Looking Good!!!
Hey GB and Dan gotta question. Let's say I know this "friend" who wanted to flower in a cabinet that was 48"x18"and 36" high? He has a closed loop cool tube with 130cfm fan pull and 2x100cfm fans exhausting the cab? His ambient temps were 78* constant. Based on the space and venting what would be a
reasonable bulb wattage and type that you recommend he use assuming all other conditions were "normal". Yes this sounds a lot like my space but forget all that. Think of the question on it's own. Think of it as a "straw poll".
I preface that I assume your friends cab, cool tube, and every other variable is similar to yours, since hte dimensions are.
ok, here is what your friend has
cabinet--18 cubic ft/6 sq ft
cool tube--1.19 cubic feet (basing the length on 3.5 feet and width of 4")
your friend is currently circulating their cabinet about 11 times a minute. They are circulating the cool tube about 60 some odd times a minute. that light should really be cool to the touch with that much air moving around it, so I would say a 400 would work. i assume your talking about the CMH, which is cooler than the HPS and MH. The 250 is what most grow sites recommend for the space, but to flower our plant, you would need more penetration to get to the lower bud sites.
i know having 2 ballasts is a pain, but if it was mine and I could have a cool tube like yours with a pyrex cylinder on each side of the loop instead of just one side, then seperated a 8-12 inches more than yours, then stick a 150 watt CMH on each side of the cool tube, they would really get good penetration and coverage. if I had a large space i would rather have more smaller, than one larger bulb.
hope that helps!