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

  1. #1

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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.



    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.


    Thanks in advance for any help.

  2. #2
    Lover of Mountains nightsky's Avatar
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    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.

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    Grow Pitcher Plants! DroseraBug's Avatar
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    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.
    "And this is what happened, and this is why the caribou and the wolf are one; for the caribou feeds the wolf, but it is the wolf that keeps the caribou strong."
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    scottychaos's Avatar
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    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!

    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

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    Lover of Mountains nightsky's Avatar
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    Unless of course ambient humidity is 9% or less.

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    Quote Originally Posted by nightsky View Post
    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.

  7. #7
    A yellow M&M Jefforever's Avatar
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    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.

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    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.

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