I am unhappy with the amount of heat build up in my equipment rack and am thinking of adding 2 12 volt cooling fans (1 lower blowing in and 1 upper blowing out) one thing that concerns me is the amount of dust I think that this will bring into the rack. Years ago when working for an auto dealer we had computers with fans that had filters (a filter and a black plastic piece that snapped onto the fan) has anyone used anything like this? Also can anyone recommend one kind of fan over another. Thanks

Make the 2 fans working in a Push-Pull manner. One fan pushes cool air inside the rack, the other pulls hot air out of the rack. Use the same air filter found in wondow's air conditioners, mounted over the one fan that pushes cool air inside the rack, the other fan doesn't need a filter, because it pushes hot air out of the unit.
Mister. T

Not to cause problems with other people, but I think you should do it a different way.

Use both fans at the bottom of the rack to push cold air into the rack. The possitive pressure build up in the chamber will cause air to be pushed out of the chamber. That will move twice as much air as using one at the top and one at the bottom.
Or use just one fan at the bottom and move as much air as one at the top and bottom. This is basic physics. Think of it like a drinking straw. Fill it with water. Blow into the straw. Where does the water go? Out. If you were pumping air/water through the straw at 1 liter per minute and you were also drawing air/water out of the straw at 1 liter per minute, then how much air/water is exiting the straw. 1 liter. Now pump 2 liters of air/water into the straw. How much water is comming out? Two liters.
Why put the fans at the bottom of the compartment? Simple. As air heats up it expands. Blowing cold air into the compartment causes a higher volume of air to exit. Example:
say your compartment holds 10 liters. also pretend that when air heats up it takes up twice the space. Now blow 1 liter of cold air into the space. It heats up, now taking up two liters of space. This causes two liters to be pushed out. 1 liter in, 2 liters out. Conversly, if the fans wer at the top, drawing out hot air:

draw out 1 liter of hot air, draw in .5 liters of cold air.

Clearly the answer is to use how ever many fans you want, all placed at the bottom of the chamber.

RWI,

Take a look through some computer sites, especially those that cater to the customizing crowd. I'm embedding some sample links from the Directron site, but there are many others. You will find a large variety of fans and filters in several sizes. On the same sites, you should also be able to find comparison studies and statistics showing how much air each type of fan moves and how much noise each produces. If you really want to get into detail, you can even find manual or automatic temperature monitors and fan speed controls.

In my "hobby" PC, I currently have five additional (80mm) cooling fans. They are wired to a control center (capable of controlling up to eight fans) that is also attached to multiple thermal monitors placed throughout the case. The control center is programmed to turn on first one fan, then another, etc. as the temperature rises. But wait, there's more...

The type of fan I chose also has an individual, automatic temperature monitor and speed control. So when the control center first turns it on, it rotates at a slow and quieter speed. But as the temperature rises, it will automatically increase its own rotation speed!

Conversly, as the fans do their work and the case cools, each fan individually slows down and the control center turns any unneeded ones back off. This keeps the noise to the minimum possible, and it's all automatic. It took me a few hours to find the quietest balance between more fans at slower speeds and fewer fans at higher speeds, but ever since it has been simply "set it and forget it."

This is the same solution I plan to implement in my rack-mounted HTPC, and in the component cabinet I eventually plan to hide my HT components in (if I ever can afford it).

BTW, I endorse Craig's recommendation above (all fans pushing ambient air into the rack from the bottom, and only a vent at the top to let the warmer air escape). This is the same method we use at work to cool all our enclosed computer cabinets. If you use filters in front of the intakes, you should not have much trouble with dust.

Hope this helps! -Bruce

This message was edited by Bruce Burson on 03/04/03 10:17.

Well I am glad I asked, I really would have though that the push/pull set up would have been best. I am thinking of cutting a strip off of the top of the back panel for the vent, if so how many inch's should I cut or does someone have another idea?

If you decide to use the push-pull system, make sure the fan that pushes cool air into the rack is mounted at the bottom, and the fan that pulls hot air from the rack on top, because as you know heat rises to the top. As far as the filter, it doesn,t have to be that big. The important thing is to make it easy to clean when you have to.
Mister. T

Ran into these guys at CEDIA. Looked pretty ...."cool".
[Link: activethermal.com]


Dave

If you have a few bucks to spend. Get this. It will do EVERYTHING you need it to and all you need do is plug it in. How much does it cost? I really dont know but when I redo my basement I'm getting one. I mean what CAN it cost really? 100 bucks? 200?

[Link: elanhomesystems.com]

DOH! I just called them. 300 bucks. I would have paid 250 even. hehe. But 300 seem alot.

Don't forget to plug all 'holes' that may exist in your current rack, otherwise all your effort is wasted.

If it's not a sealed system, any fan will not work as you want.