Grow Box Design - Help

[xanner]

I have a 400 Watt Metal Halide in a 2' x 2' x 6' cabinet. Now, I think I may have a hard time ventilating this cabinet. At the moment I have one 12cm DC 12v fan blowing air out from the top and one blowing air in from the bottom. From a top view, these are at opposite ends for best air circulation possible in this circumstance. Now, I'm just wondering if I have to ventilate the ballast (it's sort of enclosed in a top shelf that is seperate from the main chamber and this shelf area is about 2' x 2' x 10". And also what my maximum temperature should be at. It has gone up to 36C within an hour. Is that bad?

Help is really appreciated!

[Rabiez]

Hi xanner,

If it's your main grow chamber that's at 36C, then yes, it's bad. You need to get it down to 24C(ish) ideally, but anything under 30C is a good start.
Your DC fans aren't going to cut it unfortunately. You should be looking at an inline exhaust fan rated at 125m3/hour or 72cfm(cubic feet per minute) in order to cool the cab efficiently, with passive (no fan) intakes. You could of course manage this with the addition of several PC case fans instead.

If it's the ballast chamber that's 36C, then don't worry about it too much. The ballast shouldn't need ventilating if it's in a seperate chamber, although it won't hurt to do so.

[xanner]

Thanks for the reply. I've managed to keep it at 30C with added fan. I could add another intake or boost the fan power (they're running at halfspeed as we speak to keep the noise low). If not, anyone know how to underclock a 400watt ballast to 250 or 175? With the size of my cab, there's no use for that much power. If there is a way, I need for it to be cheap.

Thanks in advance!