5 Key Steps in Enclosure Cooling Design

 

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Electrical enclosures protect equipment from mechanical and environmental damage. However, by confining equipment inside an enclosure, the waste heat generated by each component builds up, raising the enclosure temperature above manufacturer recommendations for the components.

To maintain proper equipment performance levels, an enclosure cooling system is typically required. When designing a cooling system for an electrical enclosure, it’s important to follow these five key steps:

1. Determine if closed loop cooling is required

Decide whether the enclosure requires a closed loop cooling system, or if a filtered fan system will be able to accomplish the task. To do this, establish the NEMA rating of the enclosure, based on the following factors:

  • Location (indoors or outdoors)
  • Ambient temperature and exposure to wind, blowing rain, ice
  • Exposure to humidity, corrosive chemicals, liquids, or particulates (falling or sprayed)

The NEMA rating will determine whether the enclosure can be cooled by a simple filtered fan system – a less expensive option – or if it will require a closed-loop cooling system to maintain an interior temperature within the manufacturer’s specified range.

2. Choose the right temperature control solution

If a closed-loop cooling system is required, choose either an air-to-air heat exchanger or an enclosure air conditioner. Of the two, the heat exchanger is a less expensive option. However, this selection must be based on whether the manufacturer’s recommended air temperature for each component in the enclosure is higher or lower than the maximum ambient temperature surrounding the enclosure.

Because an air-to-air heat exchanger works by transferring heat from inside the enclosure to the surrounding environment, the enclosure temperature will always be a few degrees higher than the ambient temperature.

Only an enclosure air conditioner, which uses a compressed refrigerant, can cool the internal temperature of the enclosure below the temperature of its surroundings.

In addition, an enclosure air conditioner may be required to remove excess humidity from the air that could affect component operation, or when the components themselves create an excessive heat load, overwhelming the cooling ability of a heat exchanger.

3. Determine the necessary size/cooling capacity for the chosen enclosure cooling system

The size of a filtered fan system will be determined by the volume of air moving through the enclosure, in cubic feet/minute (CFM), and the difference between the internal enclosure temperature and the ambient air temperature, or ΔT. The enclosure temperature is a function of the heat generated by each of the components, as well as heat transferred into the enclosure by insolation or other sources. An online enclosure temperature management calculator can be used to assist in selecting the proper cooling system and determine the appropriate size.

The size of a filtered fan system will be determined by the volume of air moving through the enclosure, in cubic feet/minute (CFM), and the difference between the internal enclosure temperature and the ambient air temperature, or ΔT.

For an enclosure air-to-air heat exchanger, the size of the system will be determined by the combined internal heat load of the components, in Watts, minus the amount of heat conducted through the enclosure walls, divided by ΔT. (Note: if ΔT is negative, an enclosure air conditioner will be required). Heat exchanger capacity is expressed in Watts/degree F.

For an enclosure air conditioner, the cooling capacity must be equal to, or greater than, the internal heat load, which consists of heat generated by each of the enclosed components, combined with the heat transferred into the enclosure itself by the surrounding environment. The cooling capacity of an enclosure air conditioner is expressed in BTU/hour.

4. Determine the Proper Power Source

Enclosure cooling systems are designed to operate from either the standard 120, 230 or 480 VAC provided by the power grid, or on 48 VDC supplied by battery, solar, or wind power.

5. Select appropriate accessories, as needed

Depending on the application needs, accessories may be required to optimize your cooling solution. For example, a 3R shroud can be added to a filtered fan system to protect the interior of the enclosure from rain. Options and accessories for enclosure air conditioners may include a corrosion protection package, open door kill switch, remote control and monitoring, or a vibration package.

For more help in designing an enclosure cooling system, contact Thermal Edge.