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How to Properly Ventilate Racks
There are a couple of fundamentals to remember when you’re planning to ventilate a cabinet, closet, video projector enclosure, etc.
Check Air Movement
In a situation where air can move freely with little or no resistance, multiple fans should either all be used for intake of fresh air or exhaust of hot air. If air can move freely, ventilation probably isn’t much of a problem.
This is called placing the fans “in parallel.” In the real world, you’d probably use all of the fans to exhaust hot air high and out the rear of the cabinet, but they would work just as well pushing fresh air in low in the front of the cabinet.
In that case, the fans would be more visible, of course, which would have a major influence in the “exhaust vs. intake” decision.
If the enclosure presents a high resistance to air flow because of small openings, multiple shelves, etc., it’s better to use half the fans as intake and the other half to exhaust. This is called placing fans “in series.”
In the field, you’ll probably never see an enclosure that allows really free-moving air, or one that’s completely restrictive (after the installation is complete). Most fall somewhere in between, usually more towards the restrictive side.
Place Fans Where Enclosures Permit
Appearance is important in custom work, meaning the ventilation scheme is probably going to be a compromise between the ideal way and the practical way. Clients might not be pleased with grilles and fans where they’d work best, but they also won’t be happy with equipment that performs poorly and frequently breaks due to overheating.
For more information, download one or more of our white papers dealing with specific installations (freestanding cabinets, enclosed video projectors, racks in closets, etc.) from the downloads page at activethermal.com.
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Article Topics
News · Installation · Active Thermal Management · Rack-mount Installations ·9 Comments (displayed in order by date/time)
How to properly get information:
Not by visiting Ce pro website.
Another pointless article. At least attempt to answer the questions you lead with…
You title an article with leading questions and then don’t ever refer to them or even attempt to discuss them in the actual article? Very poor writing, and an obvious ploy to get people to link clicks.
Is it really that hard to get solid content? I’d rather read nothing for a day than more of these pointless not-well-disguised-link bait articles….
@ Annoyed Again:
Don’t give up the ship… Next month, rumor has it that there will be an entire article on how to, “speed balance,” rack wheels for optimum performance once the fan assembly is installed.
Not sure what I just read but it doesn’t answer much? A Google search is much more informative and doesn’t waste as much time as this article did!
The second question is answered fully in the article but the titles first/leading question never gets answered.
“Should rack fans blow in cool air or push out hot air?”
What is the answer? Seems like both solutions are fine as long as the desired rack temp can be met.
I have had racks with fans on the top and intake vents at the bottom. I have had racks with no tops or back doors and no fans. I have had racks with fans in the front at the bottom with open tops. I have had AC pumped into the control room to cool components.
Reading the responses to this article seems to indicate that very few people actually care if the installed equipment performs to spec, or if it outlasts the warranty. This is not a small matter for installers and designers who not only want to design an intelligent and well planned system, but value it’s surivability in what can be an unforgiving environement. It is not unworthy of CE Pro to suggest this forum mirroring the questions of some as to the best way to ventilate and cool equipment, and it is deserving of some respect and thought. Outright dismissal is not warranted, and rejecting the reality of heat induced failure is not wise at all.
This is a very good white paper on thermal management:
Are you guys for real? If how to properly ventilate a rack, (and its physical located enclosure), is news or informative to this site, then you’re all doomed.
If you’re not sure about what you’re doing, call the manufacturer-
I’m too busy trying to install my Pioneer 8000 car stereo head unit into my 1977 Ford Pinto’s dash without carving out more plastic than I have to go any further…
Never mind, I just called Crutchfield.
The answer to this question is not at all as simple as stated.
When racks of equipment are first laid out, or designed for an application, it is mandatory to consider heat distribution and loading before the equipment goes in. Waiting to attempt to fix a ventilation error until after it shows up is the mark of an amatuer, not a professional. The idea or premise of whether to blow air in, or exhaust it out is meaningless unless you know the route that the ventilating air will move and how much the temperature rise will be in a particular area. Blowing hot air around in a cabinet will not cool equipment, neither will re-ciculating hot air in an enclosed bay or closet.
The time to determine how to best cool or ventilate equipment starts at the point when you decide which equipment will be used and the heat load of each device. Then you need to know what the ambient air flow will be around the instaled rack and what available HVAC is available to deal with heat transfer.
While there are details to consider, such as, it is easier to exhaust hot air than to move it around with cool air blown in, first look at the principles of you own HVAC. Note that it employs both dynamics: outlets for cool dense air, and extraction of heated rarefied air. Take a lesson from existing technologies to determine what needs to be done in your own case and plan before building!