Keeping Controls Cool

Another summer is upon us, and as shop floors heat up on particularly hot afternoons, some controls may overheat and shut down production machines. If your shop is susceptible to such interruptions, you may be interested in a cooling system for electronic enclosures called Cabinet Cooler, made by Exair Corp. (Cincinnati, Ohio). The system is compact (about the size of a can of shaving gel) and is powered entirely by clean, dry, compressed air at 80 to 100 psi.

The diagram at right shows how the Cabinet Cooler works. Compressed air enters the vortex tube-powered Cabinet Cooler and is converted into two streams, one hot and one cold. Hot air from the vortex tube is muffled and vented through the vortex tube exhaust. The cold air is discharged into the control enclosure through the cold air distribution kit. The kit includes tubing that permits the cold air to be directed to vulnerable components, such as circuit boards. The cold air displaces the hot air within the enclosure; it rises and is vented to the atmosphere through the cabinet air exhaust at a slight positive pressure. Thus, the control cabinet is both cooled and purged with cool, clean air. Ambient air is never allowed to enter the control panel.

Exair offers eight Cabinet Cooler models each for NEMA 12, NEMA 4 and NEMA 4X enclosures, with cooling capacities ranging from 550 to 2,000 btu/hour. The company’s Web site, www.exair.com, provides a sizing guide to help you determine the heat load to which your control panel is subjected and the appropriate cooler model for your application. Alternately, you can provide some information about your particular application on the company’s online Cabinet Cooler Sizing Guide Form and get its model recommendation immediately. Prices are also provided.

The unit mounts to the enclosure through a drilled hole or electrical knockout. NEMA 12 coolers may be mounted on the top or side of the panel. NEMA 4 and 4X coolers must be mounted on top.

Cooler systems include a 5 micron automatic draining water and dirt filter, which protects the enclosure’s electronics from water in the compressed air line. The company also recommends a coalescing (oil removal) filter for situations where oil may also be present in the compressed air.

The units can be equipped with a thermostat to maintain a desired temperature, say 95° F, within the enclosure. A thermoswitch actuates a solenoid valve, which turns on the compressed air only as needed to minimize operating costs. The thermostat setting allows the enclosure temperature to stabilize well below the 104° F limit of the electronic components inside without wasting air to achieve needlessly lower temperatures. The unit may not operate at all in the mornings, but as the day heats up, the thermostat turns the cooler on and off as required to maintain the present inside temperature.

Another benefit is that because the enclosure is sealed with the Cabinet Cooler system, the inside is kept free of dirt and dust. Applications for Cabinet Coolers include programmable logic controllers, NC/CNC, line control cabinets, motor control centers, relay panels, modular control centers, computer cabinets and other electronic enclosures.