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

[growsomebuds]

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.

[Pyro1711]

https://www.amazon.com/iPower-Booste...uyL&ref=plSrch . This is what I use.. I use one at the top to bring in cool air from the room and a 4" hose at the bottom that leads to an outside vent. I also have a little 6 inch clip fan inside blowing on the plants.

[growsomebuds]

Yep, I'm well aware of products like yours. However, nothing in your post has any merit relating to my post. Sorry.

[Pyro1711]

You asked how many air exchanges... I told you. Sorry I did not post ACH rates, and get all scientific.

[growsomebuds]

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.

[growsomebuds]

The new tent......

[gbauto]

Right now, I estimate about 50ACH. I'm sure this is way more than necessary.

I think that I run about 10-12/hr-50 is going to be a hurricane.

[growsomebuds]

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.

[DrPhoton]

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.

[DrPhoton]

@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.

[Californiakid]

Thank you DrPhoton for the reply. I'm not sure if my rudimentary questions are frustrating for advanced minds like yours, but I greatly appreciate it.

[DrPhoton]

Not at all, you have no idea how much i learn off peoples questions. As it makes you think in diffferent ways.

[oldjarhead100]

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

[growsomebuds]

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.

[Pyro1711]

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.

[oldjarhead100]

then I apologize as well I was a boss and had to learn not to be blunt and think about what my statements would mean to the person receiving them.WTF exactly ,not an easy thing for an old Marine who is used to saying shit and get the response how high lol

[kingfish]

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.

[growsomebuds]

kingfish; I have two veg areas, and the tent is flowering one plant. Just checked on the tent and the plant is wilted as fuck. Temp is 91, soil was bone dry! So, now I'm going to leave the tent door open a bit. I'm going to move those plants on the right to the area behind the tent to mitigate some light pollution.

[growsomebuds]

Less than 40 minutes from watering the wilted plant in the tent, and putting the fan back on her, and I kid you not, her leaves are almost back to normal! Scarily though, the temp is now at 93 and humidity is 26%.

[kingfish]

You have to get the temp down. Do you have any flaps on your tent that you can open up. You only need total darkness for the 12 hour of dark during flowering period. Try not to reach 85 degrees. You can also take them outside if all else fails.

[growsomebuds]

I've always had 2 8" ports open b/c there's a 6.75" fan pumping air into it at about 175CFM after accounting for back pressure losses. I opened the tent flap, too, a bit. The plant looks quite good right now. It's the hottest it's been outdoors at 110. If running an A/C was an option, I would.

[growsomebuds]

I grew a plant during this time last year. Conditions were the same. Taking the fan off the plant to put on another one was a bad move. I also think I should have watered a day or two sooner. I always read it's better to underwater than over water.

[oldjarhead100]

a cheep moister meter works great to tell you when to water

[kingfish]

Once your plants are established. Water 'till it starts running out of the bottom of the pot.

[growsomebuds]

I assume you mean the little ones. That's what I'm doing. After growing 5 nodes, I topped to the 3rd node and removed all below. I did this about 4 or 5 day's ago.

[Flockshot]

I have never bothered to figure out how many air exchanges I was making. I run by exhaust fan on low 24/7. That's all I have ever done.

[Weed Pharma]

200 CFM in a 2'x4'x6' = 4 times per minute with no carbon filter- If a carbon filter is used, it reduces it to 3 times a minute.
Even though It can be dialed down, I usually run it at full speed most of the year.