How big a fan do I really need?

[CannabisMeds]

I have a 4 x 4 tent with an LED light, so it should be fairly cool.

I'm wondering how big of a fan do I really need for ventilation? I've been looking at these 6" duct fans, but I noticed on one of the online garden store sites that they say 'cannot be used with a carbon filter'.

I'm not sure if I'll need a carbon filter right away, but it would be nice to know I could hook one up later.

If I didn't need a carbon filter, I'm not even sure I would need a fan that large for the size of the space.

Can anyone offer up some suggestions on what to get, based on experience? I'd like to spend as little as possible right now, but I'd still like to get some fresh air to the plants, once they're inside!

Thanks for any suggestions...

 

[CronicHempHog]

I don't worry about odors as the room is sealed to the outside of the house and the only smell is close the the door of the room
because of here being so warm all the time I run an ac the tent door is usually about half open with a vornado blowing air in and theres a little clip on fan I clipped on to one of those ducts pushing air in from a different direction
im thinking its not for use with a carbon filter cause maybe it doesn't have the necessary torque on the motor
to pull through the filter efficiently I think the actual fan or blower motor they use for pulling through the filter
isn't the can type duct fan

 

[CO Finest]

Well my first thing I would think about is what lights are you going to use and how much heat are they going to make? If you run your lights in a test with a temp gauge might help you see how much hot air you are going to want to move out. Next Are you doing veg and flower in same tent and how many plants. If you are going to flower plants in that tent they are going to smell big time. If you care about the smell then you will want to run a carbon filter.If you don't care about the smell then you don't need filter. I run filters my self. I love the smell but I don't want to let everyone know I am growing the good stuff that come over. Here is company I use and never have any problems Virtual Sun 4'' Inline Exhaust Fan & Carbon Air Filter ComboVS400F-SET A 4x4 tent you could use a 4" and be fine.

If you can do it right the first time and not spend money twice working on the same thing.You can see my grow room pic I have two 5x10 tents rocking one 6" with filter Good luck I wish you the best..

 

[CannabisMeds]

Thanks for the replies, Cronic and CO Finest.

Good idea on running a heat test. I think I'll do that today. I'll be flowering only in this tent. Figuring 1 to 4 plants. This first round will be 3 plants as things now sit.

Yeah, maybe something like the link you suggested will work for me. I wonder how loud that thing is?

I'm going to do the heat test and try out my current closet exhaust fan and see how that goes.

Thanks again!

 

[KingJohnC]

You need is a fan and carbon filter that can exchange the air in your tent every 5 minutes. To calculate the volume of air in your grow tent multiply Length x Width x Height= Cubic Feet that way you can get an idea of the cfm or Cubic Feet per Minute your inline must have. The make 4" inline fans and carbon filters that you may even be able to slow down with a fan speed controller if needed.

 

[CannabisMeds]

Well, it's about 105 Cubic Feet.

So technically, a fan that pulled 21 CFM could exchange the air in 5 minutes. I think a 4" that could be slowed down a bit with a speed control might be the ticket. I do have some time to decide though.

Thanks KJC!

 

[KingJohnC]

just make sure you get an inline fan and not a duct booster fan, the duct booster fan will not handle the lengths or bends in the ducting well.

 

[CannabisMeds]

just make sure you get an inline fan and not a duct booster fan, the duct booster fan will not handle the lengths or bends in the ducting well.

Good advice. I almost made that mistake the other day when I was at the store.

This looks like an affordable option:
VenTech IF4CF412 4" Inline Duct Fan 190 CFM w/ Virgin Charcoal Carbon Filter Combo

 

[KingJohnC]

That 4" inline fan and carbon filter combination would work, just make sure to check out what the warranty on the inline fan is.

 

[Still Vegging Bro]

Good advice. I almost made that mistake the other day when I was at the store.

This looks like an affordable option:
VenTech IF4CF412 4" Inline Duct Fan 190 CFM w/ Virgin Charcoal Carbon Filter Combo

I need this.

 

[Johnny5thesim]

I use a 4 inch duct fan 190cfm with carbon filter, with a speed control on low for my 4x4.

I had a 6 inch 440 CFM one in there originally. Even on low it exchanged way too much. It was exchanging every 15 seconds or so. So I could not control temps or humidity. It was just way too much.

I’m close to harvest, and still on low speed on the 4”.

 

[Natedog420grows]

I use a 4 inch duct fan 190cfm with carbon filter, with a speed control on low for my 4x4.

I had a 6 inch 440 CFM one in there originally. Even on low it exchanged way too much. It was exchanging every 15 seconds or so. So I could not control temps or humidity. It was just way too much.

I’m close to harvest, and still on low speed on the 4”.

You really cant have too powerful a fan! The problem is you are running it on a speed controller and not a thermostatic controller. During lights on, I regulate my heat and humidity with the exhaust fan and thermostatic controller. At night I run the exhaust on a timer and control temps with a heater and seperate temp controller. I also run a dehumidifier and humidifier on a humidity controller. Controllers are your friends when it comes to automating your grow. You have to pick the correct tool for the job at hand.

 

[BedroomFarmer]

The fan you were probably looking at was a duct booster fan. You want an inline fan, you could probably get away with a 4inch fan but 6inch is best as you can dial it down and it will be quieter then running a fan at fill tilt.

A/C infinity makes some inline fans that are almost silent, spendy but quality. I have 3, their 4inch has a little less cfm then others, I use it in a 2x2, probably would work in a 2x4 max.

 

[Rosie44]

Hi As I’m not concerned with smell, I just put a 6” clip on fan in the top port of my 4x4 tent (using duct tape to secure) and another 6” clip on fan on the opposite bottom of my top fan, this one sucks the cool air in, The top blows the hot air out.
For air circulation on my plants, I use a 16” fan pointed to the back wall.

I have 2 - 600 LED’s and by using this system (which is in the basement) my temps are holding at 75F.
I just turn the bottom cool air intake fan off when lights are out.

The tent is replacing air wonderfully, and the plants are happy. Each fan cost only $18, being a retired senior, every penny counts