Mini dehumidifiers - Help please

S

static123

Well-Known Member
Hi

Need some advise please, I am growing in doors in the uk and currently the RH is sitting now at 62% in the tent since the wether has turned wet, I no this is not a problem at the moment but once they start to flower I would like to get this down as much a possible.

I have two plants a 250w HPS (temps pot level are 24/5 day and 23 / 21 night)
all in a 76/76/180 light house max tent.
RH currently 62%

I plan on adding a small dehumidifier and trays of silica gel in the hope to bring it down to a safe level for the buds.

My question is do you think this would be ok to use as its only 500ml max or will i be emptying it every few hours.

71qgWB90CaL_SL1500_.jpg


Its small so will fit fine in the tent and wont give of to much heat plus the general review are very good, plus its affordable.

What do you pros think your advise would be greatly welcome.

Big thanks :thumb::thumb:
 
Here's a thread I started when I was lookin for a dehumidifier.
Looking for help sizing dehumidifier for 8x8' room

I did get one, and it has helped a lot. I only run mine during lights-off. It raises the grow room temps a lot higher at night (vent fan system may kick in once in awhile)

It sounds like that one doesn't have fittings for a drain hose? If I was in your position I would just drill a hole through the tank and hook up hose fittings to avoid having to constantly empty it.
 
I asked about the same style of dehuey and was told by another member who had one, not to bother. They do not pull enough water out of the air to be worth using. I'm trying to dry a 120 cubic feet space.
 
I'm considering something like a 30pint or 50pint ehumidifier to put in the room(150sq ft) with my tent. I think keeping the entire intake area low will be key to keeping up with the amount of air the exhaust fan pulls(400cfm). Plus dehumidifiers this size can be setup to drain out a sink or window.
 
Atulip said:
I'm considering something like a 30L or 50L dehumidifier to put in the room(150sq ft) with my tent. I think keeping the entire intake area low will be key to keeping up with the amount of air the exhaust fan pulls. Plus dehumidifiers this size can be setup to drain out a sink or window.
Click to expand...

i am growing in a lot smaller size, 79/79/180 tent with the only intake its the three vents at the bottom, this is why i am thinking this small one would be fine,
 
Found that model, it's up to 250ml/day. So would need to be dumped every 2 days.

What's your exhaust fan if you have one? My concern with mini dehumidifiers is removing enough moisture to keep up with the amount of air getting cycled through the tent. Unless your exhaust and intake are in the same room.
 
exhaust is a 6" fan and rhino pro filter and that is just pulling it out in to the room with the tent in ( its a large room ) , i no its not ideal as should be out the window or something but unfortunately thats not possible in the house. in take its just the vents in the tent,

temps are 24 / 25 day and 23 / 21 night, its just this rh i am concerned about in a few weeks once flower starts,
 
Atulip said:
Found that model, it's up to 250ml/day. So would need to be dumped every 2 days.
Click to expand...
Hello again :)
Are you referring to the the model i posted at the top ? if so that would not be a problem with having to empty it every 2 days altho how would you work this out from my current RH to make sure it would be up to the job ?
 
We can do a bit of math, probably not very accurate, but fun nonetheless. From googling, 1 liter of air can hold .017mL of water.(100%rh 25℃) We want to lower RH by ~20%, so .0034mL water/L of air. 250mL/day, or 73,000 L of air. Tent size is 1,150 liters, so more than enough for the area(at optimal conditions). Then comes exhaust fan, we'll say 200cfm or, 5,600 liters per minute, 8,000,000 liters of air moved per day. Not nearly enough dehumidifier to keep up with air movement. If exhausting into the same room as intake, recycling the air in say a 12ftx12ftx8ft bedroom, 32,000 L of air, it seems the mini dehumidifier would be enough with some room for added moisture from plants sweating.

Myself I vent Into the attic, with 400cfm or 16,000,000 L/day. 50pint dehumidifier, 94x the moisture removed daily, so 6,900,000 liters of air per day. If I wanted to remove the same 20%, not enough to keep up with the exhaust rate. And here the house cu ft comes in, say 1500 sq ft, 8ft high, 120,000 cu ft for the house and an estimated 30,000 for the attic, 150,000 cu ft total. 4,200,000 liters of air in the entire house. So a 50pint dehumidifier could theoretically pull 30% of the RH out of my house each day.

These numbers may be way off, as I've been googling and smoking between calculations.
 
Atulip said:
We can do a bit of math, probably not very accurate, but fun nonetheless. From googling, 1 liter of air can hold .017mL of water.(100%rh 25℃) We want to lower RH by ~20%, so .0034mL water/L of air. 250mL/day, or 73,000 L of air. Tent size is 1,150 liters, so more than enough for the area(at optimal conditions). Then comes exhaust fan, we'll say 200cfm or, 5,600 liters per minute, 8,000,000 liters of air moved per day. Not nearly enough dehumidifier to keep up with air movement. If exhausting into the same room as intake, recycling the air in say a 12ftx12ftx8ft bedroom, 32,000 L of air, it seems the mini dehumidifier would be enough with some room for added moisture from plants sweating.

Myself I vent Into the attic, with 400cfm or 16,000,000 L/day. 50pint dehumidifier, 94x the moisture removed daily, so 6,900,000 liters of air per day. If I wanted to remove the same 20%, not enough to keep up with the exhaust rate. And here the house cu ft comes in, say 1500 sq ft, 8ft high, 120,000 cu ft for the house and an estimated 30,000 for the attic, 150,000 cu ft total. 4,200,000 liters of air in the entire house. So a 50pint dehumidifier could theoretically pull 30% of the RH out of my house each day.

These numbers may be way off, as I've been googling and smoking between calculations.
Click to expand...

Thank you for taking the time to work this out for me really kind of you. my head is a little sore reading these numbers but i will go over it again and see if i can understand it a bit more, from what i think your saying, the one i am looking at should be fine ?

enjoy the rest for your smoke :thumb:
 
static123 said:
Thank you for taking the time to work this out for me really kind of you. my head is a little sore reading these numbers but i will go over it again and see if i can understand it a bit more, from what i think your saying, the one i am looking at should be fine ?

enjoy the rest for your smoke :thumb:
Click to expand...

If it works at 100% optimal conditions and pulls 250mL per day then it should work in your room. I would go for a bit bigger one if you can(500mL or 1L), to cover added moisture from plant sweating and unaccounted room intake(air vents).
 
Atulip said:
If it works at 100% optimal conditions and pulls 250mL per day then it should work in your room. I would go for a bit bigger one if you can(500mL or 1L), to cover added moisture from plant sweating and unaccounted room intake(air vents).
Click to expand...

brilliant thank you
 
I don't think the math is correct.
If you are exhausting the tent into a large room, the dehuey needs to be able to handle the volume of air in that entire large room. IDK how large a "large" room is but I'll throw out an example:
Room = 4 x 4 x 4 meters = 64 cu-m
At 80% RH and 25 degrees C, air holds approximately 18.5 grams of water per cubic meter.
To reduce this RH by 20%, you would need to remove 4.6g of water vapor per cu-m.
4.6 x 64 = 294.4 g = 294.4 ml of water
Now the question is, how fast is the air in the large room replaced and how much water is being added to the air by watering, normal transpiration of the plants, and everything else. I have no way to estimate this, but I'm as sure as I can be, that little dehuey will not do the job. It is not a matter of how often you need to empty it. The problem is, it will not remove the moisture fast enough to keep up with the air and moisture being added to the room.
 
Major PITA said:
I don't think the math is correct.
If you are exhausting the tent into a large room, the dehuey needs to be able to handle the volume of air in that entire large room. IDK how large a "large" room is but I'll throw out an example:
Room = 4 x 4 x 4 meters = 64 cu-m
At 80% RH and 25 degrees C, air holds approximately 18.5 grams of water per cubic meter.
To reduce this RH by 20%, you would need to remove 4.6g of water vapor per cu-m.
4.6 x 64 = 294.4 g = 294.4 ml of water
Now the question is, how fast is the air in the large room replaced and how much water is being added to the air by watering, normal transpiration of the plants, and everything else. I have no way to estimate this, but I'm as sure as I can be, that little dehuey will not do the job. It is not a matter of how often you need to empty it. The problem is, it will not remove the moisture fast enough to keep up with the air and moisture being added to the room.
Click to expand...

My base number is off from yours. I got 3.4mL to remove, yours has 4.6mL. From another source, 17mL is 100% humidity at 20℃, so 25℃ should be about 23, which puts me at 4.6mL/cu meter. And my math took way too much conversion lol.

So 500mL/1L dehumidifier would be more ideal.
 
The key to success for any dehuey is not how much water it will hold, but rather how quickly it can remove that water.
 

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