What fans to use in canopy?

[MickO]

Hi all!

Have a question about fans. I'm trying to decide what kind of fans to put in my home-built canopy. I'm needing to cool about 1,240W of lighting (2 x 400W MH and 4 x 110W VHO).

Pictures of canopy can be seen here (http://www.ohrberg.org/angela_web/htdocs_staging/pictures/tank/canopy3.jpg) and here (http://www.ohrberg.org/angela_web/htdocs_staging/pictures/tank/canopy_done1.jpg).

I have a few "venting holes" in the top of the canopy, and there's definitely warm air raising out of these holes when the lights are on, but it's not enough. Water temp goes from 76-77F to close to 81F.

I was thinking about putting two fans on the canopy, blowing air INTO the canopy (not directly onto the MH bulbs though :) ). I have already pretty much decided to go with 110V AC fans (as opposed to 12V DC).

The question is - what kind of airflow do I need, and what's a decent noise level?

I looked at RatShack and saw two fans - one pushed 32 CFM @ 36dB, and another pushed 65 CFM @ 38dB. I guess I'm asking is 64 CFM is enough, or would I need to go to 130 CFM?

Also - does anyone have any input on how much noise two 36/38dB fans would make?

Thanks for any and all input/help!

[texasreefer]

I would go w/ the bigger ones, if you don't need the extra cooling you can just run one. I have both on different tanks. I can't really tell the difference in the noise, but I'm hard of hearing though. It helps when your girlfriend starts complaining. :)

[Valclore]

If you use rubber gromets in-between the canopy and the fan it shouldn't matter to much about the db, but I would say anything under 45db would be quite enough. Go with the highest air flow possible if you live in a hot climate it will help during the summer!! "Found that out when the 125g reef hit 84 degrees!!!" To me it seems the DC fans can move alot more air than most of the AC fans, all you would need to run them is a cheap computer power supply, 3-5$$. Check out Sunon website they have some great 120mm's that move some major air. Hope it helps.
www.sunon.com

[69camaro]

As recording engineer dB is my buisiness. The difference between 36 and 38 dB is non existent to the human ear, so get the bigger fans. You probably won't even hear them unless your within 7-8 feet. As a reference; walking down an average city street you are exposed to about 70-75 dB. Unless of course there's a garbage truck next to your head (probably 120-130 dB).

I would also suggest that you face the fans so that they blow air out rather than in. Removing heat is much more efficient than trying to force cool air in. It will create a vaccum(ish) that will draw the necessary cool air in.

[neonnight]

69camaro is right as a car nut pullin heat out will work much better then a pusher.by the way great hood never seen 1 built like that but it looks like it will work great for what you need

[MickO]

Thanks for the suggestions! The main reason I had originally decided on 110V fans was that I didn't want to mess with an AC-DC converter.

Also, if set to pull air OUT, I'd be afraid what the warm, humid and salty air would do to the fan motors. I already have some rather large holes right above the reflectors (conveniently forgot to mention this in original post...sorry), and even without fans, I do feel hot air raising. I would also think that it'd be more efficient to have the hot air exit at the top, rather than try to suck it out a ways down, closer to the water. :D

Just ideas! :) I may try to look for a cheap AC-DC converter. I'm thinking I'll need fans that draw at least 500 mA, so a 1.5A converter should be enough (includes a little headroom as well).

Thanks folks!

[Valclore]

Maybe put the fans over the vent holes you already have, as for the humidity the MH bulbs should take care of that..

[kgross]

Put the fans blowing in. The hot moist air will wear the fans out quicker. Also they will cool better blowing in because they cool by causing more evaporation of the water not by just removing the hot air.

A fan blowing in will cool about 2x as much as one sucking out.

Kim Gross
http://www.jensalt.com

[ReefVan]

Got to agree with kgross (saltwater corrosion) , go that way and if you're inclined to get fancy then do what I did, add a 110vac thermostat.

Buddy ABahn did the same and his MH setup over his 180 reef runs just fine.

Use a normal home thermostat in a plastic electrical box and wire in a 110vac dpdt relay on the rear exterior of your hood.

When the thermostat says "hot" then the juice goes thru the N.C relay contacts to power the fan. When the thermostat says "cold" then the relay coil is energized and the N.C relay contacts open to shut down your fans.

[MickO]

Sweet! Thanks for all your suggestions! It seems the consesus would be to stick with 120V AC fans blowing 'clean' air into the canopy. I will, however, be looking for different fans. I bet I could find cheaper ones online.

Thanks all!

[gonereefin']

Hi:
I've contacted EDM Fans and they have a ton of computer-type fans. Every size you could imagine. AC or DC all rated in flow amounts and noise. They will very promtly mail you a catalog of what they offer BUT the hag answering emails won't reply!! I'm so ****ed, 3 emails and no reply. I've gotta call sometime and maybe get to speak with someone with an ounce of ambition. Otherwise, they have the fans needed and priced right too.
Good luck, Randy.

[jester777]

i ordered my fans from www.hosfelt.com. wonderful service, fast shipping and very reasonable prices. i went w/ 2 115v ~95cfm. i have them hooked up to a dimmer so i can throttle them back as i don't need that much airflow just to cool the canopy, but figure i may need the extra cfm during the summer. btw i'm running 2x 400w MH.

[LarryW]

I have 2 ice cap fans with my 2 250 MH kits. They have a temp sensor that causes them to rotate faster when the temp rises, and slows down when it cools off. They are very, very quite, and besides the cost :eek2: I am very happy with them.