evacuating heat from under desk

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Farnsworth
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evacuating heat from under desk

Post by Farnsworth » Sun Aug 29, 2004 11:21 am

My pc is sitting on the floor under my desk. When the computer has been running for a while, a lot of heat builds up under the desk. The temperature around the case is far above the ambient room temperature of about 20*C / 68* F.
Mainly because airflow is blocked by the wooden sidepanels en top of the desk.

>> Picture of the pc under the desk

How can I solve this problem?

ceraf
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Post by ceraf » Sun Aug 29, 2004 11:24 am

you can try using a duct that points the exaust airflow downwards past the wooden panel.

Is the heat uncomfortable for you or your computer?

silverback
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Post by silverback » Sun Aug 29, 2004 11:33 am

The back of the desk is covering up the power supply exaust on the case. I am thinking that is where a vast majority of your heat is comming from. It looks like fron that picture the case is exausting hot air out the back of the pc then bouncing off the back support of the desk heating up the case.

Unless you a have a backshot of the pc the best I can suggest is to either move the pc so there is no restriction to the exaust or cut / create some kind of duct to go around the obstruction.

Straker
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Post by Straker » Sun Aug 29, 2004 11:55 am

i'm close to having the same problem, but my back-thing doesn't go as low as yours, and i have a bit of space at the top... only like a 1cm gap though.

Is there any space between the desk and the wall? If there's a fair bit of space there and that were my desk I'd probably just take it apart (if it's just like 4 pieces of wood and doesn't have a huge pile of stuff sitting on it) and put a few big holes in the back panel. Easiest way would be to just run the PC sideways (so it exhausts lower and hopefully under the back panel), move it to the other side so it's not inside the desk any more, or put it on top of the desk though. If it's feasible (and you don't mind the way it looks) it might be worth trying it simply turned around so it intakes from the bottom opening in the desk and exhausts towards the room.

If the desk is right up against the wall it might help moving it back a few inches too.

Farnsworth
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Post by Farnsworth » Sun Aug 29, 2004 12:18 pm

ceraf wrote:Is the heat uncomfortable for you or your computer?
The heat is especially uncomfortable for the pc, because the cpu fan ramps up after a while and stays at the same (high) level after the cpu intensive task has finished.
silverback wrote:The back of the desk is covering up the power supply exaust on the case. I am thinking that is where a vast majority of your heat is comming from.
You're absolutly right, the area behind exhaust fan is reasonably cool. The area behind the psu exhaust is incredibly hot!
Straker wrote: Is there any space between the desk and the wall? If there's a fair bit of space there and that were my desk I'd probably just take it apart
The plate at the back has a supporting function. If you take it away, the desk would fall apart.
Straker wrote: Easiest way would be to just run the PC sideways (so it exhausts lower and hopefully under the back panel), move it to the other side so it's not inside the desk any more, or put it on top of the desk though. If it's feasible (and you don't mind the way it looks) it might be worth trying it simply turned around so it intakes from the bottom opening in the desk and exhausts towards the room.
Turning it on its side is impossible, where would i place my feet?
Placing it outside the desk, would mean i have to place it in front of the heating system.
Turning ii backwards, would like crap.

Straker
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Post by Straker » Sun Aug 29, 2004 1:30 pm

Farnsworth wrote:The plate at the back has a supporting function. If you take it away, the desk would fall apart.
i said "take it apart" to make it easier to use holesaws or cut a slot so you can move your pc back a bit, so it's not enclosed by the desk any more, after you also move the desk away from the wall.
it = the desk, i wasn't saying just remove that entire board, otherwise most desks are about as stable as a card house. :roll:

if the desk is right against the wall even if you could put it on its side or backwards you'd end up with the same problem anyways. what about putting it outside the desk but on the other side? it's either that, making a cutout to move the pc back so it can exhaust properly, putting it on top of the desk or like... putting a floor fan under your desk. :) you could probably duct it but you might have a hard time getting the air down under that back board and then back up.

easiest thing to do for now would be to just make sure the desk is a couple inches away from the wall, and move the pc forward a bit as well. from the way your first post sounded, i thought your pc was exhausting completely normally, just that it was all staying under the desk. if your case exhaust fan is below the level of that back board and the PSU fan is above it, moving the whole PC forward might make things worse, hard to say.

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Post by MikeC » Sun Aug 29, 2004 2:47 pm

Looks like that support cross-support panel is the culprit. I have a desk that has a similar cross support, but does not go down so far, so that PC actually fits underneath it. Just pulling the desk away from the wall by 2 inches makes the whole area under the desk very perceptably cooler. I avoid stuff falling off that side of the desk by gluing a thin strip of wood across it, along the edge. Just a few tiny spots with hot glue so it can be easily popped off w/o any damage.

You might have to take a saw to that cross-panel, make a cutout so the PC can be pushed back farther, and then pull the desk away from the wall by a couple inches.

rtsai
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Post by rtsai » Sun Aug 29, 2004 3:59 pm

Farnsworth wrote:
silverback wrote:The back of the desk is covering up the power supply exaust on the case. I am thinking that is where a vast majority of your heat is comming from.
You're absolutly right, the area behind exhaust fan is reasonably cool. The area behind the psu exhaust is incredibly hot!
Is that some flavor of Dell computer? I think you have the same symptom as me: the exhaust from PSU fan is much hotter than exhaust from case fan.

Basically, there is no way for cool air to travel up to the PSU; the "intake vent" for the case is miniscule. Whatever air that gets in is probably being drawn through the CPU heatsink. And Dell tying the PSU cables right in front of the PSU ventilation doesn't help things, either. Like you, I've used up both my 5.25" bays with optical drives (CDRW, DVDRW). I'm probably going to end up sacrificing my CDRW bay for a PSU duct, and cutting off the plastic cable ties holding the PSU cables right in front of the vents.

Farnsworth
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Post by Farnsworth » Mon Aug 30, 2004 2:10 am

Yep, it's a Dell dimension 8250. You're right about the psu ventilation, the intake vent is nearly non-existent. Some tiny openings on the back of the psu and that's it.

But in my case, it isn't possible to sacrifice a 5.25" device. I'll have to choose between a dvd-rom and a cd-rw. I need both of them.

Ducky
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Post by Ducky » Mon Aug 30, 2004 6:06 am

Actually, even putting a little desk fan right on top of the computer should cool it back down, given the way the computer is situated.

Ralf Hutter
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Re: evacuating heat from under desk

Post by Ralf Hutter » Mon Aug 30, 2004 6:11 am

Farnsworth wrote:
>> Picture of the pc under the desk

How can I solve this problem?
My dad's PC was in a similar situation as yours. I simply measured the location of the PSU and case exhaust fans and used a jigsaw to cut two corresponding holes in the wood bracket. I also moved the desk away from the wall. He had it crammed right up against the wall, I left about 5" of space between it and the wall. These two easy fixes made a big difference in his case temps and in the temp of the air under his desk.

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