I need help, can't seem to keep my temps under control...

[zlock]

Testing out my new box today, I can't seem to get temperatures below 95*!
This is what I'm working with.




Dimensions are 22" wide, 14" deep, 28" tall. I've got a 120mm case fan (73cfm according to the package it came in) pushing the air from inside the box through a homemade carbon filter in the box in the upper right corner in the pic (yes the fan mounts to a piece of wood with a hole in it to seal up the box), and that box vents out the top via two 1 1/2" and one 1 5/8" holes (same surface area as the fan itself). For intake I have the same sized holes as the exhaust, only on the front panel along the bottom. The fan is certainly moving some air, even with the carbon filter in place theres a strong breeze coming from the exhaust holes, and the case is sealed up good and the passive intake design is working (according to the mini-bic lighter test).

The temp inside the box is above 90* when the lights and fans are on. (I have an 80mm fan blowing at the top 3 bulbs to keep the air moving around inside) For lights I tried five 40w'ers, and then I replaced two of those with 23w bulbs to see if that made a difference, and the temp stayed the same. Took the carbon filter out to see if it was causing too much restriction, but temps didn't go down.

I'm anxious to put this box to use, but I'm already having to deal with my PC case grow burning up 'cause of high temps, I don't want to jump into another grow without my temps being under control.

Any advice or suggesions? I was thinking about getting rid of the "exhaust box" (I figure its an easy way to house the carbon filter as well as keeping the light from being visible up top) and putting TWO 120mm fans on the top of the box with carbon filters hanging down into the box, with the fans pulling the air through. Do you think this would help? Any other suggestions? Thanks!

 

[RJE231]

You need more than that for exhaust, I'm trying to understand your design what are the 2 holes right in front of the fan? You intake should be 2x the size of your exhaust - as a random rule, it can be adjusted but I'm certain you need more intake diameter by a least a little.

With your filter on there your going to want some more powerful exhaust, more details on your scrubber/exhaust setup would help a lot.

 

[bigd21]

I agree adding the second intake will probably help a bit also what is the temp of the room that the box is in?

 

[zlock]

Ahh! That may be a big part of why my temps are high. I had read about the whole intake being twice the exhaust, I've been stoned the whole time i've been putting this together, I guess its starting to show :-(
Easy fix though, I'll drill another set of intake holes tomorrow afternoon.

The holes that appear to be in front of the fan are actually further into the "box" than the fan, guess it just doesn't look that way in the pic. Heres another pic to give you an idea of how this is set up.

As far as my carbon filter, its steel screen rolled up and reinforced inside with a thin strip of wood, a slightly larger roll of steel screen around the first one, lots of duct tape, filled up with activated carbon from Petco, and even more duct tape to secure it to the fan. I just finished emptying the carbon out and scrapping that design though. I'm just gonna try a roll of screen with one of those universal replacement carbon air filter things wrapped around it, I think it will flow better and wont be as sloppy as my first one.

 

[zlock]

I agree adding the second intake will probably help a bit also what is the temp of the room that the box is in?

temp in here cant be much more than 68 or so...

 

[Quazi]

Okay.

It looks like your intentions are good, but you need to think about your airflow a bit more before you go drilling a bunch of holes into this thing.

For one thing, you want the air to flow from the intake to the exhaust. It looks like you have large holes near your fan. Your fan should be flush against a single hole. There should not be a bunch of holes near it. The air from the fan should be blowing outwards. This should be your single exhaust (unless you plan on doubling what you have now). Now that you have 1 single exhaust, you want to have around double the intake.

Make sure you do your math correctly for the area of circles:
a = pi * r^2

A = area
r = radius (half of the distance across the circle)

Your intake holes should be near the bottom of your cab. You're going to want to think about how to light-trap them (and possibly your exhaust holes) now before you get light-leaks in (or out if you're worried about security).

Now that you have intake holes at the bottom and a fan pushing out air (exhaust) near the top, you now have a flow of air.

Now that you have a flow setup, let's talk about your fan. It sounds like you started with around 200W in there and you're trying to use a single, 4 3/4" fan. While the rating may be 72cfm, it's not going to be that when you consider the intakes being pulled through and the carbon filter that you are planning on putting on it. You may want to consider adding another fan (which would mean you'd need more intake) if you want to go with that high of wattage.

It sounds like your airflow doesn't currently match your wattage. But, it also sounds like you're flexible with your wattage.

I would recommend getting your airflow straight and then you can determine what kind of wattage you can comfortably put in there.

-Q

 

[green_grow]

what quazi said .
also, i don't know why you have that box thingy built around your exhaust fan, but no way is it helping with air flow. by the time the fan sucks the air around that contraption the damage has been done, the heat from the lights has had plenty of time to warm up the box.

 

[green_grow]

just took a closer look at your cabinet ... it looks like the fan is blowing the exhaust air at the back wall and from there it is just rising up to the exhaust holes . not good, you want the fan facing those holes directly, preferably mounted right on them. no offense, but your airflow is about as bad as it can be. straighten it out and temps will improve.

 

[DocPouceVert]

Carbon filter can reduce by 30% the cfm of your fan....than 75 cfm give something like 50cfm...its not that much

good luck

 

[FreezerBoy]

Looks like they got you covered but, just to hammer it home: Green is what you want, red is what you had.

 

[zlock]

Well, these are exactly the answers I was looking for! (Not hoping for though)
Looks like I'll be doing some more construction tonight! I'll keep you all updated! Thanks VERY much for the help!

 

[Charg5152]

If you get the air circulation worked out you should be fine. I always try to imagine and picture the air flow throughout my cab before implementing the design. For a cab, you want the intake to be as far away from your exhaust as possible. This way the cool intake air is making as much contact with your plants as possible. If your intakes are close to your exhaust you are only circulating a very small percentage of your cab's air. Really think about how and where the air is moving, circulating, and exhausting out of your cab and you should be able to find something that works for you.

 

[stihgnobevoli]

your biggest issue with that design is that the fan isnt sealed in that box. if you havent already made alterations to the box. before you do what everyone else told you to do which is make more intakes. you should stuff something around the fan, like cut a thick piece of styrofoam to the size of that box the fan is in. then cut a hole in the styrofoam just large enough to force your fan into. like a mounting bracket. then shove it in the hole and see if that helps. your current situation is only blowing air at the holes for your exhaust. and most of that air is just hitting the wall at the back and coming back out through the gaps around the fan. have you ever aimed a fan at a wall? that's what you're doing. air is like water, it wont flow right if theres huge leaks in your container.

 

[FreezerBoy]

Well, these are exactly the answers I was looking for! (Not hoping for though)

Dude, you are SO not alone! I had to learn the hard way, too. The fine folk here at IC will see you through.

 

[mexilandrace]

explain how your exhaust fan is set up? the more I look at that the more I am confused by what is going on?

you have the fan blowing where?

 

[zlock]

I should have posted a more current picture of the box to begin with, but heres a pic of how the fan is actually set up. Right now I'm just using duct tape to seal it up, but once I figure out whats going on (as far as if i'm gonna keep the box set-up or not, as well as the carbon filter situation) it will be sealed up and attached in a more secure fashion.
I think I am just going to go with the fan blowing directly out of the box though. I liked the idea of the box inside the box cause a) lightproof, b) provides a little help as far as sound, c) a little stealthier than exhaust fans right out and in the open, but I'm not TOOO concerned about how it looks, and the fan is a lot quieter than I had expected, so I'm not too worried about sound

 

[mexilandrace]

okay, that's your first problem, you are losing a shit ton of CFM with that set up like that.

Can you not have the fan blow out directly? even without the carbon in there you are losing air power because you are creating pressure where that fan is blowing and even with nothing in the box you have lost quite a bit of CFM

 

[zlock]

okay, that's your first problem, you are losing a shit ton of CFM with that set up like that.

Can you not have the fan blow out directly? even without the carbon in there you are losing air power because you are creating pressure where that fan is blowing and even with nothing in the box you have lost quite a bit of CFM

Yeah I'm starting to realize that while the idea sounded good at the time, it really isn't the best way for me to do this, so I'm gonna pull the growbox out now and make some measurements, draw some circles, and cut some holes, woohoo!


.....................<---ICmag
zlock--->

 

[zlock]

Update:
Spent the evening in the garage modifying my intake/exhaust system. Ripped out the "box" inside the box, cut out ONE hole for the fan to mount directly to, in the upper right hand corner in the back, and drilled another set of intake holes (now the intake is twice the area as the exhaust like it should be)
Gotta buy some hardware to attach the fan, but that should be done by tomorrow, and I'll finish the electrical part of this thing and hopefully have some new numbers tomorrow night. I've got 8 misc seeds i'm trying to get going, so hopefully by the weekend I'll have my current plant in the new box and some seeds sprouting in my PC case... and my perpetual SOG will be in its first stage!

 

[mexilandrace]

you coulda left the box and just mounted the fan the way you have it now, that wouldn't have hurt you too much at all and woulda kept it light tight.

but you are on the right track