Computer fans for cooling

[tony098]

Hi,

I'd like to mount several DC computer fans in my canopy. The DC fans ($2/each) are much cheaper than the AC fans ($20+). What kind of adapter do you use? How do you modify the fan's molex connector to hook it up to the adapter? Please be as specific as possible because I am a complete noob?

BTW, what size/brand of fans do you recommand?

Thanks.

 

[Tigger240]

you fans should have a power rating on them, and then look through your supply of "wall warts" there ac to dc converters, and there the big clucky thing that phone chargers, drill chargers, ect, use. find one that matches, or closly matches the specs on the fans, and then cut the end off of the converter. strip the wire ends and temporaly hook them up and check fan direction. if it spins the way you want, great, crimp them together and a lill electrical tape, done. if you want the fan to spin the opposite direction, reverse the wires.

to get techincal, usually, the positive out of the wall wart is marked, with white lettering, a ribbed texture, square vs round, ect. then the positive gets hooked up to the red wire from the fan, but in the end it doesnt matter as long as the fan is spinning, and in the direction you want it to spin in. i guess an arguement could be made that a fan is less effencient spinning backwards, but, everyone has there levels of quality.

 

[69vette]

<a href=showthread.php?s=&postid=8081386#post8081386 target=_blank>Originally posted</a> by Tigger240

the positive gets hooked up to the red wire from the fan, but in the end it doesnt matter as long as the fan is spinning, and in the direction you want it to spin in. i guess an arguement could be made that a fan is less effencient spinning backwards, but, everyone has there levels of quality.

It does matter. The fan will blow twice as much air running forward as it will backward. You can easily tell the difference by switching the wires around and holding your hand in front of the fan. Besides that, there will be an arrow on the fan showing the direction of air flow.

Why bother doing it if you're not going to do it right.

 

[Vincerama2]

Just a note that it's better to blow fresh air into the hood than it is to pull air OUT of the hood. Mostly to reduce damage to the fan itself by pulling humid air through it. Though in a computer case you are using the fan to pull hot air OUT. (but no moisture in a computer case!).

I'm sure someone will disagree...

V

 

[Vincerama2]

Oh, and one more point ... I used to use a "clip on" desk fan, which runs on AC (so no wasted power on AC/DC adapter) and you can generally get at Walmart for $6. Plus it was a larger fan, so it was quieter. Though you can get quiet computer fans too. Just FYI and something to think about.

V

 

[tony098]

Thanks for all the information.

Vincerama2 - I can't use a clip on fan because these fans need to go under my canopy. I do use clip on fan on the sump.

My tank, thus my hood, is 60" long but my T-5 is 48". I plan to try out with 2 80mm fans. I don't have the tool to make a hole on the side of the canopy to mount the fans, so I am going to mount them on the back which is open. What are the directions should I set? Both fans blow from back to front? Or one blows back to front and another pull air out of the canopy?

 

[tony098]

One more question. What size and RPM fans do you use? I use the Enermax 3000 RPM 80mm fan and it is weak.

 

[BlueCoast]

Coming from the more electronically nerdy versus the cooler fish nerd genus, i can only share some experience. Most computer fans work fine until there is a pressure difference applied. Just like the cheap powerhead that works fine till the head pressure gets high, if you want to move a large amount of air go for a small squirrel cage type fan and avoid the PC fans. Also larger is usually better with them, a 3" fan spins faster to equal the flow of a 5", faster spinning equals small vacuum cleaner sounds.... ask my ex... she hated my pc.

I would not run them in a push-pull scenario. While this reduces the load on each fan slightly, it does not increase the airflow significantly over 1 fan. You will be better off making 2 intake or 2 exhaust fans. I prefer to have them as exhaust fans with the coolest components farthest away, that way latent heat is not dragged through your hood. This way the hot air takes the shortest route OUT and cannot soak into your other components.

 

[Vincerama2]

Honestly, I no longer use a fan in my canopy. If there is a heat issue, I'll use a clip-on desk fan in the sump blowing across the surface of the water. Obviously that doesn't help keep lights cooler.

My canopy has holes drilled in it just above the lights. On hot days, I can open the lid, which results in at least half the canopy being open (The entire front, back and front 3rd of the canopy would be open!

I think if I were to add fans, then I'd probably blow them in from the back sides and aim them towards the lights. I believe that the directed air flow of the fans blowing onto the hot lights is more useful than pulling air OUT of the canopy, because with an open back, the air you are pulling "out" might just be air drawn from around the fan. A computer case is a sealed box with vent holes in it. When you have your exhaust fan in there, the air follows particular pathways to get to the exhaust fan. If your canopy is open in the back, then you'd have to put exhaust fans in the FRONT of the canopy, otherwise they won't gaurantee air flow pulling across the top of the canopy. (Get what I'm saying?) If you BLOW air in from the back, you can direct the fans over the hot lights. Exhausting air out from the completely open back means you need to cut intake vents in the front of the canopy, or else you are probably just drawing air into the fan minimally from inside the canopy, and more from the outside.

I don't know if I'm making myself clear. Um, I suppose it's like if you stood in your garage on a hot day and the garage door was open but you had a fan blowing OUT stationed at the garage door opening, most likley there will still be a lot of dead air in the BACK of the enclosed part of the garage. But if you blow air INTO the garage from that point, there will be a lot more flow in the enclosed area.

OK, I'm getting too confusing now... but that's what I think anyway.

V

 

[hawaiianwargod]

BlueCoast
[welcome]