not your ordinary first grow
In addition it is worth mentioning that your realistic goal should be about 5 degrees above ambient.
Meaning that if it is 78 degree's in your house.. you should be trying to get it down to, at minimum, 83 degrees. If you're able to drop it any lower then that is just icing on the cake.
It is impossible to run cooler than the ambient temperature outside your grow room. Meaning that if it's 78 degree's outside the box.. unless you get some other means of refridgeration type cooling going, the absolute best you can hope for is 78 degrees.
So when you look at your temperatures ask yourself 'am I within 5 degrees ambient or close'.
not your ordinary first grow
Nice Info. Also benefited me.
not your ordinary first grow
Quote:
Originally Posted by daihashi
To determine how much cooling you need.. take the cubic footage of your area and divide by 5 minutes.
so if you're growing in a 3x3x3 area that would be 27cu.ft.. to evacuate that in 5 minutes you would need a fan the blew about 5.5CFM. However I've never been a fan of the 5 minute rule. I like to use 1 minute for reference or faster if I can help it.
So in this case you would need 27CFM of unrestricted air flow. Computer fans do not have high velocity such as inline fans or squirrel cage fans, therefore I would recommend more powerful fans which it appears you have covered.
Unless you're running CO2, you cannot have too much exhaust.
You want them all set to exhaust. You want to create several passive intakes very low in the box. Your passive intakes must be, at minimum, equal in size and number to the number of exhausts/exhaust holes you have. Furthermore you want to try, TRY, to have all your exhausts setup to the top of the grow area in a blow hole fashion.
This will draw cool air in from the bottom of your grow box.. allow it to travel upward with the rising hot air and back out the box.
The reason you want passive intake is that because unless the intake and exhaust are running equal amount of pressure (flowing the same rate of CFM) then all you're doing by putting an active system in is creating a restriction and turbulent air flow.. basically hot air that just swirls around, inside your grow environment.
So in summary set all your fans to exhaust, put them at the top of your grow box, create as many passive intakes low in the box as you have exhausts...
I have more advice I can give, but give that a go first.
thanks a lot daihashi! i was thinking of flipping the box upside down and using the handles (where the side fans are) as intakes. maybe i'll do that and add all the fans to the top. does the arrangement matter? i'm gonna start messing with it now. i'm not gonna make any more cuts until i hear back. thanks again.
-shake
not your ordinary first grow
Nice box grow man, I have thought about using a similar setup to veg in, but have had the concerns of fire on my mind. I have been pricing and to build a similar sizes box out of 1 bys and 1/4 inch ply should only run $10-$15. Seems like a much safe alternative. Good luck I'll be keeping up on this grow. :)
not your ordinary first grow
i just went to check it out. i set all the fans to exhaust. would they be fine where they are at all set to exhaust with the passive intakes at the bottom? or should i put them all on the very top and use those holes for intakes? i can do either. just not trying to mangle the box too much.
also, one plant has little brown marks on a few of the leaves. i tried to get a pic but it was hard to tell what exactly was going on. are they too close to the lights? what would be optimum distance? the 5 second hand rule?
-shake
not your ordinary first grow
I'm unsure about the airflow, but as far as the little brown spots, I had the tips on the lower set of leaves turn brown on 2 of my plants. From what I gathered it was a sign of root rot. Caused by too much water and not enough drainage. Let the dirt get bone dry before watering. Since I started doing that I have had no further problems. The brown has not progressed any further.
not your ordinary first grow
Quote:
Originally Posted by Baka123
I'm unsure about the airflow, but as far as the little brown spots, I had the tips on the lower set of leaves turn brown on 2 of my plants. From what I gathered it was a sign of root rot. Caused by too much water and not enough drainage. Let the dirt get bone dry before watering. Since I started doing that I have had no further problems. The brown has not progressed any further.
thanks baka! i'll try that. they seem to dry out about every 2-3 days. i did use miracle grow at 1/4 the recommended amount.
-shake
not your ordinary first grow
Quote:
Originally Posted by headshake
thanks a lot daihashi! i was thinking of flipping the box upside down and using the handles (where the side fans are) as intakes. maybe i'll do that and add all the fans to the top. does the arrangement matter? i'm gonna start messing with it now. i'm not gonna make any more cuts until i hear back. thanks again.
-shake
Well.. It's best to have all the fans located in one area. For example if you want to use a blowhole, then put all the fans in that area to act as a blow hole.
If you want it to be in the upper right, then put all fans there.
However if you currently have fans acting as a blow hole and one fan in the upper left hand/right hand side of the box then that's fine also. It's not optimal but it will work almost as well as if you had them all clustered.
I can understand you not wanting to mangle your box. The worst that can happen is that you might find that you do want to cluster them together.
Change them all to exhaust, make your passive intakes (same amount and total size as all your exhausts combined.), and let us know what happens.
I suspect you'll see a 2-3 degree drop minimum.
not your ordinary first grow
Quote:
Originally Posted by headshake
i just went to check it out. i set all the fans to exhaust. would they be fine where they are at all set to exhaust with the passive intakes at the bottom? or should i put them all on the very top and use those holes for intakes? i can do either. just not trying to mangle the box too much.
also, one plant has little brown marks on a few of the leaves. i tried to get a pic but it was hard to tell what exactly was going on. are they too close to the lights? what would be optimum distance? the 5 second hand rule?
-shake
The brown marks could be from your nutrient solution splashing on the leaves, then the light hits it and cooks/burns the leaf that had solution splashed on it.
General rule of thumb when working with CFL's is to keep it about 2-3" from the canopy and no closer than 1-2" away.
not your ordinary first grow
good looking daihashi! what about the fan situation. would they be fine exhausting at their current location and just adding the passive intake low on the box? or should i put all the fans on the top? i'll do whatever is best. and i've left the door cracked where to where i can feel the best exhaust from the fans. it keps the temp at about 83.9 (ambient ~81. and the humidity is about 39%. i appreciate the quick responses and plan on making the changes accordingly, asap!
-shake
