label may indicate “Suitable for Dry Locations Only.” This ensures the intended application for the unit.