New grower needs box ventilation help

Hey guys, new grower/poster needing some help as the title states. I know this topic has been gone over a million times but can't find specific information to my setup.

I've got approx. a 4' x 4' box, 6 1/2' high partitioned into two rooms (2'W x 4'D x 6 1/2'H) The left side is going to be my flower room. I have the box completely enclosed and a door on the front with hinges and a latch. I'm running a 400w HPS with a remote ballast which is outside of the box. For the ventilation I've got two 4" inline duct fans, one at the bottom with airflow pointed IN, and one at the top with airflow pointed OUT. I'm not running any type of filter, and my light doesn't have any provisions to run duct off of it.

I just set this up the other night because my plants are ready for 12/12. The first thing I have noticed is the room is a little warmer than I expected although the plants are looking fine. So is there anything else I need? It doesn't seem like these little fans are moving a lot of air but I also read you don't want to create a "wind tunnel". Aside from my inlet fan do I need a wall grille for air transfer or anything? I read somewhere to mount a small oscillating fan inside the box positioned on the plants but again not sure if that would interfere with the ventilation aspect. Any insight will be appreciated.

Are you using a thermometer? That room is going to run in the 90s unless you are pulling in some cooler air. Even more as the plants get more canopy. I use same size light in a 3x3 tent. I have my setup in a basement where the temp stays under 60f and I have to use a cool tube to keep it cool enough.

Any clue what CFM your fans are? I believe you want to move about a third of your volume a minute.

I use one 4' inline fan and just use negative pressure ventilation. My fan starts with my filter (You are really going to want one if smell is an issue) goes through my cool tube then out of tent into fan. I have a vent that is open on the opposite side of the filter, where cool air comes in. No fan needed as the cool air will be pulled in (neg pressure vent)

You definitely will want a fan in both to provide a nice gentle breeze for the plant.

You will get lots of ideas. You will have to discover what works best for you. But I would be thinking about how to either : get an air cooled hood or figure out a way to cool your incoming air.

Welcome to RIU. Great place with lots of info. Good Luck
WE

Wow thanks for the fast reply. Currently I am not using a thermometer but definitely going to pick one up on my next trip out. Cooking thermometer says 81* (not sure of accuracy) Like you I am growing in the basement where it stays nice and cool. Heat hasn't been an issue until I completely sheathed my box in the other night (to prepare for 12/12). Nowhere on the box or the fan was the CFMs listed. They are the Suncourt style. Online it says 65 cfms.

Is the cool tube your light? Mine is the HTG style and has no flanges for hooking up any pipe or flex. I kept one side of the reflector off thinking that would help the heat rise out some. I thought about adding a floor grill on the top of the box but I think the exhaust fan would pull from that vent instead of from the box. Should I add a bigger exhaust fan or would I have to match it with the bottom one?

One other option I could do is cut in a clinch collar off the side of my reflector (opposite side of the bulb) and flex to an added exhaust fan. It wouldn't exactly be an "air cooled" setup but at least it would pull some of the heat away. In trying to keep this build somewhat cost friendly (and as simple as possible) would it be more effective to try and run exhaust off the light or add more fresh air/exhaust to the box?

The suncourt website lists the 4" inline fan at 65 cfm, and the 6" for only a few bucks more is 160 cfm. Wish they would have put this on the box or on the fan itself somewhere...I feel like I should have got the 6" ones.

I should save my 4" exhaust fan and flex my light to it. The other one I should return for a 6" and cut in a 6" inlet and outlet fan. How much cfm do I really need inside my box? Sorry for all the updates

I think that your inlet fan would be better served as a cooling fan for your light. Until you get a thermometer, it's really hard to get an idea. You cooking thermometer isn't going to tell you much unless you put it in a cup of water and leave it be for several hours. And it will not be able to quickly tell you temp changes.
You really have to try separate approaches. IMHO there is no need for an inlet fan. Your exhaust fan will pull the cooler air in. Just make sure there is plenty of inlet space. It is dark in my basement so no concern for light issues in flower.

Or maybe you run each side with it's own fan for exhaust? and have each independent from the other?
But you need to get a thermometer and you are going to want a hygrometer(humidity). Most use one unit that does both and also will tell you highs and lows for each.
http://www.amazon.com/AcuRite-00613A1-Indoor-Humidity-Monitor/dp/B0013BKDO8/ref=sr_1_1?s=books&ie=UTF8&qid=1464628617&sr=8-1&keywords=hygrometer+thermometer

Good Luck!
WE

Thanks for the help Wilderb. My basement is dark too, for the most part but I closed the box up good just incase the wife needs to do laundry, etc. Also the right side of my box is serving as a mother room which will have light on longer than 12 hours a day.

I found a CFM calculator that says find room volume in cubic feet (LxWxH) and then divide by 3. It goes on to say The air should be exchanged every 3 minutes minimum and this value will represent absolute minimum CFM requirements. So my room is approx. 52 cubic feet, divided by 3 gives me only 17.3 cfm.

So talking in approximate measurements, my 65 cfm inlet and outlet fans are definitely covering the air exchange requirements?

If I was to flex my inlet fan to my light (provide light with cool air) and add a hole next to my existing inlet fan for the outlet fan to pull fresh air from, would I still meet my air exchange requirements? And the 4" outlet fan will be enough to pull fresh air from the bottom of the box and exhaust heat from the light?

Does this sound like I am on target at all?

Keep in mind you are talking about two different things. Moving the proper amount of air for exchange and keeping the temps down. With a cool tube I was able to achieve both with one fan.
Without one you will have to be creative. I would be trying to move heat AWAY from the light. Drawing air instead of blowing air.
You are using HPS? For veg as well as flower? HPS ran hotter for me than MH.
IMHO I just don't think you are going to get enough air flow to keep temps down unless you find a way to draw that heat off that light.
Search the forum for small cab grows. Being in the tent crowd, there may be simple solutions I am not coming up with. I'm sure somebody has a DIY cooltube.
Keep working on it, you'll get it!
WE

I have a question, I have a 8x8x8 tent I built wit 2-6 inch exhaust fans suckling hot air out Te window, and a 8 inch hole cut out the tent on the opposite side of tent near Te bottom, would that be a correct ventilation? Also have 2 600w hps lights in the tent aswell...need help thank you

I changed my setup around after trying a bunch of different things. I went with a 6" exhaust fan pushing approx 160 cfm with a 7" inlet hole. I was talking with a guy who said for passive air exchange you want your inlet hole slightly larger than your exhaust hole... As far as an inlet fan I tried both ways and couldn't determine a noticeable difference. I eliminated the intake fan to simplify the system.

So mister420 maybe you want to bump that 8" hole out to a 9 or 10". Since you have two inlet fans find the area of a 6" hole, multiply by two, you will see that value is larger than the area of your 8" exhaust hole. Also you want to exchange the air in your room approx every 3 minutes so find the area of your room ( 8x8x8 ) and divide by 3. That number will give you the required CFM your fan should have. At least that is the way I currently understand it...

@Misterfourtwenty970 Yes that's correct!

@baker440

http://www.ebay.co.uk/itm/SALE-Cool-Tube-Shade-Grow-Tent-Hydroponic-Lighting-Reflector-Air-Cooled-5-6-/252158867066?var=&hash=item3ab5d6f67a:m:mEymvsV7jffrggbM4WMKfoQ

A cool tube, needs ducting and inline fan to match or close match! Cheap enough. Don't make the mistake I have seen some people make and just put a fan blowing through it. The air needs to go right out of the area and preferably up a chimney, out of a window or up into a floor space above if your in a basement.

Thanks Guys, I also have a 8000 btu Portable AC out side the 8x8x8 tent, the room is only 64 square feet total, so I'm using that ac to kool the room temp. and then from there cool air get sucked in to tent with Te negative pressure of tent exhaust, the lights don't have cool tunes there the ones with the wing Hoods.....

so should I make the Intake Hile

coreywebster said:

@Misterfourtwenty970 Yes that's correct!

@baker440

http://www.ebay.co.uk/itm/SALE-Cool-Tube-Shade-Grow-Tent-Hydroponic-Lighting-Reflector-Air-Cooled-5-6-/252158867066?var=&hash=item3ab5d6f67a:m:mEymvsV7jffrggbM4WMKfoQ

A cool tube, needs ducting and inline fan to match or close match! Cheap enough. Don't make the mistake I have seen some people make and just put a fan blowing through it. The air needs to go right out of the area and preferably up a chimney, out of a window or up into a floor space above if your in a basement.

Click to expand...

ager than 8 inchs? I do have 2x6 inch fans extracting air from 8x8x8 tent, one is located at light level and the other exhaust is some what around the Intake level but oposiTe sides of tent....?

Misterfourtwenty970 said:

so should I make the Intake Hile

ager than 8 inchs? I do have 2x6 inch fans extracting air from 8x8x8 tent, one is located at light level and the other exhaust is some what around the Intake level but oposiTe sides of tent....?

Click to expand...

If you are using both fans to extract then ideally they should both be high. If you mean you are using one as extraction and one as an intake then one high one low, One high at one end, one low at the other.. If you have a carbon filter attached then the fan can be high or low as long as the filter is as high as possible.
If you ment you are extracting with both fans one is high and the other low then you should change to both high and preferably both from one end of the tent while having passive intake from the low opposite side.
Hot air rises so the higher the point of extraction the better.
Hope that makes sense.

Edit. Just seen your post about AC, you should be fine. Extract air as high as poss, pull in cold air as low as poss. And yes larger than 8" or a few smaller ones.

coreywebster said:

If you are using both fans to extract then ideally they should both be high. If you mean you are using one as extraction and one as an intake then one high one low, One high at one end, one low at the other.. If you have a carbon filter attached then the fan can be high or low as long as the filter is as high as possible.
If you ment you are extracting with both fans one is high and the other low then you should change to both high and preferably both from one end of the tent while having passive intake from the low opposite side.
Hot air rises so the higher the point of extraction the better.
Hope that makes sense.

Edit. Just seen your post about AC, you should be fine. Extract air as high as poss, pull in cold air as low as poss. And yes larger than 8" or a few smaller ones.

Click to expand...

Yea that makes total sense what your saying, ima move the other extract fan to a higher possition in the tent and close that Hile offf, Thanks so much I been breaking my head on why I can't extract or intake cool/hot air, but u guys decoded it for me lol, biggie errors u knoe how that goes