i am getting an exhaust fan for the light, but should i add a intake at the bottom of the cabinet...how should i do that, just drill holes and put pvc elbows on them?
Drill 150-200 3/16 holes in the bottom for the intake.Lay some window screen over the entire bottom, this keeps most bugs out. This creates a more natural 'breeze' that will filter up thru the plants foliage, keeping them slightly moving. You need at least a 170 cfm inline fan to cool, push/pull thru a filter.
so if i got a fan with 248 cfm fan, would that work with a 400 hps well? also so i should cut a hole on the bottom of the cabinet and lay wit some window screening?
400w is about perfect size for the cab although with good venting you can get a 600w in it. 1kw may work with some extreme venting and cooling but it's way too much light for such a little space (6-7 sf).
2 lights is a good idea like vern said. 2 lights is always better than 1 of similar power because of shading. It gives a much more even spread of light. 2x 250w or 150w would be a good choice.
IF you are using the whole cabinet for flowering I wouldnt go less than the 400 or 2x250 would be awesome. Some of us have split the cab in 2 with a mother chamber on the bottom. I house at least 15 clone mothers in this chamber and have a flower chamber on top with a cool tube 250HPS. This is more than enough for my head, but if you have other aspirations I would go with more wattage as the 250 will give you around a QP per harvest.
the c24 is the new c13? if that is correct a 400 will work in there. it is still way over 50 watts per square foot. the 250 will work fine too. with the 400 you will have to air cool it. i use a 256 cfm fan and it works pretty good. with the passive intakes at the bottom and the window screening how is the light trapped? i have seen a bunch of people go the pvc elbow route and i have seen a bunch use darkroom louvers. the window screen seems great but where is the light going?
if the c24 is the old c22 then run a 600 watter and get at least a 256 cfm fan. air cool this hood as well.
here is my setup- even with the ducting bent i still keep temps cool