Fan controller - to use, or not to use...

Hey all,
So getting final ducks in a row for my first grow. I've seen a lot of people will use a temperature-based fan controller (fan turns on at a set max temp, turns off at a set min temp). This would be great for temp management, however I do have a question.

Should the room stay typically within ideal temp range, wouldn't this mean that my fans aren't on enough to be pumping fresh air into my room? Or is it ok for my babies to only get fresh air when it hits max and then pulls back down to minimum? Hope that makes sense.

Thanks for any and all thoughts.

There are 2 types of controllers
1 )that turns on and off at a set temp. Great for use with a cool tube or reflective hood
2 ) that will run your fan at a set speed such as 80 percent 50 percent , what ever desired rate you would like it.
Great for setting negative pressure / flow rate of air through your filter to help expand its life cycle as well saving you a small ammount kn your power bill as well

If you are not useing good or cool tube you should only be useing controller number 2 . There should be a constant negative pressure on your tent/grow room

If you are having trouble with temperatures it would be advised to get a second fan /cool tube there is also some DIY options in the fourms

pottscott said:

There are 2 types of controllers
1 )that turns on and off at a set temp. Great for use with a cool tube or reflective hood

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So I am using air-cooled, but my setup runs like this:
1) Intake fan brings air into room.
2) Aur pulled from room through hood, exhaust fan, and out.

So I guess my question still stands. Lets say that using one of these gets my temperatures ideal, resulting in the fans not running nearly as often. Would far less fresh air supply coming to room cause issues?

your exhaust fan should only run 12 hours lights on, so they get more air co2 from out side, and turn off at night , save electricity, but other obsoleting fans need to run 24 hours keep the exzisting air moving and prevents mold,

fan controller is nice only when you have a big ass fan emergency fan, when temps spike who knows why mabe a cool tube came disconnected, so on, this big monster fan . like a barral fan I use will suck all the air out and circulate the entire basement, making my sealed room not sealed, but saves my crop.

Ah. So maybe if there's some way I can set my exhaust to turn on if temps get too hot, stay off otherwise.

My room isn't sealed, and I'm in a high desert climate, so the environment outside is going to be hot for the next month or two, then start to drop below freezing.

By that I mean, have a normal schedule (off when lights are off which is what I'll probably want anyway to keep air from gettin too cold, but have it as a switch to keep air from getting too hot when fans are on.

you want your fans running all of the time, so that a light breeze is passing through your plants
so that you can see the leaves all lightly moving around, when the lights are on this will aid photosynthesis
as it will bring new co2 to the leaves , the leaves are only able to process the air directly around them they are not able to pull air towards them
so air has to be delivered to them but not so the leaves flap about too much as this will damage them

when the lights are off, keeping the fans running will help prevent mold and fungus , humidity tends to rise when the lights are off
keeping constant air movement helps to control this

you should build your garden around a design that allows for constant air movement temps from 60f lights off to 80f lights on are fine with soil
upto 85f to 90f with hydro and co2 enrichment

I can understand ur asking if temp doesn't spike enough to kick fan on then will no air ever flow - but generally ur light should act as large enough heat source that ur fan would have reason to turn on quite regularly.

But i'd too recommend using Pottscotts 2nd option of run at set, lower speed constantly - ideally as low as possible whilst remaining efficient; anything under 50% is cool certainly, if poss. Just so long as it ensures at the least a gentle, constant airflow.

And for circulation at night, a cheaper & simpler option is just a little oscillating desk fan on a regular cheap digi timer. Set it to just come on for 20 or 30 min periods every hour or so, and that'll be enough to save air stagnating & any reduce any possible humidity related problems during flowering. But shouldn't lower temps too much as it won't actually effect intake as much as running exhaust fan would.

Of course, all of this does depend on if climate where u are messes with ur grow & if u got lotta plants in one confined area/tent, etc. If u don't find airflow is a prob or u only doing a small, half dozen plant SCROG, etc then u don't need to worry so much & going ultra professional would only be a waste of electricity. Test & evaluate different combo's & see what u can get away with fan doing to be cheap but efficient.

Tho i know u American boys like to go big, so i'm probably talking way too budget for the bungalow-sized closet u were planning on using!

RedWhiteBlueGreen said:

I can understand ur asking if temp doesn't spike enough to kick fan on then will no air ever flow - but generally ur light should act as large enough heat source that ur fan would have reason to turn on quite regularly.

But i'd too recommend using Pottscotts 2nd option of run at set, lower speed constantly - ideally as low as possible whilst remaining efficient; anything under 50% is cool certainly, if poss. Just so long as it ensures at the least a gentle, constant airflow.

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Thanks for the info everyone. This message made me realize I may need to make a few clarifications.
1. My room is 10 feet x 10 feet, give or take. This isn't a small tent or closet.
2. I'm already planning on having oscillating fans running at all times in the grow room, so I'm only asking if its fine for the exhaust and intake to be shut off for night periods or if temperatures get to high. I'm not sure because I'm inexperienced, but could issues with co2 ratio occur?

Also, I'm in a very low-humidity environment, so if exhaust and intake being off causes a rise in humidity I'm not worried about it. If anything I may have to humidify my room for veg.

Im doing a dwc setup with 6 5-gal buckets. And yeah, I'm going for size.

If this is your first grow, I would suggest leaving the C02 for next run. I know a lot of people who have wasted a lot of money buying the controller and refilling the tanks when they haven't dialed in their other essentials.

I also would not leave the intake off at all and my reason being is that fresh air going in and coming out all the time will limit the chance that any mold or pest will stick around. For instance if you have a small gnat problem it would be easier to get rid of if your air is constantly filtering out than if they have a harder chance of nesting.

Just my experience I have tried to go with and without ventilation and I screwed myself. I also do this for a living now for someone else and am seeing the problems that can occur when there isn't enough air flow and humidity isn't under control.

Sorry super stoned hope something in this post helps you!

Thecouchlock said:

If this is your first grow, I would suggest leaving the C02 for next run. I know a lot of people who have wasted a lot of money buying the controller and refilling the tanks when they haven't dialed in their other essentials.

I also would not leave the intake off at all and my reason being is that fresh air going in and coming out all the time will limit the chance that any mold or pest will stick around. For instance if you have a small gnat problem it would be easier to get rid of if your air is constantly filtering out than if they have a harder chance of nesting.

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Super helpful info, thanks. Yeah another bit of clarification, when I talk about enough co2 getting to the room, I'm not meaning that I'll be pumping co2 into room, just want to make sure enough is getting in room naturally from air pumped in from outside. My only concern with having intake/exhaust on all night is that in the next couple months, outside temps are going to drop to below 30 at night, easily (by winter, even lower). Once I start harvesting, electricity costs will be less of a concern, but for the time being, it would be pretty expensive to heat constantly flowing freezing air. Staff at my local shop recommend having fans on for my day, off for night. I've also considered having revers schedules (lights off during day, on during night) to try and balance out the temp differences. Where I live, a winter day can be 70 fahrenheit, and 5 at night.

I'm just not sure where to go with it at this point. I know no matter how much research I do, there's going to be some bumps along the way with the learning curve, so I really want to make sure I'm giving my girls the best shot possible.

You do not have to have outside air for your plants to thrive. Many people have sealed rooms. Some of those sealed rooms use CO2 but many do not supplement. Your plants can survive in quite a range of temps but thrive in the 60 to 80 range. Good luck with your grow!!

Thank you!

What about smell? If you turn off your fan how can your carbon filter remove the smell.

gcnorth said:

Ah. So maybe if there's some way I can set my exhaust to turn on if temps get too hot, stay off otherwise.

My room isn't sealed, and I'm in a high desert climate, so the environment outside is going to be hot for the next month or two, then start to drop below freezing.

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yes there is a way, it's called "thermostat"

Leave the fans on all the time it will keep any temp swings from messing with your humidity. Plug it in and forget it. E-z . The smell is gone all the time. controlling the temp and humidity to a t is very expensive in cost of doing it as well as your electric bill will double I use to run a sealed room with temp, humidity and co2 controls with hydro the growth and yield were huge but so was the electric bill. All the controls for a room are great but the potential of the plant are only going to seen if your room is set up perfectly with the max amount of light, hydro with ph ppm and TEMP perfect, room temp of 75-80 (no co2)79-83(with co2) and high humidity like 75 until heavy bud set around week 4 or 5 then drop it down to 55 to 50 to 45 to 35 finish. It's a lot of work but cool to see how well it can all work.