Kooltronic Blog

When specifying an enclosure cooling solution for an electrical cabinet, there are many factors that one must consider. While some terminology is common and intuitive - with references to everyday language - other terms may be ambiguous. Nevertheless, it is important to have a basic understanding of common enclosure cooling terminologies, such as heat load, ambient temperature, and solar gain. Having a general understanding of these terms will make the task of finding a thermal management solution much easier.

Common Enclosure Cooling Terms:

 

Ambient

This refers to the environment surrounding the enclosure where an air conditioner or other cooling product will be installed. Generally, the word “ambient” is used to describe the temperature, humidity, air cleanliness, or quality (including dust) and possibly any other harsh or corrosive condition.

BTU/H

British Thermal Unit per Hour is a unit of measure for heat. Heat is also commonly measured in watts: 1 BTU/H = 0.29 Watts.

CFM

CFM is an acronym for Cubic Feet per Minute. It describes a volumetric flow of air or other gas. Concerning fans or blowers, CFM indicates how much air can be moved per minute.

Compressor

A compressor is the main component in a refrigeration system, often referred to as the heart of the air conditioner. The compressor pumps or circulates the refrigerant through the rest of the cooling system.

Corrosive Atmospheres

Corrosive environments, such as those found in chemical plants and industries where processes result in harsh chemical by-products, usually preclude the use of filtered ambient air. Corrosives generally cannot be filtered out by normal filtration methods, and techniques used to rid the air of corrosives are complex, costly, and often unsatisfactory. Cooling electrical enclosures in corrosive atmospheres requires isolation of the sensitive components subject to damage from any destructive gases or liquids. The recommended enclosure cooling solution is usually that of closed-loop cooling (i.e. heat exchangers or enclosure air conditioners). These types of cooling solutions consist of two separate circulation systems in a single unit. One circulation system recirculates clean, cooling air through the electronics within the sealed enclosure, while the other circulation system discharges the heat from the cabinet to the ambient air or into the water for removal.

If the corrosive atmosphere is within an acceptable temperature range, then air-to-air heat exchangers can be used to provide cooling for equipment within an enclosure. However, when both high ambient temperatures and corrosives are present, either enclosure air conditioners or water-to-air heat exchangers must be employed to cool the hot components.

Regardless of the cooling apparatus chosen, it must be constructed of corrosion-resistant materials or treated with corrosion-resistant coatings to ensure long, trouble-free operation. Additionally, it is important to review the particular conditions involved because, if an off-the-shelf option is unavailable, in most cases, an enclosure cooling system can be designed to meet specific requirements effectively and affordably.

Evaporator Coil & Condenser Coil

An evaporator coil extracts heat from inside the enclosure or structure, while the condenser coil releases heat outside the enclosure or structure.

Internal Heat (Thermal) Load

This refers to the heat generated by components inside an electrical cabinet. Internal Heat Load (or Thermal Load as it is often referred) is calculated based on maximum load conditions and is expressed in watts or BTUs.

NEMA

Equipment may require a NEMA (National Electrical Manufacturers Association) rating to comply with local codes. Electrical cabinet air conditioners typically carry an agency marking such as UL (Underwriters Laboratories), which designates the environmental hazard from which the cabinet contents are being protected. The environmental conditions associated with this marking should be matched to the enclosure to be cooled. Typical examples include:

     ⚠ NEMA 12 (indoor use, protection from dust and dripping liquids)

     ⚠ NEMA 3R (indoor or outdoor use and rainproof)

     ⚠ NEMA 4 (indoor or outdoor use, protection from wash down)

     ⚠ NEMA 4X (indoor or outdoor use, protection from corrosive environments)

Depending upon the NEMA enclosure type, an enclosure air conditioner can be provided to operate in most locations. Locations subject to dust, dripping liquids, rain, wash down and corrosive atmospheres can utilize special-purpose enclosure air conditioning units for those conditions. Read our blog post, Everything You Need to Know About NEMA Ratings When Cooling an Enclosure to learn more.

Solar Load or Sun Load

The heat from the sun must be considered when identifying the total heat load on a system. This solar load can be minimized if the equipment cabinet is shielded from the direct rays of the sun. However, if shielding the enclosure is not possible, then painting the cabinet a light color and/or adding insulation should be considered. If none of these alternatives are possible, the cooling capacity must be increased to address this additional heat load.

It’s worth noting that in the southern portion of the United States, the impact of heat load on an electrical system can be significant. In the northern portion of the country, however, this may not be as big of a concern for certain applications.

Watt

Watts are a unit of measure for electrical power. This unit of measure is also used to quantify the amount of heat in a system. 1 watt will convert to 3.413 BTU’s.

 

Kooltronic has been developing thermal management and airflow solutions for over 65 years. Our enclosure cooling specialists are happy to assist you with any questions regarding product selection or challenges you may be facing with your specific application.