It’s a harsh world… part 2 – Drives vs Enclosure classes

Wednesday, February 17, 2016

AC drives, and the larger Industrial Automation world as a whole, experience such a variety of environments that it’s almost a miracle that any of these components survive more than a handful of weeks, let alone years. That’s really all thanks to the engineering of the enclosures of these products, which range from finger-safe to explosion-proof. To guide engineers, IEC as well as UL (along with NEMA), create specifications and test procedures to ensure that when you select an AC drive for your particular environmental requirements, that the product is perfectly suited to live up to the challenge.

This week, we’re taking a deeper look at the world of Ingress Protection (IP) and UL Type enclosure classifications so that you’re armed with the knowledge to understand exactly what to look for and what you’re getting when you purchase a Danfoss Drives product. We’ll attempt to focus on typical enclosures for AC drives, so keep in mind that there may be other enclosure classifications out there besides what’s covered here.

Ingress Protection, or IP, ratings are a collection of enclosure classification designations created by the International Electrotechnical Commission (IEC), and collected in the IEC 60529 standard. These rating classifications are primarily focused on countries outside of North America, but are applied to many products shipped there. In fact, many commercial electronics devices, such as phones and tablets, use the IP enclosure classification ratings to show that the products are submersible, for instance. The basics for IP ratings follow, primarily, a two-digit convention, where the first digit in the enclosure classification relates to the impact of solids and the second digit relates to the impact of liquids. Each classification is paired with specific test requirements to ensure that the device enclosure meets the design goal.

Solids   Liquids  
0 No protection 0 No protection
1 Protected against objects > 50 mm (hands) 1 Protection against dripping water or condensation
2 Protected against objects > 12 mm (fingers) 2 Protection against water spray 15 degree from vertical
3 Protected against objects > 2.5 mm (tools/wires) 3 Protection against water spray 60 degree from vertical
4 Protected against objects > 1 mm (small tools) 4 Protection against water spray from all directions
5 Protected against dust, limited ingress 5 Protection against low pressure jets of water
6 Totally protected against dust 6 Protection against high pressure water jets and heavy seas
7 N/A 7 Protection against the effects of immersion (6 inches to 3.3 feet)
8 N/A 8 Protected against immersion


As can be seen in the IP rating table, virtually all variations on solid and liquid protection are covered by the specifications. So, for example, if you want something finger-safe and able to deal with dripping water, then go for IP21. Enclosure classifications don’t have to be tested for both protection against solids and liquids, though. If you want to test only against solids and not for liquids, then something like IP2X can be used. It’s the same thing if testing only for protection against liquids, where something like IPX7 can be written. In these cases, the X signifies it hasn’t been tested to meet solids or liquids protections as opposed to writing a 0 which would mean that there isn’t any protection against solids or liquids to begin with. AC drives from Danfoss Drives are available primarily in IP00, IP20/21, IP54 and IP66 classes. However, there are some special products targeting regional or application requirements that may offer something different.

There are some limitations relating to AC drives, however, that the standard IP ratings don’t account for: Indoor/outdoor operation, locations with high-pressure and high-temperature washdown, and hazardous environments (i.e. explosive areas). While these situations aren’t covered by the IP classifications, additional regional and international certification agencies build on the IP ratings to augment the IEC 60529 standard. We’ll cover these specific certifications in some of the other topics in the “It’s a harsh world…” series, so check back later if those are interesting to you.

North America, however, follows some different strategies and requirements when it comes to enclosure classifications. The North American equivalent of IP enclosure classifications are UL Type ratings. Largely based around the NEMA (National Electrical Manufacturers Association) enclosure classifications, UL Type ratings add to the NEMA classification an independent third-party verification structure similar to the existing testing requirements of the IP ratings. While you may hear NEMA ratings and UL Type ratings used interchangeably, it’s important to point out that the independent testing requirement for UL Type ratings sets them apart.

All of the UL Type classifications are listed as ‘UL Type X’ where the X is the particular characters corresponding to the environment class. This means that the testing cases must apply to both solids and liquids, whereas the IP ratings can apply to either/or. Because of this, it’s difficult to draw a one-to-one relationship between IP enclosure classifications and the UL Type ratings. The UL Type ratings also cover cases where the device will be in hazardous areas or is being placed outside, unlike the IP ratings. While many UL Type enclosure ratings exist, only a few are applied to AC drives on a regular basis. These are the ratings we’ll focus on.

UL Open Type enclosures are AC drives that don’t have much in the way of an enclosure. Sometimes also referred to as chassis drives, these are quite often low-power AC drives without a method of using a conduit directly with the drive, or high-power AC drives that have lug terminals for larger wires. What both of these examples have in common is that they would almost always be added to an external enclosure to meet the requirement of the surrounding environment. UL Open Type enclosures are closest to IP00.

UL Type 1 is intended for indoor use and provides some minimal protection against the surrounding areas. Considered finger safe, UL Type 1 also covers falling dirt. These enclosures are typically considered to be in line with the IP21 enclosure classification.

UL Type 12 is still intended for indoor use, but increases the protection of the AC drive so that it can be used in areas where dusts and other non-conductive or non-flammable particulates may be found. It also provides protection against dripping and light splashing of non-corrosive liquids and seepage of non-corrosive oils or coolants. Typically, this is closest to IP54 enclosures.

UL Type 3R is rarely seen outside North America and specifies an ability to operate outdoors as well as indoors. In addition to Type 12 protection, it also provides a degree of protection against rain, sleet and snow and won’t be damaged by ice forming on the enclosure. Outdoor applications that don’t require direct washdown can potentially save some money by selecting an AC drive with a UL Type 3R enclosure.

UL Types 4/4X provide all the protections of Type 3R with the addition of protection against low-pressure washdown and being completely dust tight. It is important, though, to check with the AC-drive supplier if the application is outside as UL Types 4/4X don’t specify in the same way as UL Type 3R. Typically, AC-drive manufacturers, such as Danfoss Drives, will specify when their product can be mounted outside. The only difference between UL Type 4 and UL Type 4X is that UL Type 4X provides protection against corrosion. Because of this, UL Type 4X enclosures are best suited for facilities where a cleaning solution is used to wash down the area including the AC drive, but the pressures shouldn’t be much higher than out of a typical garden hose spray nozzle. The closest IP rating would be IP66.

If you want to get a better idea of how UL Type ratings compare to the IP enclosure classifications, take a look at the handy table below. The light gray is the UL comparison to the solids protection of IP ratings, while the dark gray is the UL comparison to the liquids protection of IP ratings.

As you can see, enclosure classifications come in all sorts, regardless of where you are in the world. It’s important to understand the similarities and differences as the reach of your solutions expand around the globe. There are far more enclosure classifications that apply more to other devices or are particularly suited for certain applications, but we’ll expand more on these in later posts.

Check back regularly with us here at for regular updates on the best ways to ensure that your investments in AC drives are always the safest investments around. Next time, we’ll have Part 3 in the series when we look at Drives vs. Low temperatures, a perfect topic for this time of year. Additionally, let us know in the comments what environmental impacts give you the biggest challenges and how we can help you overcome them. Regardless of whose name is on the label, we’re here to help! In the meantime, you can find out more about all our products here.

Jake Roeder, Global Product Marketing Manager, Danfoss Drives
Abraham González Ponce, Application Knowledge Manager, Application & Service Products, Danfoss Drives