I think what TS is saying, is to use two smaller fans in parallel. One for the light only to deal with heat, and one to deal with the air exchange and the lower amount of heat in the tent from light hitting the leaves.
Yes, that. It's not feasible for "bare-bulb" vertical grows, of course. But it seems like the best way to go for air-cooled reflectors. I've never really been a fan of Cool Tube type setups; the grower loses about 9% of the light intensity every time the light must pass through glass (with
any type of reflector that places the light source behind glass) - but with a tube, a portion of the light must pass through glass multiple times if the actual reflector is above the tube. The design also restricts one's choice of reflector. And, while it isn't of earth-shaking importance, lol, IDK if the insulated reflector covers (to help stop radiant heat) are available for Cool Tube setups. On the other hand, I can think of a couple of situations where a glass tube might be helpful - for example, if one is going vertical, es cannot simply take a different style of device and turn it on its end, lol, because a traditional reflector would then block light from a great deal of grow room real estate. I have used a glass tube in the past (not the actual trademarked Cool Tube product... do a search for Bake a Round
). And right now I'm not even using an air-cooled setup of any type due to circumstances. Some days, as the rednecks say, it's, "Run what ya brung."
A lot of people look at the output from their grow room - no, not the
BUD - as one thing: Hot stinky air. But it's actually two things, hot air and odor. It turns out that carbon filters last longer when they're not treating heated air. Treating the two things as separate means that the grower can adjust fans separately. This seems to be an obvious thing, but...
Cold outside in your area in the Winter months? That heated air
waste product from your grow can help heat your house. Sure, you can do this with a single fan setup. But if you are not at home (or you are, but other people are, too) when your filter starts being overcome, you've just scented your house. FAR less likely to happen if that hot air is unscented because your hot light is on a different ventilation run.
With separate runs, you can expect your light/reflector might stay clean longer. First, because you're not pulling air directly from your grow room for it, second because you can have your light's fan on the same timer that your light is on - when the light shuts off, so does its fan. During dark hours, you can continue to run your grow room's odor-control fan/filter on an as-needed basis. This can cut electricity costs if you were previously running one large fan 24 hours per day, or help prevent odors from escaping if you were previously running one large fan/filter, but had it shut off when your lights did.
I've always been told that the best sort of fan (both in terms of performance and longevity) for a carbon filter was one that would work against pressure/obstruction. The fan that is solely intended to ventilate a reflector need not be rated to work against obstruction (aside from the minor work involved in moving air through a duct run of reasonable size).
It might work, however, I think the fans in series probably work just as good.
<SHRUGS> Not really. I mean such a setup might be
adequate. But it won't perform as well. It's pretty difficult to
exactly balance two fans on the same run, so one will be working harder (and doing more work, which is not - strictly speaking - the same thing). One fan will end up having its airflow "pulled" - and the other will have it "pushed" - so to speak. When someone installs one fan, then later decides that another fan must be added
to the same run, this is generally (not always) a sign that the person simply purchased an inadequate fan. Or of a less than optimum setup... I've certainly been there (and so have many other people), where I put something together - and not always with a zero budget and little time :rolleyes3 - that ended up being somewhat... lacking. Instead of redoing things properly, I added a band-aid. I need more airflow, oops. My tent is collapsing because I am out-flowing my passive intakes, oops. I have a fan and filter but I can still smell the grow at night or during random periods, oops. I wasn't thinking of anything but the price and bought this plastic PoS from China to move air through my baggy-arse Chinese grow tent,
oops. Et cetera.
Although, the volume of air in a cool tube and short run of ducting is much smaller than the volume of the tent. A fraction of the tent. You would be pulling cooler air, much faster over the hot bulb. This would significantly reduce the heat output of the bulbs, if the theory is right.
There is that. You're not reducing the heat output of the bulb, though (but I understand what you mean). You're just ensuring that no odor enters that airflow. And the airflow will tend be cooler, through the simple fact that it is not being pre-heated in the grow room.
This is tempting to test, but I don't know if I feel like reworking my tent to test this out.
Just slap another band-aid on it, then. Err... I mean add another fan to the same run. But... yeah, there seems to be something in the human mind that prevents us from easily giving up (so to speak) on what we've already accomplished in order to redo the thing. Seems like we're programmed to stick with the same thing and attempt to improve - or fix - it instead of giving full consideration to starting over. Otherwise, the phrase, "Beating a dead horse," wouldn't have been coined. Humans, eh?
