Gravity_Loss

I finally got my first grow underway and the first major problem I'm running into is temperature inside the box.

I made a custom box out of particle board that has a 2ft x 2ft floor/ceiling and the walls are 4 feet tall. I have two holes cut, one in the bottom and top, with 2 12 volt big computer fans for intake and exhaust. I also have a mini fan inside the box pointing directly at the light while it is on.

I'm using a 400 watt MH bulb (with the ballast and reflector it came with). After I force flower some clones and sex my plants, I will have 4 clones growing out of 1 gallon pots, but right now I have 8 plants in big foam cups waiting for them to be old enough to sex.

My average temperature in the box with the light off is about 75*, and with the light on, is about 90.5*. I'm really surprised this is becoming a problem, considering the box is very reasonably ventilated. Any tips that doesn't involve adding another fan to a box that already has 3 fans in it?

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farmergiles

You might want to replace the computer fans with a better fan. Those computer fans aren't moving enough air. Your cab design sounds good otherwise.

90F is just a little too much.

I'd recommend getting a carbon filter as well if the smell is going to be a problem when they start to flower.

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Gravity_Loss

The smell isnt an issue because its in the corner of my 2 car garage that is in the middle of a good bit of dairy cow farm land and numerous horses. Needless to say, the shit smell overpowers all.

These are the computer fans I'm using x2

RadioShack 12volt DC Cooling Fan - Review

They push a good bit of air. This is the small fan I have pointing at my light.

http://images1.vat19.com/usb-retro-m...an-tilting.jpg

I still don't see why this isn't enough to keep the cabinet cool. I also checked on the plants today and most of the stems had bent over. Had to put stakes in them for the time being.

__________________
Genesis 1:29
And God said, “See, I have given you every herb that yields seed which is on the face of all the Earth, and every tree whose fruit yields seed; to you it shall be for food.”

Reason is the mind's awarness of itself. --- Zen ..)

Captain Cannabis

are you running your lights during the day or night?

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stoneric

I use the 5 inch ones. They sell for 20$ at my local radio shack. I also have one on the bottom and top of my veg room with another one pointed directly between the light and the top of my canopy. I use a 250 hps in a little larger room than yours and stay in the 80 degree range at its hottest. 4 square feet isn't very big for a 400 watter. Farmergiles is right, you'll probably need bigger fans. If your gorwroom is in the middle of a cow pasture get yourself a squirrel fan. They're louder than fuck but the cows probably don't care.

Dandaweedman

I agree. Get a nice little 115v plug in style axial fan with some cfm.

I have a 4" that pushes 107 cfm that cost me $20 CAD. It's perfect for our 4'W x 30"H x 24"D mom chamber.

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Gravity_Loss

To adapt with my sleep schedule, my lights come on at 2pm and run until 8 am. I was told in the reviews on the light I bought that you need to be careful when using a timer because they don't always come on, so I check them when i wake up at 2.

I tried opening my cabinet today but it only got hotter. I got rid of the 3in fan I had blowing on the bulb and went with a 9in fan. When I do my clones and up it to 4 1 gallon pots, I will have trouble squeezing it in there. Luckily winter is coming up and keeping the plants warm is easier.

__________________
Genesis 1:29
And God said, “See, I have given you every herb that yields seed which is on the face of all the Earth, and every tree whose fruit yields seed; to you it shall be for food.”

Reason is the mind's awarness of itself. --- Zen ..)

farmergiles

If your timer works ok for a while it's probably going to work ok for years. Or shell out on a proper relay, probably about 50 bucks or less.

If you run your lights during the coldest part of 24hrs the you are getting the best of all worlds- the lights keep temps up during the night and the ambient warmth of the day keeps humidity down and the roots warm during lights out.

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Gravity_Loss

I adjusted the times. They will be turning on at 6PM and shutting off at noon. That way I can still check them before work.

It is 3:17am right now, about 70* outside, and the digital temp in the box is reading 96.3*. I more than doubled the size of my light cooling fan and it hasnt done anything to drop the temperature.

Before having to dish out the money for a squirell cage fan, would raising the light help at all? I have the light set at about 2 feet above the floor.

Edit: Would ditching the intake fan and turning the exhaust into a squirrel cage help? I'm starting to feel like I over bought on the light a bit, or under bought on the box.

__________________
Genesis 1:29
And God said, “See, I have given you every herb that yields seed which is on the face of all the Earth, and every tree whose fruit yields seed; to you it shall be for food.”

Reason is the mind's awarness of itself. --- Zen ..)

Gravity_Loss

Actually, can I get a smaller bulb, like 250w and it work correctly on that ballast? There aren't any options or switches on it, its just plug and play.

__________________
Genesis 1:29
And God said, “See, I have given you every herb that yields seed which is on the face of all the Earth, and every tree whose fruit yields seed; to you it shall be for food.”

Reason is the mind's awarness of itself. --- Zen ..)

farmergiles

Yes I would think so, you need a fan which moves sufficient air, about 200 cfm should do it for a 400w HID in a small cab.

Getting ventilation right is the trickiest part of cabinet design and can require the most expensive kit I'm afraid. At least you only have to worry about the air movement, not the smell and the noise!

No, don't try it, you'll almost certainly blow the bulb and possibly damage the ballast.

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stoneric

Maybe remodel the cab.

farmergiles

It's a small space for 400w but apart from that it sounds ok to me.

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stoneric

Don't you also have a lumen/sq ft ratio problem with a 400w in that size room? At what point is there too much lite?

farmergiles

Yeah a 3x3 or bigger footplan would be easier with a 400watter.

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Dandaweedman

How big are those northern light grow boxes? They can come with a 600 I believe.
Just need the air movement

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farmergiles

I've successfully run 1000w in a 2.5x5' floorplan with a variety of strains. It get a little tricky sometimes but it's perfectly possible.

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SmokeaJoint

You dont have to dish out big bucks for an inline squirrel cage fan either. Those are the same fans they put in window AC units to move air. Find one used on craigslist or at a garage sale. Should be under $20 and all you have to do is strip it from the unit and wire it in. The fan should be enough to keep the grow space cool enough, no problem.

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Dandaweedman

Inline fans are big bucks but handy when you need em
The squirrel cage idea is a good one, should be able to find quite a few used ones I imagine.

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stoneric

Isn't there something about bleaching or blanching or some shit when you have too much lite?