Humidity and temp issues with 4" fans

I'm hydro so lots of water. I have AC infinity 4" fans. Should be good for a 4x2x7. Thats the veg tent and the closet is a little bigger.

Flower has two 2000w leds 2 circulating fans, 3 fans under the canapy blowing up. 4" hole for air.

Veg is two 1500 leds 2 circulating fans 2 crap clip on fans

Everything is on full blast 24/7
Lights on 81deg 65% rH kPa 1.1-1.4
lights off 69/70deg 65-70% kPa .6-.8

outside temp never over 74 deg or 55% rh

Fans are going to full blast with the lights off to get the humidity down. Not helping. What can I do? I have small dehumidifers but hard to fit and going to fill up so fast. Do I bump up to 6"fans?

Thanks in advance

Do you have an extraction fan venting outside?

Fans will move the moisture laden air around but it won't drop RH.

According to the folks at PulseGrow, lights out VPD is nowhere as important as VPD when lights are on but they do suggest you try keep it close. I forget how "close" close is but I think it something like 0.2. If you're not familiar with that site, this is the link to the "learn" page and that issue is in the FAQ's, if I remember correctly.

I opted for a Waykar dehu. My grow is in a garage so I have to deal with a 20' x 20' space but if you don't…

The big issue with high RH with lights out is bud rot. I learned my lesson the hard way.

This was my first photo after doing 5± auto runs. With autos, I run 20/4 so RH doesn't get time to rise too much. Photos, with the 12/12 cycle, are a different story. I had two 6" fans under the canopy but we had a wet spring here in SoCal (2023) and I got bud rot two days before chop. That hurt. I really liked that plant but I had to toss it out.

If you increase your extraction to lower your rh your temperature will also lower.

I personally wouldn't be too worried, you have lots of circulation, which helps stop dead spots and micro climates creating higher chance of rot.

For what it's worth, extraction size is based off start ambient air temps, not off the size of your grow space .

Small dehumidifiers are nothing more than a novelty item.

bongboy8200 said:

I'm hydro so lots of water. I have AC infinity 4" fans. Should be good for a 4x2x7. Thats the veg tent and the closet is a little bigger.

Flower has two 2000w leds 2 circulating fans, 3 fans under the canapy blowing up. 4" hole for air.

Veg is two 1500 leds 2 circulating fans 2 crap clip on fans

Everything is on full blast 24/7
Lights on 81deg 65% rH kPa 1.1-1.4
lights off 69/70deg 65-70% kPa .6-.8

outside temp never over 74 deg or 55% rh

Fans are going to full blast with the lights off to get the humidity down. Not helping. What can I do? I have small dehumidifers but hard to fit and going to fill up so fast. Do I bump up to 6"fans?

Thanks in advance

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First of all i dont think your values are critically wrong, you can flower like this all though you need to be careful moving air on top and below cannopy to avoid mold. Secondly, if you want to drop rh at night you can try heating the growspace a few degrees.

Agree w Rocket. More extraction won’t impact humidity (unless you’re venting outside), you’ll neither need to increase temp or get a bigger dehumidifier.
ive flowered at 65-70% rh but it’s a bit risky. Good luck.

bongboy8200 said:

I'm hydro so lots of water. I have AC infinity 4" fans. Should be good for a 4x2x7. Thats the veg tent and the closet is a little bigger.

Flower has two 2000w leds 2 circulating fans, 3 fans under the canapy blowing up. 4" hole for air.

Veg is two 1500 leds 2 circulating fans 2 crap clip on fans

Everything is on full blast 24/7
Lights on 81deg 65% rH kPa 1.1-1.4
lights off 69/70deg 65-70% kPa .6-.8

outside temp never over 74 deg or 55% rh

Fans are going to full blast with the lights off to get the humidity down. Not helping. What can I do? I have small dehumidifers but hard to fit and going to fill up so fast. Do I bump up to 6"fans?

Thanks in advance

Click to expand...

Put the dehumidifier outside the tent and run it with the door open until it drops. Fans will not lower humidity and you have to lower that.

Thanks everyone for the help. It’s easier to just post to everyone that helped. That was from the computer. Here’s pic.
The 4in fans blow out of the tents and closets. Flower is lights off. Veg tent still lights on.
So you guys can see there’s lots of fans. I had a little bud rot in the past. When I first grew. These I shouldn’t have crammed 3 autos into that one bigger tote and been chopping away moldy pieces 3xs now. Thought it was under control and a branch that had it on it. Found again last night spread to another bud on the branch and chopped another 11g away

Looks like nice setups!

yeah, if that 2nd pic of the C69 is your flower tent, those conditions are prime for bud rot/mold. Your extraction fan is running 100% and you are at 70f/72%rh. . When the rh exceeds the ambient temperature, it’s going to get wet in there.

Dehumidifier time. Big one in your lung room.

bongboy8200 said:

I'm hydro so lots of water. I have AC infinity 4" fans. Should be good for a 4x2x7. Thats the veg tent and the closet is a little bigger.

Flower has two 2000w leds 2 circulating fans, 3 fans under the canapy blowing up. 4" hole for air.

Veg is two 1500 leds 2 circulating fans 2 crap clip on fans

Everything is on full blast 24/7
Lights on 81deg 65% rH kPa 1.1-1.4
lights off 69/70deg 65-70% kPa .6-.8

outside temp never over 74 deg or 55% rh

Fans are going to full blast with the lights off to get the humidity down. Not helping. What can I do? I have small dehumidifers but hard to fit and going to fill up so fast. Do I bump up to 6"fans?

Thanks in advance

Click to expand...

I put a 9 inch fan in mine. Three speeds. $16 at Walmart.

8Rhizome8 said:

I put a 9 inch fan in mine. Three speeds. $16 at Walmart.

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Beautiful setup!

Triplefastaction said:

Looks like nice setups!

yeah, if that 2nd pic of the C69 is your flower tent, those conditions are prime for bud rot/mold. Your extraction fan is running 100% and you are at 70f/72%rh. . When the rh exceeds the ambient temperature, it’s going to get wet in there.

Dehumidifier time. Big one in your lung room.

Click to expand...

Thanks man. It’s been sitting right outside of the intake. I have an intake fan I can hook up. I can’t fit anything else in here. What should I do?

Fans blowing directly onto plants strips moisture and causes wind burn (ime) which could easily lead to rot, ime plant health is key it's yellowing dead and dying leafs rhat invite mould, healthy ones appear to resist it?

I use a oscillating fan to keep air on the move but only indirectly wafting my plants.

I've grown in 65/75% forever I've found healthy plants don't get rot it's getting on for a decade since I've had any.

My extraction fan doesn't ever turn off its just swaps between slow/faster so condensation isn't a thing it's always feels fresh inside my tent...it's a cunt to heat without HID that's another story.