Hot stuff for cooling down

DN Staff

November 18, 2002

6 Min Read
Hot stuff for cooling down

Here's a triplet of recent enclosure developments that may come in handy in keeping your cabinet of electronics from losing its cool.

Seal's the deal. From polycarbonate-enclosure and precision plastic-component maker Fibox (Glen Burnie, MD) comes a basic enclosure vent, which features a molded-in-place gasket. This arrangement not only ensures a tight seal but eliminates the separate gasket that had to be installed before, making for easier, quicker assembly. The vent comes with the same footprint and mounting-hole pattern as previous devices for drop-in replacement.

The single-piece ventilator is injection-molded polycarbonate. The die on the two-component injection-molding machine that forms the ventilator opens and partially ejects the part. It then rotates the newly formed vent housing to the thermoplastic elastomer (TPE) gasket material injector. The housing itself serves as the mold for the gasket, providing for a better overall seal. Compared to the constancy and tolerances possible with the separate gasket, "The integral design is more stable and dimensionally critical," says David Crooks, Fibox general manager.

The new gasket cuts the cost of robotically installing the gasket, is less susceptible to assembly errors, and has tighter tolerances. "Tighter seals provide for higher IP and NEMA ratings," Crooks notes. The vents are rated at IP44, preventing intrusion by objects down to 1-mm diameter and water spray.

For forced ventilation, a compatible polycarbonate fan holder mounts to the inside of the cabinet under the ventilator housing. A pair of fans normally would be used, one to draw air in and the other to exhaust it. The basic vents also are employed in pairs on opposite sides for cross ventilation.

The edge of the Fibox polycarbonate ventilator housing (bottom) also serves as the mold for the TPE gasket.

Cool module. For engineers who have to stuff more power-dense electronic systems into enclosures, more efficient use of air conditioning, and ease of its installation and use are always cool news. Take, for instance, enclosure manufacturer Rittal's (Springfield, OH) TopTherm line of air conditioners. Not only is thermal efficiency a given, but design engineers made optimization and minimizing the number of mechanical form factors across the line a priority to lower costs. Modularity reduces the number of spares required (such as needing only four types of air filters), and is easier to assemble and service, resulting in less cost to the customer and manufacturer alike.

Some features cut heat generation and cost. One of the best, according to Steve Pucciani, product manager, Thermal Management, is the three-phase units with dual voltage (400/600V, 50/60 Hz) capability. This design eliminates extra heat-generating transformers and wiring-and the same units could be sold in both Europe and the U.S., easing price pressure.

Mounted air conditioners keep internal electronics in a cooler-than ambient air stream. Large separation of the internal cooling airflow's inlet and exhaust in Rittal's wall-mounted TopTherm units eliminates need for extra air-routing baffles (left). Patented internal air routing for roof-mounted TopTherms features a center air intake and up to four corner outlets and allows for direct ducted cooling of componenets.

Two controller options, Basic and Comfort, tailor performance to needs. The Basic provides temperature control and the Comfort version not only governs temperature but monitors systems through microprocessor control. "Key technologies are digital control and diagnostic capability, and networking," says Pucciani. He notes, "The Comfort controller has routines that can tie with a laptop to do diagnostics and check for component faults, and network with other controllers." A networking example could see several air conditioners cooling the same large cabinet integrating their operation. For example, all might increase their output to aid one undergoing greater localized heat load or suffering from reduced output due to a problem. The future will see air conditioners linked to PLCs to furnish air conditioner data for overall system health monitoring and history recording, adds Pucciani.

On Rittal's "roof-mounted" (i.e., atop an enclosure) TopTherm air conditioners, the external flow cooling the compressor enters through a front grill and exhausts through the sides and rear and optionally through the top. This allows for freedom in placing cabinets next to one another without exhaust interference. Wall-mounted units, placed on the side of an enclosure, can be completely external to the cooled volume, or partially or completely internally mounted, depending on space availability.

Hot software and analysis. What's the best way to keep excessive heat from building up in network equipment? Most IT managers say keeping the room containing the enclosures that house the equipment cool, according Brian Mordick, product manager at enclosure maker Hoffman (Anoka, MN). He notes the problem is that this solution may be energy inefficient and lead to condensation when warm air hits cold surfaces. Add to that the potential for corrosion if dust is present, Mordick adds.

He says to find the best solution for heat buildup under various conditions, cabinet design engineers at Hoffman can use simulation software backed up with lab tests to determine if full or limited ventilation, and using fans, air conditioners, or chillers are needed. The question, Mordick says, is not,

"How do I keep the network equipment cool, but how do I feed the equipment cool, dry air and help to dissipate the heated air it generates? Thus they eliminate hot spots that cause failure and network shutdown."

Increasing the cabinet perforations is not always the best strategy. As the graph shows, the enclosure with a perforated front door and rear door partially perforated at the bottom, with a fan on (Case 6), shows the best thermal air conditioning.

"It's not just perforate and add fans," notes Trent Jones, engineering manager for Hoffman's Datacom Products, but rather to channel cool air to the equipment and provide a path for the heated air to leave.

For simpler, straightforward applications with light heat loads, for example, the company offers its Network datacom cabinet as an economical solution. This unit is perforated on the lower back door and base with roof fans. If flexibility is needed for higher heat and complex internal layouts, its Proline is a more modular design and comes with accessories. Baffles and blocker plates, for instance, can be used to deal with specific heat locations and airflow patterns in the cabinet and room.

The company offers thermal analysis services to aid in customizing Proline to customer needs. "Depending on the detail level the customer is looking for, 70-80% don't need a complex thermal analysis but close consultation," says Jones. "But if, for instance, specific BTUs in certain locations are desired, then our applications engineers would do analysis because the software is complex," he notes.

Mordick adds, "Another software option is Hoffman's Thermal Selection and Sizing software available on It can be downloaded for free to help engineers begin determining their needs."

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