HELP: temperature control

J

jacket_off

New Member
I am starting my first grow and have some temperature issues to deal with.

Box info: I have built a (mostly) stealth box 18" x 18" x 45" (~ 8.5 cubic feet). I am using THIS 180W LED grow light. choose LED for minimal temperature & power. I have a small passive intake hole and a 120mm 100-CFM PC fan on the top of the box as the exhaust. There is also a small fan at the bottom (pointing up) to help circulate the air.

The box is in my attic, ambient temp ~85 at the moment. With the light and fans on for over an hour the temperature inside are at 97.5 (a bit too high for growing). I have searched the internet extensively and have not been able to find any good information on ways to lower this temperature. I can't modify the house or run vents outside the box. but i can modify my box however i need... any ideas would be greatly appreciated.
 
R

Rentaldog

Well-Known Member
Hmm, is it possible to widen your intake and exhaust ports? If you can do that and put a bigger fan on the box it should help to keep the inside of the box the same temperature as your room. Other than that, only thing I could think of would be to move the box to a cooler location or find a way to cool the attic. Portable a.c. would do the trick, but it would seem odd :-P
 
J

jacket_off

New Member
I could definitly add a bigger exhaust and widen the intake.

The bigger air scrubber filter i would need to make for flower time would be a bit of an issue tho. Cant have that smell coming out too much.

Also i havent found any good information on intake size. All ive seen is "use a passive intake not active". My box is 99.9% sealed besides the intake hole. The intake hole is about 1.5 inches and the output is about 3.5 inches. Any ideas on how big is too big and how small is too small?

I have a 200mm (About 7") pc fan i could put in. But i dont know how big of an intake should feed these things.
 
DonAlejandroVega

DonAlejandroVega

Well-Known Member
jacket_off said:
I am starting my first grow and have some temperature issues to deal with.

Box info: I have built a (mostly) stealth box 18" x 18" x 45" (~ 8.5 cubic feet). I am using THIS 180W LED grow light. choose LED for minimal temperature & power. I have a small passive intake hole and a 120mm 100-CFM PC fan on the top of the box as the exhaust. There is also a small fan at the bottom (pointing up) to help circulate the air.

The box is in my attic, ambient temp ~85 at the moment. With the light and fans on for over an hour the temperature inside are at 97.5 (a bit too high for growing). I have searched the internet extensively and have not been able to find any good information on ways to lower this temperature. I can't modify the house or run vents outside the box. but i can modify my box however i need... any ideas would be greatly appreciated.
Click to expand...

add a real exhaust fan
 
Jus Naturale

Jus Naturale

Active Member
I couldn't tell you where I saw it, and have no actual experience with it, but I've heard your passive intake should be twice the size of your exhaust.

Cheers and good luck!
 
J

jacket_off

New Member
Is there really a big differance between a 4" vent fan and a 4" pc fan with the same cfm rating? I wouldnt have a problem switching it to a vent fan if there is actually a diferance
 
R

Rentaldog

Well-Known Member
You know, I don't think a bigger hole would be too bad. Just build a filter big enough for the plants you grow, then run ducting from it to the exhaust port.You want to pull air through the filter, then out of the box.
 
J

jacket_off

New Member
so first off i managed to get the ambient temperature around my box down to about 76 (was ~86) and i also increased the size of my intake. went for a 1.5 inch circle to ~ 6" x 4".

now my inner temp is about 85.5 when the light has warmed up.

i realize that 85 is definitely acceptable for this, but i feel like i should try to get it lower... should i increase intake more? I read somewhere that a higher humidity can help with lowering temps, right now inside box humidity is at 30%RH. anyone have experience using humidity to decrease temperatures? and if i should increase the humidity any ideas on how without a humidifier machine would be useful.
 
S

scarecrow77

Well-Known Member
If your using a passive intake it must be bigger than your outake..you will also want a fan blowing fresh air towards the intake fan..its a fairly small box for 180 watts.imo..6" outtake 8" intake..thats providing your using pc fans..it be diffrent with proper fans
 
J

jacket_off

New Member
as for the size i had to build it out of a piece of furniture i already had. i love the idea of having a fan blow better air to the intake. will go get a fan for that tonight. and for the 6" out 8" in, i assume you mean square inches?
 
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