Proper enclosure climate control is a delicate balancing act.

With increased component density comes increased heat. That’s an acceptable “given” whenever components are packed into enclosures of any size or configuration. Another “given” is that these electronic components don’t do well in extreme heat. Combined, they define one of the most serious concerns in today’s industrial installation: climate control. However, when buying enclosures many people don’t think about climate control until it’s too late, or they don’t really know how to efficiently analyze what they need.

Why do electronic components fail? That’s a fair question that should be answered before embarking on an installation plan. Research done by the Air Force dating back to the 1980s, referring to land-based electronics, and studies done by the Uptime Institute and the U.S. EPA, underline what, to some, may be considered common sense. The most likely contributors to electronic failures, according to these reports, are:

• 57 percent because of heat
• 21 percent because of vibration.
• 16 percent because of humidity.
• 6 percent because of dust.

Accordingly, 73 percent of failures can be traced to heat and humidity. And, dust or dirt collecting on these units can reduce the ability of the equipment to cool itself (dissipate heat) and, thus, contribute to failure. Ultimately, nearly 80 percent of all failures can be traced to a climate control concern.

One of the obvious ways to spot a deficiency is a system failure. Unfortunately, this is also the worst way of finding out that you don’t have what you need. A system crash can be measured in thousands of dollars lost per minute, and downtime is not good for the bottom line.

Questions to Ask to Prevent Failures

Consider your application:

• What is the maximum ambient temperature you can expect (ever)?
• What is the desired internal temperature? Very often it doesn’t need to be as cool as you might think (too cool can lead to condensation issues).
• What is the size of the enclosure. How much space has to be cooled?
• Where will the location be? Indoors? Outdoors where you have to account for “solar loading” heat from the sun?
• What is the required NEMA rating?
• What will be the level of heat given off by various components? (Designers can have difficulty coming up with this one.)
• What are the power requirements for each of the various components?

For every 18°F (10°C) you run a unit above the optimal temperature recommended for that component, you can reduce the life of that electronic component by half or more. In the warranty, OEM suppliers often basically say, “all bets are off,” if components are run at 100°F or higher - ever. Many list the optimal temp to be 95°F.

The most efficient temperature controls revolve around a unit’s incoming air supply and the airflow around each component. The more airflow (volume) the more heat it can dissipate. As airflow increases, the temperature of that moving air doesn’t have to be as cool. Increasing airflow can reduce dependence upon cooling systems and that can reduce energy costs.

The best way to maximize the efficiency of the cool air is to move it directly to the electronic components. Air that passes between an enclosure’s frame and racks or rails does little good when it comes to reducing heat.

What Do You Need, and Where?

There’s always a question of, “When do I use fans, when do I need air conditioning?”Fans don’t really cool anything below the temperature of their surroundings; they just move the air around at whatever temperature it is when the fan starts. For this reason, you should use fans when the outside air is cooler and drier than the air inside the enclosure.

Fans should create a positive pressure to push air through the space - pulling air in at the bottom and pushing it out at the top. Putting a fan at the top blowing down will “suck” air in from the top and move it to the bottom, but it can also suck in dirt and dust. Additionally, basic physics dictates that warm air rises, so if a fan just moves air at its current temperature, moving warm air from the top won’t have the same cooling effect as moving cooler air from floor area - even though the temperature may be only slightly different.

Additional Options

Air-to-Air Heat Exchange. In this closed loop system, inside air and outside air circulate independent of one another. The two swap temperatures within the system. Benefits include:

• Only air moves around and doesn’t bring anything into the system from outside, which means there is no need for filters.
• Easy maintenance.
• Suitability for conditions where outside air is always cooler than inside the enclosure, so heat will be dissipated easily.

Air-to-Water Heat Exchange. This is a choice when outside temperature can, or will, be warmer than inside temperature. Cool water is used to cool moving air. These popular climate control products are available in both roof- and wall-mounted units.True air conditioners, in most cases, are set to come on at 95°F (35°C). Thermostats are usually set to cool down about 5°F, so when set at 95°F (35°C) they cool to 90°F (32°C). When set properly, the system will run less, run a little warmer, reduce electric costs and solve many condensation problems. (However, units set too cool may actually increase condensation issues).

As electronic component technology continues to evolve, controls and data storage components get smaller. At the same time, these new components are generating more heat and often requiring more electrical power. As these component densities expand, selecting the most efficient climate control products becomes even more of a balancing act, with the risk of system failure on one side and potential for significant cost savings on the other. PC