How to use dehumidifier

A dehumidifier is made to remove excess moisture in a room but sometimes the dehumidifier gets too hot for a flowering room. If you run a dehumidifier in a room and don't exhaust it, it becomes too hot, but if you do exhaust it you have to replace the room with the air that has been taken out by the dehumidifier. By replacing the room with fresh air you are in turn bringing in more moisture, right? So what gives? Exhaust the heat from the dehumidifier or don't? When I asked this before somewhere else I was told "Exhaust from the dehumidifier is the dry air it has created for you. If you vent it to the outside then there is no point in using a dehumidifier in the first place." Does anybody know the answer to this?

Air conditioning.

venting your dehu out of the room? That's pretty funny shit right there! Hmmm, I think I'll dry the air and immediately expell it out of the room. Might as well just stick an exhaust fan in the wall.. It would do the same good.

Or try just running the dehu when the lights are off and fight stretch

So only run it when lights are off?

I keep it on at all times with the guage set to 55%. Usually it only kcks on at night though....

Isn't 55% too humid? I thought it was suppose to be nearer to 40% max? Anyways I don't know or I wouldn't be asking. Do you keep your fans on while the dehumidifier is running also or cut them off?

I have two dehu that work full time. But my room is crammed full of plants and I have a co2 burner going.

Run it only at night. Fans? Which fans? My oscillating fans also run 24/7.

Shoot for 50-65 in veg but 40 during the second or third week till the end in flower. Lower during the last week if you can get it.

the dehumidifier in the grow room is used to keep the rh about 70% when vegging and about 50% when flowering, 30% the last week for sticky stuff, 40-45% is needed for a drying room, if the outside air is 60% and your growroom is around 60% or above with a fan running that is normal, the only way around this is to use a dehumidifier switched to full power connected through a stand alone digital humidistat connected to your fans, for instance when flowering, when your room reaches 48% humidity the humidistat cuts the dehumidifier and turns on the fans, when the room reaches 52% the humidistat cuts off the fans and turns on the dehumidifier this is a constant effect. maintaining temperature with the fans and humidity with the dehumidifier.
dehumidifiers are made for closed areas, when you turn your fan on its just like opening a window.

here is a humidistat on ebay :

http://www.ebay.co.uk/itm/DIGITAL-HUMIDITY-STAT-HUMIDIFYING-DEHUMIDIFYING-P1-/230615646425?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item35b1c380d9

(these humidistats are normally used with both a humidifier and dehumidifier maintaining humidity at a constant rate anywhere on the planet)
and are 240 volts.


when people have your problem in a house they buy air conditioning systems that have built in dehumidifiers that work together.
which is harder to maintain on a small scale.

the only other way round it is to dry the air in a large bedroom to say 45% with a large dehumidifier and suck that air in to your growroom with your fan expelling it outside at say 55% maintaining the growroom at 50%, a dehumidifier will not heat a large room.

i use one in my large growroom and the 6" fans are on constantly, i had to buy a bigger dehumidifier to maintain my 48-52% flowering humidity a smaller one before this had the same problem as you, as we get a lot of rain and damp in winter outside where i live.
i have 10 plants only just now, but that is 20 litres of nutrient water being poured in there and some of it evaporating every 2 days as well as the outside air being 55% and i suck the air in from the rest of the house as it is a little drier before it gets to my inlet fan.
when i dry my buds for 5 days i turn the outside fans off, reduce the humidity to 40% and use 2 oscillating fans and open the growroom door once a day to empty the dehumidifier.

Now I see. Wow I never knew. Thanks for feedback.

I do it the other way, I have a large space, with 2 flower rooms that run lights alternately (is that even a word...its late, anyways 1 room on while the other is off 12/12 in both) the rooms share a wall and a common hallway the deH is in room A) runing constantly at 45%H.While the lights are on the door to the hallway is open-thats the intake of cool but somwhat moist air it goes through the room dryes up and heats up and gets exhausted in room B)since the lights are off and rooms are not heated it keeps room B ) warm , and since there is positive preassure and the room not hermetically sealed some air goes back in the hallway to repeat the cycle and some (same dry but cooler air from room b) goes back dirrectly into room A) through the second blower (passively since the second blower only in the on position when room B) is on) ...The trick is to have a DeH big enough to dry up entire space, I get about 4 6 gallon jugs a week out of mine....

Wow, 24 gallons a week! You must live somewhere moist!

That setup sounds like a great solution too if you are working with a bigger space. Way to adapt to your situation.

AltarNation said:

Wow, 24 gallons a week! You must live somewhere moist!

That setup sounds like a great solution too if you are working with a bigger space. Way to adapt to your situation.

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Dude, I go through about 6 gallons a day. While your local conditions play a role, I have a sealed room with big plants. The bigger the plants, the more they transpire, they more I have to get rid of that water. Its pretty crazy really. I have 12 plants in week 6 and they are going through 20 gallons of water a day!! Its funny, the drier you make it, the more they transpire...and the more you have to take thee water out of the air.

legallyflying said:

Dude, I go through about 6 gallons a day. While your local conditions play a role, I have a sealed room with big plants. The bigger the plants, the more they transpire, they more I have to get rid of that water. Its pretty crazy really. I have 12 plants in week 6 and they are going through 20 gallons of water a day!! Its funny, the drier you make it, the more they transpire...and the more you have to take thee water out of the air.

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12 plants - 20 gallons of water a day, wtf are you growing, i have 10 plants and they use 20 litres every 2 days.

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WeeGogs said:

12 plants - 20 gallons of water a day, wtf are you growing, i have 10 plants and they use 20 litres every 2 days.

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Well, this was taken about 10 days ago...



this is a bottle of PH calibration solution behind the stalk..


so, its kind of crammed in there.