Ventilation - help stealth grow

Hello Rollitup, say hello to the idiot! I made the huge mistake to order a "setup" which obviously was stupid as hell. Which set me with a 65cfm fan and a 175m3/h carbon filter - stupid, stupid and stupid.

Im gonna go for a micro grow with two small tents, one for cloning and one for mothers. Its very important to create a stealth grow with negative pressure

Flowerroom - 8.8 ft3
Mothers - 4.5 ft3
Together - 13.3 ft3

As you can see Im easily 10x above what I would need, calculating 1 airchange every 2-3 min to avoid stress on the plant.

If I understand it right from the Icmag-sticky I would need 2.5-4 cfm or the double if Im using a charcol filter - which I will. Correct?

Is it possibly to create a negative pressure with such small volumes moving in and out?

My idea would be for the intakes to be inside the motherchamber and lead the air from the top, to the flowerchambers bottom and sucking it out from the top thru the filter.

Is this possible or should I just concentrate on the flowerchamber by itself and just vent the smaller cab normally without a filter as its only pre-flower.

I guess I will have to rebuild the filters and buy new fans, I dont think there is a controller that could make the fan run at 10% and still being able to suck out air.

I feel like an idiot, but its better than changing the air 6 times per minute haha.

Thank you,

From my exp, where ever you are vegging will smell a little bit and wherever you are flowering will be quite smelly.

You could daisy chain your grow areas (watch for light leaks into flowering), but you would have to rig something up to suck the air from your veg tent to the flower tent, then another vent to suck the air through the filter in your flower tent and exhaust it. Usually you would suck the air through your carbon filter instead of blowing it out your carbon filter.

For your cubic feet, you could probably go with a small computer fan. I have seen some 40mm fans that pull 7 cfm, but you have a filter, so you may want to look at a bit higher. Maybe a 50 or 60mm fan. Usually you can find a dc adapter you never use anymore to power them. If you use a lower voltage, they will run slower, though. Just splice the wires together. Solder +shrink tub if you can, or use butt connectors, or just tape them (you probably will do this) Off the top of my head I think the filter will lower your air flow by... 20%ish

As for negative pressure, it depends on how well your areas are sealed. The better the seal, the easier it is to control your air pressure. Negative pressure is all about your exhaust pushing out enough air to keep your intake constantly sucking air in. Minimum, I would go 1:1 for intake to exhaust hole size, but some people recommend having 2x the area for a passive intake. Again, depends on your exhaust fan. The lower the pressure, the harder your fan has to work to move the air.

As for running the fan lower, I have seen some people splice in a dial dimmer into the power cord, if it is AC. They go for about $6 at homedepot. I can't vouch for how well it works or what kind of minimum it gives.

http://www.homedepot.com/p/600-Watt-Rotary-On-Off-Dimmer-White-R50-06602-0IW/203878272

Thank you for the input. Ive done some research and this is the fan I got, but the 107m3/h version.

http://eng.blaubergventilatoren.de/products/tubo-100

It doesnt say its "dimmable", however I have found the exact same fan on a different brand (probably a china rebrand then) that says it can be controlled and I found "plugs" on ebay - Cornwall rpm dimmer. 0-300w, seems nice.

Im thinking of redesign the filter, maybe pack it harder making the fan suck harder and regulate it down. Having to use an additional fan for the "channel" would be a bummer, thats the part I want to avoid with a setup like this.

Sealing is up to the tents, but im gonna silicon and ducttape every connection, hoping for the best.

Or I will have to go for the pc-fans but Ive heard bad things about their pressure being very low.

Keep the ideas coming please, Im sure I havent decided on anything yet.

Here I am again, answering my own questions buy hey - maybe it will help someone else...

Im gonna rebuild the whole carbon filter, using another design. Well spent money haha!

Im gonna use "real" ventilationunits, the body of the filter is going to be a 100mm T-connector made from PVC. Im going to use some silicon on the caps and add the pre-filters I got when I bought the filters. This could give the 100mm pipe 200mm openings to draw air from, hopefully It wont act as big breaks. Filling up the whole thing with active carbon.

Cornwall rpm dimmers ordered, hopefully they will work and not break the fans.