Dehumidifier for a small space

[Major PITA]

Hey gang-

Now that my clown car of a grow room is fully loaded, RH is getting out of control during lights-out. I can keep it around 75F and 40% RH with the lights on. When the light is off my temp drops to low-mid 60's (I'm good with that) but the RH climbs up near 90%.

I'm wondering if anyone has experience with the mini-dehumidifiers (Peltier technology - no compressor) used in a very small space. I get it that they don't work well in larger spaces, but I'm dealing with less than 120 cubic feet of space (3'x5'x8').

Any/all feedback and experience is appreciated.

 

[Rifleman]

Could you increase exhaust during lights out?

 

[fanleaf]

Subbed. I don't have nowhere near 90% humidity and I live in a very humid area but I have also considered getting a very small unit like the thermometric 1 room units that are cheap just for late flowering.
Good question and I too look forward to hearing from those who have used them. The little ones with like a 17oz collection tank.

 

[Major PITA]

Could you increase exhaust during lights out?

Right now I could but it would pull the temperature down. As it gets colder, it won't be possible w/o the room getting too cold. I have a tiny heater that helps lower RH while it keeps the room warm during lights-out in the colder months. This is as bad as it gets: too warm for the heater but still rainy and humid.

 

[electro gypsy]

I see these for around $50-$60 USD. I've considered the same for one of my tents, but leaving fans and venting on during dark time seems to have taken care of it.

Compact, portable and affordable, the Eva Dry Electric Petite Dehumidifier is an easy way to help prevent mold or mildew in damp or humid environments. Sized perfectly for bathrooms, closets, a boat or an RV, this mini dehumidifier weighs only 1 lb and works without a compressor for extremely quiet function and low energy consumption. Automatic shutoff and an easy indicator light let you know when to empty the reservoir. The small dehumidifier holds up to 16 oz. and is ideal for spaces 800-1000 square feet.
Features: LED Power Indicator, Peltier Operation, Washable Air Filter, Removable Bucket, Quiet Operation, Automatic Shut-off
Dehumidification Rate: 8 Ounces Per Day
Water Removal Options: Front Access Bucket
Capacity (volume): 1.000
Dimensions: 8.500H x 4.500W x 6.000D
Recommended Room Size: 800-1000 sq. ft.
Number of Fan Settings: 1
Weight: 3.500
Battery: no battery used:

 

[Major PITA]

Thanks eg. Yeah - there are ton of them out there. Some users love 'em while the next guy says they are useless.
I hate to be the $50 guinea pig, but I may have to bite the bullet and see for myself.
I hoped, with all the grow tents in use, somebody else would have beat me to it.

 

[electro gypsy]

Well 8oz a day is a little better than a Dri-Z-Air desiccant system.. but even with two of those you'd be replacing the desiccant every few days. 2 bucks a pop.. ugh. Moving the air and venting are probably the ticket.

 

[Fuzzy Duck]

I use a dehumidifier these days after a bad rot issue which hit 90% + RH lights off & i mainly put it down to using hempy buckets with perlite/vermculite mix which can hold more moisture than my normal 6.5 liter air pots tho, that is just my opinion tho.


I believe ambient RH value of intake air either from passive or active plays a part also !

I'm a passive vent man myself & i don't use A/C either, all i know is that on average that the house hold RH is 50%/60% most of the time which may varie a little bit depending on out door weather with RH going up on wet/damp days etc

It is pretty normal to see an RH spike during lights off tho & more likely not a greater issue in low RH parts of the world !


Bud rot spores exist in all air it is just looking for ideal conditions to spawn & normally low temp drop during night/lights off coupled with higher RH to which it may effect MJ around the mid flowering period & the larger more dense buds first.


So after some research i come across some info of keeping base lights off temp around 20/21c with RH best around 60% or under... 70% + may induce rot, but over 80% will be more likely an issue & i may add some strains are more prone to rot than others.


Mmm dehumidifiers ah well lets just say depending on size will only treat X volume of air per hour & more likely smaller volume than your extraction fan so it is a case of on how to best use them & may well avoid the mini types !

I've heard of some people using active intake from out side using a dehumidifier inside the tent with ok results ?

I'm very passive & use my own out side of the tent during lights off running on full setting with an average RH around 50% lights off, it treats 180 cubic meters of air per hour & my extraction fan removes 380 cubic meters of air per hour, but over time with passive vent the dehumidifier treats enough air to keep things tame.

 

[Major PITA]

My only air extraction is through the lamp's cool tube to the outside. All is good when the lamp is on since it is pulling air a good part of the time. It is only when the light is off I have a problem since its vent fan isn't running. I tried venting separately. It does help reduce RH, but it cools the room too much. The dehumidifier is only needed when the vent fan is off, so the room is not exchanging much air during those hours.

 

[Fuzzy Duck]

Good info

Sounds like you are running your fan with air cooled hood during the lights on period only.

It may suggest you are using carbon filter > hood > exhaust whilst lights are on, it is just the way i read it !


Best to keep the fan running 24/7 it may mean i slightly different config of what ya got going...

Either that get a another fan for some think like this...

Carbon filter > extraction fan > exhaust.

With...

Fan > air cooled hood > exhaust... can work either way around either blowing or pulling air through hood but some say blowing air through is better ?


It is pretty common practice to keep exhaust running 24/7 tho, ya more likely notice a difference once ya make a channge & if not look at a dehumidifier to be used during lights off.

 

[Major PITA]

You read it right.
My grow room is not in a heated space. If I run my exhaust fan 24/7 it gets way too cold in there. That's the only reason I have it off when the light is off. During the winter months my lights-off temp would get below freezing with the fan pulling in air.

 

[Fuzzy Duck]

May well suggest looking at radiators with a built in thermostat to help improve conditions

Might look at oiled filled types with some models coming under 200w & may avoid those types which blow warm out running 3kw a tad bit on the juicy side of the elctric bill.


Other wise those cooler night temps may stunt growth a little bit.

 

[Highpotanoose]

Thanks eg. Yeah - there are ton of them out there. Some users love 'em while the next guy says they are useless.
I hate to be the $50 guinea pig, but I may have to bite the bullet and see for myself.
I hoped, with all the grow tents in use, somebody else would have beat me to it.

I'll save you the $50 major

Had one in my 48"x48"x84" room barely drop the RH 2%

Added a full size in my lung room now all good

I run it 15mins every hour when lights on set at 35% and from 1 hour before till 1hour after lights out

*summer time pretty much runs 24/7 to keep it in check*

Side note is if you put it in your space your could prob run only during lights out and it would heat your room

they put out a fair amount of heat

Added to much to my room I had to move it to lung room but I need to run during lights on also

 

[Major PITA]

I'll save you the $50 major

Had one in my 48"x48"x84" room barely drop the RH 2%

Added a full size in my lung room now all good
I run it 15 every hour when lights on set at 35% and from 1 hour before till 1hour after lights out

*summer time pretty much runs 24/7 to keep it in check*

Good to know! Much appreciated - both of you! That's $50 more I have to put on a better solution.