PSU fans - which way is up?

[JohnnyLucky]

My old pc has a power supply with a fan located on the rear of the unit. The fan exhausts warm air out the back of the power supply. I noticed many new power supplies have fans that are no longer located on the rear of the unit. In the stock photos used by retailers the fan is located on the "top" of the power supply. I assume the power supplies are positioned and photographed that way so potential customers can see the fan.

When installing a new power supply should the fan face the "top" of the pc case as in the stock photographs or should it face the "bottom" of the pc case? Do the fans act as intake fans blowing air into the power supply or do they exhaust air into the pc case? How does that affect overall cooling?

Are there any links to articles and reference material on this subject?

 

[asdasd123123]

It will suck in air from the bottom, and blow it out the back.
That is the basic ATX standard, and shouldn't be different on any ATX psu's.

Independent of how many fans it has, although the better ones have 120mm fans on the underside. These models are very quiet and cold.

 

[JohnnyLucky]

Thanks for the information.

I bought my first computer in 1988 and went through the upgrade route. I think I stumbled into Tom's Hardware Guide in 1996 or 1997 while looking for upgrade information on some new fangled thing called the Internet. I built my last computer in 2000. It's still running with all of the original parts - Intel Pentium III 600Mhz cpu, 128MB of memory, IBM Deskstar 16GB hard drive, Plextor cd-rom drive, Diamond video card, Princeton Graphics CRT, HP Deskjet printer, and Windows 98SE. The only thing I replaced was the original dial-up modem with a cable modem. The pc does just fine for web browsing, email, and family photos. I'm amazed that something hasn't broken, fried, fallen apart, or gone up in smoke.

Decided it was time to build a new pc and discovered I haven't kept up with the latest technology. I started doing some research and discovered retailers and manufacturers never mention anything about power supply fans other than size. Articles and reviews were full of technical information but rarely had anything technical information about power supply cooling.

 

[asdasd123123]

I refurbish computers in that weight class, and sell as web-surfing bots.
They sell as butter in the sun. =)

 

[JohnnyLucky]

My new pc case arrived a few days ago. It came with one 120mm fan mounted in back. A second 120mm can be mounted at the bottom front. There's an air funnel on the side for the cpu/heatsink/fan. I think I'll get a couple of high volume Panaflo fans. I am a senior citizen and hard of hearing so fan noise is not an issue for me.

I have this sudden urge to try my hand at case modding. Think I'll go down to the hardware store and see if I can find a nibbler.

 

[ecosoft]

JohnnyLucky

I, too, am an "old Dude" (67) and I also "found" Tom's back in the '96-'97 timeframe when I graduated from a 386/33 to a 486/100. As you have discovered, everything x86 PC has changed significantly since then!

Regarding power supplies, cheap = grief ... especially with today's video GPU's requiring 19+ amps 12V ON A SINGLE LINE! I know of no one beyond PCPOWER & Cooling that manufactures 12V single rail PS's, which is absolutely necessary for the latest vid card designs. Check this site and read their PS Myths Exposed article PCPOWER & COOLING

Separately, PCC&C elucidate their fan/PS case design ... well worth reading, whether you are partially deaf, or not. The PS generates heat, which over time kills components, so the better the cooling the longer the life, all else being equal. Have fun with your project

 

[ZOldDude]

My new pc case arrived a few days ago. It came with one 120mm fan mounted in back. A second 120mm can be mounted at the bottom front. There's an air funnel on the side for the cpu/heatsink/fan. I think I'll get a couple of high volume Panaflo fans. I am a senior citizen and hard of hearing so fan noise is not an issue for me.

I have this sudden urge to try my hand at case modding. Think I'll go down to the hardware store and see if I can find a nibbler.

I always remove the rear fan guard on a case for the near 70% increase in airflow.
It is not that you are makeing the hole 70% larger but the fact that you remove the obstuction cuased by air turbulance which forms an "air dam".

Proper forthought in case airflow does not involve more than two well placed fans and your PSU should never be used to remove hot air from the case as it lends to a shorter lifetime of the PSU as well as lowered AMP output and "dirty" voltage if you veiwed it on a scope.

If you have ever done work with heating/cooling ducts in homes/offices you will know what I am saying.

A good PSU will avoid the bottom mounted 120mm fan as this is mostly a marketing ploy rather than a functional one.
PSU's with a 80mm fan mounted on the end have both more room inside for added heatsink area as well as pulling air from one end to the other which provides better cooling by avoiding the "air dam" problem cuased by injecting air at a 90 degree angle.
Both the 80 and 120 mm fans used move the same amount of air (differant RPM's)...one is just smarter.

Also avoid a "modular" PSU's as the connections to the PSU are a source of power loss and will result in problems down the road.

 

[JohnnyLucky]

ZOldDude,

I've done some research and I'm thinking the same sort of stuff you posted. I can't remember where it was but I ran across information that was posted by aeronautical engineers that work with wind tunnels. In addition to the usual stuff about fans, airflow, and noise they also explained about all the different things in a pc that can can restrict air flow. Fan grills and grill guards were on the list. Fortunately I'm single and live alone. Don't have to worry about little fingers and paws poking around.

I followed a link to PC Power and Cooling in a previous post. They had a handy psu selector program. Zeroed in on the Silencer 610. The fan is located at the back of the unit. That's more in line with front to back air flow. But for the life of me I don't know what I'm going to do with 6 SATA connectors.