Dehumidifier

Rainbow Warrior

Rainbow Warrior

Well-Known Member
Hi there, about to buy a dehumidifier for my room 3x3x6ft, 600w.

I’m in the 2nd week of vegging, keeping humidity btw. 50-60%, but spiking at nighttime up to 70+RH.
Controlling humidity with the Inkbird IHC 200.

Growing 1 Tomato (scrogging).

What size do I need?
Any cheap(ish) options?

Any help appreciated...

RW
:peace:
 
InTheValley

InTheValley

Well-Known Member
Not much room to accommodate a large dehu. If your in a tent, best to dehu the room the tent is in, if a closet, maybe a couple small low watt dehu would be an option. The problem is many run high watts. Midea has a 30 pint model, that uses 250 watts on lowest setting, and hear it works very well. available at the Mart-of-wally. ($199)lol..

need more info bro, tell us about your set-up.

edit: just seen your other thread, best to get just a couple low 60 watters, and leave them on continuous
 
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Rainbow Warrior

Rainbow Warrior

Well-Known Member
Just found a small 100 Watt one.

The problem with tiny ones is that u can’t adjust the RH. Most of them (here in Europe at least) go down to 40%, which is a bit low for vegging. I only really need it at night time, when the RH goes up by too much.

The one I found is an adjustable one, and it was below 100£, so happy all round!
And it’s super quiet.

Thank you for ur advice though!
 
InTheValley

InTheValley

Well-Known Member
Rainbow Warrior said:
Just found a small 100 Watt one.

The problem with tiny ones is that u can’t adjust the RH. Most of them (here in Europe at least) go down to 40%, which is a bit low for vegging. I only really need it at night time, when the RH goes up by too much.

The one I found is an adjustable one, and it was below 100£, so happy all round!
And it’s super quiet.

Thank you for ur advice though!
Click to expand...
can you tell which one bud?
 
Josh33

Josh33

Active Member
In my experience I wouldn’t put the dehumidifier on side the tent I did that one time and it dried the plants out the leaves were all crispy I put the dehumidifier in the room where the grow tent is and hooked it up to a humidity controller so it would kick on and off when it needed and that worked better for me
 
Josh33

Josh33

Active Member
Definitely. In flower anything over 55 is really bad and point your fans at the wall not at plants the air will keep nice circulation in a tent like environment. ( again this is all in my opinion I’m not a professional by any means)
 
Rainbow Warrior

Rainbow Warrior

Well-Known Member
Josh33 said:
In my experience I wouldn’t put the dehumidifier on side the tent I did that one time and it dried the plants out the leaves were all crispy I put the dehumidifier in the room where the grow tent is and hooked it up to a humidity controller so it would kick on and off when it needed and that worked better for me
Click to expand...
Did the humidifier have the option to Set it to a desired RH percent?
Problem i have is night time; RH sometimes spikes in the low to mid 70’s....

RW
:peace:
 
Josh33

Josh33

Active Member
Yeah I think 70 is kinda high even in veg but yes my dehumidifier had a rh meter on it but I hook it up to one of those inkbrid humidity controllers I have the inkbrid humidity beaker tip inside the tent and I set the humidity controller to the rh I want inside the tent this way it will only kick on when needed , sounds like in your case it would kick on at night when you said your rh is going up to 70 but then it wouldn’t kick on all day cause your rh is where it should be
 
ttystikk

ttystikk

Well-Known Member
Josh33 said:
Definitely. In flower anything over 55 is really bad and point your fans at the wall not at plants the air will keep nice circulation in a tent like environment. ( again this is all in my opinion I’m not a professional by any means)
Click to expand...
This is not true, full stop. Only at the very end of the following cycle does low humidity help much if at all.

Plants need humidity to properly transpire; too low and the stomata don't open, limiting CO2 uptake. This hurts yield.

Continuous airflow is the best approach in a small grow. Most people want low RH to prevent mold and mildew and good airflow does this.
 
Josh33

Josh33

Active Member
Well shoot I’ll have to turn the humidity up in my flower room I wonder if I can get more of a yield per plant
 
ttystikk

ttystikk

Well-Known Member
Josh33 said:
Well shoot I’ll have to turn the humidity up in my flower room I wonder if I can get more of a yield per plant
Click to expand...
Study up on VPD, vapor pressure deficit.

It's the optimum range where plants open their stomata and are most receptive to CO2 uptake. It is temperature dependent; RH rises with temperature.

If RH is too high, plants can't transpire properly and don't pull nutrients up from the roots. If it's too low, stomata stay closed to prevent wilting and plant growth slows down to lack of CO2 uptake.

Fluctuating RH levels create ideal conditions for powdery mildew. This is the main reason to keep it in check at night.

Most people go about reducing RH improperly; they install a device that removes water from the air. Usually the problem is a temperature drop because lights aren't emitting heat anymore. Therefore, keeping the temperature level throughout the day/night cycle is more effective.
 
Josh33

Josh33

Active Member
ttystikk said:
Study up on VPD, vapor pressure deficit.

It's the optimum range where plants open their stomata and are most receptive to CO2 uptake. It is temperature dependent; RH rises with temperature.

If RH is too high, plants can't transpire properly and don't pull nutrients up from the roots. If it's too low, stomata stay closed to prevent wilting and plant growth slows down to lack of CO2 uptake.

Fluctuating RH levels create ideal conditions for powdery mildew. This is the main reason to keep it in check at night.

Most people go about reducing RH improperly; they install a device that removes water from the air. Usually the problem is a temperature drop because lights aren't emitting heat anymore. Therefore, keeping the temperature level throughout the day/night cycle is more effective.
Click to expand...
Awesome thanks for the info I’ll have to do more homework and study vpd do you have a more appropriate suggestion on rh levels a round about or something I would appreciate it
 
ttystikk

ttystikk

Well-Known Member
Josh33 said:
Awesome thanks for the info I’ll have to do more homework and study vpd do you have a more appropriate suggestion on rh levels a round about or something I would appreciate it
Click to expand...
70% RH at 85F for LED grows is optimal. Gotta keep that RH consistent, however.

HID grows prefer cooler temps, just below 80F, RH around 65%.

I realize those RH numbers are a lot higher than the conventional wisdom but they're backed up by botanical science and agronomy.
 
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