Antec 900 - PSU Fan Operation?

[altazi]

Ok, this is tricky. The Antec 900 has a 200mm fan on the very top of the case that sucks hot air up and out. Also, the 900 puts the PSU at the bottom of the case. PSU fans typically suck in warm air from inside the system, through the guts of the PSU, and finally blow this now-hot air out the back, outside of the case, right? My questions:

1. With the PSU installed in bottom of the Antec 900, wouldn't it make sense to reverse the PSU fan direction, so it sucks in cool air from outside the case, and exhaust the (slightly) wamer air into the case, where it would then be sucked out by the top 200mm fan? This seems like it would make a smoother airflow pattern, and increase the overall CFMs of air moving through the case.

2. Which PSU style would be better - fan out the back end, or fan on top (bottom, but PSU would be mounted upside-down in the 900 case)?

Thanks!

Altazi

 

[g-paw]

PSU and rear fans blow hot air out, generally if you want to bring cool air in, you do it with a front fan. With that case you shouldn't have a heating problem unless your into serious over clocking in which case you should get a better HSF

 

[kbits]

I agree with Altazi. PSU should always blow out. The air from the PSU is substantially warmer, and blow that in the case isn't a good idea from the beginning imo. I had a Antec Overture using that patern, and it was one of the worst case I saw for cooling. That part didn't help I'm sure.

I do however understand what you mean by air circulation, but fresh air from the front, and hot air out from the back (both bottom back and top back) is your best bet I think.

 

[lzclzclzc]

all i have to do to reverse the wind direction is to flip the fan correct? wat about the PSU, it only blows one way right? and that is out

 

[nastymat]

2 things sprung to mind..

1. hot air rises so the psu at the bottom will be pulling in nice cool air keeping it cool.
2. You want to exhaust more air than pump in, if there is more coming in than going out you'll have dead spots. So keep the psu pumping out not in.

 

[altazi]

Good points, NastyMat. Thanks!

I guess no matter what, I'm not stuck with things the way they are (or will be, since I haven't gotten all of the parts for the system yet.) I can always move things around based on the thermal performance, until I find the best configuration.

But. . . With the Antec 900 (which I already have), the PSU sits on the bottom. A PSU with the fan on the back end is no problem, but what about PSU's that have their fans on the top. Since hot air rises, this fan would then be working contrary to this principle. Comments?

Thanks!

Altazi

 

[nastymat]

The fans on top of the psu will be drawing air in from the bottom of the case i.e. where the cool air is. So all is good.

I am looking for a new case and the 900 is the one I think I will go for.

 

[Findail]

2 things sprung to mind..

2. You want to exhaust more air than pump in, if there is more coming in than going out you'll have dead spots.

I hate to hijack Altazi's thread, but is Nasty's quote true? I swear I read somewhere just the opposite -- that you want positive pressure in the case, not negative. Of course, I could write down everything I know about case airflow on a postage stamp (and not one of the big ones, either), so I could just be confused.