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At my wit's end trying to cool a terrarium (with diagrams!)

So in my previous house, the ambient temperatures were always around 75 F (23 C) and I kept my terrarium down in the basement where the temperature would get to about 65 (18 C) at night with the fluorescent lights off.

I recently moved and am now in a house at around 80 degrees with no basement, and am about to go mad trying to figure out how to achieve a temperature drop to keep my nepenthes happy. I recently tried a method I read somewhere about pumping air from a minifridge to the terrarium, but my results have been dismal.

Here's a diagram of my current setup.

terrarium.gif


Few basics, it's a 4x2.5x1.5 tank, 55 gallon. Acrylic sheets are between the lights and the terrarium (lights are about half a foot above). I have a humidity pump on either side keeping the humidity from 80-100%.

The recent thing I've tried involves the minifridge. I've got a piece of tubing that leads to the open air of the fridge out to a funnel and fan in the terrarium (sealing hole in the fridge with silicone putty around the tube). The idea being to suck air from the fridge into the terrarium. My results have been poor, and I'm sure there's all sorts of reasons why that might be the case (tube too thick, tube too long, terrarium not sealed enough, fan not powerful enough). The air coming out just doesn't seem all that cold.

I'm not sure what to do now and am welcoming all advice from people more experienced than myself. Before the fridge thing, I tried bottles filled with ice with a humidifier blowing across them, but that only got the temperature down to 74 at the least. That was a wee bit of a hassle and required a lot of attention.

I've read about peltier coolers, but those seem frightfully expensive and difficult to get it working perfectly.

I've also considered instead of using air, using a waterpump that takes cold water from inside the fridge (from some kind of tank), and then lining the inside of the tank with tube, to then lead back to the fridge to cool again.
alternative.gif


Thanks in advance for any help.
 
For 6 months out of the year, it's easy to get highland or even ultra-highland temps here. Having the plants in the basement here would extend that to easily 9 months out of the year.

But - I don't have basement, and my growrack is in a room on the upper floor, with a southwest facing window. In other words, it gets warm to even hot in there quickly, except in winter.

The only success I've had is to dedicate that entire room to being temp controlled, not just the growrack/terrarium itself, unfortunately.

I tried to cool just it, and was never successful. I tried venting a fridge also. I tried frozen bottles. I tried pumping portable A/C air into it, but this destroyed the humidity in there.

Now, I have a portable room A/C that is vents the warm air out the nearby window. In the summer, I have it set to 75F in the day. My growrack is mostly sealed to keep humidity in (humidity is very low here year round, and a humidifier is contained within), and this causes heat to build up from the light ballasts. I've found that keeping the room at 75F in the day keeps it below 78F+/- or so inside the growrack.

At night in the summer, I set the A/C to 58F. It takes a while to reach it, and it pretty has to run continuously at night to keep it that low. Inside the terrarium, it will drop to about 60F, even with lights off.

This time of year, it is still too warm in the daytime, so the A/C is on in the day, but at night I open the window as it has been in the low 50's lately, and will keep dropping.

I cannot wait to get a place with a basement, at which time I will build a grow room (as opposed to just a rack or terrarium), and it will be SO much easier to temp control.

Good luck. I've found the hardest (and most expensive) part of this hobby has been temp control.
 
I'm a novice at this myself and have been grinding through options of how to accomplish the same thing. My guess would be that the ambient temperature around the tank is just cancelling out the efforts by the freezer and the tube may not be carrying enough cold air out. I don't think you mentioned the use of insulation. You might try lining the terrarium with as thinnest insulation you can find on all sides but the front so that it doesn't take up to much precious space. What about a larger diameter tubing? Or basically just set the freezer directly adjacent to the terrarium and build some kind of large diameter insulated bridge with a fan at the terrarium/fridge pipe interface? I'm just brainstorming here. How about placing the mini fridge above the terrarium somehow since colder air is denser and it will tend to drop?.

I'm currently building a plexiglass terrarium and plan to do this. I'm going to try a high powered peltier first which I'm predicting will be a waste of my time and money but we we'll see. If that does'nt work I'm going to figure something else out. Once I set a goal I become kind of obsessed with it.
 
How about just growing plants that dont need all the machinery? ;)
choose a nep that grows happily on the windowsill..in natural light and ambient humidity,
amazingly, all you have to do is water it! :jester:

do you really want to be tending to all this technology every day for decades?
some things just arent worth the effort IMO...

(I speak from experience..I once made yeast Co2 reactor for the planted aquarium..SO not worth the effort..now the tank lives happily with just a light on a timer. )

Scot
 
Unless of course ambient humidity is 9% or less.
 
I tried to cool just it, and was never successful. I tried venting a fridge also. I tried frozen bottles. I tried pumping portable A/C air into it, but this destroyed the humidity in there.

I've thought of this. I've got an ultrasonic fogger that can restore humidity pretty quickly. Still, it'd be not ideal =/

Now, I have a portable room A/C that is vents the warm air out the nearby window. In the summer, I have it set to 75F in the day. My growrack is mostly sealed to keep humidity in (humidity is very low here year round, and a humidifier is contained within), and this causes heat to build up from the light ballasts. I've found that keeping the room at 75F in the day keeps it below 78F+/- or so inside the growrack.

At night in the summer, I set the A/C to 58F. It takes a while to reach it, and it pretty has to run continuously at night to keep it that low. Inside the terrarium, it will drop to about 60F, even with lights off.

That may be the way to go. Might I ask what brand/type of portable AC it is?

I cannot wait to get a place with a basement, at which time I will build a grow room (as opposed to just a rack or terrarium), and it will be SO much easier to temp control.

I hear you. I miss my basement.

I'm a novice at this myself and have been grinding through options of how to accomplish the same thing. My guess would be that the ambient temperature around the tank is just cancelling out the efforts by the freezer and the tube may not be carrying enough cold air out. I don't think you mentioned the use of insulation. You might try lining the terrarium with as thinnest insulation you can find on all sides but the front so that it doesn't take up to much precious space.

Hmm...maybe so. I was wondering abit about if I needed to get warm air out as well.

What about a larger diameter tubing? Or basically just set the freezer directly adjacent to the terrarium and build some kind of large diameter insulated bridge with a fan at the terrarium/fridge pipe interface? I'm just brainstorming here. How about placing the mini fridge above the terrarium somehow since colder air is denser and it will tend to drop?.

I've definitely been considering something like that. One of my worries was in getting the hole bigger and bigger, it becomes harder to go backwards if it ends up not working. Also it seemed like the fridge would need to work even harder and harder. Although I suppose I may just need to do that anyway.

I'm currently building a plexiglass terrarium and plan to do this. I'm going to try a high powered peltier first which I'm predicting will be a waste of my time and money but we we'll see. If that does'nt work I'm going to figure something else out. Once I set a goal I become kind of obsessed with it.

You're braver than I am :) Good luck with that.

How about just growing plants that dont need all the machinery?
choose a nep that grows happily on the windowsill..in natural light and ambient humidity,
amazingly, all you have to do is water it!

Partially because I like a lot of the plants that require a little bit more care, and I used to live in an area where it was perfectly doable.

do you really want to be tending to all this technology every day for decades?
some things just arent worth the effort IMO...

Well. No. Which is why I want to come up with a setup that mostly takes care of itself. The previous basement setup only required me to come down and water it twice a week and fill up the humidity things once a month.
 
My suggestion: Don't do the water pump idea.

I've used it for 3 years and it's ineffective. But I still use it.

I think the most effective thing to do is live in a coastal town. Either that or have a nice, permanently cool basement. A lot of people have that.

EDIT: My water pump thing is an open circuit, the water dumps into a bucket and goes back into the mini-fridge.
 
While effective, neither of those are very feasible :)

A friend has mentioned though an idea of a pump of cold water and copper tubing to lead into the terrarium and loop along the bottom.
 
Fill your humidity thing once a month? That would be great! Mines a 3 gallon capacity, and is only humidifying a growrack, and I have to fill it every other day. I love the desert, but there are drawbacks it seems ;)
 
  • #10
I am not sure the minifridge could keep up but that wasn't your question. Seems to me that in order to take air out of the fridge without alot of back pressure you need to let air into it somewhere. Ideally you would want to remove the cold air from one side and let air in the other so that it has a chance to cooldown again. Maybe have the air intake blow right over the cooling coils in the freezer section..Other than that.. insulate everything you possibly can. Tube, sides of the tank etc..
 
  • #12
An engineering friend did a bit of research for me, and gave me a lot of very good advice. The big thing I took away from all of it is that I was fighting a losing battle with my house's ambient temperature. Getting the terrarium down in the feasible range that I wanted (around 60 degrees F) was just going to be pretty difficult.

The solution I went with ended up being that I'd be better off placing the terrarium in a place where the ambient temperature would help and not hinder the process.

In my old home that was a cellar. Thus, I decided to try creating an artificial cellar.

I talked to some hydroponics fellows, and they mentioned how a grow tent could do a decent job of keeping a temperature in. That paired with a portable air conditioning unit might get me what I wanted.

All that, and it kind of looks like a monolith.
doomcube.jpg


Its size is 4x4x7, but let's peek inside, shall we?
opening.jpg


Inside, there's the control tower. The air conditioner sits on top because the venting tube needs to reach a window, and longer tubes can decrease efficiency. You can also see where I've taped up vents to insulate the tent.
controltower.jpg


The side of the grow tent, showing the vent leading to a window.
airvent.jpg


Electrical stuffs (+ cat tail). I still need to clean this up a bit to make sure it's all organized. The timers are there to control the two sets of fluorescent lights, and the rest of the plugs are for the terrarium humidifiers and fan.
electronics.jpg


The tank currently sits on the bottom of the tent (where the colder air will gather).
planttank.jpg


I also ran a tube of air from the AC directly to the terrarium (although I need to check just how much this helps). The AC has an auto setting and a cool setting. I just wish the auto-setting worked a bit better. I set it for 62 and the thing just stops around 72. I've taken to switching it to auto during the day and cool during the night.
acvent.jpg


A view of the AC tube. The AC itself sucks humidity from the air, but the terrarium is enclosed and thus keeps a happy humidity of around 80-100%
tube.jpg


Regrettably, as the tent is big and opaque, it's tricky monitoring the thing. I went to a hardware store and picked up a remote temperature sensor that let's me monitor how things are going.
monitor.jpg


Results:
Daytime terrarium temperature: 80 degrees F
Nighttime terrarium temperature: 63 degrees F
Terrarium humidity range: 80-100%

Ideally, I'd like to push the nighttime temperature to 55, but I think for now this is as good as it's going to get. I'm at least pleased to be at a decent point that I believe I can build and develop upon.

On the happy side, my plants appear to be improving greatly. A number of them that had stopped producing new leaves are now starting to pick up their growth again. Even the N. Lowii seems to be pitchering well.

Costs:
There is the unfortunate 'cost' of having an enormous black cube like this thing taking up space in a room and blocking a window. Unfortunate, but one I'm willing to make to ensure plant health and happiness. I am open to decorating solutions to the cube though.

This was not a particularly cheap solution, but overall I found the costs not too horrid.
The tent itself was around $180.00 (http://www.texashydroponics.com/shop/product.php?productid=2843&cat=329&page=1)
The air conditioner was $340.00 (http://www.amazon.com/gp/product/B000PGQ8YQ)

On the other hand, I'm intrigued at the idea of using this tent (as it stays fairly cool) into a make-shift root/wine/cheese cellar as well.

Anyhew, that's the direction I went. I welcome any comments/critiques as I'm still feeling my way in the dark with all this.
 
  • #13
Talking to someone, they suggested moving the AC out and venting its cool air into the tent. That would certainly give the AC more air to suck in. However, I'm wondering what length of tubing would be the maximum I could use without the air losing too much of its coldness.
 
  • #14
Love the cube. Looks like you found a solution.
 
  • #15
wow. thats alot of work... well if your going to go that route, I think you need to just put in a grow rack instead of the tank, get a small humidifier to keep the RH up in the tent and just build an indoor HL nep greenhouse...

rather than the small tank in the big tent :)
but we can't always get what we want now can we...
 
  • #16
wow. thats alot of work... well if your going to go that route, I think you need to just put in a grow rack instead of the tank, get a small humidifier to keep the RH up in the tent and just build an indoor HL nep greenhouse...

rather than the small tank in the big tent :)
but we can't always get what we want now can we...

Maybe in the future!
 
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