Excess heat can cause electrical components, such as PLCs, VFDs, and power supplies, to lose efficiency and reliability, and may even cause them to fail early. In an industrial setting, these components are housed in protective enclosures, which trap waste heat and raise the temperature of the enclosure air above their maximum allowable temperature.
But choosing a cooling system for an enclosure can be tricky. Different cooling technologies are available, each with its own benefits and drawbacks. The cooling capacity of the system must be large enough to maintain the components within their manufacturer specified temperature ranges. However, over-sizing the system will not only waste energy and increase costs unnecessarily, but may also cause stressful fluctuations in temperature for the components and reduce the operating life of the system itself.
Before selecting a cooling system to protect sensitive equipment from excess heat, use a free online Enclosure Temperature Management (ETM) Calculator to help determine the optimal size and type enclosure air conditioner for your application.
Enter the information for your project in the appropriate fields, and the app will calculate the necessary cooling capacity and provide recommended cooling solutions. The following will help you determine the correct information for each field in the calculator.
Cooling Solution Type
Choose from three types of cooling systems, including filtered fans, air to air heat exchangers, and air conditioners. You may perform the calculations for one or all three types, and make comparisons.
Knowing the total space to be cooled is essential. Enter the height, width, and depth of the enclosure in inches. The cooling system must fit on the side of the electrical enclosure, within its depth and height.
Knowing the dimensions of the enclosure also allows its surface area to be calculated. The exposed surface acts as a heat transfer mechanism that either absorbs heat from the surrounding area, or gives off heat from the interior, depending on which has the highest temperature.
The desired enclosure temperature must be at or below the maximum operating temperature of the electronics in the enclosure. In order to determine this, you may need to consult the manufacturer’s specifications for each component, and find the one with the lowest maximum allowable temperature. It’s good engineering practice to design the enclosure cooling for a temperature that’s 20 ºF below the equipment’s maximum temperature, in order to minimize the possibility of overheating.
For the ambient temperature, enter the maximum ambient temperature for the location. If the ambient temperature is higher than the enclosure temperature, there will be additional heat gain. Be sure to include the effect of any equipment in the vicinity of the enclosure, such as boilers or ovens, which may increase the ambient temperature.
The heat load is the amount of heat that must be removed from the enclosure by the cooling system. The total heat load in watts includes the heat given off by of all items of equipment in the enclosure.
To determine the heat load, consult the manufacturer’s’ specifications to ascertain the power loss for each piece of equipment due to inefficiency. The efficiency of most VFDs is between 93 and 98 percent. The balance of the energy consumption is lost as heat. The power dissipated is calculated by subtracting the efficiency from 100 percent and multiplying the result by the power consumption of the drive. The heat loss of a 95 percent efficient, 100 horsepower drive can be estimated as 5 percent of 100 horsepower which equals 5 horsepower or 3729 watts.
Take into account the thermal losses of all ancillary equipment, available from the manufacturer’s specifications, and add them to calculate the total heat load.
Enclosure Material, Color, and Insulation
Typically the enclosure air conditioner should match the enclosure itself, in both material construction and paint color. Enclosures located in corrosive environments may require stainless steel or aluminum construction to prevent rust and corrosion.
Some enclosures are insulated to prevent excess heat transfer to the interior through the walls, or to maintain a minimum temperature in cold climates so that electrical equipment will operate properly.
Location and Air Flow Conditions
The enclosure location, whether indoors, outdoors, or in a shaded area, will affect the amount of solar insolation transferring heat into the enclosure. The impact of external heat gain may be significant.
Air flow conditions will also impact the heat load in the enclosure. Breezes or steady strong winds tend to transfer heat away from the enclosure walls, to a greater or lesser degree.
The ETM Calculator is a simple way to begin the process of selecting and specifying the correct enclosure cooling method for your application. For help in determining the heat load and other factors applicable to your situation, contact the experts at Thermal Edge.