exhaust questions

do you need 2 exhaust fans for a grow tent? would a 250 cfm cool a 4x4 grow tent?

depends on the light

in a 4x4 youd want a 600-1000 watter so id go with something like this to adequately cool that

http://www.htgsupply.com/Product-GrowBright- 6in-High-Velocity-Inline-Fan.asp

cheap and effective.

this will allow enough air to be pulled in from the bottom flaps or holes but it never hurts to put one of those fans you mentioned in there.

im using a 400watt

well the 6 inch fan will certainly cool it adequately

and anything smaller would be a waste of money since itd only be a few bucks more for the 6 inch.

and it will last you for future grows unlike those booster fans that start losing there luster after about a year.

ok but do i need a fan on the duct pumping air in too?

It never hurts to add them but the negative pressure of the fan pulling out will cause a good amount of air circulation by itself.

FoilageTrees said:

ok but do i need a fan on the duct pumping air in too?

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Yea, with the Fan Sucking air out of the tent, it automatically sucks air into the Tent via the Bottom Flaps, so no need for the second fan.

Rusty Shakelford said:

Yea, with the Fan Sucking air out of the tent, it automatically sucks air into the Tent via the Bottom Flaps, so no need for the second fan.

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what flaps would that be? what about when its time for the 12 off? wont flaps allow light in? just asking cause im in the same boat as the op....

richard805 said:

what flaps would that be? what about when its time for the 12 off? wont flaps allow light in? just asking cause im in the same boat as the op....

Click to expand...

if you use another duct for the intake you can make it light proof

richard805 said:

what flaps would that be? what about when its time for the 12 off? wont flaps allow light in? just asking cause im in the same boat as the op....

Click to expand...

Most tents have Vents at the bottom. Yours may have the Flaps or just the Round Opening for ducting.. None the less, your tent should really be in a Dark Room to avoid any light leaks.

as long as you dont have another HID light thats leaking light into your tent youll be good with small incandescent light leaks

Theyre not powerful enough to breakdown hormones and reverse flowering/cause hermaphrodites.

Also when it comes to the fan feel free to add the extra fan in just for some air movement across the branches.

because even though you have the big fan pullin out 400+ cfm there isnt much leaf movement from the plants just using the passive intakes

So i always add another 6 inch fan that i can aim to blow across the canopy.

Also, some tents are so small that even with the bottom flaps open 400+ cfm is enough to suck in the sides of the tent and potentially bend your poles or break your corner pieces.

Just be careful I have had strains that turned hermi with very little light leakage. Some can handle it no problem. I have blueberry that will turn on me if I just hit it with a flashlight for a min and all the others could care less. I've got 200 plus strains under my belt and I wouldn't take that risk better to just black out the room or if you have to use light because you live in the room get a couple 5 watt led lamps to see with. If you just need light to work on them green bulbs don't disrupt night cycles. I use a green led head lamp to work at night its great. They make t5 ho green bulbs and any green led works. I don't trust anything that is filtered green like a green lens over bulb wont work it needs to emit green light.