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Air exchange 2x per minute?

J

jrmedic

Member
Air exchange 2x per minute?

I recently built a 3000W 10 x 10 x 7 flower room with 5x 600W vertical bare bulbs in an X pattern, 4 plants in a + configuration. There is a Honeywell fan under each light, and four 16” oscillating wall fans. With the lights running at night in a cool, dry climate, the 12” 1700 cfm exhaust fan cools the room to 65 degrees, with 35% humidity. I installed a hydrofogger and this raised RH to acceptable levels for VPD to fall within the guidelines, but temps are still quite low as the fogger also cools the room (in addition to creating rain-like conditions - not sure I like it). The room is not sealed and intake is a 12" x 24" darkroom louver set low in one corner; the scrubber attached to the 12" exhaust fan/scrubber mounted high in the opposite (diagonal) corner.

My question is, should the 12” exhaust fan run 24/7 on full speed at all times, day and night? Or is it acceptable to have it turn on when humidity and/or heat falls out of my desired range (which is how I have been doing it these first two weeks of flower)? I currently have it connected to a temperature controller when lights are on, and a humidity controller when lights are off. With both controllers, the fan turns on full speed, then shuts off, many, many times.

Any help is much appreciated.

jr
 
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Buddler

Buddler

Well-known member
Veteran
Sounds like a nice setup I used to run fan fulltime with a speed controller set on low but found my RH was to low,I would go with second option fo sure what a bout a dehuey for nite time keep heat up and rh down no need to run noisey fan at night it can solve a lot of probs with temps and RH,especially late in flower molds etc. Best of luck to you..B
 
L

LSWM

Active member
Sounds like you have most bases covered.

They make thermostic and humidistatic fan controllers that have a low setting and a high setting rather than turning the fans completely off and on.

I wouldn't worry about 2x air exchange and I would focus more on vpd. The off and on controllers will create a problem if you need to maintain negative pressure to control smell. Personally I run a negative pressure room 24/7 no matter what to maintain stealth.
 
M

Miraculous Meds

Well-known member
lswm gave u some good info. there are controllers that reduce the speed based on set temps n rh. so u constantly have carbon filtering n neg pressure. Another way is too downsize ur exhaust fan. also u can add a carbon filter just scrubbing so if ur exhaust turns off due to low temps, u still have a form of air filtration running. the two big things to take care of if u let the exhaust fan turn off is controlling the odor and air circulation. make sure those are covered and u can let it cycle off if u want.

I am most likely going to set up the exact same grow as u here soon. to help control n address the issues u have, I am going to run another flower room on the opposite hours, that recirculates with the off room. the added heat n humidity from the on room, helps equalize the environment in the off room.

Ultimately u have to do whatever it takes to keep the night temps n rh as close to identical as the day time, as possible. an extra flower room is a better alternative to electric heaters, n dehuey's imo.
 
J

jrmedic

Member
Thanks to Buddler, LSWM, and Miraculous Meds for replying :tiphat:

Buddler said:
Sounds like a nice setup I used to run fan fulltime with a speed controller set on low but found my RH was to low,I would go with second option fo sure what a bout a dehuey for nite time keep heat up and rh down no need to run noisey fan at night it can solve a lot of probs with temps and RH,especially late in flower molds etc. Best of luck to you..B
Click to expand...

The purpose of the exhaust fan is to hopefully avoid needing AC and a dehuey.

LSWM said:
Sounds like you have most bases covered.

They make thermostic and humidistatic fan controllers that have a low setting and a high setting rather than turning the fans completely off and on.

I wouldn't worry about 2x air exchange and I would focus more on vpd. The off and on controllers will create a problem if you need to maintain negative pressure to control smell. Personally I run a negative pressure room 24/7 no matter what to maintain stealth.
Click to expand...

Well my neighbors aren't as close as they could be, fortunately, so stealth isn't concern #1: VPD and preventing mold, mildew and any associated problems are.

I'm running 80*/75% with lights on - and to get these #s the exhaust fan is off. When temp creeps above 80* the fan kicks on for a short time and RH drops to about 65%; then it steadily climbs back to 75% until the temps reach 80* again and the fan kicks on. I'm just wondering if I have enough circulation/air exchange to prevent mold, mildew etc. by not having the exhaust fan running 24/7 ...

Can you recommend or link me to one of those thermostatic/humistatic controllers that adjust fan speed? I've tried several temp controllers and none actually controlled the speed of the fan (even tho they claimed to) and just kicked it on and off at full speed. I've worked around this by using a fan speed controller plugged into the thermostatic controller, but I can't get the fan speed below 50% - the controller heats up and shuts the fan off; then the fan won't turn on again for about 30 minutes. ??

Miraculous Meds said:
lswm gave u some good info. there are controllers that reduce the speed based on set temps n rh. so u constantly have carbon filtering n neg pressure. Another way is too downsize ur exhaust fan. also u can add a carbon filter just scrubbing so if ur exhaust turns off due to low temps, u still have a form of air filtration running. the two big things to take care of if u let the exhaust fan turn off is controlling the odor and air circulation. make sure those are covered and u can let it cycle off if u want.

I am most likely going to set up the exact same grow as u here soon. to help control n address the issues u have, I am going to run another flower room on the opposite hours, that recirculates with the off room. the added heat n humidity from the on room, helps equalize the environment in the off room.

Ultimately u have to do whatever it takes to keep the night temps n rh as close to identical as the day time, as possible. an extra flower room is a better alternative to electric heaters, n dehuey's imo.
Click to expand...

It's my understanding that the exhaust fan should be capable of twice the room's cubic feet in order to exchange the air twice per minute. If I'm doing that 24/7 I can't get to my desired temp and RH.

I've been running 80*/75% lights on and 65*/60% lights off. Lights off air circulation is four 16" oscillating wall fans, 5 muffin fans, and a 12" fan in front of the intake blowing into the center of the room.

So I'm wondering if this is enough air exchange/circulation to prevent mold, mildew etc. with these temps and humidity ... ?
 
Mikell

Mikell

Dipshit Know-Nothing
ICMag Donor
Veteran
Wall fans.

The fan is shutting down due to overheating. Grow store fan controllers are not that effective, look for the variac style. Rives and Jhhnn give good explanations of why to use this type if you do a thread search.
 
J

jrmedic

Member
Wall fans? Sorry, not sure I understand. Wall fans are still working.

I have the 12" exhaust fan connected to a thermostatic controller rated for 15 amps and thus far it has not shut down. It only shut down with the speed controller, which I no longer use.

Thanks for the tip on the variac, I'll look into one. :tiphat:
 
B

betshtick

Member
Switched from sealed to all fresh air grows a couple years ago...

I think 2x/min is overkill unless you /need/ that much to stay within your temp/RH sweet spot. Might try lowering the speed/CFM on those fans... They cycle quickly because they are changing the temp/humidity of the air so quickly and those little day/night controllers don't have much of a deadband.

If you aren't sure you're changing your air enough with the temp/RH dialed in, you could always get a Co2 meter and see if it's dropping much below your local atmospheric level. Avg. atmospheric is ~400ppm nowdays according to http://co2now.org/,
 
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L

LSWM

Active member
Those 16" oscillating wall fans should keep air moving plenty to prevent mold.

75% humidity is pretty high in late flower, but I've never had mold problems even with those numbers so your mileage may vary.
 
L

LSWM

Active member
Fans don't like to run at a very low speed. If you are trying to run them that slow you need to downsize. A controller can only help so much.
 
M

Miraculous Meds

Well-known member
LSWM said:
Fans don't like to run at a very low speed. If you are trying to run them that slow you need to downsize. A controller can only help so much.
Click to expand...

good call. I think it was rives that told me running them less than 50% speed or so, allows them to overheat n burn them out.
 
J

jrmedic

Member
LSWM said:
https://www.hydroponics.net/i/135898

That Titan controller should work as well as the grozone tv1.

Titan sucks as far as build quality and customer service, so if you can find an alternative... I would use that.
Click to expand...

Thanks.

I've used that Titan, the Grozone TV1 and a Blueprint. None of them controlled the speed of the fan - just turned it on and off; the Grozone is the one I'm currently using. (They all look like they came out of the same factory, with different stickers).

I talked to tech support with the inline fan mfgr and he said it's no problem to have the fan turn on off so I'll keep it plugged into the controller for now. Still looking into the possibility of a variac down the road, as I'll lower humidity towards the end. Ideally I'd like to run the fan 24/7 at about 50% and have a controller kick it up as needed to stay within my setpoints. Wonder who makes one that actually works ...
 
M

Mrrite008

Member
jrmedic said:
Thanks.

I've used that Titan, the Grozone TV1 and a Blueprint. None of them controlled the speed of the fan - just turned it on and off; the Grozone is the one I'm currently using. (They all look like they came out of the same factory, with different stickers).

I talked to tech support with the inline fan mfgr and he said it's no problem to have the fan turn on off so I'll keep it plugged into the controller for now. Still looking into the possibility of a variac down the road, as I'll lower humidity towards the end. Ideally I'd like to run the fan 24/7 at about 50% and have a controller kick it up as needed to stay within my setpoints. Wonder who makes one that actually works ...
Click to expand...

My Phason Controls VTC1D along with a Vortex VTX Series inline fan has served me well. Probably the two most reliable pieces of grow equipment i've purchased!
 
DunHav`nFun

DunHav`nFun

Well-known member
Not around much these days , but air exchange twice per min served me well for 20 yrs HARD croppin , but I still had to employ AC in my lungrooms to maintain perfect environment.....that said...

What was mentioned about wall fans earlier might have been misunderstood the way I ran my rooms were wall fans above the plants blowing in 1 direction , and fans at floor level blowing in the opposite direction to create a "vortex" of air moving around the plants but never directly ON the plants to prevent excess transpiration and increased nutrient uptake......anyways....

Intake and exhaust air only takes care of part of the equation guys...Wish more folks knew about lungroom function , but it`s fallen through the cracks mostly over the yrs,,,,regardless...

Good luck....DHF.....:ying:.....
 
Foreman000

Foreman000

Member
Fred I'm kinda in the same position with just a exhaust running 24/7 for smell & negative pressure. I use an ac also. Are you saying 2 times air exchange is not possible without a lungroom. This is one of the next thing on my list items for my room. Nice topic for a thread jrmedic I'll be paying attention. K+
 
DunHav`nFun

DunHav`nFun

Well-known member
Sorry Foreman , been chillin at the beach since day after Turkey Day and haven`t been online a lot.....now....

Air exchange twice per minute will go a long way in controlling ambient temps in your room without need for a lungroom OR an a/c running smaller rooms , but since you have the need for an a/c to help control environment , without a lungroom your conditioned air gets sucked out the exhaust scrubber combo never to be seen rather used again.....

My rooms had thru wall sealed portable a/c units for insurance in deep summer , but for the most part all the environment was created with big ass wallbanger a/c`s as needed on controllers in the lungrooms , pumped in and sucked out twice per minute while being re-mixed and re-conditioned with all the rest of ambient air elsewhere from grow areas.....Hope that helps....Oh...

I did grow in basements...I advise it 1000% for easier environmental control........anyways....

Peace....DHF....:ying:.....
 
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