Antec rep, a question about your power supplies

Enclosures, modding, blowholes, and the power needed to run it all.

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Antec rep, a question about your power supplies

Postposted on Wed Mar 12, 2003 12:09 pm

I just finished my first build using a Chieftec case, the blue one with a window, looks like this:

http://www.newegg.com/app/Showimage.asp ... 210-04.jpg

I used the Antec SL 350 power supply. Being a novice at this, I looked at people's opinions in this and other forums and concluded that your company makes good power supplies.

However, I was a little disappointed by one design feature of this power supply. After very carefully choosing a case with good ventilation, I was very surprised to see that the large fan (on the bottom) on this PSU is set up to blow hot air into the case!

WHY, WHY would you set it up this way? It makes no sense to blow hot air into the case, when the whole idea is to keep the case as cool as possible. I have no intentions of returning the power supply, but it seems that this is a design flaw in what seems to be a well engineered product. And yes, I am an engineer, (mechanical) so I feel qualified to make this criticism.

Your response, sir.
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Postposted on Wed Mar 12, 2003 12:19 pm

actually i think you should return it because i've never heard of any PSU manufacturer who blow air back in the case. it's probably a special case with your PSU. Either return it or open the PSU up and flip the fan around.
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Postposted on Wed Mar 12, 2003 1:26 pm

Yeah, the fan was probably installed wrong. Either flip it around (and void the warranty) or get a replacement.
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Postposted on Wed Mar 12, 2003 1:32 pm

Actually, the original ATX spec called for the fan on the PS to be installed on the inside of the case, and to blow air IN. This was to keep the case pressurized to reduce dust intake. That was then, now with power consumption in PC's being multiple what it was, heat naturally becomes a problem. The spec was changed.

I do agree that you most likely have a bum powersupply. Get it replaced.
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Postposted on Wed Mar 12, 2003 1:37 pm

PS fans blowing in is the original spec for ATX. Nobody follows it though. So it's probably a backwards fan install.

http://www.formfactors.org/developer/specs/atx/atx2_03p1.pdf

Check the first paragraph in section 4.
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Postposted on Wed Mar 12, 2003 4:43 pm

No, the fan I'm talking about is not installed backwards. And even if I turned it around it would still blow into the case. Take a look at the PSU here

http://www.antec-inc.com/pro_details_po ... dID=25350#

That second fan that is shown on the top face is inside the case, so no matter which way it blows, it will blow hot air into the case, although on mine, that fan is on the bottom surface.

That second fan was actually designed to blow into the case, as weird as it may seem.
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Postposted on Wed Mar 12, 2003 4:54 pm

RMA it. The PSU's are suppossed to exhaust air from the case (otherwise the PSU would have 2 exhaust fans, which doesn't make a lot of sense).

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Postposted on Wed Mar 12, 2003 5:23 pm

huh? Still confused here.

The fan on the back of the power supply should be exhausing air outside of both the power supply case and the computer case.

The fan on the base of the supply which is contained within the case should blow air into the power supply, which in turn is passed to the exhaust fan and then to the outside of the computer case.

If both fans were exhausting to the outside of the supply, the air circulation would overheat the supply, and also if both fans were blowing in. This would be the case of an RMA.

If the back fan was blowing in to the supply and the base fan was blowing out of the supply into the computer case and the air containing the CPU, this means you will warm the guts of the PC a lot more than otherwise, but the supply is getting the benefit of cooler air, which may be intended if it is a high power supply. What does this mean? Install another fan on your case for added exhaust right next to the base fan of the PSU so the warm air from it will not make it to the CPU.

-LS
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Postposted on Wed Mar 12, 2003 5:28 pm

Are you POSITIVE it's blowing and not sucking air? Generally the lower fan on a PSU is a 92mm fan that runs at a low RPM. Best way to tell if it's sucking air is to take a small piece of paper/plastic and see if sticks to it.
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Postposted on Wed Mar 12, 2003 8:37 pm

Ok, everyone, I just fired it up and here is what I found.

The fan that is visible from the back of the case blows out the case, no mystery there.

Now, the big fan (probably a 92 mm) that is on the bottom of the PSU sucks in air..a piece of paper sticks to it. BUT...it blows it out a large grille on the back face of the PSU and two smaller ones on the sides. I know because I took a piece of paper about the size of the large grille made a bunch of cuts in it, sort of like piano keys, and held it against the grille and it pushed the paper out. Definitely did not suck the paper on to itself. The same thing happend when I held two smaller pieces of paper against the small side grilles, the paper blows away from them. Which means air is coming out of the grilles and, I assume is being pushed out by the bottom fan.

I just did something that was not smart but confirmed it. I held a match to one of the side grilles and the back grille....no doubt about it, the air is coming out of those grilles and, obviously into the case. And, just as obviously, turning the big fan around will not change things.

I'm more convinced now that the large fan sucks in air from the bottom of the PSU and exhausts it into the case. Is it possible that when the PSU heats up the flow changes direction? I can't really see how that would happen. I'm stumped for an answer.

Ok, Mr. Antec man, gurus, and anyone else, what is the deal? I can't help but think that this PSU was designed to do just this. Not what I expected at all from a leading manufacturer of PSU's. I can deal with it, but I did a of a lot of homework to try to maximize the cooling on my first rig, and I just didn't expect the PSU to work against me.
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Postposted on Wed Mar 12, 2003 8:54 pm

It's designed that way. All PSUs with double fans are. The grilles on the PSU are there for ventilation and not for blowing air back into the case. Your PSU is fine and you have nothing to worry about.
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Postposted on Wed Mar 12, 2003 9:12 pm

NeXus 6, oh yeah it's designed that way...but the net result is that warm air from near the top of the case gets sucked in, warmed more as it passes over hot power supply thingies and is then blown back into the case. It act like a case heater, basically. Why not exhaust all air used to cool the PSU out of the case and pull cool air in from the bottom of the case at the same time?

Now my puny Toshiba that I'm typing this on, with an ancient Celery 366 MHz processor has one fan in bottom of the PSU blowing warm air down on the CPU and then out the case on the bottom! Talk about revese engineering! I can excuse the stupidity of this design, it's a cheap machine without need for much cooling. But with a high end PSU, I just don't get it.

Oh well, if that's the way all PSU's are designed, I'll just have to get a case with a top blowhole for my next rig.

Thanks for the info and opinions, everyone.
PC 1-- P4 2.8GHz, ASUS P4G800-V, 1.5 G 3200 3
50w psu, WD 120 gig HD, ATI 9600SE, XP Home w/SP2
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Postposted on Wed Mar 12, 2003 9:55 pm

man ur confusing me :D . anywho, as long as the air from the 92mm(bottom) is sucking in then it's correct. The side vents are meant for air to come in but u describe it as coming out. still with the 80mm(backplate) sucking air out, the bulk of hot air is still exiting your computer. Its not as though all hot air is being pushed out those side vents. only a small amount might be. the PSU is the way it should be.
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Postposted on Wed Mar 12, 2003 9:55 pm

Are you saying it's sucking air in from the "top" of the case? It's supposed to be sucking hot air off of the CPU, so I think you have it installed upside down. Am I wrong?
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Postposted on Wed Mar 12, 2003 10:49 pm

No, I don't have it installed wrong. The big fan is at the bottom of the PSU, but the whole PSU in located in top space of the case, where all of the warm air naturally rises to, that's what I meant.

sn_85, they way it's working is this: the fan at the back is blowing air out, but I don't know where it's drawing it's air from. The fan at the bottom of the PSU is sucking air in, and apparently blowing out the side vents and the back vent, or grilles, as I call them. My little experiment with the lit match definitely tells me that air is coming out of both side grilles and the back grille. So I have to conclude that the bottom fan (the big, slow turning one) is sucking air into the PSU and blowing out through the grilles and into the case.

I would like to hear from the Antec rep on this, and have him confirm that this is the design of the unit.
PC 1-- P4 2.8GHz, ASUS P4G800-V, 1.5 G 3200 3
50w psu, WD 120 gig HD, ATI 9600SE, XP Home w/SP2
****************
PC2-- XP 2100B (at 2.1 GHz, 175 MHz FSB) Epox 8RDA, 512 MB Corsair Value PC 3200, WD 40 G, Lite-on CDRW
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Postposted on Wed Mar 12, 2003 11:05 pm

If it's bothering you so much, why don't you tap up the grilles?

My PSU is setup the same way(as it should be). There is very little air coming out of the vents...I really don't see what the big deal is.
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Postposted on Wed Mar 12, 2003 11:57 pm

the back fan is drawing air from inside the PSU. thats why it is blowing air out. here is how the 2 fan PSU works.

air is drawn intot the PSU by the 92mm fan. this air goes over the heatsinks inside the PSU and cools it. the air that cooled the heatsinks of the PSU is now being sucked out of the entire system by the 80mm fan in the back.

i put my hand over the side vents of my PSU and felt absolutely no air pressure blowing out. i have 2 fans on my PSU too and turned the fans to high.

this is the way is supposed to be. if you call antec you probably wont get an answer back.
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