4x4x2 tent ventilation question

[EzExtractions]

sup guys i have a 4'x4'x2' (LxHxW) tent with a 400 watt mh light dimmed down 50%.

The light is vented with a cool tube attached to a 6'' Inline fan.

I plan on attaching a carbon filter to the opposite side of the cool tube, and let the carbon filter just rest on the floor standing up (I have no more room up at the ceiling of the tent to mount the filter with straps).

Now my main concern is that the fan wont move enough air to control the odors of a flowering plant. The inline fan im pretty sure is rated for 450 CFM.

My other thought was to get a small (5000btu) portable a/c unit and stick it in the tent. Then just get ride of the cool tube and use a normal reflector.

at that point the inline fan could be used solely for the purpose of exhausting odors, and not keeping the light(and tent) cool.

Money is not really an issue so im not trying to take the cheap way out, i know the portable a/c units are $250+ but if my temps are already getting up to the high 90*F and its not even may yet, then my plants dont stand a chance come summer time.

does any one have any suggestions?

 

[Hiker]

Hi EZ

That 450 cfm fan should be plenty! Are you worried that adding the carbon filter will cause too much resistance?
Let's be pessimistic and assume the fan loses 50% from the filter. Then lets assume you're losing another 50% due to friction in the ducting. That still leaves ~110 cfm. Your tent is 32 cf. That's a lot. Here's a thought. Try it with that fan and your filter and see how it works. You can always add another fan later if you find things aren't working the way you would like.

 

[EzExtractions]

Hiker, thanks for your reply! So i installed the carbon filter (and yay i found room on the ceiling to mount it!), i then put my speed/fan controller at half speed, closed all the vents and zipped up the door and let it rip, Lets just say it has enough suction to suck the walls of the tent in just a little bit. Id say thats adequate ventilation! and that was at my fan only running at half speed (220cfm).

Thanks again for your advice~!

 

[Hiker]

Glad it worked! A negative pressure is a good thing. That's how you control odor. You're making sure everything goes through the filter.

One question though. You have it setup filter -> fan -> outside the tent, right?

I know you can blow out the filters too, but I think the work better the other way. Plus, if you are intaking through the filter, you can use a prefilter. That will extend the life of the carbon filter.

 

[EzExtractions]

if negative pressure is how i control odor then should i have the fan running at all time? the sound of the fan running kind of raises suspicion of a grow (i live in apartment) to the neighbors. So i have it on a thermometer and a timer, it only runs when the lights are on, and only turns on when the temps get above 90*F. When i switch the lights to flower, should the fan be running 24/7 to control odor? the way you explain seems like it has to be, or at least for most of the day.

Possibly i could put it on a 24 hr 15 min interval timer, and have it run like every other hour or something?


As for the way i have the ventilation set up , everything is inside the tent. air gets sucked in the carbon filter (with pre filter) , through a small section of duct, through my cool tube, through some more duct work, into my inline fan, then into some more duct work that is vented outside the tent.

Its been working great for keeping the temps down, only needs to run (at 50%) for about 5-10 minutes (depending on ambient temp) to cool down the tent.

Thanks for your input so far!

 

[Hiker]

Unfortunately, yes. To control odor best, you need that fan running 24/7 to maintain that negative pressure. This ensures all the odor molecules and up getting sucked through the filter. Otherwise they will find their way out. You've already hit upon the dilemna though. How to have 2 different fan speeds? If you have the budget, there are controllers out there to do this. They let you set 2 fan speeds. You can tell it to run the low speed all the time and then switch to high speed when temps are above a certain threshold. That would do what you want to do I think.

Another option would be a second smaller fan put inline with the existing fan. The small one runs all the time. It is not able to cool the room, but it does move a small amount of air all the time to maintain the negative pressure. Then your thermostat will kick on your bigger fan whenever it gets too hot. You wouldn't even need any timers. It wouldn't matter when the lights are on really. If it gets to hot, whether they are on or not, you want the room to vent, right? The fan will probably only come on when the lights are on anyway as that's when the heat is being generated. Now I'm not 100% sure this would work the way I'm proposing. We need a real HVAC guy in here.

I grew in an apartment once. Stealth can be challenging, but doable. What fan are you using now? Not all fans are equal in regards to noise. I have 2 8" fans. A Hurricane and a Soler & Paleu(sp?). The Hurricane sounds like a jet engine. The S&P is much much quieter. It cost more and doesn't move as much air, but I'm saying there are options. The way I use the 2 fans, having those different strengths and weaknesses works for me.

 

[EzExtractions]

I like the idea of using another small inline booster fan running 24/7 if you think it will work the way you explain, it seems logical, like as long as there is some air movement then it should control odor. I have a 6'' inline booster fan already,where do you think the best spot to put it would be? i was thinking right before the carbon filter.

The fan is an ebay cheepo MTNGearsmith. the electric motor is very loud you can hear it slowly get louder as it gains RPM's.

again thank you for your help so far, EDIT: BTW i made a journal with pics, please check it out! 1 Gal Hempy Blue Cheese Tent Grow

 

[Hiker]

posted on your journal