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Topic # 136313 22-Nov-2013 16:54
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With the warmer weather my desktop get afternoon sun and the internal fans (CPU and power supply) are running at full tilt.

 

The case has a pre-cut grill and screws for another fan, the screws are at 70mm spaces.

Am I correct in assuming that one of the case fans of 80mm square frame (assuming the screw holes are not right on the edges) with a 4-pin Molex will do the job?  If the screw holes are different I can easily re-drill to suit.

R.

 

 

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  Reply # 939193 22-Nov-2013 17:34
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70mm centres sounds right for an 80mm fan. 80mm fans are pretty standard for the back of cases.

There's a chance your motherboard has a header for an extra fan, otherwise, if you can find a mollex connected fan, it'll do, molex fans aren't speed controlled though, just on.

Would probably pay to check all the vents and heatsinks for dust.




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  Reply # 939200 22-Nov-2013 18:15
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Yep, would suggest a (literal) spring clean of your case first. Most of the time it is simply additional dust making cooling less efficient.

 
 
 
 




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  Reply # 939206 22-Nov-2013 18:22
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Case and components are regularly cleaned for dust and crud ... all good. It's just the direct sunlight that's warming the study up.

My motherboard has the 3 pin connector for temp control, as well as spare 4 pin power lines, so no problem there.

Is it best to have the fan blowing air in, or sucking it out? At the moment the PSU fan is blowing out, and I guess the CPU fan blows downwards.

R.

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  Reply # 939223 22-Nov-2013 19:09
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Consider a fan controller. I couldn't get the automatic fan control working well, so I bought one. Not sure what make/model as I put stickers on it to identify which fan each dial's for.

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  Reply # 939228 22-Nov-2013 19:15
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Generally you want a slight positive pressure ie: slightly more active intake than active outake, this is so passive outake occurs meaning dust is forced out not sucked in.




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  Reply # 939232 22-Nov-2013 19:26
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Will test the on-board controller first (the other fans whirl up and down quite well, but separate controller is nice ide ... thanks. I have CoreTemp running so can see the temperatures going up and down.

So 'air in' is the way to go .... thanks for the diagrams. Not sure how powerdul those bolt on fans are, but would a thin fibre or foam filter be a good idea?

R.

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  Reply # 939377 23-Nov-2013 07:37
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It is correct that 70mm is the normal spacing for an 80mm fan. You can get these for just a couple of dollars off dx or alix. Local suppliers clearly make good money on these items with their markups. Having said that, I should note that it is also the same mounting hole spacing for 90mm fans (go figure) and they shift a lot more air. You can get those from Alix.

I buy these:

http://www.aliexpress.com/item/90mm-Computer-PC-Host-Cooling-4-Pins-IDE-Chassis-Crystal-Fan-Cooler-9cm-20931-01/923593722.html

That is a high flow 90mm fan with 70mm spacing and a 4 wire connection for full control. They cost a little more than the 80mm ones but they sure blow a good puff.

You did not say where the hole in your case is as that will affect whether you should blow in or suck out.

Also, where is your power supply and where is its fan intake?

In the descriptions that follow, I will assume that you have a tower case.

If you have a traditional case with the PSU at the top and the extra fan position at the back to the right of the motherboard IO panel when viewed from the rear then you probably want to setup the fan to suck air out of the case there.

Why? In a standard case, the cpu cooler will be sucking cool air in from the left hand side panel (viewed from the front) there will normally be a cutout in that panel for that purpose and perhaps even a small duct attached to the panel to ensure that the air being pulled in by the cpu cooling fan is coming from outside the case. The cpu fan will be expelling air into the general area surrounding the fan. If you set a fan on the back of the case adjacent to the motherboard IO panel then, if you have that fan blowing in to the case, you will be increasing the pressure in the part of the case that takes the outflow from the cpu cooler. You will thus reduce the airflow over the cpu cooler which is not what you are trying to achieve. So, a fan on the back panel should suck air out of the case. That will increase flow over the cpu and suck air directly out of a hot spot.

If you have a fan position on the left hand side panel (as viewed from the front) then you should set a fan there to blow air into the case. Fans there are normally used to cool graphics cards by raising the pressure and lowering the temperature of the air around the graphics cards air intakes.

If the fan position is in the front panel then you should blow air in to the case from there.

If that does not describe your setup then tell us more.



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  Reply # 939382 23-Nov-2013 07:52
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Morning jpoc,

Many thanks for your comments.

Yes, you have it quite correct as per my tower. I have mesh/cut-outs for mounting a fan on the left-hand panel, one near the bottom and the other about two-thirds of the way up. The top one has a small cuff/venturi duct as you described.

TradeMe has a few fans at around $5.00.

R.



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  Reply # 939826 24-Nov-2013 12:44
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What do you guys think about the fan units that are monuted on an expansion slot bracket?

e.g. http://www.ebay.com/sch/i.html?_odkw=expansion+slot+fan&_sop=15&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.X+slot+fan&_nkw=+slot+fan&_sacat=0

R.

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  Reply # 939845 24-Nov-2013 13:17
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That would create negative pressure, but doesn't control the direction of the airflow.

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  Reply # 940015 24-Nov-2013 22:05
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Rickles: What do you guys think about the fan units that are monuted on an expansion slot bracket?

e.g. http://www.ebay.com/sch/i.html?_odkw=expansion+slot+fan&_sop=15&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.X+slot+fan&_nkw=+slot+fan&_sacat=0

R.


You could put it in the highest slot on the motherboard - assuming a tower case - that would be the position closest to the cpu. That would suck hot air from the cpu cooler and eject it from that case.

That would be a good thing but if it was placed below another PCI/PCIx card. it would be less helpful.


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  Reply # 940349 25-Nov-2013 13:49
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Rickles: What do you guys think about the fan units that are monuted on an expansion slot bracket?

e.g. http://www.ebay.com/sch/i.html?_odkw=expansion+slot+fan&_sop=15&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.X+slot+fan&_nkw=+slot+fan&_sacat=0

R.


Better to get a nice flow in and out through the whole case imo.

What case do you have?



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  Reply # 940354 25-Nov-2013 14:09
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I have an Eastec case ... and just bought a fan that will screw onto the left hand side panel (viz. air in = positive pressure).

Have been recording temperatures 3 times per day, and will see just what difference the fan makes.

Thanks for eveyone's opinions.

R.

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  Reply # 940375 25-Nov-2013 14:57
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I've always found the postive vs. negative air pressure debate to be fairly minor - I generally spend a lot more time working on airflow routes than the proportion of fans I have pushing and pulling. I want the airflow to go exactly over the components that need it the most, and in the most logical order. Therefore I use intake fans where I want the air to come from and exhaust fans for where I want the air to leave...

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