Chilling Terrarium Substrate with Peltier Water Cooling Block - The Planted Tank Forum
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post #1 of 8 (permalink) Old 01-28-2016, 04:45 AM Thread Starter
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Chilling Terrarium Substrate with Peltier Water Cooling Block

I have an idea in mind and I am interested to hear opinions about it.

I intend to chill the substrate of a terrarium enclosure to grow some special plants. My current idea is to use a Peltier with the chilling face attached to a water cooling block (like the one shown below) that is in turn connected to a length of rubber hose buried as coils in the substrate and with a small pump recirculating the chilled water as a closed loop.



There is a chiller assembly manufactured like this for use with small aquariums (Chill Solutions CSXC-1 Thermoelectric Aquarium Chiller), but if I build it myself I can save a hundred dollars or more.

Does anybody have opinions about this? I hope to chill the substrate by 10-15F to about 60F. By just chilling the substrate, rather than the whole enclosure, I should be able to get a greater drop in temperature with a smaller Peltier drawing less power.

Is there a best kind of small and reliable pump to use for this kind of thing? What about a best kind of thin hose? I think that quick-disconnect fittings could be handy. What about filling all of the space in the closed loop with water? Is there a way to draw air bubbles out?

Thanks for considering this!
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post #2 of 8 (permalink) Old 01-28-2016, 05:42 AM
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Usually you would want to run a t in one of the lines to a reservoir. Don't forget to run a heatsink and fan on the hot side of the peltier.
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post #3 of 8 (permalink) Old 01-28-2016, 06:06 AM Thread Starter
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Usually you would want to run a t in one of the lines to a reservoir. Don't forget to run a heatsink and fan on the hot side of the peltier.
The water in the coil won't just empty into the reservoir if I do this?

Yes of course I would build it with the complete heat sink + fan. That unit on Marine Depot is complete with everything.
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post #4 of 8 (permalink) Old 01-28-2016, 06:08 AM
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I highly doubt you can achieve 10-15F drop with a small peltier, plus copper or titanium coil(expensive!!!) would be a much better choice than rubber hose in terms of heat transferring efficiency. Even if you are able to build one to achieve the desired drop, power efficiency to run and cost of material to build the whole system is likely going to be worse than, say a 1/13 HP compressor based cooler.

Here is a video showing someone who managed to achieve 6.6C(30.7Cambient->24.1C, ~12F drop), in a guesstimated 10G tank. However, as you can see his hot side is water cooled with a decent sized radiator, running 3 fans(power supply, peltier and radiator block), 2 pumps(hot and cold). His TEC is rate at 154W max.

https://youtu.be/UhVNNZJkH38

IMHO, it might be just easier and cheaper to get the job done with a mister with water cooled by an used small compressor based cooler.
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post #5 of 8 (permalink) Old 01-28-2016, 06:25 AM Thread Starter
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I would not be able to install it with copper or any kind of metal. What if I really use a lot of rubber hose?

The Chill Solutions is apparently pretty strong. The manufacturer claims a >10F temperature drop for a 10-gallon aquarium and the customer reviews support that. Of course the heat transfer would be a lot better with the aquarium water running running right through the unit, but for my project there will only be a few gallons of soil substrate.

Here's a pretty good video review for the Chill Solutions chiller...

https://www.youtube.com/watch?v=nnFRlVDzFyY

Last edited by hydrophyte; 01-29-2016 at 04:40 AM. Reason: edit
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post #6 of 8 (permalink) Old 01-28-2016, 02:43 PM
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Floor heating coils are usually pex pipe if you were going to try this idea you might try that although metal would be more efficient.

You're basically building a computer water cooling set up. xoxide was always the go to for peltier and water cooling options when I was into computers.

You would need a computer liquid reservoir. They function in the same way your coolant reservoir in your car does. Operation the system with the reservoir open for a half hour or so will purge the air most of the time.
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post #7 of 8 (permalink) Old 01-29-2016, 04:49 AM Thread Starter
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Floor heating coils are usually pex pipe if you were going to try this idea you might try that although metal would be more efficient.

You're basically building a computer water cooling set up. xoxide was always the go to for peltier and water cooling options when I was into computers.

You would need a computer liquid reservoir. They function in the same way your coolant reservoir in your car does. Operation the system with the reservoir open for a half hour or so will purge the air most of the time.
Thanks so much for the tip on the xoxide.com site. It looks like they have good options for pumps and reservoirs. What do you think about using this reservoir + pump combination for the closed loop circulation?

https://www.youtube.com/watch?v=DkmkGBdDiCk

I think I have figured out how the make the substrate heat exchanger. I'll just use several lengths of PVC pipe connected with elbow and tee fittings, something like this...

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post #8 of 8 (permalink) Old 01-29-2016, 07:43 AM
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Lol, cap the horizontal grid either side into a T, one side entry, one side return. Get old bar fridge, water pump and hose. Drill holes in bar fridge, coil hose inside, with one end connected to intake and return respectively.... with pump somewhere in between. Use one of the commercial temperature controllers to switch the pump on when a set temperature is reached. TA DA!

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Hi. I'm back.
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