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Essential Considerations for Cooling Outdoor Enclosures

electrical-towers-in-the-sunset.jpgAir conditioner applications are common for electrical enclosures used outdoors. Typical industry installations include: Telecommunications, Transportation, Kiosk and many more. However, these installations can present a few unique challenges. In most situations, a cabinet’s internal temperature needs to be at or below ambient. In order to achieve proper cooling within the enclosure, several factors such as environmental conditions and the NEMA (National Electrical Manufacturers Association) type must be considered when designing a system for the outdoors.


Protection from External Conditions:

To ensure internal components are properly cooled and not compromised, cabinets must be sealed from water, dust, fumes, oil, corrosives and contaminants; and for outdoor applications, rain or snow. To optimize performance, these units should utilize a closed-loop cooling system. In addition to providing the necessary cooling, closed-loop systems will protect enclosure contents by sealing out hostile elements that are in the environment. In closed-loop systems, there are two separate circulating systems implemented within the unit. One system cools and recirculates the clean cool air throughout the enclosure, while the other system uses ambient air or water to remove and discharge the heat. A heat exchanger may also be an option, however heat exchangers only have the ability to cool at ambient (air-to-air units) or marginally below ambient (water-to-air units). If a heat exchanger is used, the same guidelines, such as environmental conditions and proper sealing, need to be accounted for.

Solar Load:

The sun should be a strong consideration in almost every outdoor application. Solar load (also known as solar gain) can add to the internal heat produced in the cabinet. The effect solar load has on an electrical enclosure is very similar to that of a car parked outside on a sunny summer day. The temperature inside a car rises rapidly even if it is only in the sun for a short period of time. For an enclosure with sensitive electronic components, solar load can have the same devastating impact, compromising internal parts if not accounted for. Therefore, selecting the proper cooling unit that will prevent overheating and ultimately a malfunctioning piece of equipment is paramount.

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NEMA Rating:

Units rated NEMA 3R, 4 and 4X are the best options for outdoor conditions. NEMA 3R style units are typically suggested for less stringent environmental conditions, while NEMA 4X is recommended to protect against harsher environmental conditions. It is important to know what external conditions each rating is intended for in order to be able to make the best choice for a particular application:

  • NEMA 4/4X: Enclosures that are constructed for indoor and outdoor conditions, providing protection from the following:
    • Falling dirt, splashing water, hose-directed water, rain, sleet, snow, windblown dust.
    • External formation of ice on the enclosure.
    • NEMA 4X has the same qualifications as NEMA 4 with the addition of corrosion protection. Typically this means the units have specially coated coils and are manufactured with a stainless steel shell.
  • NEMA 3R: Enclosures that are constructed for indoor and outdoor use, providing protection from the following:
    • Falling dirt, rain, sleet, snow.
    • External formation of ice on the enclosure.

When selecting a unit, it is important to match the NEMA rating of the enclosure with the same rating of the cooling system. This is done to ensure the components within the enclosure are properly protected. For example, a NEMA 4 enclosure should be packaged with a NEMA 4 air conditioner. If this is not done, the system will only protect against the conditions of the lower NEMA rated unit, and this could compromise the entire application.


Topics: Cooling basics, Heat Exchangers, Air Conditioners

Sep Sabeti

Written by Sep Sabeti

Sep is a Design Engineer at Kooltronic