It is important to consider all possible factors that will adversely affect equipment operation. One notable factor that can negatively impact a successful enclosure installation is heat, which is a by-product of electrical and electronic components. Heat can come from inside a control cabinet, as well as outside via the surrounding air. If not dissipated, heat has the potential to cause failures and malfunctions to sensitive components commonly packaged within electrical enclosures, computer server racks, and other product compartments – the vital controls for drives and displays used in many industries, such as:
As an example, nearly all of the power of electronics or microprocessors is converted into heat. Additionally, devices that transmit power often have voltage drops or efficiency losses which are also converted into heat. Consequently, this internal heat load will cause the enclosure temperature to rise to an unacceptable level. Heat gain or loss is measured in Watts or BTU’s (British Thermal Units) – these units of heat are converted with the following formulas: Watts = BTU /hr. ÷ 3.414 and BTU/hr. = Watts x 3.414. There are spreadsheets or calculators available to help you calculate Heat Load.
Ambient air, the air outside the enclosure, can also be a potential source of heat gain. In some environments, the ambient air may be cool enough to allow the enclosure to dissipate heat. However, ambient air in warmer climates may be so hot that it adds to the heat load.
Solar load in an electrical enclosure can be offset by using thermal insulation, white or light colored reflective paint finishes, and/or a roof or sun shield. Enclosures can also be constructed with a double wall to help protect against solar load; though this tends to be a costly solution.
Outside air entering an electrical enclosure carries both heat and humidity, and a high relative humidity in the air potentially increases the heat content. Additionally, condensing water vapor or the formation of dew from high humidity (particularly in outdoor enclosures) will damage the electrical and electronic contents within the enclosure. Therefore, it is best to properly seal electrical cabinets and feeding conduits to avoid this type of heat gain, and prevent the harsh effects humidity can have on the components.
There are many ways to successfully mitigate unwanted heat. Addressing the requirement and including a thermal management solution to the system from the onset is always preferable. If needed, an enclosure cooling sizing program will help guide you to the best choice for your application. Factors such as heat load (that must be removed), operating voltage, and NEMA (National Electrical Manufacturers Association) style will also help narrow your enclosure cooling choices. Based on the environmental conditions a fan, blower, heat exchanger or enclosure air conditioner may be necessary.
Remember - you can avoid costly field retrofits and downtime by planning ahead and considering the factors that may negatively affect your equipment.
