I'm currently running a 250w HPS in a cooltube in a stealth closet which is 100cm/60cm/200cm (3x2x6). Now that winter is coming I'm not having problems with temps anymore.. currently they are around 26C, peaks at 28C. Unfortunately i cant hook up the cab with fresh air from outside cuz the cab is in my room. All i can do is keep my windows open. I'm planning to upgrade my 250w HPS to 300w HPS (using a 600w dimmable ballast)... my question is will i be able to maintain the temps if i upgrade my exhaust fan from 180m3 to lets say 360m3 or even 420m3?
Would you not just go for the 400 watt HPS? I'm not certain on this but I'm guessing it will be more efficient than dimming a bulb. You will get more heat from a bigger bulb but with a cool tube you should be able to control it. I have a 400 watt bulb in a cool tube and I'm finding it hard to keep my temps up, but it's got air from outside.
Thanks! Regarding the efficiency.. thats what i'm trying to find out. Thing is with 400w I might get problems with temperature.
if you are upgrading your fan as well you will have no problem with a 400, you might not even need the fan upgrade.
Lumens are an old way of measuring power of a light - it is adapted for the human eye, not for what plants see. Look into CMH bulbs, e.g. http://forum.grasscity.com/indoor-marijuana-growing/912644-ceramic-metal-halide.html There is a 100 page thread somewhere on cannabis.com or something but I can't seem to find it, I'm sure you will if you look hard enough. -OH
If you get 600W ballast then stay on 600W. Temperature difference between 300W and 600W is only 3 degrees. I have tested my 600W light with Digilux bulbs in DR90 (90x90x180 centimeters) with Vortex fan (450 cfms) cooling the light. So I run 300W for 2 hours and measured temperature and then run 600W and temp difference in the tent was only3 degrees... Need more lumen run it full blast and as close to the plants as you can with out burning them . I had my reflector 30 centimeters from the canopy when plants were young and moved it down to 24 centimeters when plants grew bigger. Result: over 8 oz of dry bud from 2 plants (DWC)