Mistakes can be costly when it comes to enclosures housing industrial control equipment. Not only are the individual components, including variable frequency drives (VFDs) transformers, and power supplies, expensive to repair or replace, but they control the equipment upon which the entire operation of the facility depends.
If these components lose efficiency or experience damage, they may cause interruptions, temporary shutdowns for unplanned maintenance and repairs, or even a complete halt to operations, putting the business in jeopardy.
Manufacturers’ specifications generally indicate the maximum allowable temperatures for electronic equipment is in the 35ºC to 40ºC range. The heat that builds up inside a control panel enclosure often far exceeds this temperature and is a major cause of intermittent or catastrophic failures, such as when VFDs overheat and trip, causing plant outages.
To prevent excess down-time, service repair costs, and loss of service life, all leading to decreased productivity and profits, avoid the following three mistakes in cooling industrial control panel enclosures.
1. Choosing the wrong type of cooling system
Choosing an enclosure cooling system requires an understanding of the environment in which the control panel will be situated. Factors that need to be taken into account include ambient high and low temperatures, humidity levels, exposure to solar radiation, the need for protection against dust, dirt and pollution, and whether the enclosure is indoors or outdoors. This information can be used to determine the correct NEMA type for the enclosure.
NEMA, the National Electrical Manufacturer’s Association, has developed specifications for safe operation of electrical enclosures ranging from NEMA 1 enclosures, which operate indoors in an environment free of pollution and splashing liquids, to NEMA Type 4 and 4X enclosures, which are watertight and designed to protect against all types of weather and direct hose blasts in factory wash-down environments.
For NEMA 1 and 3R enclosures, an open loop cooling system, such as a filtered fan package, can often provide enough cooling to maintain the enclosure temperature within the manufacturer’s recommended operating range.
Under ideal environmental conditions, fans offer the most cost effective solution to adequately cool sensitive electrical components. Cooling fans perform best indoors with mild ambient temperatures, where minimal levels of dust and dirt exist, and away from moisture and corrosive chemicals.
However, if the enclosure falls into a NEMA Type 4, Type 4X or Type 12 rating, it will require a sealed closed loop cooling solution, which prevents ambient air, dust, debris, chemicals and liquids from direct contact with the components inside the enclosure.
As long as the enclosure will be located in an area with ambient temperatures below the maximum air temperature for the enclosure components, an air to air heat exchanger may be good cooling solution. Heat exchangers are sealed systems, which keep contaminants out of the enclosure.
However, if the ambient air temperature is close to or above the required enclosure air temperature, then an enclosure air conditioner will be required. Air conditioners also provide additional benefits such as controlling humidity inside the enclosure.
2. Ignoring humidity and corrosion
Some electrical and electronic components are sensitive to humidity and must be kept dry to prevent electrical shorts which can cause equipment failure. In high humidity environments, an enclosure air conditioner works to eliminate humidity by condensing it out of the air.
Some enclosure air conditioning systems provide innovative ways to deal with the resulting moisture, including a condensate evaporator that uses the heat from the refrigeration cycle, which prevents water drips and puddles on the surrounding floor.
In colder locations, water will condense on equipment and surfaces when ambient temperatures drop below the dew point. In these situations, some enclosure air conditioners can be equipped with heating elements to keep internal temperatures above the dew point.
In addition, some industrial enclosures are situated in environments with corrosive fumes or liquids, such as in marine areas or water treatment plants, with chlorine and other disinfectant wash-downs. In these locations, the enclosure must be sealed so that no dust, dirt, or pollutants are able to contaminate surfaces. However, corrosive liquids, vapors and dust can negatively affect the outer surfaces of the enclosure and the cooling system.
To reduce rusting and corrosion, the cooling equipment can be specified with a stainless steel or aluminum housing. Additionally, anti-corrosive coatings can be applied to condenser coils and copper tubing.
3. Specifying incorrect cooling capacity
Once the NEMA type for the enclosure is specified and the type of cooling system has been selected, it’s important to correctly determine the required enclosure cooling capacity. If the cooling system is not sized to maintain cabinet temperatures within the manufacturer’s specified operating range, the components will lose efficiency, require additional unplanned maintenance, and possibly even fail.
The cooling capacity must equal or exceed the enclosure heat load, which consists of the total heat dissipated from all components in the enclosure. The losses generated by each component can be estimated from information found in the manufacturer’s catalog by subtracting the component’s efficiency from 1 and multiplying the result by the power consumed by the device.
Heat transferred through the enclosure walls as a result of the ambient temperature, local heat sources, and solar radiation must also be included in the total heat load. The most effective method to account for all these factors in determining the cooling capacity required for the enclosure cooling system is to use an online enclosure temperature management calculator.
Caution must be taken to not select an air conditioner that is significantly oversized. A unit with too much cooling capacity will cycle too often and may not maintain the desired enclosure air temperature.
To avoid making these or other mistakes in an industrial cabinet cooling system, contact the experts at Thermal Edge.