Mr_Micro said:Hey TORO!
Even in a double tower case with cool tubes, massive ventilation, and all that jazz I don't think there is any way to run a 250 watt HPS without turning your box into an oven. Even if you had one of those fancy water cooled cool tube systems I don't think you could pull it off.
The maximum you could fit in a double tower is going to be a 150 watt HPS or CMH, and even then you're going to have a real challenge trying to keep your temps low enough to grow anything in there.
My suggestion is, if you really want to go the HID route, is a big server case (24" or taller) with either a cool tube or a 5/32" glass heat shield completely sealed off from the rest of the box with it's own intake and exhaust fan (at least 50 cfm). Once you have that set up you should be able to run either a 70 watt HPS or or a 100 watt CMH.
Mind you I've never tried a CMH setup in a PC case, but I know they do run a bit cooler than a HPS so you might be able to get away with a 100 watt setup.
For your stealth growing needs I'd check out the design of "The Nanomachine" PC case that I have a link to in my signature. Mind you that's a very small scale version, but you could easily build it on a larger scale with a glass heat shield between the light and the growing chamber and a separate ventilation system for the light. It will also allow you to store the ballast in the rear chamber of the case away from the growing section where it can be easily ventilated and not raise the heat in your growing chamber. It'll take a little creativity, but that's the style of box I'm planning on building for my next grow. It'll ultimately be set up with a 70 watt HPS or CMH, not sure which yet though.
As far as the whole CFL vs HID thing goes... well, my buds have always turned out better with small HPS lights (50 and 70 watt) than they have with two or three 42 watt CFLs. But my best results I've ever had came from a SWC grow with a 50 watt HPS combined with a 42 watt CFL in a PC case. Using CFLs alone will still give you great buds, but they'll probably be a bit airier than HPS and less trich coated as well. The upside of CFLs though is that you can pick and choose your spectrum, so by using blue light in veg you can get much shorter stockier plants than you could with a HPS (which will cause them to stretch a bit). A CMH may take care of this issue, but I've yet to try one for myself so I cant say for certain right now.
Anyhoo, hope that helps and gives you some stuff to think about when planning your stealth box
While all of your other input and advice I have read has been great I've noticed you're very conservative on lighting and heat. You cases are all well designed and have lots of details worked out but I'm sure you could stick bigger lights in nearly all of them and get bigger yields with only adding a little more coolin. You can hold your hand half an inch from a 400w HPS bulb under a reflector and it is just warm.
I'm going to put this 250w HPS in a double wide cab and that will actually be the same wattage i'm running in CFLs (125w in the single cab right now) which also means heat should be comparable to an extent and i just have a little fan blowing on the lights with no problems. Even if the HID is twice as hot with 4 90CFM over tempered glass in an independent cooling circuit the lens is going to be cool to the touch and I am very comfortable making that assumption and will be happy to post temperature read outs when I'm done.
Once I get the HPS running i'll probably get the CMH bulb. For $150 shipped I am thinking about getting the HTG ballast, wing, socket, and 250w bulb setup. another option i was looking at is getting a lumatek 250w digital ballast but then I need to buy a cord and socket plus reflector separately and can go straight to the 250 CMH bulb. another thing i was thinking of was getting a hot spot diffuser too.
