how much "CFM" will be needen?

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norcalweedz

Active Member
thanks for all the great advice every one. another question though lol. my grow room is 4ft L x 2ft W x 8ft T, i went to this site on the internet to calculate how much cfm will be needed for a this room size. it came up with 80 cfm, that seems a bit low to me mabye not. it did not specify wether that was every min or two. any help would be great. also im using a 250 watt hps/mh light set up if that info was needed.:bigjoint:
 
Toppers

Toppers

Well-Known Member
That sounds about right to me (althought someone more knowledgable should chime in w/ the correct formula you need).

If it helps:

I run a homebox small (6' x 2.5' x 2.5') with a 250w Sun Systems attached ballast (i.e. more heat from ballast being right there.) and a 90 CFM hydrofarms fan running consantly. It keeps it SUPER chilled with the flaps up. Like, 12" away from the light the canopy barely gets over 74F. This fan is strong for such a small area.

Hope that helps.
 
greenearth5

greenearth5

Well-Known Member
im wondering the same thing.... i have 42 sq ft to deodorize and plan on upgrading my 150 to a 400W ... im courious on how big of fan/filter to get... and how many times per minute i need to circulate the air

I remember coming across some mathematical formula to determine how many cfm i would need but i cant find it again
 
kmo8762

kmo8762

Well-Known Member
Toppers said:
That sounds about right to me (althought someone more knowledgable should chime in w/ the correct formula you need).

If it helps:

I run a homebox small (6' x 2.5' x 2.5') with a 250w Sun Systems attached ballast (i.e. more heat from ballast being right there.) and a 90 CFM hydrofarms fan running consantly. It keeps it SUPER chilled with the flaps up. Like, 12" away from the light the canopy barely gets over 74F. This fan is strong for such a small area.

Hope that helps.
Click to expand...
How well do you like your sunsystem light? I'm in the market but don't know much about them.
 
kmo8762

kmo8762

Well-Known Member
greenearth5

greenearth5

Well-Known Member
I keep my actual light bulb about 3 inches away from the tops of the plants.. i also keep a box fan blowing on my crop... check out my grow journal below...:joint:

kmo8762 said:
Ok, but how do they perform. I won't be using a cool tube, I've got a monster fan to pull air thru the entire grow room. I've read that an attached ballast produces more heat than a remote, my area is small so I want the light as close a possible without any burn.
Click to expand...
 
Toppers

Toppers

Well-Known Member
I like the Sun System 2 a lot, quality unit. This is how much space it takes up in a Homebox S just to give you an idea.

But if I did it again, would go with remote ballast. I'm pretty strong and it's hard as hell for me to install/remove this thing off the chains, it's pretty heavy.

 
D

dirtyoz

Well-Known Member
Dont be afraid to get a higher CFM fan than you think you need. You can always install a fan speed control and turn it down. I would go with a 6 inch unit and 6 inch ducting. That way it will be way quieter when turned down.
I did the same thing with a 4" setup @ 150 cfm , but wish I had gone to the 6".
My closet is 2 x 4 x 8. Dont forget about the temperature of the makeup air (The air replacing expelled air), it makes a difference too.
 
NewGrow60sToker

NewGrow60sToker

Well-Known Member
CFM= Cubic Feet per Minute

My room is 4 x 2.5 x 7, or 70 Cubic Feet

If you want to completely exchange the air in a room in 5 minutes, take the cubic feet and divide by 5 and that would = the CFM you'll need.

5 Minute Exchange = 70/5 = 14cfm

4 Minute Exchange = 70/4 = 17.5cfm

3 Minute Exchange = 70/3 = 23.33cfm

2 Minute Exchange = 70/2 = 35cfm

1.5 Minutes would = 46.66cfm

1 Minute Exchange = 70/1 = 70cfm

My room is 70 cubic feet and I went with a 6" 130CFM/Scrubber/Filter.

Overkill, yes, but I'll tone it down with a speed control.

Hope that helps.
 
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