Cooling fan question....

PaintGuru · 11-08-2004, 09:33 AM

What is a good CFM amount to get for a muffin type cooling fan? I'm going to install 4 into the top of my canopy and the cheapest one I found has a flow of 107 CFM. I have no idea if this is a standard amount, way too low, or what? Thanks.

jdbassin · 11-08-2004, 09:49 AM

How big is your tank?, What type of lighting do you have?, How far above the water are the bulbs?. is your hood completely enclosed or is there a lot of open space like in the back?

jd

PaintGuru · 11-08-2004, 10:40 AM

Oh you want real details eh?

93 gal cube (30"x30"x24"). It has an overflow, so while the back is open, there is very little clearance between the wall and the tank, so I think the air exchange is greatly reduced. 2 MHs, one-250W 20K on for about 8 hrs, one-400W 10K on for about 3-4 hrs...each are about 4-5" off the water surface. My plan was to put them on the top of the canopy so I don't have to look at them and have 2 blowing in and 2 blowing out. Hope that helps with your questions

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jdbassin · 11-08-2004, 11:46 AM

Wow that's awful close to the water most recomend 8 to 12 inches for halides. With four fans 2 in two out(You'll find a lot of differing oppinions about that subject) about 90 cfm's each or better should work, but With the bulbs that close to the water and huge amounts of airflow your gonna have a lot of evaporation i would imagine. is there any way to get the halides higher up off the water? I think a lot of problems are going to come down to the bulbs being too close to the surface. You also run into the risk of burning yourself or splashing water getting on the bulbs and causing them to burst.

jd

PaintGuru · 11-08-2004, 11:58 AM

Quote:

Originally Posted by jdbassin

Wow that's awful close to the water most recomend 8 to 12 inches for halides. With four fans 2 in two out(You'll find a lot of differing oppinions about that subject) about 90 cfm's each or better should work, but With the bulbs that close to the water and huge amounts of airflow your gonna have a lot of evaporation i would imagine. is there any way to get the halides higher up off the water? I think a lot of problems are going to come down to the bulbs being too close to the surface. You also run into the risk of burning yourself or splashing water getting on the bulbs and causing them to burst.

jd

I recall may people discussing how close they get their MHs to the water and many go with the 4-6" range (I know, everyone has their own opinions...actually I think mine is closer to 6"...I'll check when I get home). This really wasnt a problem with my 180g, so i really though this would be ok with my current setup, but I am seeing much larger temperature swings then I did before. I really cant change things now (height), so my plan has been to cut back the 400W lamp to a short "burst" of 3 hrs or so, and leaving my 20K as a more indirect type lighting (the 250W doesn't seem to add much heat, it's the 400 that is the problem). I'll go ahead and order those fans then

jdbassin · 11-08-2004, 12:10 PM

the four 107 cfm's you mentioned should prob be fine. i suppose if not you could always add 2 more

let me know how it all turns out. id love to see pics of that tank. I love the squares. do they offer an adjustable rate fans? mine are adjustable from 40 to 100 cfms. maybe if they had something in the 100 to 175 cfm adjustable range it would give you some room to play and not have to worry about being stuck with something that is either all on or all off. just a thought. I hope I'm helping some here.

jd

PaintGuru · 11-08-2004, 12:42 PM

Yeah I don't know if these are adjustable...they are just cheap little computer 110V computer fans

. I plan to use timers to turn them on and off earlier if there is a problem with them cooling too much, but I think I'm pretty close right now and just need a little bit extra cooling. I'll do trial and error to see if 2 blowing in and 2 blowing out is best, or if all 4 blowing in would be better. I'll send pictures when I get everything going. Thanks.

wanareef · 11-10-2004, 09:42 AM

If you think about it, blowing in, would increase the life of the fan in a harsh enviroment - like salt air. But then there are those that have both, in and out.

I have ours blowing in and the side exposed to the tank, is rusting.

Mine are just below the lights, blowing across them and above the water surface. Both are 250w's with 4x URI actinics = 1160w's

Geoff · 11-10-2004, 10:43 AM

i have all of mine blowing out. this is my thinking. FWIW

where is all of the air going to go when it is in the canopy? it is easier to increase the pressure of an area than it is to create a vacuum. with the air blowing out you are lowering the pressure in the canopy which helps in the evaporation of the water. also with the fans blowing out all of the hot air is being removed and cool surrounding air is being pulled in. you are not recirculating the air inside the canopy.

G~