Corsair VX450 PSU with Bottom-mounted PSU case

jbsteeves · Post by **jbsteeves** » Fri Mar 06, 2009 3:21 pm

I have a Corsair VX450 PSU, and I'm looking to buy a new mid-tower case.

This PSU has a 120mm fan on the bottom, and I was wondering if this would create a problem with airflow if I put it in a case where the PSU is bottom-mounted. The fan on my heatsink (OCZ vendetta) blows air upwards, and the exhaust fan blows air outwards. In a bottom-mounted case, the PSU fan would be blowing air downwards.

Would this create an airflow problem or an airflow 'short circuit', if the HSF blows upwards, the PSU fan blows downwards, and the exhaust blows outwards.

baconandeggs · Post by **baconandeggs** » Fri Mar 06, 2009 3:42 pm

I'm looking to buy a new mid-tower case.

such as and antec 300?

do you mean is there a problem with negative pressure, where the fans in the case are blowing air out of the case is greater than the air being brought in? short answer is no.

negative and positive airflow

jbsteeves · Post by **jbsteeves** » Fri Mar 06, 2009 3:57 pm

do you mean is there a problem with negative pressure, where the fans in the case are blowing air out of the case is greater than the air being brought in? short answer is no.

It's not a concern with the positive or negative pressure. I was wondering if the combination of a PSU that blows air down, a HSF that blows air up, and an exhaust fan that blows air out, would cause problems with the direction of the air flow (eg. airflow 'short circuit').

JamieG · Post by **JamieG** » Fri Mar 06, 2009 6:52 pm

jbsteeves wrote:It's not a concern with the positive or negative pressure. I was wondering if the combination of a PSU that blows air down, a HSF that blows air up, and an exhaust fan that blows air out, would cause problems with the direction of the air flow (eg. airflow 'short circuit').

The PSU fan sucks air through the PSU and out the vent of the back of the PSU. (The 120mm fan is acting as an intake for the PSU and pushing the air out the back, it is not sucking cool air from the vented back of the PSU and exhausting it down into the case). Basically, there's no short circuiting really, but the rear exhaust fan and PSU fan sometimes compete for airflow.

A problem is where you have a top mounted PSU that sucks air in from below and a CPU cooler blowing hot air up, then the hot air from the CPU cooler is sucked into the PSU, heating it up and thereby causing the PSU fan to spin faster to cool the PSU components, which causes more noise.

This is why tower-style CPU coolers normally are orientated to face the rear of the case and for the hot air to be sucked out by the rear exhaust fan and not the PSU at the top. (Some cases have bottom mounted PSUs partly to avoid this problem.)

Hopefully that answers your query!

dhanson865 · Post by **dhanson865** » Fri Mar 06, 2009 7:29 pm

jbsteeves wrote:PSU fan blows downwards, and the exhaust blows outwards.

PSU fans never blow down. PSUs with bottom mounted fans blow up into the center of the PSU and then the air exits to the rear.

jbsteeves · Post by **jbsteeves** » Fri Mar 06, 2009 7:40 pm

dhanson865 wrote:
jbsteeves wrote:PSU fan blows downwards, and the exhaust blows outwards.
PSU fans never blow down. PSUs with bottom mounted fans blow up into the center of the PSU and then the air exits to the rear.

In a case where the PSU is bottom-mounted, the PSU fan would be blowing air downwards into the PSU. I'm trying to figure out if this will create an airflow short-circuit (since the HSF blows upwards, and the exhaust blows out).

dhanson865 · Post by **dhanson865** » Fri Mar 06, 2009 8:21 pm

In a traditional case mounting the PSU fan never blows down as the fan is on the bottom blowing up.

In a bottom PSU case such as the P180 you can install the PSU normally or upside down. My inclination would be to have the PSU fan on the bottom even in a bottom PSU case.

Just because the case looks different doesn't mean the PSU has to be upside down.

http://www.silentpcreview.com/article249-page4.html

Any type of ATX PSU can be installed: Single 80mm fan, single 120mm fan, or dual fan. It can be mounted right side up or upside down as desired.

or take a look at some of the tons of threads about the P182 and bottom mounted fan PSUs

http://www.google.com/search?hl=en&q=p1 ... tnG=Search

baconandeggs · Post by **baconandeggs** » Fri Mar 06, 2009 9:21 pm

i think the OP means blow 'down' as in into the PSU since it will be mounted at the bottom of the case. ie if it was top mounted PSU he/she would probably say blow 'up'

bgiddins · Post by **bgiddins** » Fri Mar 06, 2009 9:46 pm

I have the Antec 300 (bottom mount PSU) with the VX450.

Cooling is not an issue - I've never heard the term "airflow short circuit" - I still get front to back airflow through the case.

HSF blows up - directly into a 140mm exhaust fan
120mm rear exhaust fan blows out
PSU fan sucks down, blowing through PSU and out back of case

I did add 2 120mm fans on the front of the case, but they're really only there for my 5 HDDs.

Corsair VX450 PSU with Bottom-mounted PSU case

Corsair VX450 PSU with Bottom-mounted PSU case

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Re: Corsair VX450 PSU with Bottom-mounted PSU case