Hi all. I am ditching my cash crop boxes after this last grow. At 3 feet tall,they are just too small for any decent lights. I have had success with hydro, and am ready to move up. I bought a tent 36 x 36 x 72. I bought lights. 600 watt ipower system with a vented hood. My first question, should I have bought a 400 watt lighting system instead with this size tent? I dont want any major heating problems.I can return this system without even opening it, if its too hot for this size tent…and order the 400 watt. I plan to run a scrubber inside the tent, hung up top and vented into the light via the usual fan setup. I guess because of the heated air coming off the fan from the light…you cant vent this into the same room as your tent?? How warm is this air going to be that comes out? Otherwise, I have to get it up and out the top into my attic and hopefully near an outside vent. Also...does it matter if I mount the fan inside the tent, or outside. I ve seen it right after the light inside, and I`ve seen it on the floor outside the tent. Thx in advance for your time. _
I have a 600w light and it does give off heat, I do to think it’ll be too much for your tent. The air cooled hood will help with the heat as well.
I have mine inside hooked straight to the filter and just blowin out. I know it matters where it’s sitting, but I’m not that technically knowledgeable to explain it, @Countryboyjvd1971 I believe he is a hvac and can explain it better
Thanks for the tag @Hawkeye_diesel
I agree with Hawkeye on the the lights they may be a little more than you need @slick using 50watths per square foot you need 450 watts so you’d be a bit higher with 600 useless it has a dimmable balast
As far as the exhaust goes I would mount filter and use a short piece of flex duct from filter to hood and another short piece from other side if hood to exhaust fan you can mount fan inside or out side of tent but your going to want to remove the heat from the tent that light will produce a bunch of heat
I’m running around 83 degrees inside my tents using leds lights and my tent is in my basement that is 68-70 degrees
How far away from tent is attic ? You can mount fan motor in attic it will be quieter for you and more efficient it easier to pull air than try to push it up
And @Hawkeye_diesel is right I’m a commercial HVAC tech with 25 years of experience in NYC
No problem, I knew you could help out on the fan more than myself
Thx for a quick response and your time. I should have posted here before I bought anything. Anyway…I think I will return the 600 watt system and go with 400. I will feel better about that. This is going in a shallow (2foot) closet thats about 5 feet wide. Doors are off closet. I was thinking of running the duct out the top of tent and right into the ceiling. It’s not really an attic. It’s a low crawl space. I am in Miami. It gets freakin hot up there in the summer. Was gonna mount the fan up there pulling air with mabee another few feet of duct running off fan blowing into the crawl space . So I didn’t want to mislead when I said attic. The ceiling will be a few feet from the top of the tent. I’ll cut thru that and run a straight hose from light hood out the top of tent…thru ceiling to fan to short piece of duct. Does the fan generate heat? If not or doesn’t matter…I would rather mount the fan inside the tent and run a long duct the same way…out top to crawl space. I don’t know what would be more efficient. Thx again.
The least amount of equipment in your growing space will be your best option… 
@Countryboyjvd1971 recommends that way and since he is a specialist in HVAC for 25 years and knows his stuff well. I listen to him for running air through the tents.
Agree with @peachfuzz the less inside the tent the more room you have for lights to go up. The fan is a very low risk of causing excess heat in the attic.
We have several specialists in other fields here that make it a whole lot easier for us to get the best out of our grows. I knew very little about cannabis growing when I came here and just had a great harvest.
This is a great place to grow.
I run a 600w MH/HPS in one of my 48x48x80 tents and it works well. To combat the heat I have a 6" intake vent straight to the light hood with a 6" fan hooked to an exhaust vent out of the hood.
I also have a 6" exhaust pulling through a carbon filter inside the tent straight outside. This way you have fresh room air pulling across your light, extracting heat from the light itself, and exchanging the air inside your tent with a second.
With it being setup this way I manage temps easily and it allows the plant to grow closer to your light than otherwise. At peak flowering I had the tips of the plant almost touching the glass on the hood without burning.
Great ppl. First, thx for your time and input. I respect that. JTheH…your running 2 fans then. I dont know how much noise these fans make, but it must not be too bad. Im going to get the 400 watt lighting system and return the 600. Can I get by with a 190 CFM fan with the 4" inlet, as opposed to the next size up…the 460 with the 6" inlet? I will prob mount it in the crawl space just above the tent thru the ceiling and then another few feet of duct out of the fan. That`s the plan so far. I have a window air conditioner in that room, and was just going to open the bottom tent vents and keep the room cool. With one fan pulling from the top thru the light hood and to a filter inside. Was hoping one fan at 190 would be ok. Plz tell me what fan, make and model you would recommend. When all this stuff gets here, I wanna set it up right one time, with the right equipment. Thx again! 
You should get a 6 inch exhaust fan with a speed adjuster. You probably can “get by” with a 4 inch fan - but why handicap yourself from the get go? Spend the extra cash - in the end, you’ll be happier that you don’t have to struggle to keep your space cool. 
Apollo Horticulture 6" inline fan, comes with a built in speed controllers, I have the fan and filter combo, but you can get it without I believe and isn’t really that loud to me, now my ears are different than everyone else’s though haha. I was Artillery for 5 years, so that might explain it is also have their 4" inline with speed controllers also built in and I wouod day combined mine are probably a little louder than say a 20" oscillating fan
Appreciate the love brother. Thank you
Every and anytime.
Well…most importantly, thank you for your service hawkeye_diesel. And thank you for your great info and taking the time to help. Thx to everyone for your time and opinion. The 6 inch apollo with speed control…pulling from the crawlspace up top is what I’ll start with.
Well…sorry to be a pain guys …I think this 600 watt system is dimmable. Its ipower brand. What is my best option....if the 600 watt is dimmable....keep it and run it at 75%....or return it (its not opened) and get the same brand but 400 watt?? Thx again all.
I think you should be alright with the 600w, but let some of the more experienced growers she’d more light on the situation.
IMO - You can never go wrong with more light. My personal rule of thumb is 100w per square foot. The problem is keeping it cool. No matter the size of your HID, you’re gonna have to keep the temps down. I’d suggest looking into a “cool tube” style hood for your lamp. Combine it with you’re carbon filter and fan - then vent it out of your closet/tent. 
The dimmable ballast only affects the light intensity… it’ll still burn 600w+ per kw/hr. Its so seedlings transplanted under that intense light won’t get burned. You’ll want to increase the intensity as the plants get bigger.
Ok…ty majic markers. I have a cool tube also. It’s beautiful and huge. Was gonna do exactly what everyone said. Filter hanging inside near top with 6 " duct to cool tube…out tube and out top of tent thru ceiling to crawl space above hooked to a apollo 6" 440 cfm adjustable fan pulling air up to crawl space. I am thinking if I run it at 75% setting…the heat won’t be too much. Thx again for your time.