Ventilation, computer fans question

[Giantsfan24]

I'm building a small grow box and I need it to be stealthy so I'm building a homemade carbon filter much like what stratlogic, I believe, has done: mesh wire, panty hose, etc. It will be mounted across the interior back side of the box.

I'm going to be connecting that thru either pvc or duct work to a computer fan with an additional light weight carbon sheet, small one, in the fan grill on the outside of the box.

I will have a small, 250W HID system, utilizing MH and HPS, that will be air cooled connected to another computer fan that is run thru a thermal fan controller. I was considering having it have a passive intake also connected to the other side of the fan but I don't think that may be necessary.

The passive intake will be in the bottom of the box covered by black landscape material for light control...this won't be my only light control for this intake but this post is getting too long..

My plan was to run the carbon filter fan only during flowering and the fan connected to the light through veg.

Will I have a problem with odor if I run the carbon filter fan setup for the flowering stage off of the thermal fan controller so in essence use it as an exhaust/cooling fan only coming on when temps dictate or should it be run 24/7?

I have 18cf of air to move so 3x per minute - my fan through the filter will be 90 cfm and the fan exhausting the light and controlling temps will be 54 ish cfm.

The box is in my garage and I'm worried about the temp getting too low in the winter. It's 23 degrees f right now outside, 50 degrees in my unfinished box. It will be insulated with Reflectix and very well sealed. 23 degrees is not normal for my area, I might add and the lowest we generally get at night is above freezing. This is a cold snap for us.

It's going to be a great box and I can't wait to get pictures up for my first grow.

Sorry this is so long.

Happy Thanksgiving!

 

[free2blaze]

I would suggest setting everything up as if you were growing but without the plant/s and monitor your temps, your carbon filter is a good start and might do the job if you are only growing one or two plants, you could also try some odor eliminating products, there is one I seen a post about on here called ona block,
if odor is a serious concern I would also suggest doing all the online searching you can do about odor control, there is alot of info but also if it is a real big concern not growing might be the better suggestion, one plant flowering can create alot of smell.

 

[Giantsfan24]

I would suggest setting everything up as if you were growing but without the plant/s and monitor your temps, your carbon filter is a good start and might do the job if you are only growing one or two plants, you could also try some odor eliminating products, there is one I seen a post about on here called ona block,
if odor is a serious concern I would also suggest doing all the online searching you can do about odor control, there is alot of info but also if it is a real big concern not growing might be the better suggestion, one plant flowering can create alot of smell.

There are many here who are growing in a stealth-like manner and controlling smells quite well. I am only planning on two plants as my space is small and that will take care of my med requirements.

Good suggestion though. I've already learned a lot from just sticking the temp gauge in my unfinished box! I've read about ona too...seems like the way to go..

Thanks!

 

[cflgrow]

Hey GiantsFan.

I started off in your boat... small stealth grow, wanted a kick-ass smell-neutralizer, thought a home-made carbon scrubber was the way to go.

I built two... they ended up being pretty big (you can click the link in my signature if you're curious), but it didn't really feel worth it in the end. The amount of smell they were clearing, vs. how big, awkward and pricey they were (I spent a lot on my activated carbon) wasn't satisfying.

I heard about ONA and decided to give it a try. The Folger's tin with holes and a computer fan method is what I used. I pay $25 for a liter of ONA, and it lasts me about a month to two months, depending on how long I leave the fan on for. During that month, my house is completely smell free, with 10 plants in the flowering phase.

For your two plants, you could easily make a $25 bottle of ONA last you from seed to harvest.

If you're not familiar with how to control your ONA consumption, or even how to use it, just let me know I love the stuff now that I've switched over.

 

[Giantsfan24]

Hey GiantsFan.

I started off in your boat... small stealth grow, wanted a kick-ass smell-neutralizer, thought a home-made carbon scrubber was the way to go.

I built two... they ended up being pretty big (you can click the link in my signature if you're curious), but it didn't really feel worth it in the end. The amount of smell they were clearing, vs. how big, awkward and pricey they were (I spent a lot on my activated carbon) wasn't satisfying.

I heard about ONA and decided to give it a try. The Folger's tin with holes and a computer fan method is what I used. I pay $25 for a liter of ONA, and it lasts me about a month to two months, depending on how long I leave the fan on for. During that month, my house is completely smell free, with 10 plants in the flowering phase.

For your two plants, you could easily make a $25 bottle of ONA last you from seed to harvest.

If you're not familiar with how to control your ONA consumption, or even how to use it, just let me know I love the stuff now that I've switched over.

cfl..thanks so much for the advice. Over the last 48 hours I've decided to purchase a Phresh filter and also use ona...just as you say.

I've also picked up a carbon filter that is cut to fit in a furnace intake that will work well as a double check to fit inside the fan filter grills.

My box is pretty tight so I don't think I'll have a real problem and if I do, I'll buy some exterior air cleaner. They aren't that expensive..

Now if I could only match bassplayer's quarter lb yield on two plants no more than a foot tall..I'll be in business!

 

[Giantsfan24]

Well the "Phresh" filter turned out to be anything but so I sent it back and built my own..f'in thing was huge....very pleased with how my diy filter turned out and it was easy as hell.

I spent probably $20 on it.. 4" by 6" pencil holder from Staples, pantyhose..got to talk to a cute sales chickie about those...a small mesh wire cylinder I built, an "odor filter for pet smell", that would normally fit on a furnace intake, at Lowe's and some duct, "backer rod" to hold the carbon in place, zip ties...the usual.

The carbon was the aquarium carbon that you can find at Walmart. I haven't tested the filter out yet but it certainly looks the part! Pics to come.

I tested out the overall box ventilation as free 2 blaze suggested..thank you for that advice...and temps were too high...

I think I have a couple of issues: The cfm rating on my computer fans is too low for the amount of resistance, the passive intake isn't sufficient for the needs of the box.

I'm running a 250w HID hood and am trying to get the temps in control without having to duct the hood. In my small space, the ducting is cumbersome. Based on the second test below, it's an achievable goal.

I've run two tests:

Test 1:

The filter connected to a computer fan drawing air from the passive intakes through the filter and out of the box and the hood connected to one duct to a computer fan. Result = she's a no good! Temps way too high..got up to 100 degrees before I shut it down.

Test 2:

The next test I ran was with no resistance: I took the filter off the fan and the ducting off of the hood exhaust just to see if the two fans would cool the box without anything to impede air flow with the light on. The fans were open and pulling air from inside the box and the passive intakes. Result = the temps never got above 80 degrees.

Well, that was positive but not good enough. The goal of the ventilation, for me, is to provide recirculating airflow AND bring temps down when they get too high, not just maintain them.

My Next Test

From here, I'm considering the following approaches:

1) I've ordered higher cfm fans. They'll be here next week. I'll test those the same as the prior tests and see what my results are.

2) Add a lower cfm intake fan than the exhaust fans to aid with intake airflow. I was trying to avoid this to maintain negative pressure but I think I'll be ok if the cfm from the intake is lower than that of the exhaust..yes??

3) Increasing the amount of passive intakes.

4) My last resort is to duct the hood. I'll try one at a time. One for exhaust first then with both intake and exhaust. Again my goal is to avoid too much duct work. I want the inside of the box as clean as possible to give the plants as much room as possible to breath.

Any suggestions are welcome. I owe the success of this project to these boards and all of you..most of my ideas have come from reading your posts.

Thanks!

 

[Thew1sest]

Also, this got me the first time I wired up the computer fans to the power source, but make sure you parallel wire the fans to the source instead of a series, the series causes the fans to use the current in half of what they should. The higher cfm fans should help draw the air faster between your carbon filter, I have a small oscillating fan inside that constantly blows in a somewhat upward direction to increase circulation, and create a stringer bigger stem. It also lowers the temperature a bit too.

 

[Giantsfan24]

Also, this got me the first time I wired up the computer fans to the power source, but make sure you parallel wire the fans to the source instead of a series, the series causes the fans to use the current in half of what they should. The higher cfm fans should help draw the air faster between your carbon filter, I have a small oscillating fan inside that constantly blows in a somewhat upward direction to increase circulation, and create a stringer bigger stem. It also lowers the temperature a bit too.

Hey Thew...Thanks a ton for your advice.

I didn't wire my own computer fans. I got them through an online site and have them wired through a thermal controller that turns the fans on when the heat gets to 85 and runs til the temp comes down to 75 then shuts off. They connect seamlessly through 3 pin connectors...see unlike you my growing friend, I'M not wiring friendly and was very afraid of messing up something with electricity...not for me..

I figured out today that my hood was not oriented correctly for my box and the new orientation allows me to completely vent the hood without the duct work being cumbersome. I'll have an intake fan with lower cfm blowing air into the light from outside the box and a fan with slightly more cfm sucking the air out of the fan area. That should totally fix the heat issue and with the glass on, totally enclosed lighting system, shouldn't have too much of an issue with smell. (I have a plan for odor too should that not be the case )

The new fans that I'm getting, I should only need one as, like you, I got a small 4" clip on fan for inside the box, will be connected to the carbon filter and then plugged directly into the outlet bypassing the thermal controller but connected to a speed controller. I should, hopefully, only need this when flowering and the smell is present and it will run 24/7. With the speed controller, I'll be able to customize the noise level and get the most efficiency out of the fan/carbon filter combo..hope it works! LOL

I've also decided to add 12" to the top of the box so I'll have what I think will be the perfect grow space for my needs. Should I run into any issues with heat, I'll
#1 - Add a couple more 3" holes for passive intake and if that doesn't work I"ll

#2 - Put in the other fan I have, plug that into the speed controller too and have air sucked into the box from outside.

I may install the fan first before drilling any more passive intakes but we'll see.

I'm telling you I'm going to beat this heat issue if it kills me! Wish me luck!

 

[Thew1sest]

Believe me the wiring isn't half as bad as it seems I promise! If I can wire up computer fans to a power source anyone can Sorry I may have read this wrong as well but you plan to blow air onto your lights? I'd have the exhaust pulling the hot air away from the lights and blowing it out of your grow area. With cold air (usually from the bottom of your area) coming inside. Hot air rises, cold air falls. Hope any of my rambling advice helps!

 

[Giantsfan24]

Believe me the wiring isn't half as bad as it seems I promise! If I can wire up computer fans to a power source anyone can Sorry I may have read this wrong as well but you plan to blow air onto your lights? I'd have the exhaust pulling the hot air away from the lights and blowing it out of your grow area. With cold air (usually from the bottom of your area) coming inside. Hot air rises, cold air falls. Hope any of my rambling advice helps!

I have a 42cfm computer fan blowing air in and a 63cfm sucking air out.

The smaller cfm fan will be placed high in the box so the ducting is out of the way but I'm building a vent that will actually draw air from the floor of my garage where it's the coolest. The difference in cfm will take care of the sucking part...low cfm blowing in, higher cfm sucking out.

My box is small and I want to make sure I don't have ANY heat issues. Wiring...yeah...me?...not so much! I'm anal and don't want to take a chance.

I see a lot of homemade stuff here but for me...wiring isn't where I take a chance. I let someone else do it and know it's right.

I just figured out the rest of the box and all I'm waiting on now is the 115 cfm fans to come in so I can connect that to my carbon filter and I'll be done with the box...YES!

Then come the tests to see if I indeed have any skill!! then off to get clones. I can't wait for that, I'm telling you!

 

[Thew1sest]

Yeah its definitely a difference with everything hooked up, remember to account for extra CFM needed to pull the air through the carbon filter. Good luck! Looks like you have most of your Homework done. Easily one of the the most important parts of growing.