Controlling Humidity

[Stevena12345]

I was curious how many people are using a dehumidifier in their grow room? When your AC is on it lowers the humidity significantly obviously and a dehumidifier isn't really needed. But when that AC goes off humidity sure does rise. So I am wondering how many people are using a dehumidifier? I do not want to use it during lights on, because of the mixture of that heat with the heat from the lights blowing over the canopy. I thought it might be ok for the dark period tho. My AC stays on most of the time so its not on much anyways. Also if your not using a dehumidifier, I was thinking of trying a water heat pump as I know that allow you to get rid of that heat that would therefore be coming from a dehumidifier. If I am correct there. Thanks for your input.

 

[delae632]

Do you have a climate controller? I just leave my dehum on and let the climate controller do the work. AC's will lower rh, but not enough to forego a dehum. You need a dehum if you really want to get your environment dialed. The heat that's produced is negligible if you have an AC anyways.

Just my .02

 

[Stevena12345]

I want apsolutely everything dialed in, but isn't that hot air swirling around (Even at a mixed rate with cool air and proper air circulation) going to be a little too much hitting the plants especially at canopy level related to the heat from LIGHTS ON? I could see lights being off maybe it not being an issue. And I have begun to read about water heat pumps that I believe lower the humidity but do not exhaust hot air from the back? Are you familiar with how these things work? All I know is they seem damn expensive so not really something I could get even if that would work. I mean unless you have a very big room, which IMO is a waste when you can have a smaller room and better light reflection, that heat from the dehumidifier going to be too much. There is no way it has time to mix in with that cold air from the AC before at least parts of the plant are being hit. Unless perhaps you put the dehumidifier very high up in your room. The heat from your dehumidifier doesn't make any direct contact with your plants or canopy? I was thinking of putting it up high in my room or having a fan blowing the hot air up. How do you have yours?

 

[delae632]

I think you might be overthinking this. How big is your room? How many lights? What size AC? What's your climate like where you live? Are you familiar with the Vapor Pressure Deficit chart? What temp/rh are you trying to achieve?

 

[fishwhistle]

D is right,you want that humidity to a certain level,you just want to be able to control it the way you want when you want.Lights out is when you see a big spike and your dehuey will do its most work as your a/c wont be running as much(no lights/less heat)to control it on its own.

 

[Og Gong]

The first stage of dehumidification is AC cooling. The second stage is when a heater is used to help raise the temperature in the room so the cooling will continue dehumidifying. Depending on the deadbands.

If you had a ac unit with a built in humidity control you will see the ac and heater run at the same time to dehumidify when the room is at or below setpoint.

A dehumidifier is a reverse ac unit. The intake or return air passes through a cooling coil to remove moisture the warm air that it puts off is the condenser.

 

[Stevena12345]

I am familiar with the VPR chart and I am trying to achieve 74 degrees. and 50-55% humidity. I have ONLY been concerned about the heat from the dehumidifier coming into any contact whatsoever with my plants. But as long as you have proper air circulation and the back of the machine is not facing the dehumid, then I would see it not being an issue. Also I was planning on setting my dehumidifier onto something so the heat is closer to the top of the room.Good/Bad idea?
I have recently purchase a 14000BCU that also comes with a heater Og Gong, but What you are implying with the AC unit also having the heater run at the same time to dehumidify I have never heard before. Almost sounds like having one of those would eliminate the need to have a separate dehumidifier all together. Thoughts on this? Thanks for the feedback.

 

[Og Gong]

The hardest conditions to simulate are hot and wet 40deg celcius/90%rh and cool and dry 10deg celcius/10%rh.

If you have 2 independent systems like a cooling only ac unit and a separate heater or an ac unit with a gas heater built in you can simulate a dehumidifier. (not on a heat pump). It is possible for both to operate at the same time to reach and maintain the humidity setpoint.

A dehumidifier adds heat into the room slowly and removes moisture slowly. A heater adds heat into the room quicker. The ac removes the moisture in the room quicker. All comes down to preference and setup and design.

 

[delae632]

I'm still confused. I still think you're overthinking/overcomplicating this. Use an AC, use a dehum, get a climate controller. Period...case closed. lol If you want it to be 74* then your humidity should be around 65-70%, according to the VPD chart. No need to raise the dehum off the floor, but it wouldn't hurt either. They usually blow WARM air straight up anyways, right? If it's a space issue then I could see getting it up overhead, but if not then it just sounds like a waste of time imo.

Why is your ONLY concern the "heat" from a dehum coming into "any contact with the plants"? The air they kick of is warm at best. What's wrong with a little warm air lightly mixed in your air conditioned room? It's not like it's on 24/7. I don't get it...am I missing something here? Are you growing in a small space or something? I've had a dehum going in my room for ages and never had (or ever even heard of ANYONE having) problems due to the negligible amount of warm dehum air touching their plants.

 

[Og Gong]

D is right it shouldn't be a problem with the little dehumidifier, keep it simple. Forget what I said above. I was stoned and started talking about my job from a service tech point of view. Stay with the simplest setup so you don't get confused.

 

[Junk]

I think you might be overthinking this.

That's exactly what I was thinking.

For what it's worth, I cycle my humidity intentionally throughout the lights on period. I'm in last week of flower or so now, so I let it cycle between 40% to 55% & repeat. 2-3 cycles per day depending on last watering. The reason I do this is is because I don't like 40% full time at end of flower, & to better match VPD. I can keep em swollen without the issues I've heard of with bud rot if you run a constant 55-60%

 

[FooDoo]

I'm at 60-70% week 9 and no bud rot

 

[Junk]

What strain?

I've never had the misfortune of having it. But a friend who has been growing for over 20 years said that he has had problems at 60% with particular strains. I'd rather err on the side of caution. But I find a constant 40% to be too low, & afraid to let it be at a constant 60%.

Maybe you will give me the courage to try it. You have NEVER had any bud rot running that high? Even with extremely large cola's?