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blowdro
09-10-2010, 03:31 PM
:D I would like to get a growlab 120 which is 3'11''x3'11''x6'7''. I want to use a 600 watt air-cooled light. I was having trouble figuering what size fan and filter I needed for this size tent. I think I got it,what I got was 50.4 cfm.Can someone tell is this right.THANK YOU for any help.:D I used the formula in ventalation part 1.

brbubba
09-13-2010, 07:56 AM
79"x47"x47"=174511 in^3
(174511 in^3)x((ft^3)/(12^3 in^3))=100.99 ft^3
100.99 ft^3 x 1.05 (5% for air cooled light) = 106.03 ft^3
At the recommended one air 1 air change per 3 minutes:
106.03 ft^3 x (1 air change)/(3 minutes) = 35.35 or 36 ft^3/min (cfm)

You may have had some extra temp factor thrown in, I don't know. Apologies for the extended notation, just making sure all my units cancel out.

Here's the calc with the max non air cooled rating:
100.99 ft^3 x 1.15 (15% for air cooled light) = 116.14 ft^3
At the recommended one air 1 air change per 3 minutes:
116.14 ft^3 x (1 air change)/(3 minutes) = 38.71 or 39 ft^3/min (cfm)

blowdro
09-13-2010, 08:52 AM
thanks brbubba

brbubba
09-13-2010, 09:49 AM
thanks brbubba

No problem, just double check my numbers for yourself and possibly add any other secondary factors. Good luck!

blowdro
09-13-2010, 02:22 PM
Brbubba I tried to come up with that answer but I still dont see how you came up with that thanks anyway by the way what does ^ mean is it a divide symbol.well I divided 3 into 36 and got 12cfm am I on the right track.

brbubba
09-13-2010, 04:38 PM
Brbubba I tried to come up with that answer but I still dont see how you came up with that thanks anyway by the way what does ^ mean is it a divide symbol.well I divided 3 into 36 and got 12cfm am I on the right track.

That means cubed or cubic feet. ft^2, ft^3, etc.

I converted your feet to inches for sake of simplicity and multiplied all the dimensions. Then I converted back to feet, 12 inches per foot, but you have to apply the cube to the 12 as well when dividing. This gives us the ft^3 or cubic feet of the space. Then we add the correction factor for your light. Once we have that 106 ft^3 we know we have to completely replace that much ft^3 of air every 3 minutes, so we divide that number by three.

Here I used word equation editor so you can see it properly. Being a stickler on the units is a habit since it forces you to double check your work.

93

blowdro
09-14-2010, 02:12 PM
brbubba if Iam thinking right then I should be able to use a 4 in fan and filter but will that be enough for the 600 watt light and the smell. thanks for all your help.

brbubba
09-14-2010, 02:36 PM
The filter will affect the calculation. As long as the fan is moving enough cfm then I am sure it would be fine. I'm not a ventilation guy, I'm just doing the calcs for you based on this site's guide.

I don't know what you are growing, so I have no clue what smell issues you would have. If you want to know about carbon filters and ozone generators, I'm definitely not the guy for that.

Again, I can help you with any calcs, but my growing experience is in areas that don't have ventilation concerns.

blowdro
09-14-2010, 04:52 PM
I want to grow tamatos and peppers to start off with then I will move on to other veggys I know peppers smell real bad. thanks again. This is the first time I 'm growing anything. So I'm happy and excited.

brbubba
09-14-2010, 06:35 PM
I want to grow tamatos and peppers to start off with then I will move on to other veggys I know peppers smell real bad. thanks again. This is the first time I 'm growing anything. So I'm happy and excited.

Never really noticed any bad smells from peppers, hot or otherwise. I've grown habaneros and had bug issues, but no smell issues. Personally I think Tomato plants smell the worst. You are venting outside and not into your living room right? Seriously, if you take care of your system there really shouldn't be a bad smell. If you are still concerned about it down the road you can consult any of the "mary jane" forums which cover that extensively. I may not be into that stuff, but those guys do some damn fine work. With that in mind you might want to redo your calcs with a carbon filter in place.

Taking that into consideration you are back up around your original estimate, about 45/50 cfm.