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darien87 23rd May 2007 06:28 PM

Cabinet cooling

I bought 2 of these fans and a bare wire standard plug yesterday from Radio Shack.

My plan was to wire them both to the plug and plug them in to the back of my receiver so that they would turn on every time I used my receiver. I was thinking of having one at the bottom of the cabinet to pull in cool air, and one at the top to blow out hot air.

I was planning on wiring them parallel, but the fans just have 2 black wires. There is no marking as to which is positive and which is negative. What am I supposed to do? Did I buy the right fans?

Thanks for the help.

Pjotr 23rd May 2007 06:43 PM


Your link shows "120VAC 3" Fan”.

Up to my knowledge, the AC mains has no plus or minus :bigeyes: These fans are intended for direct connection to the (American) mains.

Cheers ;)

darien87 23rd May 2007 07:07 PM

Thanks for the info Pjotr.

Another question I have is, can I wire both fans to one plug or do I need to wire them each to their own plug? Anyone out there with U.S. knowledge?

gootee 24th May 2007 03:41 AM


If the sum of the fans' two power ratings, in VA (Volt-Amps) or Watts [or the sum of their current ratings (Amps)], is less than the power rating [or current rating] of the plug you're planning to use, and that of the AC mains circuit it will plug into, then you should be able to wire them in parallel. Since they are small fans, it should be no problem at all, even without looking at the ratings of anything.

If there's any way to tell the two fan wires apart, besides color, e.g. if they each go to a certain part of the fan, the same way on both fans, you might want to pair the wires to the plug, appropriately, in case it matters with the type of motors your fans have.

Try not to run the wires (nor place the fans) near any other circuitry or devices, inside your enclosure.

MAKE SURE that your wiring job is safe and very, very durable and secure. If you don't know the accepted methods, don't do it.

For what it's worth, most of the literature I've read about ventilation fans seems to imply that a fan blowing in from the outside is usually more effective than one sucking air out of the enclosure. I realize that you are planning to have one of each. But if you have enough square inches of other exit holes, you might want to at least consider having both of them blowing inward.

You might also want to consider using some sort of filters. The replacement window air conditioner filter material (a sort of "open cell" plastic foam, usually on the order of 1/4 inch or thinner) has been a favorite of many who replaced fan filters on older Tektronix oscilloscopes, et al. I didn't look at your fan link. So I don't know how applicable it might be.

Good luck!

- Tom Gootee


darien87 29th May 2007 04:02 AM

Well I hooked the fans up yesterday, each to it's own separate power cable. They work fine, except they are HELLA loud. I noticed that when I put my finger on them and slow them down a little, the noise goes down quite a bit.

I was wondering if it is possible to do something to make the fans spin slower? Would wiring a resistor in do the trick? If so, what type of resistor and how do I wire it to the fans?


I_Forgot 30th May 2007 01:20 AM

A resistor might work, but you'll have to experiment to find effective values. It would be better to look for a small 48V transformer.

Usually if you want quiet fans, you get 220V fans and run them on 117VAC. They turn slowly and quietly.


calimusix 31st May 2007 04:05 PM

Heres what I use
I bought a super quiet fan from

It has a thermostat for on/off and I can barely hear it, A friend of mine has two that I couldn't hear at all.

They told me you want to have the fan exhausting the air from the top.


darien87 31st May 2007 04:30 PM

Thanks for the info Cali, but $50 for a fan?!?! Yikes. I'm going to try a couple of potentiometers from Radio Shack, (about $3), to slow the fans down a bit and see if that gets rid of the noise. If that doesn't help, maybe I'll look into those fans you recommended.

I_Forgot 31st May 2007 06:47 PM

Get a cheap lamp dimmer from walmart or a hardware store. You should be ble to get one for $3 or so. It will work.


darien87 31st May 2007 09:55 PM

Funny that you mention that. I was told by a manager at Radio Shack to do the exact same thing. The guy at Radio Shack said that using a potentiometer might just end up burning up the fan.

But I ended up buying a couple of fans off eBay.

Hopefully, these will work. They're rated at 27.5db. My Radio Shack fans are rated at 36db. Hopefully 27.5db is quiet enough for me.

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