2nd cooling fan

[LazyLinus]

I'd like to install a second cooling fan in the case, and have a couple of question. Where should I connect it to avoid RFI? Should I have it drawing into or exhausting out of the case? Should I disconnect the current fan?
The second fan will use 12 watts of 120VAC/60 Hz, so I should have enough extra to supply it. The current fan drawns into the powersupply, then exhausts into the case, but there isn't alot of airflow over the CPU heatsink and after an hour or so, it's hot to the touch.
If you need more info, just ask. Thanks in advance.

[Ghost_Hacker]

I would not disconnect the second fan. You'll always want that fan moving air around the power supply. There are three places to place the fan. The top of the case is a good place for blowing out hot air. The side is a good place to blow cool air in. The back is good for blowing hot air out and the front can do either. On most of my cases the front fan blows cool air in while the top/back fan blows hot air out.

In your case I would get two fans. One for the top to blow hot air out and one for the front/side to blow cool air in . RFI shouldn't be a problem.(If the case were mine I would reverse the power supply's fan to blow out hot air. NOT RECOMMENED FOR THOSE WHO HAVE NOT DONE THIS BEFORE).

You might also want to buy a good heatsink/fan for the processor.


Hope this helps

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[This message has been edited by Ghost_Hacker (edited 01-29-2001).]

[sleddog]

I agree with Ghost.

If you want to cool the case you have to create an air *flow* through the case. You can't really do that with one fan; it requires at least two. The 'standard' setup, if there is such a thing, is an intake fan bootom front and an exhaust fan top back. This creates an airflow diagonally through the case, with you cpu in the middle. Just keep one thing in mind: hot air rises. Exhaust fans should towards the top of the case. Cool air should be brought in at the bottom.

Now the problem with this is your power supply fan. It is bringing air into the case at top, which throws our nice airflow all out of whack. The simple answer is to reverse the fan -- easy to do but potentially dangerous as it requires you open up the power supply, and there is high voltage inside. If there's a friendly neighbourhood computer shop or electronic repair shop nearby, they could do it for you in about 2 minutes.

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sleddog
[sleddog.f2s.com] (http://www.sleddog.f2s.com)

[Paleo Pete]

OK, I'll throw my 2¢ in too.

I agree with the above completely. Turn the power supply fan around and add the new one at bottom front, sucking air in, and the power supply fan blowing out the top back. I keep mine set up that way and it works very well.

I also strongly advise great care if you open the power supply, in agreement with both the above posts. The reason being, the power supply contains capacitors that hold a very unhealthy and possibly deadly electrical charge for several days, unless you KNOW how to discharge it. If you're the slightest bit uncomfortable with that, by all means take it to a computer shop. All it takes is one slight wrong movement and you've gotten a major jolt of high voltage before you even realize it.

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[LazyLinus]

Ok, so the first fan stays in, but I need to swap the power leads to change the flow direction, no prob there. And since I would have to hack up the case to put the 2nd fan anywhere else, it's going to be placed in the back center, drawing air in. I don't have to worry about convection currents, because the 2nd fan will exchange the case air volume in about 30 seconds. I have airflow through the case now, but it's pretty weak. That's why the 2nd fan is being added.

This leaves just one question unanswered: where to hook it up? To a switched supply on the unstepped side of the transformer?

[Ghost_Hacker]

I would add it to the stepped side of the Transformer. Provided that your power supply can take the load.


Also to change the fans flow direction you just need to turn the fan around. Since it "blows" in the direction of the sticker on the fan's hub.
If the sticker faces toward the outside of the case the fan will blow in that direction.


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"It's just a whisper in my Ghost"

[Ghost_Hacker]

After rereading your first post I have a question. Do you have a "computer case" fan or just a fan period?

If the latter is true than this is a fan you don't want to install to the inside of your case. The noise from the line would not be filtered enough to prevent problems. You may be able to install it to the outside of the case with no problems. Also I do not think you could install such a fan to the stepped side of your transformer. It would proably need to be "installed" to the unstepped side. But that could in turn mess up the primary signal.


Good Luck


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