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Using VSDs outdoors? Avoid IP ratings you don’t need

14 April, 2020

HVAC contractors and consultants sometimes specify IP ratings of IP65 or higher for variable-speed drives used outdoors, but a high IP rating is not the same as “weatherproof”, as ABB’s Carl Turbitt explains.

Variable-speed drives and the elements don’t usually mix, so when it comes to installing VSDs in outdoor areas where they might be exposed to the weather, there are two generally accepted methods for protecting a drive:

•  ensuring that it has a suitable IP (ingress protection) rating; or

•  placing the drive in an enclosure with a suitable IP rating.

 

Contractors and consultants sometimes specify the former on the basis that an IP65 or IP66 rating will be sufficient for outdoor use. As well as being more expensive, this assumption is also incorrect. Ingress protection is not the same as weatherproofing. While dust and water (as defined in IP standards) are certainly abundant in the great outdoors, specifying IP65 and above for outdoor installations fails to take into account the nuances of weather conditions. This can end up doing more harm than good.

When VSDs are installed outdoors there are lots of things to consider before selection and installation. IP rating alone is not a good indicator for outdoor suitability, because it will not necessarily protect against certain conditions such as: 

•  Ambient temperature and sunlight  Outdoor installations typically have much wider temperature ranges than those indoors. Direct sunlight causes the VSD to heat up and, because this additional heat is not designed to be dissipated, over-temperature trips can result. Sunlight also degrades plastic parts over time, and can render LCD displays unreadable.

•  Cold  VSDs have operating limits for cold conditions. Extreme cold can damage the VSD, but more importantly the “dew point” is reached and water condenses out of the air. Water inside a VSD should always be avoided, because it leads to moisture forming on its internal surfaces, causing damage.

•  Airflow  VSDs generate heat and need cooling air. When a drive is installed outdoors, the incoming and outgoing airflows have to be able to move freely.  

A high IP rating will not necessarily protect against these issues. IP66, for instance, ensures that a product is dust-tight and protected against heavy seas. Clearly, a VSD installed on the roof of a building is unlikely to encounter heavy seas, nor will its IP rating protect against sunlight or cold.

Instead of paying more for high IP ratings, you can instead simply place the VSD in a suitable enclosure, which performs the same job at a much lower cost. Installing the VSD on a north-facing wall ensures that it is not exposed to direct sunlight, while keeping it powered up at all times (which many VSDs are, anyway) protects the drive from cold and condensation. 

  

ABB has produced an e-book offering advice on installing VSDs outdoors. To download it, and other ABB e-books, visit this dedicated Web page: http://bit.ly/2jWzOHO.




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