What's new
By:
GrowWeedEasy.com
You're browsing as a guest. Sign up to join the conversation, share your grows, and get help from thousands of fellow growers — it's free and takes less than a minute.

How many air exchanges do you guys run in your tents?

growsomebuds

growsomebuds

New member
Hey all, I set up my 1st tent a few day's ago. Then I bought one of these.
https://www.allelectronics.com/item/cf-481/24vdc-235cfm-coolong-fan/1.html
Been buying these periodically for 10+ years for various projects. $100 fans for 1/5th the price b/c their surplus.
Any-who, I mounted it to a one sq. ft. board, and placed it over an 8" port on top of the tent. I wired it to a DC-DC converter, giving me a nice voltage range.
I was wondering what kinds of air exchange rates you guys like to run in your tents. Right now, I estimate about 50ACH. I'm sure this is way more than necessary.
 
The new tent......
 

Attachments

  • photo53878.jpg
    photo53878.jpg
    4.4 MB · Views: 0
Did I miss something? Nothing of what you wrote refers to air exchanges. My fan is rated at 235CFM max. Let's just say w/ a little bit of back pressure(there really isn't any), it's 200CFM. With a tent volume of 120cu ft, that comes to 1.66 air exchanges per minute or 100 air exchanges per hour.
 
LOL, Yeah it seems like it. ACH are actually at 100, not 50. lol I left two of the 8" ports fully open. Even when I start to unzip the door, a good amount of air starts to blow through.
 
Air exchange rate is usually between 1-3 times the total volume per minute. This depends on many factors such as volume, heat and temeprature difference. For small indoor environments, 1-2 times is usually sufficient. I have a 500cfm fan for two 112 cubic feet tents. So just over 2 times the exchange rate per minute. I have had to install airflow systems for greenhouses which require larger exchange rates due to the higher amount of energy and humidity.

Again the requirements of the air exchange rate is dependent on these variable factors.

Ask any further questions if you need more information.
 
my tent is 5'x8' I used an 6 inch exhaust and a six inch in inline into the room had it 4 years never had an issue with, to much or not enough I know thats not technical and may not be relevant. this is a great forum and gives lots of advise .the thing is most people give there experience or what they run , If you chose to listen or ask questions of Pyro you might of found out that he is a smart guy and was willing to help but instead you unvalidated him I would be very surprised if he ever helped you again , I do believe this is the first time I've ever seen someone put down because they tried to help and by someone that hasn't been around very long , So I would suggest that if you want help in the future you not be so rude or inconsiderate of others who took the time to answer your post
 
Yes temperatures above 86°F is not ideal, this impacts photosynthetic efficiency. Read my article on environment conditions to learn more. The ability to bring these temperatures down with exhaust systems, depends on two factors.

The temperature difference between the inside and outside temps. The lower the intake temperature is and hence the larger the temperature difference, the better the cooling effect will be. The ability to reduce temperatures with exhaust systems will always be limited by the intake temperature. Which will naturally be the lowest the internal temperatures can be.

And the air exchange rate. The faster air can be exchanged, the closer the internal environment temperatures are to the intake temperature. Until a point is reached where both are the same.
 
Perhaps my response was pithy, but his response really didn't have any useful information that I could benefit from. I'm a mechanical engineer, yet growing weed is an entirely new endeavor for me. I was asking for peoples ACH rates b/c it's a metric that is useful to me. Pyro included a link to a product that did tell me the max CFM's of his product. He made no mention of his tent volume. That would have helped. In retrospect, I should have asked him to supply me w/ that info. To Pyro, I apologize if my manner of response rubbed you the wrong way. We engineers can be assholes at times.
 
Last edited:
May I ask you guys a question to clarify?

DANGERDAN
You stated the air exchange rate 1-3/minute.

In a tutorial by Sirius he states 1/1-3minutes.

That is a significant variation, I've been setup with the lower exchange rate. 46ach currently. By what you say I'm holding my plants back by shorting co2?
I'm I understanding correctly?

Thanks guys. I have not gotten into the technical aspects yet. But it is time to learn.

Dan I read your threads and learn a ton, but its like trying to drink from a firehose at times. I'm a little slow.
Thank you for all of your effeort.

@growsomebuds
Great thread. I was wondering about this, but didn't get around to posing the question.
 
Last edited:
Spoken like a HVAC engineer. I love it! Not willing to invest in any kind of A/C, I see that I will need to add another intake fan on the tent, and I will dial the RPM's back a bit, since the one fan is a bit loud for my tastes. That, of course, will improve ACM. The temp delta between the indoor environment of my workshop and outside is ~16F. I do understand that exhausting the air from the tent directly to the outdoors and not just to the inside of the shop is ideal. It's just not an option for my building and the neighbors adjacent to my property.
 
I usually have two grows going at the same time. My vegging area is a open table under a 6 tube T5. I only use my tent for flowering. I keep my tent open during the light on period and use a osilating fan. I also have a 10" fan in the tent that stays on 24/7. I've been using this method for going on 10 years now.
 
It's all good... I miss understood your question, I thought you were asking about how many fans were being run. And yes, I could have posted my tent volume. No harm done.
 
@Californiakid

What the GWE articles suggest is replacing the air 0.25-1 times per minute, but they use time rather than volume to represent the variable. Most people will use volume exchange rate per minute to characterise this variable.

They also only suggest using lower than 1 exchange rate per minute if living in cold areas, this is related to the same reasons i talk about with temperature difference.

"All the air in the tent should be replaced by new air every 1-3 minutes for the best results. I recommend aiming to replace the air every one minute unless you live in a cool place."

Starting off with 1 exchange rate per minute is the best base for most situations, any more or less will depend on the variables i have suggested, such as temperature difference, internal heat source, humidity etc. Co2 is not a major factor for exhaust systems, the exchange rate does not have to be that high to satisfy the co2 used by plants.

I understand my articles can be complicated, thats why i always welcome further questions. :)
 
Not at all, you have no idea how much i learn off peoples questions. As it makes you think in diffferent ways.
 
You must log in or register to reply here.
Back
Top