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Cooling Systems

Discussion in 'Growing Areas' started by Foozil, Dec 13, 2018.

  1. Foozil

    Foozil Member

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    Just wondering how people cool their cold terrariums for species like Den. cuthbertsonii, petiolatum, dichaeoides, and other things in that group. I hear aquarium coolers, small AC units and evaporative coolers can be used but thought I'd ask here before buying any.

    Thanks,

    Apologies if this was posted in the wrong place by the way.
     
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  2. carl

    carl Active Member

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    I use an air conditioner mounted in a basement window, with cold air ducted into the 8x2x2 growing space. Drops night temps down to low 60s-upper 50s in the summer. In winter, I use outside air.
     
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  3. Foozil

    Foozil Member

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    Fantastic, thanks for the info
     
  4. nodrog6

    nodrog6 New Member

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    I use an aquarium chiller connected to a computer radiator/fan setup in the tank. In line, I also have a cooler as a reservoir with an aquarium pump. I found that it's really important to vent the aquarium chiller exhaust out of them room and do a good job insulating the tank/tubing. If you don't, you'll get temperature gradients within your tank and water will condense on your radiator since the system has to work really hard. I recommend using water proof fans for the radiator.

    Temps I get are 70-72 in the day, 52-54 at night. I use an Inkbird ITC-310T to control the temperature with a schedule.
     
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  5. ezluckyfreee

    ezluckyfreee Member

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    What are the advantages to using a cooled water/radiator setup, as opposed to just ducting cool air from an air conditioner (possibly with a modified thermostat) into the tank?
     
  6. Ray

    Ray Orchid Iconoclast Supporting Member

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    I have never done either, but I would think that a window a/c unit moves a large volume of somewhat dried air, while the aquarium chiller setup, with the heat exchanger inside the tank, would not require the air flow volume to achieve the same effect, while allowing the RH to stay higher.
     
  7. nodrog6

    nodrog6 New Member

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    That's a great question and even after building the chiller/radiator setup, I'm still not sure it was the right decision. I've only built the heat exchanger system and I'm interested to hear what people using air conditioners or other systems think.

    Budget
    Chillers and air conditioners are both pretty expensive. Luckily, I was able to find an aquarium chiller secondhand for very cheap. I struggled to find an air conditioner in my price range that met my temperature requirements. The costs of the radiator, waterproof fans, and chiller exhaust fan aren't negligible either. I'm not sure which system runs more efficiently power-wise. Buying a used air conditioner or chiller makes this category a toss up.

    Temperature
    The air conditioner needs to pump out air at a few degrees lower than your target nighttime temperature (i.e. 45-50°F). I could not find an air conditioner that does so in my budget and I wasn't willing to experiment with cheaper ones that have unpublished numbers. If the air conditioner has a programmable temperature setting, it needs to remember that setting after a power reset if you use a relay to control the temperature.

    Aquarium chillers go down to these temperatures really easily and the JBJ Arctica chillers remember the temperature on power reset. My heat exchanger gives me extremely consistent tank temperatures. I get about 1°F variance both during the day and night, which is near the accuracy limit of my temperature sensors. My nighttime temps are ~53°F year round. I'm sure there are air conditioners out there that will do the same. I know OrchidKarma used one and obviously had great success.

    One downside of my particular chiller is that there's a few minute delay between when the power turns on and when the compressor turns on. Something to watch for.

    Humidity
    Radiators condense water and will drip - watch out for rust and make sure your fans are waterproof. The heat exchanger system lets me use a really tiny fogger as a humidifier. If I leave it on, it can fog the entire tank in a couple minutes.

    I live in Colorado, which is very dry. Like Ray mentioned, I didn't want an air conditioner to blow low-humidity air into the tank whenever I needed to cool it. I assumed that this could be a problem at night when the air conditioner would be running more often. A more powerful humidifier would probably be more suitable for an air conditioner setup. I'm not sure if condensation in the pipe is an issue or a vent flap is necessary on the tank's cool air inlet.

    Setup/Maintenance
    The radiator/chiller system has a lot more components and it's a pain to keep clean. The radiator is bulky, so you have to be careful about its positioning in the tank. That said, I've never had my heat exchanger system leak or fail. Air conditioners seem simpler. In either case, if you have electrical cables running in your tank, don't forget to waterproof any connectors.

    If I were to build the system again and I could find an affordable/reliable air conditioner, I would use that. While I've had great results with my system and I'm very happy with it, it is tempting to trade less complexity and components within the tank for a (possibly) less consistent or higher nighttime temperature. The grass is always greener and I won't be swapping to an air conditioner anytime soon. I'd rather just build a greenhouse.
     
  8. carl

    carl Active Member

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    I bought my air conditioner from Walmart, the cheapest one they had, around $100. It's mounted in a basement window, and I made a hood out of pink styrofoam insulation sheets to allow me to use clothes drier duct to move air into the plant enclosure. The outlet air is around 40-45F. The thermostat senses ambient basement conditions, not the area cooled, and I run it at max cool and max airflow.

    I have since modified my setup to use sheet metal ductwork (4" diam), wrapped with insulation (don't remember the R-value, it was left-over from another project). The only uninsulated segments is the flexible metallic dryer duct connecting the a/c hood to the insulated ductwork.
     
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  9. Ray

    Ray Orchid Iconoclast Supporting Member

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    I remember seeing a couple of other alternatives - One was to use a wine chiller and convert it by adding lights and humidity (I saw this done with a small refrigerator once, as well), and another is to build an enclosure on top of a small dormitory refrigerator, circulating air through the floor of the tank into the fridge. All I can say is that it had better be self-defrosting.

    Another variant on that dorm fridge is circulating water through metal tubing coiled in the fridge, to avoid condensation issues.
     
  10. nodrog6

    nodrog6 New Member

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    That's awesome Carl! Did you insulate the tank as well? Does the humidity change at all when the a/c is on or you're using the winter air?

    In an AOS video talk on terrariums (mostly small and intermediate), the presenter had bought a large, horizontal, food display fridge. I'm not sure if they finished the project though.
     
  11. ezluckyfreee

    ezluckyfreee Member

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    I'm currently following this (DIY Air Conditioner - Cooling Systems for Highland Nepenthes) tutorial. Which has a cheap alternative for an aquarium chiller. I bought the parts for the water cooler itself, the cooler box and the window AC, for less than $40 canadian.

    The problem I'm currently having is that the spray foam doesn't seal so the box leaks lol.
     
  12. carl

    carl Active Member

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    I did put styrofoam insulation sheets around three of the four sides of the enclosure - either 3/4 or 1 inch thick, I forget which. I do also have a mist system using a misting pump (150 psi) and r/o water for humidification. The misting system runs several times a day.

    A plan is to automate all this, using an Arduino microcontroller, some sensors, and SSRs. I need to get off the stick and finish that project, though. Not particularly difficult if you know software and basic circuit design.
     
  13. ezluckyfreee

    ezluckyfreee Member

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    If anyone is reading this later, I did get DIY Air Conditioner - Cooling Systems for Highland Nepenthes working. It cools my 3ft x 3ft exo-terra to 12c below ambient.

    However, it's much easier to skip the foam bit. Make the smallest possible cut in the wall of the cooler to get the condenser tubes through. It's a huge pain to seal it up otherwise. I also didn't use a cold air duct like he did, and just bolted some 120mm fans (https://www.amazon.ca/AC-Infinity-C...ds=muffin+fan&qid=1555211351&s=gateway&sr=8-2) to a heat exchanger for cooling CPUs, and put them in the tank. The fans are on 24/7 and serve as air circulation, and the pumps circulate cold water/propylene glycol mixture through them when the tank gets too warm.
     
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