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Small Quiet Cooling Fan

1636 Views 16 Replies 9 Participants Last post by bowser, Feb 14, 2004

bowser

Discussion Starter · Jan 22, 2004

I have a modest home theater which includes a credenza to hold the audio components. The problem is that the credenza was not designed to contain audio equipment and the equipment is getting hot during normal operation.

I purchased the following small cooling fan from Rockler, a woodworker supply house, to help remove some of the heat, however, it just makes too much noise.

http://www.rockler.com/ecom7/showdet...id=20&catid=19

I believe it is rated at 23 cfm and 30 dB.

Does anyone know of a similar sized fan that is very quiet.

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greywolf

· #2 · Jan 22, 2004

Noise and CFM are pretty much proportional. It's not really the fan but the air movement that makes the noise. Putting the fan away from the surface and sending the air through a baffle system allows the air to move but quiets it much like a car muffler does. I like to use a 12VDC computer fan powered by a variable power supply such as this:

http://www.radioshack.com/product.as...%5Fid=273-1667

I can adjust the power to meet the room noise floor.

Bighitter

· #3 · Jan 22, 2004

Also a larger fan spinning the same speed as a smaller fan will push more air and sound quieter due to the greater surface area to distribute the wind resistance over. 120mm fan running at 7volts will be quieter than an 80mm fan running at 7volts while still pushing more air.

ag96

· #4 · Jan 22, 2004

I am trying to use AC (alternating current, not air conditioning!) fans on an entertaiment center I'm building for my media room, so that I can plug the fan directly into the switched outlet on the receiver. It works great...except that the fan makes a bit of noise. Before I installed it, I plugged it directly in to the wall and it seemed to make considerably less noise. I don't know if I need to insulate the fan from the surface of the wood somehow (like felt or something), but my next approach was going to be to put a step-down transformer in to reduce the voltage from 120 to about 25, and see what that does. It moved a ton of air at 120.

They are only 92mm fans, by the way, and they were about 20 bucks at the local electonics store.

Starsky

· #5 · Jan 22, 2004

You might want to check out the Comair Rotron Whisper line of 120v AC fans:
http://www.comairrotron.com/datasheets.html

ag96

· #6 · Jan 22, 2004

I'll give those a shot if my $5 RadioShack 1:6 transformer doesn't do the trick

flounder

· #7 · Jan 24, 2004

I also had purchased a 4" cooling fan (115 AC) from Radio Shack for a home built entertainment cabinet as well. I can tell that the fan is going to be a bit louder than I was hoping for now that it is installed.

I plain on putting a dimmer switch between the fan and the power source to try and slow the fan speed down just a bit to soften the noise. I will let you know how it works out.

Flounder

Diver

· #8 · Jan 25, 2004

The comair rotron tip was right on. The WR2A1 moves 48CFM at ony 27 dB (If I recall). I use these at work to replace noisier muffin fans in an attempt to reduce background noise for personnel.

I like the Radio Shack variable voltage transformer idea.

How you mount the fan to the cabinet makes a diference (as pointed out). cabinet resonance, caused by fan vibration, will increase sound. Decouple the fan from the cabinet. make a gasket out of cork, neoprene, try mounting with neoprene backed washers, maybe try rubber isolated stand offs. other ideas?

Placing any fan at the end of a duct will result in a loss of flow due to head pressure/back presure. The commair website has an excellent section explaining this, and more than you ever wanted to know about the engineering that has gone into making fans that are ideal for different applications. I prefer to support a company who invests in this kind of engineering, over a cheaper product who copies the ideas of other companies, without having to invest a dime in research & development. (That's a spin on "Buy American," rather than buying cheaper Chinese pirated products.) =)

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ag96

· #9 · Jan 25, 2004

Flounder has the correct solution - this is another case of me trying to over-engineer a solution

It occurred to me today, after I hooked up the 25V transformer and got NOTHING out of the fan, that I should just go by a damn dimmer switch and control it that way. I'm not sure why the transformer didn't work, other than the fact that 25V OBVIOUSLY isn't enough to run the fan. The transformer is rated for 450mA, whereas the fan states that it requires 130mA. When I get a dimmer on the fan, I'll have to set the dimmer on the lowest setting that runs the fan, then check the voltage with a DMM just to satisfy my own curiousity.

Mark Hoy

· #10 · Jan 25, 2004

Get a variable output DC wall wart from Radio Shack. Get a 12v fan from Pabst (or similar low noise fan built for computer systems). This allows you to plug into the 120v output from your receiver.

Drop the voltage as with the variable supply to 9v and see if it's quiet enough for you. Some 12v fans don't always start below 7v so be careful. You could also try some 6v fans (perhaps a couple, one to push air in and the other to exaust air.

Edit--> use the example that Greywolf suggested, this one has too many low voltages that you don't need.

Mark Hoy

· #11 · Jan 25, 2004

One of the mistakes I made while installing my enclosure was not creating a large enough hole for a large fan. I attempted to keep the system cool with a smaller fan, however smaller fans make much more noise since they spin faster. A larger slower fan is quieter. If you can, mount the fan with rubber washers and have a replaceable filter to cut down on dust.

I ended up creating a larger hole with a wood file. Would have been so much easier before everything was mounted to the wall. It's a wall unit so it's not so easy to change anything.

flounder

· #12 · Jan 25, 2004

Not sure if the dimmer switch is the way to go or not. I noticed a warning on the switch that says not to connect it with an appliance with a motor or the switch may burn out.

Anyone out there who is smart about reducing AC current care to comment on why?

I can just imagine getting a phone call from my wife asking why the stereo cabinet is smoking !!

Flounder

Starsky

· #13 · Jan 26, 2004

I tried cutting my own gaskets out of neoprene, total PITA and not much room for error. I'd recommend these . $10 bucks a pair, a little pricey but and worth every penny.

Also, if you're pulling air into the cabinet a foam air filter will reduce niose a little and keep some dust out.

ag96

· #14 · Jan 26, 2004

Flounder, it probably involves the inductive load required by the motor. In the case of a small cooling fan, I SERIOUSLY doubt it is going to damage the switch. I picked up a $10 dimmer (I think it was a Lutron Skylark or something, it was the cheapest Home Depot had

) and connected both fans in parallel to the switch - it works like a champ. The fans won't run at anything less than half power though. Assuming the rheostat is linear (which might not be valid), that would explain why the 25V the transformer was putting out wasn't cutting it.

Diver

· #15 · Jan 31, 2004

Starsky,

Thank you, God bless you! The time it would take me to cut a gasket out of Neoprene is worth much more than $10! I've added your link to my "Favorites/HT/Cooling Fan" folder for future reference.

trpltongue

· #16 · Feb 5, 2004

I've come up with another very good (IMO) alternative. You can pick up an attic fan thermostat at HD (~$19) or at Grainger, also pick up a female electrical cord end and a male electrical cord end (~$2 each). Then pick up a 9V AC/DC transformer, 600mA (at least) from Parts Express (~$5). And finally, pick up 2 Panaflo FBA08A12L1A fans. These are widely regarded as the best, quietest fans you can buy. They go for about $5 each. Now here comes the fun part.

Wire the male electrical cord end to the attic thermostats incoming AC line. Wire the female electrical cord end to the attic thermostats outgoing AC line. Wire the fans in parallel to the 9V transformers output. Plug the male electrical cord end into any outlet and plug the 9V transformer into the female cord end. Set the temperature that you would like on the attic fan thermostat.

Now regardless of whether your equipment is on or not, if your cabinet gets above the set temperature, the attic fan thermostat will kick on and turn on the fans. If the fans are too loud with 9V (doubt it) you can wire a rheostat onto the 9V outlet and turn all the fans down.

I'll take some pictures when I get it all wired up.

Russ

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bowser

Discussion Starter · #17 · Feb 14, 2004

Thanks for all the great input.

I went with the Papst 8412NGL cooling fan, Radio Shack 3-12 VDC power supply, and the NoiseKiller 80 gaskets. It all works great and I can only hear the fan when the sound is turned off. I normally run at the 9v setting which produces about 10 dB of noise, since the 12v setting produces about 12 dB.

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