lowering temp in a small cab?...

[squib]

So this is my first grow, and I am having temp issues. Cab is 180cmX112cmX80cm. There is both and intake and an exhaust fan, as well as a small fan in the cab to strengthen stems. A humidifier puts the humidity at about 65% or so and the temp sores around 30c. Right now I rely on the cool spring air to cool my room but temps are still too high and will climb much when summer comes. So suggestions please...

 

[squib]

Also looking at others weekies mine are a bit premie

Also looking at others weekies mine are a bit premie

My three are a bit small and strechy for a week I think. Comments... they are under a 250watt MH, should I run a flouro tube or two to up the light? (keep in mind the above heat issue)




thanks all
-squib

 

[Guest]

Ventilation Ventilation Ventilation

Ventilation Ventilation Ventilation

Go with floros until you can control the heat. Starting seedlings under a 250 MH is overkill IMHO (and as you know it creates a lot of heat). It would help us help you if you stated the CFM rating on your fans. Cheaper Solution - If you have a powerful exhaust system you could suck out some of that heat, delete the Intake fan (called a passive intake) and cut a few more Low holes to bring in fresh cool air. More Expensive Solution - A reflector with a glass insert and its own ventilation system will reduce the heat of a 250 MH dramatically.

 

[monkeyman]

What are the cfm on that fan?
What are your ambient temps like?

That looks like a bathroom fan to me which probably does not have enough pull to vent that cab the way its supposed to be. You probably want to look into getting an inline fan which should be able to get your cab to just a few more degrees above ambient. Also you might want to consider turning your light into a cool tube set up.

 

[On the Button]

A more powerful exhaust fan will do wonders. I have similar dimensions with a 400w light, but my exhaust fan is larger than what I need. I also have the exhaust intake right next to the bulb in line with the reflector. With temps normal all I have to worry about it bleaching of the fan leaves. Inline fans are good but I hear squirrel fans are more efficient.

 

[Guest]

I was having the same problem my temps would go into 90+ and ambient temps were in the low 70's.

check out this thread you'll find it helpful
http://www.icmag.com/ic/showthread.php?t=21586&goto=newpost

you can start seedlings under that light even though most people will say not to, I did, and didn't have any problems, except once since I was using peat cups and they dry up quickly. although I would recommend starting them under cfl's, so you don't have to water as much.

anyway this is is how I fixed my problem, I couldn't get my temps. below 90's and I was using a 4" 172cfm vortex fan and had an 8x8 darkroom louvers vent (this is a passive intake vent) didn't have a passive intake fan. Is your cab in your closet? if it is, then you're circulating the same hot air that's being exausted into your cab through your passive intakes. so what you need to do is exaust that heat somewhere else, in your bedroom, or attic, anywhere else.

I couldnt' do any of those things and didn't want to due to security issues. All I did was turn my cab with the vent to the side and brought it closer to the doorway. Now my temps are usually in the 70's with AC off, sometimes they get to 80's if apt. temp. is really hot, then I just open the closet door. I also have a 16" osciliatting fan in the closet, but it wasn't helping any until I moved the cab.

I believe your exaust/intake ratio should be 3:1, I might have it in backwards but I think your passive intake has to be greater than your exaust, just check that thread. I believe mine is about 5:1 . In that link I believe on the last page or 4th page, somebody knows the formula. Even though my ratio is 5:1 my temps still weren't going below 90's, so you need to get that intake vent facing the doorway and closer. If you read that thread you should be able to find a solution. I have the same 250W MH, except mine has an air cooled hood, which is directly connected to the hood so that definately helps, but it still didn't help with lowering temps until I moved that cab. so you need to get fresh air from your bedroom into your cab from making passive intakes as the person above suggested.

 

[On the Button]

I agree and even have a fan blowing the air from under the door from the cabinet as a circulation fan.
A larger exhaust fan does wonders ....

 

[Guest]

even if he gets a more powerful fan, he's still going to circulate the same hot air back into the cab isn't he? that's what everybody was trying to tell me, I had a 172cfm fan, and an oscilliating fan inside the cab, a 16" wall mount fan and didn't do anything, I was about to purchase another fan, and people were saying you can get all the fans you want but it won't do anything unless you exaust that hot air some where else or find a way to get fresh air into the cab (through passive intakes)

 

[On the Button]

touché

My exhaust goes into the roof

 

[CB420]

1)if that room is wrapped in tin foil, what you basically got going on is an easy bake oven for your plants, rip that out, and just paint the walls flat white or even better get white black reflective paper from your hydro shop

2)never start with a HID lamp, IMHO, MH sucks, just use fluoros for the first two weeks, then if you must, use the MH, or even better, get a 430 watt dual spectrum bulb from your hydro shop

3)forget a vent fan, just cut a big square out above the light in the roof, and then just put an ordinary fan at ground level blowing the grow room, this will vent out the hot stale air and allow new fresh air to come in

 

[squib]

sounds good,

sounds good,

all: thanks for the info
dnb: its a wardrobe so the air comes from my room and I keep the window open. I will try to get a tube to exhaust out the window.
CB420: There are no hydro shops here and I dont have the luxury of simply buying things online, I wish though... (shipping costs are crazy and there are language barriers) but I will do the flat white, thanks.