Equipment Ventilation - Blow in?? Push out?? - AVS Forum
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post #1 of 24 Old 12-13-2010, 04:07 PM - Thread Starter
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Equipment Ventilation - Blow in?? Push out??
Author: Frank Federman, Active Thermal Management


We're frequently (OK, sometimes) asked "Is it better to push cool air into a cabinet or pull the hot air out?" Other FAQ's ask whether all (there's usually more than one) fans should push or pull, or should you use half for each function.

There are a few fundamentals to remember when you're planning to ventilate a cabinet, closet, video projector enclosure, etc.

Read the complete article at HomeToys.com
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post #2 of 24 Old 12-13-2010, 07:25 PM
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I've tested both push and pull configurations on my media cabinet.

Temperatures were about the same with each setup, but the pull configuration resulted in a lot less dust inside the cabinet. Just something to think about...

David
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post #3 of 24 Old 12-13-2010, 09:23 PM
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It is dependant on the design of the cabinet, we computer guys know quite a lot about fans, I would say if the equipment is clustered inside 4 wood walls I would use exhaust to get rid of the dissipated heat and let the equipment use its natural ability for cooling (so it dumps more heat into the ambient and the fan takes it out) if its a more open space I really don't see the necessity of a fan but if you want one I would point to the problematic area and draw cool air.

AV equipment is designed to be in some sort of clustered area if you think the one you have its a bit small or air doesn't circulate very easily measure the volume of the space and buy a fan that exceeds the volume in its rating (CFM = Cubic Feet per Minute)
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post #4 of 24 Old 12-14-2010, 02:07 AM
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post #5 of 24 Old 12-14-2010, 08:39 AM
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That's a terrible article that just links to a bunch of other stuff on that site. You should do better.
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post #6 of 24 Old 12-14-2010, 09:00 AM
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Regardless of which route is chosen, it'd be nice to have a filter of some sort on the intake side to reduce the amount of dust that gets sucked in.

BMW: Happiness is the next curve.
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post #7 of 24 Old 12-14-2010, 09:51 AM
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Quote:
Originally Posted by bmwracer View Post

Regardless of which route is chosen, it'd be nice to have a filter of some sort on the intake side to reduce the amount of dust that gets sucked in.


I agree, IMO, push filtered air in and create positive pressure to keep dust out. Just make sure you have some type of airflow or temp monitoring in case you get lazy or forget to keep them clean.

I want my HDM
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post #8 of 24 Old 12-14-2010, 10:59 AM
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Servers have employed the pull method to reduce the amount of stagnant around the internal parts for many years. Typically the front of the racks have cool air and the backs are for exhaust (front facing front and back to back row configuration). If you have filtered air running over components that should be sufficent as long as the rest of the area is clean. Just remember that filtered air is not dust free, just a lower amount. Keeping the area around the components is just as/more important...

If you must use a filter (makes the fans work harder to pull the same amount of air) put it on the intake side.

Check out my build - The Den
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post #9 of 24 Old 12-14-2010, 11:48 AM
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I use the rack mounted fan panel that is pictured in the article. It is mounted at the bottom front of my 6' cabinet. I also have a thermostatically controlled fan at the top rear of the cabinet that turns on at 87 degrees and blow air out of the cabinet. The thermostat rarely kicks in so the fan panel must me pretty efficient at keeping a full stack of components including multiple amps cool.

You know, a guy could get into this HT thing and drop a couple of bucks!
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post #10 of 24 Old 12-14-2010, 06:14 PM
 
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I use two silent computer fans, wired in parallel to a multi-voltage DC wall wart, set to blow into the entertainment center. They are on the bottom, blowing the cool air up into the center.

This is because there is no other place to effectively hide the fans.
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post #11 of 24 Old 12-14-2010, 07:44 PM
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intake low, exhaust high.
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post #12 of 24 Old 12-14-2010, 07:48 PM
 
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Bingo
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post #13 of 24 Old 12-15-2010, 04:44 AM
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A push pull design is the surest way, but can't always be achieved in this situation, at the very least, having a rear fan pulling hot air out the back from the highest possible placement is best, even if its firing air out the top of the stand/rack PC case fans are meant to be used vertically and move the most air and have the least motor resistance in that fashion.

I recommend Scythe 120mm fans they move about 30+ CFM. I have 7 of them in my gaming tower and under usage I picked up a total SPL around 25 +/- dB A weighted. single one is 10-15dB (a weighted) noise, two of these would be more sufficient than a single fan of higher cfm and noise (not gonna lay out the math here you can look that up yourself)

I would say it would be easier to place a few 3-4in holes in the bottom of the stand where the source of heat is greatest or have a ventilated shelf if its rack system. This way cool air will be sucked in like a vacuum. If you stand has the clearance having a bottom mount fan is the best option, just remember the stand's legs have to allow enough air clearance for this to work. You will otherwise burn out the fan's coil and start a motor fire.


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post #14 of 24 Old 12-15-2010, 04:34 PM
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Quote:
Originally Posted by punahou80 View Post

That's a terrible article that just links to a bunch of other stuff on that site. You should do better.

Agreed. First you click here, then you click again to go to the site. Then you read the "article" (more accurately called a blurb) which leads you to click on more foolishness I refused to click again so I dunno how good the next site/link is going to be but after this I wasted 5 mins of my time and ended up not really learning anything at all. I learned more from the AVS ppl posting on this very thread!

The funny part is it says "don't hesistate to call" at the bottom and provides a phone number. Given the overall discontent one would come to after reading this I wonder if they are not being spammed with calls trying to get more information? LOL.
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post #15 of 24 Old 12-16-2010, 06:30 AM
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I guess the real question is, did this article Suck? or did it blow?
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post #16 of 24 Old 12-16-2010, 08:27 AM
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Quote:
Originally Posted by ES_Revenge View Post

The funny part is it says "don't hesistate to call" at the bottom and provides a phone number. Given the overall discontent one would come to after reading this I wonder if they are not being spammed with calls trying to get more information? LOL.

That's because this was nothing but a blog post from a company selling cooling products. Of course they want you to call.
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post #17 of 24 Old 12-16-2010, 07:04 PM
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I know it isn't exactly pretty, but I use landscape fabric (doubled up) as a filter on the intake side of one of my mechanics' computers in our shop. Works great captures a ton of dust and is cheap to simply replace once it is dirty.
Just my $0.02
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post #18 of 24 Old 12-17-2010, 03:12 AM
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Quote:
Originally Posted by stickboy2k View Post

I guess the real question is, did this article Suck? or did it blow?

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post #19 of 24 Old 12-18-2010, 12:02 PM
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my small cab/console that holds large denon avr, dvd, cd, and cable box has a fan that runs 24/7, yep, all the time. not exactly "eco" friendly but i opted to simplify so no fancy temp controllers, no on/off temp switches, has been running 24/7 since about 2003, but one day i might build myself a nifty PWM fan controller, etc. its a 3" 120vac fan (used in military grade electronic gear) that if given full 120v the thing moves a lot of air and is fairly noisy, so i slowed it down with two power resistors. the fan speed is low and basically whisper quiet, but it moves air. fan is mounted inside the cab in upper-left most corner and it pushes air out. the cab itself has doors on the front which do not close air tight so the fan pulls air from the front doors and then up and out. when the avr is up on power the air coming out does get warmer.

the thing to remember is that is is ok for devices to run warm/hot as long as the temp does not exceed its operating specs, etc . having just a low cfm fan to help pull cool air over the devices is a good thing, etc. too much cfm is not good as that just makes noise and will pull in more dirt, etc.

another reason not discussed is fan specs. push/pull designs mean the fan(s) will have different operating environment. as example, push-in means the fans will be operating at almost the temp of "in" air, while a pull-out means the fans will be operating at almost the temp of the hot air being pulled out, etc. fan bearing life (MTBF) and electrical efficiency may be significantly different for the two designs, etc. and to note, turning fans on/off is what kills them.

irfan has it correct, you definitely want the exit up high because heat rises. this is why placing fan up high and moving hot out makes more sense because most cabs are not sealed, there is essentially no well defined "intake". holes in the cab for wires, space around doors, etc, serve as the "intake". if you push/pull air into the cab then the air flow will not be as ideal since now you are essentially trying to move hot rising air against its natural flow pattern (up), etc. and caution, having a big gaping hole in the rear on one side with fan up high on the other side may not be doing anything for your device, the air simply enters the back on one side and goes out the other, be sure you create a flow path that allows cool air to traverse the device(s).

my vote is to always push/pull hot air out and mount fan as high as possible in the cab, and on the side that makes most heat (perhaps multi fans if the cab is multi chambered and has little cross flow between, etc)

DK
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post #20 of 24 Old 12-19-2010, 08:14 AM
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Well, I just got their price list. The 2 and 3 fan units shown in the picture cost $299 and $329, respectively, plus shipping. No thanks. I need to work out a cheaper option and God knows I do need one with Onkyo TX-NR3008 and PS3 spewing enough heat to warm up the room. Well sort off...
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post #21 of 24 Old 12-19-2010, 04:57 PM
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just order a couple 120mm USB powered fans from amazon. then hook them up to a powered USB hub. Usually cheaper to do that than to get 12v AC fans. For mine I had to remove the stand that came with the fan and mounted them to the IT cabinet. Thermaltake 120mm's are what i got.

I used this one: http://www.amazon.com/Thermaltake-Mo...2868267&sr=8-1

just take off the stand and brackets
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post #22 of 24 Old 12-26-2010, 09:06 PM
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Quote:
Originally Posted by xtvium View Post

Well, I just got their price list. The 2 and 3 fan units shown in the picture cost $299 and $329, respectively, plus shipping. No thanks. I need to work out a cheaper option and God knows I do need one with Onkyo TX-NR3008 and PS3 spewing enough heat to warm up the room. Well sort off...

any decent 3-5" computer fan will work (sealed ball bearing, etc), typically 5 or 12vdc, just power it from a dc wall wart. i will suggest the largest fan possible running at the lowest speed to avoid noise.

most computer places sell fans like this and they even have variable speed controllers that sit inline with the fan. newegg, ebay, and the like also have them, etc. will run you maybe $15-$30

depending on how hot your stuff gets will dictate how many fans are needed, etc.
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post #23 of 24 Old 02-01-2011, 11:22 AM
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irfan, thank you so much for posting about the Thermaltake fan, it's been perfect for cooling our Denon 4310, just blowing across the top at about 1/3 speed has made a 20-degree F. difference.

It's very quiet at the lower speeds. We've ordered several more for "summer desktop fans", ideal to run off the monitor's usb port, the adjustable speed is great.

Quote:
Originally Posted by irfan View Post

Thermaltake 120mm's are what i got.
I used this one: http://www.amazon.com/Thermaltake-Mo...2868267&sr=8-1

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post #24 of 24 Old 02-01-2011, 04:43 PM
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youre welcome axial99... i also just ran across these dual USB fans by Cabcool:

http://www.coolerguys.com/840556090588.html

They come in 80mm and 120mm, and dual or single, and DC/AC/ or USB.

I got them for the desk my computer will be housed in, one dual for the top one for bottom
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