Exhaust and Intake Fan Controller

Making a new setup and plan to have a speed controller on the exhaust to work with what my current temps are at and adjust accordingly as we have cold winters and hot summers.

I plan to run a Hurricane 6" inline fan exhaust and I haven't picked out an intake yet but have read to choose one half as powerful as the exhaust, is this correct?

Once that's decided should I control the intake fan along with the exhaust? Separately? Together? Or just let it run at its normal speed always and just let the exhaust do the adjusting?


Thank you,
Turbine

Passive intake doesn't interest you at all?

Why do people still use active intakes? I dont get it

His name is Turbine!

Why do they? I had a situation where I was growing in my closet and used panda paper to create a zip up door/tent situation. Using a 180 CFM fan in that sealed environment it would suck the doors in. Same can happen in a tent, you can have to much negative pressure. Passive is def easier and would be how I try it first off but if you have an issue you may want to look into active. Also I ran some tests in my specific situation and I got a 2 degree drop in temps in my closet with an active vs passive.

In my opinion it's easier to control the negative pressure via a fan speed controller on the exhaust fan, rather than coming up with a complex intake system

Everyone situation is unique....Where I am in the summer it gets hot. My spare room gets sun all afternoon and is hotter than any other part of my house. I pretty much had to run my little 4" inline full throttle to maintain a decent temp. For me it was as easy as going to the local CVS buying a 5" round little desk fan getting my extra ducting rigging up some tape to connect it. Took me 5 minutes but yes you def want negative pressure and if that little fan was more powerful there could have been some adjusting required to balance the pressure. Anyway, I agree that it is typically not required but depending on where your growing the area etc. it may be needed.

Negative air pressure makes my plants smell more.

Thanks for all the great replies guys.

I agree I dont want too much negative pressure forcing the smell out, but I've tried doing passive intakes before but they just didnt seem to do much.

I tried following a guide to create the proper amount of sqin of passive intake for the CFM of my exhaust but it would have required far too many holes for my practicality.

My biggest problem is this is somewhat of a stealth build so I can have a large cruise ship looking light beams coming out the side, lol, so thats why I figure I could have active in and exhaust out all nice and neat.

I think its safe to say putting the controller on the exhaust is my best bet, but as far as what size intake fan, would going with a 4" hurricane (to match my 6" exhaust 435 CFM) at 171 CFM work out or is that too far a differential now?

for me in my closet with it sealed off (like a tent) running through carbon filter pulling air in from the room (passively) creating negative pressure meaning fresh air pulled in through the closet or tent should mean that smelly air is not leaving your area. Positive pressure would let smell escape. But there is a balance or negative pressure can be too much. If your gong to spend the money on intake just spend the extra $25 on an additional speed controller and you will be able to dial in your environment. Just know each fan adds more noise more heat more power. Light leaks can be offset with ducting or creating bends however you rig it.

Would there be a problem having a 171 CFM intake and 435 CFM exhaust (carbon filter on it mind you)?

Not sure if that makes for too large a differential

Turbine said:

Making a new setup and plan to have a speed controller on the exhaust to work with what my current temps are at and adjust accordingly as we have cold winters and hot summers.

I plan to run a Hurricane 6" inline fan exhaust and I haven't picked out an intake yet but have read to choose one half as powerful as the exhaust, is this correct?

Once that's decided should I control the intake fan along with the exhaust? Separately? Together? Or just let it run at its normal speed always and just let the exhaust do the adjusting?


Thank you,
Turbine

Click to expand...

If this is a totally new setup, then you prolly don't know if you need an active intake. Start with what you have, passive intakes work plain and simple. If you feel the need later on to add an intake you can, but my guess is you won't.

Not totally new. Have the same setup going now, half the size, but no watering system or nice fan.

Gets waaaay too hot in the summer which is why I thought to go active.

You think I can still get away with passive with some ductwork to prevent light from escaping/entering? (not that they need it for veggin but I cant have light escape for stealth reasons)

Not sure of your setup, lights, space n size, so can't tell you if passive will work with your new exhaust

Outside ventInside vent for a 2x3 closet running 300W (1200W equilivent) of CFLs and a 75cfm fart fan in the ceiling, temps never got over 85-87 all last summer

Quick rundown of what the plan is, already have some of the equipment.

8.5ft long x 2.5ft deep x 4ft tall

2x Sunleaves Pioneer VIII

planning on a 435CFM exhaust with an inline carbon filter

JSJ, those temps are kinda high....and your 300W of CFL is not the same as having 1200W. In fact it won't even be a strong as a 400w HPS and will run hotter. Turbine here is the deal adding an intake fan is not going to solve your extreme heating issues. How hot are you in the summer? Where is this box located? Your exhaust is overkill for that area but whatever, its ok to do that....get the speed controller. Ambient temps are going to dictate how hot your grow area gets. If it is 70 degrees in your room where this box/tent is then your grow lets say runs 8 degrees warmer. If its summer and your room gets to be 80 then your then your 88. Now if your intake is coming from another room, or area where fresh "cooler" air is being pulled in then yeah it will cool it down more. Don't expect any miracles by adding an intake unless it is ducted to an AC. I gave you my example with my 400 in a closet in a spare room. Spare room is 75 degrees my closet runs 4-5 degrees hotter with my ducted hood and exhaust set up. I went from passive to an active intake so all I am doing is cooling my 80 degree grow space with 75 degree cooler air and well that dropped my closet grow area 2-3 degrees. Don't get me wrong sometimes every degree counts. Things to also look into are fan placement inside the grow area. Running lights at night and off during day. More vertical space in your area will help, sometimes a humidifier will help lower temps slightly. 1-2 degrees here and there can add up but like i said it is the surrounding environment that you need to control as well.

Thanks a lot for that, makes a lot of sense.

The room this box is in is about 8x10 and has central Ac and heat so I don't think ambient temps should be a problem except for rare days such as a few days when it was 105 here in Nj last summer.

So I guess I should have no need for an intake fan and can just run ductwork as needed and allow the exhaust to pull the air through just as quickly as it exhausts out the end.

I've read an article on here before about how to properly size your passive intake and ended up with a massive amount of sq in to try and make holes from. How would you suggest to size what my needs will be?

Don't know if this matters for anything but was planning on having two intake ducts and two exhaust so air can be brought in and taken out in key locations.

Intake would be around dirt level and right above the canopy.

Exhaust right below the light, higher than the intake. And above the light to exhaust any excess heat.

What do you think?



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Also,

I think the reason I got turned off from a passive intake was due to having an insufficient exhaust fan so my temps were too high and I assumed making it active might help that.

Although, with much more air flowing won't I have problems with low humidity. That was the issue I had last summer in this same room, box half of this ones size (just one pioneer viii) and the light was so hot it was like a desert for my babies and they required waterings very often because of how dry it would get.



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rwbrock said:

JSJ, those temps are kinda high....and your 300W of CFL is not the same as having 1200W. In fact it won't even be a strong as a 400w HPS and will run hotter.

Click to expand...

Those temps aren't high considering like I said it was last summer. My bad for forgetting this is riu and everything has to be written out in detail. lol And I have compared any amount of CFLs to any other lighting source, simply stated how many actual watts of CFLs I was running, which all CFLs give an equivalent wattage, never said it was the same as having 1200w or compared it to an ups, but you did get one thing right, 1200 equivalent watts of CFLs sittings inches away from the plants is definitely hotter than a 400w hps sitting 12 inches away from the plants. Which only adds validation to my original comments that a passive intake works, plain and simple. In my opinion active intakes are only useful in certain situations, take my grow room for example. It sits inside a hot ass attic. I am running two active intakes only for the reason of needing a positive pressure in the room so that any air leaks will be letting the tempered air escape instead of sucking in the hot attic air.Turbine, my original suggestions still hold true, you have more than enough exhaust for your setup and I see no reason for that setup to have an active intake.J