UV Disinfection Design Basics – NEMA and IP Enclosure Ratings
By Brian Grochowski
Moisture and particulate can greatly affect the lifespan of a control cabinet. In addition, exposure to challenging environmental conditions can affect the function and longevity of the panel. The control cabinet supplied with a UV disinfection system is no different, and in many cases, its exposure to harmful contaminants is exacerbated by the harsh environments found within typical municipalities, food and beverage, pharmaceutical, power and energy, and aquatics applications.
While a considerable amount of time goes into system sizing, lamp type selection, establishing water quality and system performance, it is equally important to ensure that the control cabinet is designed for the specific conditions it will face.
Cabinets can be built for exposure to condensing water, wash-down with water under pressure, or total and permanent submersion. NEMA and IP ratings were created to define the levels of protection a cabinet should provide, based on the conditions it will operate within.
An IP rating considers protection against ingress of solid foreign objects and water, while NEMA ratings consider not only these, but also other factors such as corrosion and construction. It is possible to say that a specific NEMA type is equivalent to a specific IP rating, but it is not possible to say that an IP rating is equivalent to a NEMA type. The comparison of NEMA and IP enclosure ratings is only approximate. It is the responsibility of the user to verify the enclosure rating necessary for the given application.
NEMA stands for National Electrical Manufacturer Association. NEMA ratings are standards that are useful in defining the types of environments in which an electrical enclosure can be used. Typically, UV system control enclosures have a NEMA type 4 rating, but this should never be taken for granted. Also, a NEMA type 4 rating may not provide sufficient protection for a specific application, so understanding the different NEMA ratings is important.
General-purpose. Primarily used to provide protection against dust, spraying of water and noncorrosive coolants. Meets oil exclusion and rust resistance design tests.
| Enclosure Rating | Popularity | Enclosure Rating Definition | |
| NEMA Type 1 | Popular | General-purpose. Protects against dust, light, and indirect splashing but is not dust-tight; primarily prevents contact with live parts; used indoors and under normal atmospheric conditions. | |
| NEMA Type 2 | Rare | Drip-tight. Similar to Type 1 but with addition of drip shields; used where condensation may be severe (as in cooling and laundry rooms). | |
| NEMA Type 3, 3S, 3X | Rare | Weather-resistant. Protects against weather hazards such as rain and sleet; used outdoors on ship docks, in construction work, and in tunnels and subways. 3X includes corrosions. | |
| NEMA Type 3R | Popular | Intended for outdoor use. Provides a degree of protection against falling rain and ice formation. Meets rod entry, rain, external icing, and rust-resistance design tests. | |
| NEMA Type 4, 4X | Popular | Watertight (weatherproof). Must exclude at least 65 GPM of water from 1-in. nozzle delivered from a distance not less than 10 ft for 5 min. Used outdoors on ship docks, in dairies, and in breweries. The 4X model has corrosion resistance. | |
| NEMA Type 5 | Rare | Dust-tight. Provided with gaskets or equivalent to exclude dust; used in steel mills and cement plants. | |
| NEMA Type 6, 6P | Rare | Submersible. Design depends on specified conditions of pressure and time; submersible in water or oil; used in quarries, mines, and manholes. | |
| NEMA Type 7 | Popular | Hazardous. For indoor use in Class I, Groups A, B, C, and D environments as defined in the NEC. | |
| NEMA Type 8 | Rare | Hazardous. For indoor and outdoor use in locations classified as Class I, Groups A, B, C, and D as defined in the NEC. | |
| NEMA Type 9 | Rare | Hazardous. For indoor and outdoor use in locations classified as Class II, Groups E, F, or G as defined in the NEC. | |
| NEMA Type 10 | Rare | MSHA. Meets the requirements of the Mine Safety and Health Administration, 30 CFR Part 18 (1978). | |
| NEMA Type 11 | Rare | General-purpose. Protects against the corrosive effects of liquids and gases. Meets drip and corrosion-resistance tests. | |
| NEMA Type 12, 12K | Popular | General-purpose. Intended for indoor use, provides some protection against dust, falling dirt, and dripping noncorrosive liquids. Meets drip, dust, and rust resistance tests. | |
| NEMA Type 13 | Rare |
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IP (or “Ingress Protection”) ratings are defined in international standard EN 60529 (British BS EN 60529:1992, European IEC 60509:1989). They are used to define levels of sealing effectiveness of electrical enclosures against intrusion from foreign bodies (tools, dirt, etc.) and moisture.
In general, UV system control cabinets have an IP56 rating. Again, getting confirmation of this from the vendor is important, as well as determining if this level of sealing is adequate for the intended installation point. The table below shows the different IP ratings. The first number defines the level of protection against penetration of solid objects into the housing. The second number defines the level of protection against penetration of liquids into the housing.
| Number (1st Digit) |
Degree of Protection (Solid) | Number (2nd Digit) |
Degree of Protection (Liquid) |
| 0 | No protection against contact or entry of solids | 0 | No protection |
| 1 | Protection against accidental contact by hand, but not deliberate contact. Protection against large objects (greater than 50 mm) | 1 | Protection against drops of condensed water. Condensed water falling on housing shall have no effect |
| 2 | Protection against contact by tools, wire, etc. Protection against small foreign objects (greater than 12 mm) | 2 | Protection against drops of liquid. Drops of falling liquid shall have no effect when housing is tilted to 15° from vertical |
| 3 | Protection against contact by tools, wire, etc. Protection against small foreign objects (greater than 2.5 mm) | 3 | Protection against rain. No harmful effect from rain at angle less than 60° from vertical |
| 4 | Protection against contact by tools, wire, etc. Protection against small foreign objects (greater than 1 mm) | 4 | Protections against splashing from any direction |
| 5 | Complete protection against contact with live or moving parts. Protection against harmful deposits of dust | 5 | Protection against water jets from any direction |
| 6 | Complete protection of live or moving parts. Protection against penetration of dust | 6 | Protection against conditions on ship decks. Water from heavy seas will not enter |
| 7 | Protection against immersion in water. Water will not enter under stated conditions of pressure and time | ||
| 8 | Protection against indefinite immersion in water under a specified pressure |
When considering the purchase of a UV system, or other device with an electrical/control enclosure, it is important to consider the location and environment in which it will be mounted. Will this be in a wash-down area? Is corrosion resistance important? Some UV systems can be supplied with long cable lengths (up to 365 feet) to connect the UV vessel with the electrical/control enclosure. If that is the case, it might be feasible and more cost effective to mount the cabinet in a less harsh environment. Considering these points and working with a knowledgeable supplier can help to ensure the UV disinfection system is optimally designed and built for its’ environment.
More information on NEMA and IP ratings can be found at:
https://www.nema.org/Products/Documents/nema-enclosure-types.pdf
https://www.nema.org/Standards/ComplimentaryDocuments/ANSI-IEC-60529.pdf
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