Placement for a 120mm fan - something different?

[sleddog]

I have a 10-year-old Delta 120mm fan than came out of a server. Work fine and is very quiet (yes, Delta *can* make a quiet fan!) Problem is I have no place to install it. Because of case design (smallish mid-tower) it just won't fit in either the front or back panels.

So I'm thinking, what about the bottom, facing up, blowing in? Lots of room there. I would also add some custom feet to raise the case up maybe another 1" or 1-1/2". What do you think?

 

[Tomsawyer]

Hmm how much dust under there? Seems like a great idea, after all heat rises and the coolest air should be down low. But is it worth cutting a hole in the bottom of your case?

 

[Tim-]

A common trick among us tube hifi folks is to mount a large quiet fan in a box with an exhaust grill, and a duct fashioned on the other side, and run the duct to amplifiers or whatever to draw heat from them. It allows the fans to placed out of the immediate listening area. Can't see why the technique couldn't be used to pull air through a computer case. You could run a hellacious fan and never have to hear it. Using dryer duct, you can move a LOT of air!

 

[sleddog]

Tomsawyer (Feb 08, 2001 07:04 p.m.):
Hmm how much dust under there? Seems like a great idea, after all heat rises and the coolest air should be down low. But is it worth cutting a hole in the bottom of your case?

Won't be much dust there once I switch the fan on Seriously, I could use a filter if it posed a problem. Regards to cutting a hole, should be a piece of cake compared to the torture of fitting an 80mm exhaust fan in the rear. The case has a "stepped" back panel with space alotted for a 60mm fan, but a 1/2-hour with the jigsaw, hammer & chisel changed that....

 

[sleddog]

Tim- (Feb 08, 2001 07:25 p.m.):
A common trick among us tube hifi folks is to mount a large quiet fan in a box with an exhaust grill, and a duct fashioned on the other side, and run the duct to amplifiers or whatever to draw heat from them. It allows the fans to placed out of the immediate listening area. Can't see why the technique couldn't be used to pull air through a computer case. You could run a hellacious fan and never have to hear it. Using dryer duct, you can move a LOT of air!

Hmmm, that's got me thinking... why use a fan at all, how about an 8" chimney? Probably need a damper installed for those really windy days... wouldn't want small parts to be sucked away....

 

[Tim-]

How about a chimney with an auxiliary blower for those non windy days...? In HiFi setups, the box with the fan would sometimes be mounted over a hole in the floor so that it draws air from the amplifier through the duct and exhausts it below the floor. This provided a somewhat permanent but VERY quiet cooling solution. The same could be done with the chimney or a window mounted plate.

 

[sleddog]

Non-windy days? You mean there are places that have those?

Actually, I *am* using a window solution... but drawing cold air in rather than exhausting. First I had it ducted directly into the PC, but this gave real temperature extremes. My Duron fell as low as 19C, then a wind or outside temp change would alter the airflow and cpu temp would climb rapidly. At times I would get some condensation on interior metal surfaces.

I've changed it so the cold air intake hose (4") simply delivers a cold draft to the bottom front of the machine, where the intake fan can pick it up, mixed with room air. There's a cardboard "valve" on the hose so I can turn it down on real cold days and not chill the room. Temps are much more consistent (cpu low 30s) and any hint of condensation is gone.

Hey, you never commented on the120mm fan placment in the bottom of the case (I'm looking for improved warm weather cooling in anticipation of summer!). Do you think it will be effective?

 

[GauntMan]

I´ve got a very nice setup. In the bottom front of the case I have a Papst 4412FGL 120mm pushing 55.3cfm at 26dBA. I´ve used a filterholder from a vaccuumcleaner on the intake so dust is no problem. I´ve extended the caselegs to about 40mm using 30mm wooden sticks and Epoxy. Back in the top I have an equal fan pushing the air out. I sawen a hole in the case and put a grill on the outside. Very nice looking. I also put covers over all the other holes in the case to get the air where I want it to go. I´ve turned off the powersupply-fan since the top fan draws air through it. Because the fans only are running at 1600rpm they don´t make much noise. This is also because there are no obstructions close to them.

The temp then? Well my Cely2-600@900, 1.85V have never gone more than 1 dregree above room ambient temp. At the time of writing I´ve been running SETi for two hours and the CPU is 25C (room temp 24C). I´m using a NoName cheap cooler. I´ve put a on/off switch on the top fan in case I want to make the PC virtually noiseless.

I´m happy, I suggest you give it a try.

/GM

 

[sleddog]

When you say "bottom front" do you mean the fan is mounted on the bottom of the case (horizontal) or on the front of the case (vertical)?

 

[GauntMan]

Bottom of the case (horizontal). Same goes for the top fan.

/GM