Fan Directions & Optimisation

[shkm]

Just building my new PC and I'm having a little issue with fans. Main parts in question are: Coolermaster CM690 case, Thermalright Ultra-120A and a socket 775 motherboard.

My basic problem is defining "which way up" for the fans, together with the heatsink. There's a pre-installed fan at the rear of the CM690--just next to where the CPU would be--which confuses me when coupled with the heatsink fan. Should I have the fan on the heatsink blowing air into the heatsink or taking it out? And which side should it be on?

The Ultra-120A's offical installation instructions show a fan which I think is blowing air into the heatsink--I'm looking at the blades--which, if I choose to copy, would ideally have my rear fan blowing air out, or so I think.

Cooling specs for CM690 are:
Front :120 mm Blue LED fan x 1, 1200 rpm, 21 dBA,
Rear : 120 mm standard fan, 1200 rpm, 21 dBA,
Top : 120 or 140 mm fan x 2 (optional),
Bottom : 120 mm fan x 1 (optional),
Left: 120mm fan x 2 (one is optional)-up to 140mm fans

My clueless idea for optimal airflow would have the bottom fan blowing in; rear out; front (lower) in; top out; left, I'm not sure about because it may not even fit, and it would be directly above the heatsink if it does.

Any chance of some clarification here? I had never really thought much of airflow (which gave me excellent overheating problems) in the past, and never installed a heatsink with a seperate fan. Also, I'm very tired writing this, so please forgive what is probably horrendous grammar.

[longshanks]

Front fans in a case should be bringing the air 'Into' the case. Rear case fans should be 'Taking' the air out of the case.

As for the heatsink fan, that should be blowing towards the heatsink, this way cooling it.

You will notice that on most fans, on one of the edges, you will find 2 arrows. One shows you which way the fan is 'Blowing' the other shows the orientation of the fan.

[peterb]

Depends on the layout of the case, but the fans should be consistent, ie either suck in at the front and blow out the back, or suck in the back, blow out the front, which way round depends onbthe internal layout (For example, my oldish case sucks air in at the back and deposits the incoming air at the inlet fan of the PSU where it is sucked in and blown out at the back higher up. The processor is also by the inlet fan, so that gets the cooler air too. - I don't have a front extractor fan, but it doesn't seem to be a problem)

On another system I tried reversing the flow from back to front to front to back, but it made little difference, although the case only had a single rear mounted fan anyway - in fact the biggest imperovement was standing the machine on a couple of strips of wood to give better air flow into the front vent (it is a microatx case)

However you may need to consider where the computer is located. If it on the floor, near a central heating radiator, then there is little point in sucking in hot air from the radiator in at the back and exhausting it at the front - in that case exhausting at the back would be a more sensible option.

[Salazaar]

Just remember not to set it up with the CPU fan blowing into an intake fan

[Shooty*]

I read somewhere yesterday that using an intake fan on the front of your machine may actually inhibit cooling, and that it's better to just use an outtake fan on the back, to pull air through.

Sounds like carp to me, but anyone got any views? They also said not to use dust filters as it can impede air. Again, I think air's fairly small, so should be able to get through the mesh OK

At the moment, have a fan controller. I'm seriously toying with the idea of putting the fans back on mobo control to free up a 5.25 drive bay...

[Disturbedguy]

This is something worth looking at, when I upgrade am planning on adding some fans.

I think ill mess around with the placing of the fans in reguards to airflow.

[tiggerai]

I did a lot of looking into this a few years ago, experimenting with different configs (in a closed case of course...) - This was when Overclocking T-Birds was all the rage, and temps would hit silly numbers!

At the time I had 4 fans, 1x 120mm (top) and 1x 80mm (back) Exhaust which was then balanced with 1x80mm in the side window (bottom, so the opposite side to the HSF, so the exhausts pulled this cooler air over the HSF and warm bits and then out.) and the front plus a HDD cooler intake from the HDD bays

Seeing as the CPU etc is the bit that gets warm, you want to have an exhaust as close to it as possible (the back one), to stop the inside air temp in the case getting too high and therefore heating everything else! Having an exhaust on the top is always good as heat rises so you want to be extracting the warmest air.
Having the 2 intakes as low to the floor (lower = colder in physics when i was at school) will help draw in colder air.

I never found that the front intakes inhibited cooling, as long as there is decent enough airflow (I have been known to chop the bottoms off the front of cases to allow more air throught easier. Means the exhaust fans dont' have to work so hard to extract the air in teh case, and keeping it all moving is the aim of the game, don't want it sitting there do we?!

The problem with meshes are that they get dusty easier as the dust is concentrated in one area, meaning you need to clean them more often to keep it all moving.

if I get bored one day I might re-create said experiments... but this is my 2p from way back when. I'll draw a diagram if I get bored today.

[Pob255]

As I've had some recent experence with the CM690 I'll give you my thoughts.

In the case the PSU is at the bottom and the top fan fit very close to the top of the motherboard.
So . . .

Get 1+1 additional 120mm fans. read on
Try to aim for 1 fan around the same spec of the fans in the case.
2nd fan up to you, this is for the thermalright 120Ultra (side note go for the Ultra120 extreme, not the basic Ultra120)
if you cannot find fans that match the case fans air flow wise, then consider ether of these:
- Remove both the rear and side pannel fan, and mount both at the top, use the two fans you've bought to go on the cpu and sidepannel
- Remove the rear fan and use it on the CPU cooler, use the two (matching) fans you've bought to go at the top of the case

Now when you get your CM690 case, remove the rear fan and mount it in one of the top slots, mount a 2nd fan in the other top slot. (both fans point up, so air blowing out of the top of the case)
Now when you mount the Ultra120, rotate it through 90 degrees so it's pointing up/down and mount the fan on the bottom blowing air up through the cooler and up to the top of the case (and so into the waiting fans above)


This set up will give you 2x120mm in and 2x120mm out
In Fans:
1 fan will blow over harddrives
1 fan will blow over the graphics card
Out Fans:
Both will be takeing air from the CPU cooler and warm air raising off the motherboard.

PS you will only be able to mount 1 fan on the side pannel with most aftermarket coolers, as they will block the higher side pannel hole (it's the optional one)

Hope this helps

[shkm]

Wow, didn't expect such in-depth responses. Thanks a bunch, I'll be employing some of these ideas and seeing how it goes.

[Pob255]

Let us know how you get on.

I must admit to likeing the the CM690 it's an overall nice case, so many good features and not that high a pricetag.
Only real thing it could do with is just a little more space, the motherboard sits in quite tight with fans at the top of the case esp if you have a largeish cooler pointing backwards.
In fact I'd advise against useing the top fan slots if you plan to use the rear fan and front/back cooler layout

On my friends recent build that I helped with, we had about 4mm between a Scythe Mine and top fans, which made trying to pulg the 8pin motherboard power cable in a bit tricky. This is a powerfull rear fan and two, low speed, weak fans in the top and the Mine point backwards.
I would of got him to build it upwards as I sugested above, had I know how tight the space was or could convince him to remove the mine and reseat it pointing upwards (he had real problems mounting the Mine and he refuses to remove it unless it breaks, so rather unlikly esp as he knows he can replace the fan without removeing the Mine)

[ajones]

Have always worked to the rule:

Front and bottom suck into the case (preferably over the HDDs)
Top and rear exhaust out of the case

Never been sure about side fans though...

All fans should be oriented to direct the airflow in a general front/bottom to top/rear direction.

[tiggerai]

Have always worked to the rule:

Front and bottom suck into the case (preferably over the HDDs)
Top and rear exhaust out of the case

Never been sure about side fans though...

All fans should be oriented to direct the airflow in a general front/bottom to top/rear direction.

Agreed - the side fan was part of a custom window... so without it would be a huge hole.

I would think it would stop hotspot pockets from appearing by adding another dimension to the airflow.

[Pob255]

Well I cut a hole in my side pannel to mount a 120mm fan to stick in a fan, to blow cool air over the graphics card and disrupt any possible hot air that might get trapped there so it doesn't recycle it's own hot air. (seeing as the graphics card is generally the 2nd hottest thing in a pc)

[tiggerai]

Well I cut a hole in my side pannel to mount a 120mm fan to stick in a fan, to blow cool air over the graphics card and disrupt any possible hot air that might get trapped there so it doesn't recycle it's own hot air. (seeing as the graphics card is generally the 2nd hottest thing in a pc)

Exactly... why do people always manage to say what I'm trying to say in a much more logical manner?

[Koolpc]

Well I cut a hole in my side pannel to mount a 120mm fan to stick in a fan, to blow cool air over the graphics card and disrupt any possible hot air that might get trapped there so it doesn't recycle it's own hot air. (seeing as the graphics card is generally the 2nd hottest thing in a pc)

Did it make an impact on the temps?

[Pob255]

I hoenstly cannot say as this was all part of the changes I made to an old server case to fit an ATX system into it an keep me bussy over the summer.

I seem to remember I get about 2c lower under load with the side fan turned up to max than with it truned to down to min on my fan controller, but I think this is more to do with feeding the graphics card cold air.

What did have a major effect on my graphics card temps was fitting an aftermarket cooler (that 2c is with the replacement cooler, a Gigbyte Vpower, which is basically the same as the 7900GTX and the 90mm fan was a major improvement over the 40mm stock one and sucks in more air)