Question about fans, inline fan and humidity

TriggerX

New Member
So I’m a new grower, just had my seedlings sprout out of my soil in my 5x5. My temps rn are 79-81 so I know my humidity should be pretty high too cause I’m in early veg. Thing is I have trouble keeping the humidity up to the 70% that’s recommended. When the exhaust is running 24/7 on low settings I get around 55% humidity. I can get it to 63% if I have the exhaust on for a minute and off for 6. After asking around and googling I found some people saying you only need exhaust to keep humidity and heat under control and the oscillating fans do all the air movement. I have 3 oscillating fans (thinking of getting a 4th cause the tent looks weird not having a fan on all corners). Idk if I feel safe turning the exhaust fan off completely, but do you think it’s a good idea to keep the exhaust fan off for even longer? Like 10min instead of 6, just so I can get 68% humidity? Also I would use a dome of some kind to keep humidity but it’s annoying having to go into the tent to mist the domes every morning and night. Plus the domes don’t let the oscillating fans from doing any low stress training to the young plants. With the exhaust fan schedule my vpd ends up spiking up and down because the humidity goes from 58-68%, would that stress out the plant? Pics of humidity spiking below.

Edit* I was able to smooth out the spikes a little by setting my inline to activate at 69% with a 4% buffer and running the inline fan at speed 1 instead of 2. That way the exhaust runs for about a minute before shutting off, less air movement but it’s okay cause at that speed, it pulls 227cfm and a 5x5x6.6 only needs 165.
 

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1212ham

Well-Known Member
So I’m a new grower, just had my seedlings sprout out of my soil in my 5x5. My temps rn are 79-81 so I know my humidity should be pretty high too cause I’m in early veg. Thing is I have trouble keeping the humidity up to the 70% that’s recommended. When the exhaust is running 24/7 on low settings I get around 55% humidity. I can get it to 63% if I have the exhaust on for a minute and off for 6. After asking around and googling I found some people saying you only need exhaust to keep humidity and heat under control and the oscillating fans do all the air movement. I have 3 oscillating fans (thinking of getting a 4th cause the tent looks weird not having a fan on all corners). Idk if I feel safe turning the exhaust fan off completely, but do you think it’s a good idea to keep the exhaust fan off for even longer? Like 10min instead of 6, just so I can get 68% humidity? Also I would use a dome of some kind to keep humidity but it’s annoying having to go into the tent to mist the domes every morning and night. Plus the domes don’t let the oscillating fans from doing any low stress training to the young plants. With the exhaust fan schedule my vpd ends up spiking up and down because the humidity goes from 58-68%, would that stress out the plant? Pics of humidity spiking below.

Edit* I was able to smooth out the spikes a little by setting my inline to activate at 69% with a 4% buffer and running the inline fan at speed 1 instead of 2. That way the exhaust runs for about a minute before shutting off, less air movement but it’s okay cause at that speed, it pulls 227cfm and a 5x5x6.6 only needs 165.
Welcome, and forget the domes. :wink:

I program to control temp/humidity as smoothly as I can. It's enough air to prevent a reduction in co2 and all is good.
 

SBNDB

Well-Known Member
Sounds like you’re figuring it out but don’t sweat it too much also. 55-65% will do you right. 70 is the absolute highest i would ever go, fuck the chart.
 

TriggerX

New Member
Sounds like you’re figuring it out but don’t sweat it too much also. 55-65% will do you right. 70 is the absolute highest i would ever go, fuck the chart.
What’s funny is that I looked over at my humidity just now and it’s 75% and that’s cause I set my inline fan to 1.00 vpd with a .10 buffer. Right now it’s 84 degrees in my tent so 75% is 1.00 vpd. Problem is that even if it follows the vpd chart I don’t have the leaf’s temperature. Gonna look for my infrared medical thermometer and see if it can read the leaf’s temp so I can offset it and get a more accurate vpd. I know what you mean by fuck the chart but it’s also easier to set up the controller to follow the vpd instead of temp and humidity.

Found the thermometer, leaf’s temp was 3 degrees cooler. Hopefully that keeps my humidity to 70 or below. 75 founds like a mold problem.
 
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SBNDB

Well-Known Member
If you’re using LED lights just keep the temp 77-82 lights on and RH 50-65 and you’ll be fine. If you can drop the temps and humidity down during lights out to 67-70 and 50-55 RH then thats good too.
 
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