The first fundamental:

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 to exhaust hot air. (If air can really move that freely, ventilation probably isn’t much of a problem, but we’ll continue with the lesson.) We say that these fans are “in parallel”.

In the real world, you’d probably use them all to exhaust hot air high and in the rear of the cabinet, but they would work just as well pushing fresh air in low in the front of the cabinet. (They’d be more visible, of course, which would have a major influence in the “exhaust vs. intake” decision.)

If, however, 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. These fans are “in series”.

Getting back to the real world, 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.

The second fundamental:

You’ll put the fans where the enclosure lets you. Free-flowing or restricted, appearance is important in custom work, meaning that the ventilation scheme is probably going to be a compromise between the ideal way and the practical way. You might not be happy with grilles and fans where they’d work best, but you certainly wouldn’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 Technical Info page at

As always, don’t hesitate to call (661-294-7999) or email for help.