Sucking through the rad and out 'OR' blowing through the rad and in???

big_ray_t · 9 Apr 2012 at 19:39

Debating with myself over what will be better. To have my 3 120mm roof fans sucking warm case air through the rad then to the outside or to push cold external air through the rad and into the case.

I should imagine both has pros and cons. Firstly, the fans will look better in the orientation to blow into the case

Seriously though, will blowing outside air through my rad then into the case make that much difference to the case temps??? If not, surely this would be a more efficient way of cooling my loop.

What are your thoughts???

jinxpad · 9 Apr 2012 at 20:02

If you have your 3 fans pushing colder, air into your case then what you will find happen is that your ambient case temperature will eventually rise anyway because you won't have enough air being pushed out from other area's of your case.

The result (at least in my mind) is that your components will see a rise in temperature which won't be offset because the warm air doesn't have anywhere to go as quickly.

Where as if you have your fans are in a pull configuration pulling the air out of the roof of your case, (which is made easier by the fact that heat rises) you will generally have a cooler internal ambient case temperature.

You could always try it and see how your results are

big_ray_t · 9 Apr 2012 at 20:22

Yeah, I see your point and it is something I was considering but thought that a couple of exhaust fans may help that.

Something that does worry me about the 3 120's sucking out is that I may get to a point of negative air pressure inside the case (unless I have 3/4 120's into the case) which could be a problem :confused:

no_1_dave · 9 Apr 2012 at 23:50

I tested 3 fans pushing air into my case through a 120.3 rad.
My overclock failed & my GPU temps went up massively. The inside of the case became like an oven. I am just glad I didn't leave it like that because it really did get that hot that you couldn't touch the motherboard.

You need the air exhausted through the rad at the top.

I have 3 fans pushing air through my top rad (120.3) from inside my case and a fan pushing air through my rear rad (120.1) from inside my case. I have the Corsair 700D so my only intake fan is underneath. This is perfectly fine, it keeps temps nice and cool. Maximum temp of my 470s after 4 hours of BF3 is 60c and that's with my i7 overclocked all the way and my 470s are volt modded & overclocked. Fans are silent

Neo-Geo · 10 Apr 2012 at 00:35

I would always have cool air coming from the outside of my case and moving over my rad to dissipate the heat as it goes over the fins of the rad.

no_1_dave · 10 Apr 2012 at 01:41

Neo-Geo said:
I would always have cool air coming from the outside of my case and moving over my rad to dissipate the heat as it goes over the fins of the rad.

And dissipate the heat from the fins into your case?
Tested and failed in the "good idea" department.

How about have cool air go through your case & then out through the rad dissipating the heat outside of the case? The air inside the case will remain cool because there is nothing to heat it up as it goes from the intake to the rad. With everything water cooled how will the air in the case be hot? It won't.

Bubo · 10 Apr 2012 at 08:27

Other problem with sucking air into the case through the rad is that you will end up with dust/fluff blocking the rad much quicker than the other way round, which may be awkward to clean depending on access. With blowing air out and the right filters on the other intake case fans you may even never have to clean the rad of dust.

ray t · 10 Apr 2012 at 08:33

That's what it will have to be then. Sucking through the rad and out. Shame really, as the fans in that orientation don't look half as good through the rad grill, lol

paradigm · 10 Apr 2012 at 09:23

I was pondering the same thing, mainly because blowing IN would generate some much needed airflow over the VRM heatsink.

I'm now going for push/pull on either side of the rad, blowing OUT of the case, hoping that adding fans to the bottom of the rad will give a little bit extra directed airflow over the VRMs. The only downside to this is that I'll need to use different fans for push and pull (only got the space for 12mm high 120mm fans under the rad), going for Scythe Slip Stream Slim 2000RPM under the rad, and Alphacool CoolMove Power 2000RPMs above.

Will I have a problem with mismatched fans?

TwsT · 10 Apr 2012 at 10:53

I pull in through one rad and push out through the other just wondering what to do with the 5th fan in my case as i can't leave a blank hole (lian-li case needs a fan to hold the grill in place)

I have 2 GT 120mm 1850's pushing in the front through my 240., and 2 Lian Li 140's pushing through the top 280 Rad exhausting out. Do I put the 3rd GT as in or out?

no_1_dave · 10 Apr 2012 at 12:32

TwsT said:
I pull in through one rad and push out through the other just wondering what to do with the 5th fan in my case as i can't leave a blank hole (lian-li case needs a fan to hold the grill in place)

I have 2 GT 120mm 1850's pushing in the front through my 240., and 2 Lian Li 140's pushing through the top 280 Rad exhausting out. Do I put the 3rd GT as in or out?

You should be extracting air through both rads and use the fifth fan as an intake.
At the moment you are pushing hot air though the top rad making it almost pointless having it. At the same time you are heating up the inside of your case meaning any passive coolers (ram, NB etc) aren't able to cool as effectively limiting any overclock potential you hope to gain from water cooling and reducing their life expectancy.

jinxpad · 10 Apr 2012 at 17:33

paradigm said:
going for Scythe Slip Stream Slim 2000RPM under the rad, and Alphacool CoolMove Power 2000RPMs above.

Will I have a problem with mismatched fans?

I don't think you'll have a problem with mismatched fans although I may be wrong... But you will definitely quite a loud rig..

paradigm · 10 Apr 2012 at 18:33

jinxpad said:
But you will definitely quite a loud rig..

I definitely the whole thing?

Noise doesn't bother me (never understood why people want a silent PC), and they will only be on full speed when under load.

malfunkshun · 11 Apr 2012 at 08:59

TwsT said:
I pull in through one rad and push out through the other just wondering what to do with the 5th fan in my case as i can't leave a blank hole (lian-li case needs a fan to hold the grill in place)

I have 2 GT 120mm 1850's pushing in the front through my 240., and 2 Lian Li 140's pushing through the top 280 Rad exhausting out. Do I put the 3rd GT as in or out?

Without knowing the fan specs I can only speculate, but I imagine that the location of the 5th fan is key. That said I am a bit of an advocate of negative pressure, so I would use it as exhaust if I could.

Duff-Man · 12 Apr 2012 at 09:34

Where possible, you should have ambient air drawn in through your radiator.

Why?

The key metric for cooling is the difference between the temperature of the air drawn into the radiator, and the temperature of the water - usually called simply "delta-T". For a given heatload, and a given watercooling setup (radiator config, fixed fanspeed and flow rate) the delta-T will rise to allow the heat to be dissipated. Therefore, if the input air temperature is (say) 5 degrees higher inside the case, then you will see an equivalent rise in water temperature, and so in the temperature of your components.

Venting through radiators should only be considered if there is very poor ventilation in the case. Exhaust fans are, for the most part, unnecessary in watercooling setups. Open ventilation is generally preferable from a thermodynamics point of view. With a reasonable ventilation area (i.e. ~25-50% the area of intake radiators) and relatively un-obstructed airflow the pressure rise inside the case will be minimal, and intake fans will still perform close to their maximum.

In particular, you should avoid having some radiators drawing air in, and others pushing air out.

ray t · 12 Apr 2012 at 10:29

So having the outside air drawn through my rad and into the case, is the best idea for a cooler loop??? Does this warm air then not too much of an adverse effect on the mb components then?

Duff-Man · 12 Apr 2012 at 11:00

ray t said:
So having the outside air drawn through my rad and into the case, is the best idea for a cooler loop??? Does this warm air then not too much of an adverse effect on the mb components then?

Yes - where possible I would definitely draw cool air in.

As for cooling the mb components - no, the fact that the air is a little warmer won't make too much difference:

With a "good" watercooling setup, you are looking at a difference between water temperature and air temperature of <10C. In contrast, the difference between air temperature and the temperature of your motherboard components is likely to be much higher (~30C typically with indirect air cooling).

It's the difference between the air temperature and the component temperature that makes the difference. So, effect of a (say) 5C increase in air temperture is felt much more strongly by the radiator than by the motherboard components that you're trying to cool (mosfets, RAM etc).

TwsT · 12 Apr 2012 at 11:55

no_1_dave said:
You should be extracting air through both rads and use the fifth fan as an intake.
At the moment you are pushing hot air though the top rad making it almost pointless having it. At the same time you are heating up the inside of your case meaning any passive coolers (ram, NB etc) aren't able to cool as effectively limiting any overclock potential you hope to gain from water cooling and reducing their life expectancy.

Air that comes out of the top is pretty cool though whilst i see what you mean.
The system temp with a 4.4 OC and a gtx 680 both on the loop is 25-28 idle and pops up to 40 ish under load.

I will have to show you some pics when I've finally finished it.

It's http://www.overclockers.co.uk/showproduct.php?prodid=CA-183-LL&groupid=701&catid=7&subcat=187

I could have the GT pulling in as it would pull the cold air in across the top and allow the 2 X 140 fans to pull the cold air up from the GT.

TwsT · 12 Apr 2012 at 12:01

malfunkshun said:
Without knowing the fan specs I can only speculate, but I imagine that the location of the 5th fan is key. That said I am a bit of an advocate of negative pressure, so I would use it as exhaust if I could.

2 x GT 1850 120mm on the front drawing into the case through a 240 M EK rad

2 X lian li 1000 RPM 140mm fans exhausting through a 280MM XSPC rad

So the options are, intake pushing cold air across the top of the case allowing the 140's to pull cooler air up

or Exhaust to pull the warm air out but also fight for the air with the 2 X 140's in the top.