Air Exhaust/Ventilation - Veteran growers input please

Hey guys,

My equipment arrives on Tuesday and I am sorting out temp/humidity/ventilation ideas. I have put together a diagram and welcome advise from seasoned growers. I have not used an inline fan/filter combo before. I am venting out an existing 4" stove vent( vent fan on stove is broken.. lucky me no drilling into the walls ! )

I will have to reduce from 6" to 4" before exiting the house.(6" air cooled hood) Would this be an issue with this design? I calculated that 190 cfm inline blower would evacuate the 31" x 31" x 63" tent 340 times per hour ! I hope the high evacuation will make up for the negative air flow caused by the filter, and the 6" to 4" reducer.

Also should I run the digital dimmer ballast at 100% for 600w, or dim to 75% for 450W. I dont want to wast electricity, or create excess heat without improving grow results. My calculations say to dim it as the extra wattage would be a waste, but then again this is why I am asking a seasoned pro.

Thanks guys !

i use a 400CFM inline fan for my 600w closet lighting rig. I doubt 190CFM's with filter attached is gonna keep that 600w cool enough.


Have a look at my closet build thread. It may give you a better insight.

https://www.rollitup.org/grow-room-design-setup/441212-my-new-closet-re-design.html




J

I agree with jon here, not enough CFM for your needs. If you were only cooling the lamp, that would be one thing. When you introduce the filter and that reducer it's another thing. At 2.5 X 2.5 keeping that box cool is going to be tough with passive intakes. Just my thoughts, lets see what the others say.

Thanks for the input guys, I will opt for the 400cfm and take your word for it. Exactly what I was concerned with. I dont want to spend time worrying about temp getting outta control and not creating enough negative pressure to adequately vent.

Would it help to add a inline 6" duct fan at the bottom? I have one, and there will be an intake there.

The duct fan would help your intake, but is not essential. I use 2x5inch passive vents in my closet and everything works great.


I would double check your filter is capable of 400CFM and look for a speed controller for your fan so you can dial it in properly.




J

The tent will have 3 - 12" x 5" passive vents the bottom.

Yeah, I was shopping speed controllers last night. Speedster makes one for about $25.00. Seems like it would work ok. Just a simple AC/DC current regulator. Do you run your fans on a thermostat or always on?

I just checked the filter and it says 440 cfm optimal. So looks like I am changing my order to a Vortex 6" 440 CFM fan/6" 440 CFM filter, and one speed controller. Then a quick trip to the local hardware store for a 6" to 4" reducer. I wish I could exhaust with 6", but the 4" vent is already there and a 6" hole saw for my drill is rather expensive.

The area is staying at about 75-80 degrees as I have monitored it the last several days so as long as I exhaust the heat.. all well and good with temp. Then when winter comes I can back off the speed controller and allow the temps to rise a bit. Thoughts ?

them temps are perfect and like you say in the winter you you can reduce your fan speed to raise the temps, sounds like you've got it all under control, + Rep to you.

p.s you want that filter as high up the room as you can so maybe have some ducting coming off the light going up to the filter, that way it extracts all the hot air above in the room. may also drop your temps by a degree or 2.

Are your temps 75-80 when running your lights?

If these are ambient temps you may need to contemplate AC.



J

jondamon said:

Are your temps 75-80 when running your lights?
If these are ambient temps you may need to contemplate AC.
J

Click to expand...

These are ambient temps. AC is going to be necessary during the summer, but we are heading into winter so I am trying to put off that purchase until next spring.... if I can First I want to get the best ventilation/cooling I can with ambient temps, then move to the AC if needed.

Understanding that temp/ventilation is paramount I am considering changing the design a bit. I am thinking one vent fan for the hood, the 4" 190 cfm, and a 6" 440 cfm with filter for the room.

I am not sure the one 440 cfm can handle double duty. How about you?

Well after much head scratching and smoking I have redesigned my new grow. I think this will work out much better. I really only wanted one fan, but am realizing that I would much rather have a nice garden and yield than skimp on another fan.

You have 2 190CFM fans on your design.


If you are still getting the 440CFM Fan then use it on your hood!


Also the 440CFM Fan attached to both hood and filter would work.



I like how you've pretty much "jacked" my design lol.


Nice work





J

I thought it may be better to have one fan dedicated to venting the hood, and one for the grow.

You said to check out your thread I checked it out good, real good! I saw those colas in your journal too! Nice work, very nice.

I have already ordered the 4" 190 cfm fan/filter. It has not shipped yet as I ordered late Friday so I have asked them to call me to change my order. So I have today and tomorrow to make up my mind.

I am thinking of just keeping the order as is 4" 190 cfm fan/fiter, and adding the extra 4" fan for the hood. Or should I just go for the 6" 440 cfm fan for the hood, or the 440 for both. So many possibilities !

Are you running just the one 440 CFM fan? If so, is there a Y connector in the attic so it draws from both hood and scrubber ?

the only thing i would maybe do would be to add a t after your scrubbed air and then have a little 3in line blowing that nice clean filtered fresh air back into your tent. most people dont use that clean air because they run that scrubbed air through their lights, so the air is hot and basically useless. but in your case you would be just shooting that perfectly cleaned air free of spores and dust right out side? where is the scrubbed air venting to? what kind of cooling setup are you running besides the air cooled hood?

i use 2 fans just like your design.

400CFM fan for lighting rig with speed controller , just like your design NO grow room air passes through it

Then i have a 180CFM fan and filter scrubbing the air.


IMO you MUST use at least 280CFM's to cool your hood,

440CFM Fan with filter attached to hood if you want 1 fan for all.

My design was created over the space of a year and was designed to give me more control.





J

Mrfootball420 said:

the only thing i would maybe do would be to add a t after your scrubbed air and then have a little 3in line blowing that nice clean filtered fresh air back into your tent. most people dont use that clean air because they run that scrubbed air through their lights, so the air is hot and basically useless. but in your case you would be just shooting that perfectly cleaned air free of spores and dust right out side? where is the scrubbed air venting to? what kind of cooling setup are you running besides the air cooled hood?

Click to expand...

The idea of running air back into his tent is FLAWED as you would be sending Co2 depleted air back in and plants need the Co2 for photosynthesis, so unless he plans to buy a Co2 generator/tank and controller the levels of Co2 would QUICKLY diminish and the plants would suffer.




J

Thanks Jondamon ! I will order the 440 cfm fan to vent the hood and the 190 cfm to scrub/circulate the air.

I have opted to return the tent when it arrives or refuse delivery. I am putting their customer service to the test ...lol The 31" x 31" x 63" seems way too small when the hood is 25.4" x 21" then with 6" vents on the sides....... just is not going to give me the flexibility I will need maneuvering the lights and filter placement. I am opting for a 48" x 48" x 78" for some wiggle room.

This forces me to move the tent to another area of the basement because of heating/air ducts hanging low, but places it right next to a 2.5' x 14" window I intended on blacking out. I will use this window to exhaust my air, and that leaves the original 4" duct open. I will replace it with a intake vent with dampener.

back to the drawing board, I will post back.

Thanks for getting me on the right track and for your input.

jondamon said:

The idea of running air back into his tent is FLAWED as you would be sending Co2 depleted air back in and plants need the Co2 for photosynthesis, so unless he plans to buy a Co2 generator/tank and controller the levels of Co2 would QUICKLY diminish and the plants would suffer.




J

Click to expand...

but there is still negative pressure no matter what so there is always going to be fresh air drawn in the tent at a higher rate then the plants can consume. having a 3 in tube blowing back in clean air shouldnt affect that should it? i dont see why it would. i would think it would only benefit the garden and help with good circulation and cleaner air.

Mrfootball420 said:

but there is still negative pressure no matter what so there is always going to be fresh air drawn in the tent at a higher rate then the plants can consume. having a 3 in tube blowing back in clean air shouldnt affect that should it? i dont see why it would. i would think it would only benefit the garden and help with good circulation and cleaner air.

Click to expand...

I think from what I have read is that Jon is spot on. I am scrubbing the air to not only remove the odor when flowering, but to also remove heat and help circulate the air. If I exhaust the scrubbed hot air back into the tent this will raise the temperature. My ambient temps are hovering at 75-80 degrees which is fine, but when the lights are introduced this will raise the temp in the tent I imagine by at least 10 degrees even with venting. I really need a continuous exhaust of the hot air to help maintain temps and supply plenty of fresh Co2. I agree that the plants will be getting more air than they can consume, but adding recycled hot air would be disastrous in my opinion. Now you could take your idea and bring in fresh cool scrubbed air, but the benefits outweigh the cost in my opinion.

I built a five by five room eight feet high. .I use a six hundred hps. .I bought a three speed max fan that's 300com..the fan hangs above my light and sucks all the hot air and stick sucks it out six inch ducking through the wall to a fan can filter outside..the filter is a thirty pound carbon filter and you don't smell shit. It was the best addition ever to my garden cuz now the wife will let me do whatever i want.....but one thing ill say its way better to imo suck the air out of the room then to the filter rather than sucking it through the filter then outside...those filters are absolutely amazing...