Ventilation setup - Any problems with this? All air over light...

[lampost]

I'm setting up a first grow and the last remaining hurdle is ensuring adequate ventilation. Here's the set up:

4' x 4' x 6'-6" Grow Tent w/ a 600W HPS. Not a cooltube, but Easycool (I think, basically same concept with larger reflector). It's got a 6-inch "port" for ducting on both ends.

So, my grow room has a volume of 104 CF. The grow tent I'm getting has 4-inch vents, and it seems the largest fan I can find in a 4-inch inline is like 172 CFM. This is the expensive Vortex. So, that would give me over 1.5 air changes per minute, which seems plenty adequate to me, although I've seen various opinions on this. What do you think?

Now here's the weird part. I only have 3 x 4-inch vents. So here is my plan. I'm going to have duct coming off one of the 6-inch ports in the light and the other port in the light will be an open intake. I'll have to get a 6-in to 4-in reducer and then route that out one of the 4-inch ports. This will have the 172cfm vortex fan pulling air through the light and out of the grow tent. The other 2 x 4-inch ports I was going to just leave open as intakes (with a filter since it's in a dingy basement). So basically all of the air in the grow tent will be pulled through the one open end of the light, over the light, and out the grow tent. Is that OK? What do you think are my other options in a tent with limited ports like this? I'd like to get away with only one ventilation fan (and of course another inside to circulate the air) which seems possible if it's sucking enough air.

Also, I have a lot of questions about how/where to mount the inline fans and such. If anyone has any good links/posts or anything, please steer me there.

lampost Reviewed by lampost on 11-19-2009. Ventilation setup - Any problems with this? All air over light... I'm setting up a first grow and the last remaining hurdle is ensuring adequate ventilation. Here's the set up: 4' x 4' x 6'-6" Grow Tent w/ a 600W HPS. Not a cooltube, but Easycool (I think, basically same concept with larger reflector). It's got a 6-inch "port" for ducting on both ends. So, my grow room has a volume of 104 CF. The grow tent I'm getting has 4-inch vents, and it seems the largest fan I can find in a 4-inch inline is like 172 CFM. This is the expensive Vortex. So, Rating: 5

[lampost]

Also, forgot to ask... what is the material for ducting that is usually used? Is it like that black flexible plastic stuff? I can see it needing to be flexible as the height of the light is adjusted and it's location changes in relation to the port of the tent.

[killerweed420]

Sounds like it should work. On one of the inlets you may want to add an inline fan to blow cool air into the tent but I would wait and see how your temps run first.
I use the mylar type flexible hoses. I don't know how tough those tents are you may want to mount the inline fan on a wall next to the tent.

[lampost]

^Thanks. Yeah, I haven't seen too many setups so I'm still curious as to how the fans are mounted. I was assuming you mounted it to the edge of the reflector or the edge of the tent, but that's a good point. I'll probably rig something to hang it from the inside somehow.

Also, I'm wondering how it would affect the air flow if I were to use a 6" fan and blow it through a 6"x4" reducer to exhaust. What will that restriction in the air path do to the total overall air flow? I'm thinking it would cause higher pressure between the fan and the reducer and slightly reduce the total air flow? Would this be negligible?

[senorx12562]

^Thanks. Yeah, I haven't seen too many setups so I'm still curious as to how the fans are mounted. I was assuming you mounted it to the edge of the reflector or the edge of the tent, but that's a good point. I'll probably rig something to hang it from the inside somehow.

Also, I'm wondering how it would affect the air flow if I were to use a 6" fan and blow it through a 6"x4" reducer to exhaust. What will that restriction in the air path do to the total overall air flow? I'm thinking it would cause higher pressure between the fan and the reducer and slightly reduce the total air flow? Would this be negligible?

I've been told to always have the fan blow through the light instead of sucking the air through, because the hot air from the light is not good for the fan's bearing(s) and lubricant. I've seen two different types of flexible ducting, the kind that is like aluminized paper with a "slinky" type of framework, and some more rigid aluminum that provides its own structure, and accordions out to lengthen and turn (but be careful, it doesn't accordion back in). The latter is more expensive, but seems like it would provide less airflow resistance. Be careful about the aluminized paper kind. I used it in building my room, only to discover that some of the aluminum flaked off or cracked and was letting light in, like a starry night. If temps become an issue, you may have to draw all your cooling flow from outside the tent to avoid already-heated intake air. My reflectors are not at all airtight, so I lose way more airflow going through the lights than the reduction in diameter would cause. I run two 8in 700ish cfm fans through 3 lights each (w/ 6 inch flanges) and both flows exit through 1 8 inch exit.