What's more important: keeping lights close or relieving heat?

I have been struggling with heat issues and have finally gotten my average heat down from 100+ to 86-88 with lights on. I know that's still higher than ideal, but that's about the best I am going to be able to do before I can buy some better equipment in the fall. In the meantime, my new growth is still showing some signs of minor heat stress (leaves curling up slightly). I have my 400W MH about 10" from the canopy, and my plants are 26 days old. Should I leave the light where it is or back it off some?

As an aside, my newbie advice to other newbies: When buying your first HID light, get the cooltube or some kind of vented hood. I severely underestimated how much heat these suckers put off. Spend the extra dough; it's well worth it.

back your light off, it doesn't need to be that close anyhow. also put a fan blowing over the top of your canopy, it will help some. there are charts on the net that will show you the most effective distance to have your light away from your canopy, i would check those out if i were you. as far as hoods i do not personally care for vented hoods or cooltubes, most don't have very good footprints and they block lumens so unless your are running a ton of lights or doing some kind of vertical grow i would not use either, just get some a/c.

I originally had my light at 12" from the canopy, but somebody on here who acted like he knew what he was talking about said 12" was way too far away and that I should have it at 8 inches. At this point, I'm not sure what the right answer is. Everybody seems to say something different.

I started out with my 400W light, one oscillating fan and one exhaust fan. Temps jumped to 100+ with lights on. I then added an active intake fan. No change. I then added an AC unit in the room running at 73 with the active intake fan pulling air from the AC into the box. Temps dropped all the way to a frigid 90-93 degrees. I then bought a piece of tempered glass to make a homemade hood, using ducting to draw from the light to exhaust. I also added another intake fan drawing air from the air-conditioned room into the box. This has brought my temps down to 86-88 with lights on. I have three fans in the box with two pulling air conditioned air and one oscillating across the canopy, and one modified squirrel cage fan pulling exhaust from the box.

I hear people say all the time that a 400W MH should not be too difficult to control the heat. I have not at all found that true with this light. Maybe it's just a crappy light. I don't know (it's the HTG brand). In the fall, I'm looking into a better light and an inline exhaust fan. Until then, I am pretty much stuck at 86-88.

So if 8" is not correct as I was told here, then is 12" correct? The guy who told me 8" said at 12" the plants were not receiving enough light. Ugh! This is frustrating.

you need a way stronger exhaust fan to draw the cool air from the a/c into the grow space, get that and your problems with be over.

Robert Paulson said:

you need a way stronger exhaust fan to draw the cool air from the a/c into the grow space, get that and your problems with be over.

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Agreed. I think my exhaust, while having enough CFMs for the space, is not strong enough to remove the intense heat coming from the lamp. I do have a modified squirrel cage pulling air into the box, though, as well as two more passive intakes. I ran ducting from the active intake fan directly to a rectangular piece of ducting that I mounted directly over one of my AC vents. I was hoping this would pull enough cool air into the box to compensate for my fairly weak exhaust. Apparently not. I need an inline fan, but I just can't afford one until September.

I did go ahead and move my light up another 2". So consensus: is 12" about right for a 400W MH?