It may seem an odd time to think about cooling electrical enclosures, but now is the time to plan out a strategy for dealing with summer’s heat. A small amount of planning now will allow you to have a game plan in place to prevent equipment failure during the hot, humid conditions that summer brings and keep your plant production running at a level to meet your goals.
Cabinet coolers use a vortex tube to create a low cost, reliable way to cool and purge electronic control panels or small enclosures. A vortex tube produces cold air from compressed air without any moving parts, which makes them ideal to combat heat, dirt, dust and remote locations. Figure 1 briefly explains how a vortex tube creates cold air from a source of room temperature compressed air.
Stand-alone vortex tubes are used to cool heat welds, ultrasonic horns, glue beads, brazing operations and a variety of other spot-cooling applications. Vortex tubes with the aim of cooling electronic enclosures are typically installed inside a housing assembly that meets the NEMA integrity of the cabinet. The housing assembly has a mounting fixture to attach to the cabinet; a muffler; a cold-air exhaust and a fixed hot-air exhaust. The fixed hot-air exhaust is essential to optimize performance and is designed for maximum refrigeration. A variety of vortex tube cabinet coolers are on the market, but all work on the same principle.
Myth 1: Vortex-Based Cabinet Coolers Waste Compressed Air
While I was attending a compressed air conference once, the presenter listed areas where he thought compressed air should not be used. One of his bullet points was cooling electrical or control cabinets. The presenter went on to mention that vortex-tube-based enclosure coolers tend to waste air and said that there are many other ways to cool enclosures more efficiently.
Saying all vortex-based enclosure coolers waste compressed air is like saying all automobiles waste gas. While certain automobiles can waste gas, it is not a waste if the right automobile is chosen for the occasion. For instance, one could use a 14 mpg, eight-cylinder Camaro to drive only themselves with no luggage from Ohio to Florida and burn through several tanks of fuel. That would be a waste of gas because they are using a large-displacement motor and full-size car that is altogether too large for the application. Instead, if they were to ride a medium-displacement motorcycle, which gets at least 55 mpg, they would use a fraction of the fuel compared to the “muscle car.” Bottom line: Using the optimized tool to get the job done does not waste; it utilizes all resources effectively and efficiently.
Comparatively, installing a 5,600 BTU/hr vortex-based enclosure cooler without a thermostat to cool a shoebox-sized enclosure with a single sensor that generates minimal heat, wastes compressed air. This would be like that Camaro hauling one person in the earlier analogy. While the cooler gets the job done, the efficiency is simply not there.
Properly sizing the cooler for the electronic heat load is an integral part of optimizing compressed air cooling. Once the appropriate size cooler is determined, using a thermostat control in conjunction with the cooler will maximize system efficiency. This means the cabinet cooler will only utilize compressed air when the enclosure needs to be cooled. More often than not, enclosures need cooling during those critical hours when production is at a peak and the temperatures outside or inside the facility are also peaking. By correctly identifying which type and size cabinet cooler fits the given application, thousands of dollars in equipment damage and downtime can be saved, and compressed air can be utilized where it can exceed over other methods. Figure 2 shows the typical components that are contained within an intelligent compressed air cabinet cooler system with thermostat and electric solenoid control.
Myth 2: Other Options Are Better Than Vortex-Tube-Based Coolers
At the same conference presentation, the speaker suggested there are better options to cool electrical cabinets such as refrigerant-based air conditioners, fans and heat exchangers. As noted, there is a time and place for almost anything. Some of the places cabinet coolers excel are areas that are remote, hot, dirty, dusty or corrosive. In other words, they are best suited for a multitude of industrial environments.
These industrial environments are where the maintenance required to keep a refrigerant-based air conditioner operating optimally costs thousands of dollars in replacement parts and labor hours every year. Troubleshooting guides for these air-conditioning units require a strong knowledge of how they work, not to mention the litany of items that need to be replaced or cleaned: evaporator coils, motors, wheels, compressors, condensers or capacitors. Many times, in addition to those mechanical and electrical components, a regulated coolant may be present in the system that can be a hazard in the event of a leak. Typically, this replacement and maintenance must be done by a licensed contractor. These maintenance costs must be considered as operational costs of the cooling unit when looking at the costs of owning an air-conditioning unit vs. a compressed-air-driven enclosure cooler.
Vortex-tube cabinet coolers offer a number of advantages over refrigerant-based air conditioning or fans. First, a compressed-air-driven cabinet cooler has virtually no moving parts to wear out or replace. This lack of moving parts, filters and coils means that the environment will not have an operational impact on the cabinet cooler systems.
Second, cabinet coolers can create a positive pressure inside a sealed enclosure. This positive pressure can prevent dust from entering that cabinet. Dust inside of electrical cabinets will cover heat sinks, chip-sets and internal fan blades to prevent air movement. Dust also can create a layer of insulation on hot parts that will prevent proper heat transfer.
Third, cabinet coolers prevent condensation and liquid from entering the cabinet. A NEMA 4-rated cabinet cooler will prevent the intrusion of water in a wash-down environment. When the air supplied to a cabinet cooler is clean and dry, there will be very low humidity in the cabinet, which will prevent condensation.
Likewise, when comparing a vortex-tube-based cooler to a fan or a heat exchanger, the vortex-based cooler will be pushing dust out of the enclosure. By contrast, the fan could be pulling dust into the enclosure through a filter, which can clog. The dust will eventually cause a failure. Additionally, the dust pulled in by the fan will restrict the volume of air moved by the fan, lowering the heat transfer from the heat sinks or the circuitry. If the ambient environment is a hot or corrosive environment, then the fans and heat exchangers are simply moving hot air from outside the enclosure into the already heated internals. Both of these units rely on cool ambient environments that are generally clean as well as climate controlled.
Cabinet coolers utilize vortex-tube technology to cool electrical enclosures via compressed air. Cooling via vortex tubes can provide a vital role that justifies the utilization of compressed air. The key components to using cabinet coolers efficiently are to size the cabinet cooler appropriately and to employ a thermostat so that only the necessary amount of compressed air is used to cool the enclosure. Fans and air-conditioners are not well suited for some industrial or remote environments. Air conditioners may require costly maintenance. Fans can bring dust into the cabinet, which limits the fan’s cooling capacity. Vortex-tube-based cabinet coolers will work efficiently with little maintenance in industrial environments because they do not have any moving parts, create positive cabinet pressure and prevent water intrusion.
Fans and air conditioners have their place to cool in climate-controlled or relatively clean, cool environments, but the mechanical components may not be able to withstand dusty, hot or remote parts of the factory or process. When used correctly, vortex-based cabinet coolers do not waste compressed air. They utilize it efficiently to preserve critical electronics when they are most needed.