Cooling a Vivarium

[fiercedeity]

Hello, I've recently made an order for some highland Nepenthes in my Vivarium. Keeping the day temps at 85* will be easy, dropping the tanks temp to 55* at night will not. The plants need this drop in temperature else they'll stop growing and die. So I've been thinking of methods to cool them and the best so far is this:

1. Get a PC radiator for a liquid cooling system

2. Get an aquarium chiller

3. Prop the radiator inside the tank with a small fan behind it and recirculate fluid from the aquarium chiller.

Now that's all fine and dandy, but there's one problem... aquarium chillers cost a fortune, and I honestly can't afford one with the salary that I'm paid. (America needs to get it's act together )

So what can I do? Is there a way I could make an aquarium chiller? Or do you all have a better idea for cooling the tank? After all you guys probably know way more about refrigeration then I do. The tanks dimensions are 24X12X12 inches.

[airefresco]

For your application I would look in to Peltier panels (TEC). You would need a power source, two heat sinks, 2 fans and thats it. The hard part is controling the peltiers as you can´t use thermostat on/off as it eventually kill the peltiers. You should be able easy make something suitable for less than 100 dolars. It´s same thing that is used in wine chillers.

[Brian_UK]

As Airefresco suggests use a Peltier unit, these are the sort of electric unit fitted to picnic/camping portable cold boxes.

Maybe pick up a cheap one somewhere (Ebay?) and see what effect it has before you spend more one a proper system.

[fiercedeity]

I've done some reading on peltier chip cooling in the past. Perhaps it might do the trick. I have read a few other forums in which this method was applied and failed. I don't think the peltiers made that big of an impact on the tanks. I'm going to compare their progress and see if there are any links in their errors and possibly find a viable solution.

[mad fridgie]

I to like peltiers, but you do need to know what you are doing, another option, on the cheap, buy a second hand fridge, but a big bucket of water inside, cool down over the day, pump water to vivarium at night, control pump on thermostat.

[fiercedeity]

Just as I remembered. Peltier chips have a fairly low efficiency compared to compression units. It's a shame too, they're so quiet compared to a fridge.

(This is where I was going to post URL links to sites showing examples and failed attempts, but this site apparently won't let me do that till I get 15 posts. GOOD JOB)


Maybe they're doing something wrong? Maybe I'm missing something here. But I really would love for this to work as an option for my tank, it's a lot less bulky then a fridge. Any ideas to make this work?

I to like peltiers, but you do need to know what you are doing, another option, on the cheap, buy a second hand fridge, but a big bucket of water inside, cool down over the day, pump water to vivarium at night, control pump on thermostat.

Ha, I actually have a mini fridge that I ripped apart outside. I was thinking of stuffing all of it's guts under a table and putting the main cooling "fin" into the terrarium to have it cool the tank... But it seemed a little bulky so I put it on hold, just in case I find a better method.

[Brian_UK]

You may have already looked here on your researches but it is a useful resource.

http://www.tetech.com/index.html

[fiercedeity]

You may have already looked here on your researches but it is a useful resource.

Whoa! Those are amazing! And expensive... But just what I had in mind! Now to backwards engineer one into something I can use... Any tips on a DIY system?

[Magoo]

Hi and welcome.
So what planet have you arrived from, and what the hell is nepanthes and a vivarium, and where is your location fro ro.
Are you visiting us from the "other side".
Curious Magoo

[fiercedeity]

Hi and welcome.
So what planet have you arrived from, and what the hell is nepanthes and a vivarium, and where is your location fro ro.
Are you visiting us from the "other side".
Curious Magoo

Ha! Well I'm a collector of rare tropical Nepenthes. A plant found mostly in Borneo. The tip of the leaf grows a long vine and at the end of it grows a large, colorful, ornate pitcher. The pitchers themselves are actually stomachs the plant uses to feed and contains a variety of digestive enzymes. They have even found the remains of small primates in some and the largest of the species can hold about a gallons worth in fluid. They have an extremely fast micro evolutionary rate, unheard of in most plant species. This causes a rapid diversity in plant varieties, shapes, and colors. I'd love to post some links and all but this damned forum has a 15 post minimum till I can paste a single URL. So just google image these words up, you might be surprised that what your looking at is just an extension of a leaf...

"nepenthes villosa"
"nepenthes hamata"
"nepenthes lowii"
"nepenthes bicalcarata"
"nepenthes edwardsiana"
"nepenthes truncata"

The only bas part is that I have a bad habit of buying the rarest varieties which also require special attention. N. Villosa needs a night temp of 55*... And that's why I'm here. Some on the others need a constant 80* temp. And others just enjoy living around the house. They're really fun to grow.

Well an aquarium is for fish, a terrarium is for terrestrial animals, and a vivarium is for plants.

I live in a small town in Virginia, Front Royal. It sucks. It's a culturally dead area full of rednecks who are as ignorant as rocks... Sorry, I shouldn't have insulted the rock like that. Still I want to move away but there's no damn jobs hiring... sigh

[airefresco]

Whoa! Those are amazing! And expensive... But just what I had in mind! Now to backwards engineer one into something I can use... Any tips on a DIY system?

Apparently it´s all down to the heatsinks with peltiers. If you get the heatsinks right they can work quite well for smaller applications like this. As you say though, they are not terribly efficient, but they are cheap and quite and simple to construct.

You can get the actual peltier plates for more or less 10 dollars on ebay. Then you need to apply a heatsink to either side of the plate and a couple of fans. I have a wine chiller in the workshop right now and on that the hot side heatsink is much bigger than the cold side heatsink. That I believe is running with 2 x 35w peltiers and on a empty fridge will get the temperature from +25ºc down to about 12ºc in about 15 minutes, so they do work if done right.

If this was my project I would start out with a somewhere around 40-50w peletier, a normal computer cpu heatsink/fan on the cold side and a bigger (maybe twice the size) heatsink/fan on the hot side and use that as a base point to see how cold the air is leaving the plate. Once tweaking that I would build a second, exactly the same so in effect you have one plate cooling 12x12x12 cube and another cooling a 12x12x12 cube, rather than one plate trying to cool a 24x12x12 cube. If anything goes wrong with one of them, at least you still have half a system working.

If I remember when I´m in the workshop later, i´ll take a picture of the wine chiller setup, so you can see how the plate/heatsinks/fans are constructed.

[airefresco]

Ok I measured the wine chiller and the volume is not that much different to the of the vivarium you have. The internal dimmension are 300mm x 200mm x 920mm. The big difference though is inulation. I am assuming that the vivarium is glass on every side. If you were able to insulate some of the sides at least, it would help. I would up the size of the panels to compensate for the heatloss through the glass.

This is one of the two identical plates on the wine chiller. The hot side heatsink is 150 x 130 x 45mm (not including the insulated part), The cold side heatsink which is 85 x 85 x 10mm.

As a test you connect 12v DC straight to the peltier, but it would need some proper control when everything is working.

I hope this is of some use to you.

[fiercedeity]

Ok I measured the wine chiller and the volume is not that much different to the of the vivarium you have. The internal dimmension are 300mm x 200mm x 920mm. The big difference though is inulation. I am assuming that the vivarium is glass on every side. If you were able to insulate some of the sides at least, it would help. I would up the size of the panels to compensate for the heatloss through the glass.

This is one of the two identical plates on the wine chiller. The hot side heatsink is 150 x 130 x 45mm (not including the insulated part), The cold side heatsink which is 85 x 85 x 10mm.

As a test you connect 12v DC straight to the peltier, but it would need some proper control when everything is working.

I hope this is of some use to you.

Actually it really is, thanks. But as far a permanent 12V DC source, could I use one of those adapters that plug into the wall? You know, those things with round plug at the end? Is there some way I could hook that up as a permanent power supply?

[airefresco]

Yes and no. The power supply must powerfull enough to take the load and then a bit of spare, just in case. So you need to calculate what the total load is. For example say you have a peltier rated at 50w and then two fans at say 10w then you would need a power supply that is able to take at least 70w. Those numbers are purley as an example, your load I expect would be larger than that, but you would have to calculate that when you´ve sourced all the parts. I doubt the power supplys you have in mind would be powerfull enough. A computer power supply would do the job while you get things started.

This is where the controls part comes in. When you´ve got something that works you need a way to stop the peltier without distroying it. This where I am a bit sketchy, but from what I can gather if you just simply stop the peltier (like with a thermostat or switch or something) the plate over time can become damaged through the temperature difference accross the panel. You have to reduce the voltage gradually while the sides balance out. So you would have power supply - controller - peltier. Like I said I´m a bit sketchy on the controls side of things, but i´m sure someone will chip in shortly to fill you in and tell you i´m completely wrong with my understanding.

[fiercedeity]

Yes and no. The power supply must powerfull enough to take the load and then a bit of spare, just in case. So you need to calculate what the total load is. For example say you have a peltier rated at 50w and then two fans at say 10w then you would need a power supply that is able to take at least 70w. Those numbers are purley as an example, your load I expect would be larger than that, but you would have to calculate that when you´ve sourced all the parts. I doubt the power supplys you have in mind would be powerfull enough. A computer power supply would do the job while you get things started.

This is where the controls part comes in. When you´ve got something that works you need a way to stop the peltier without distroying it. This where I am a bit sketchy, but from what I can gather if you just simply stop the peltier (like with a thermostat or switch or something) the plate over time can become damaged through the temperature difference accross the panel. You have to reduce the voltage gradually while the sides balance out. So you would have power supply - controller - peltier. Like I said I´m a bit sketchy on the controls side of things, but i´m sure someone will chip in shortly to fill you in and tell you i´m completely wrong with my understanding.

Hmmm, that's a problem. I already have a device that is designed to turn the power off when a certain temp is reached. It's not designed to step the power down at all but to just stop.

[Brian_UK]

From what little I've been reading on the web it seems that switching Peltiers full on and full off is not a problem for the device itself but for the temperature control.

The hot side will bleed it's high temperature back through the cold side thereby raising the 'cooled space' temperature. So keeping the hot side fan ON will help or having a controlled flap over the cold side to isolate the Peltier from the cooled space.

[fiercedeity]

From what little I've been reading on the web it seems that switching Peltiers full on and full off is not a problem for the device itself but for the temperature control.

The hot side will bleed it's high temperature back through the cold side thereby raising the 'cooled space' temperature. So keeping the hot side fan ON will help or having a controlled flap over the cold side to isolate the Peltier from the cooled space.

Well I have a nice 3.5L X 3.5W X 2H inch heatsink that I could use for the hot side and 1.5 X 1.5 X 2 inch heatsink for the cold side. Sound good? Or do I need a bigger heatsink?

[airefresco]

The bigger one might do for the cold side, although it is a little too thin. The hot side needs something much bigger, something around 6 inch. I assume your measurements are in inches.

This pdf gives a very good explanation in how to setup TEC´s. Some of it looks daunting at first, but if you read through it a few times, it starts to make sense. It really is not as complicated as it first appears to be. There´s also an excellent section on heatsink selection.

You could of course cut all this trouble out and just buy a pre-made one, but where´s the fun in that?

[fiercedeity]

Ok I measured the wine chiller and the volume is not that much different to the of the vivarium you have. The internal dimmension are 300mm x 200mm x 920mm. The big difference though is inulation. I am assuming that the vivarium is glass on every side. If you were able to insulate some of the sides at least, it would help. I would up the size of the panels to compensate for the heatloss through the glass.

This is one of the two identical plates on the wine chiller. The hot side heatsink is 150 x 130 x 45mm (not including the insulated part), The cold side heatsink which is 85 x 85 x 10mm.

As a test you connect 12v DC straight to the peltier, but it would need some proper control when everything is working.

I hope this is of some use to you.

The larger of the two heatsinks should work very well for the cool side, I counted 88 fins total which should be plenty of surface area for the job. But I think I'll go online and browse for a larger heatsink for the heat side like you said.

Oh don't worry about control, I got that figured out. I'm using an old PSU for a computer as the power source. I'll rig the PSU to run by jumping pins 12 and 13, hook the molex up to the peltier, and have my Zoo Med Hygrotherm Humidity & Temperature Controller turn the peltier on and off when the tank see's fit. It should work, in theory... The Hygrotherm is said to have up to a 1000W of control power.

Well, wish me luck. I'm gonna get to work putting this all together. I'll stop by if I hit any bumps and give a report whether it works or not.

[airefresco]

That will work as a test, but you will burn the peltier out if you run it like that constantly. You need to have a peltier controller between the zoomed (depending which controller you have) or power supply and the peltier, you could even damage your zoomed controller running it like this. Which ZooMed controller have you got? If it´s the rheostat one, I don´t think you can use it for this application.

[fiercedeity]

That will work as a test, but you will burn the peltier out if you run it like that constantly. You need to have a peltier controller between the zoomed (depending which controller you have) or power supply and the peltier, you could even damage your zoomed controller running it like this. Which ZooMed controller have you got? If it´s the rheostat one, I don´t think you can use it for this application.

No, its the Hygrotherm model. It controls up to 1000W of power. Has a programable screen to keep day temps in a certain range by turning on/off heating and cooling devices. A second plug is to control the % of humidity in the tank, and thus turns on/off said devices. Plus it has a light cell for special night temps. Which is exactly what I need to keep everything in working order for my tank. It also has a probe that goes in the tank and moniters the temp and humidity.

[airefresco]

Right OK, I know what you have now. So run the power supply from the Hygrotherm, then connect the TEC straight to the power supply. When you get a TEC controller sorted, that will then go between TEC and power supply. I thought you planning on plugging the peltier straight in to the Hygrotherm and that would be a big no no. Don´t run it too long like this though. Just long enough to make sure it works as you need, then sort out a controller.

[fiercedeity]

Right OK, I know what you have now. So run the power supply from the Hygrotherm, then connect the TEC straight to the power supply. When you get a TEC controller sorted, that will then go between TEC and power supply. I thought you planning on plugging the peltier straight in to the Hygrotherm and that would be a big no no. Don´t run it too long like this though. Just long enough to make sure it works as you need, then sort out a controller.

Yeah, AC power for a DC TEC would be very bad. However I don't know what a TEC controller is really, I did some google searches but came up with a bunch of random devices and no real correlation between any of them.

[airefresco]

The controller is going to depend on your electronics skills. If you are not very knowledgeable about electronics than it is probably best if you just buy a controller. It likely wouldn´t be able to work from the Zoo Med though. If you are able to make you own, then you can link it in to the zoo med (or not if you don´t want) and save yourself quite a bit of money. Here is an example of a TEC controller. If you can understand this, then you could make one.

[fiercedeity]

Good new! I have tested my cooling device and have found positive results! At first I tried it in my tank with no insulation and had little success. It went from 75 degrees to 70 and then jumped up to 79. I thought this would happen, so I tried it again with an insulated box and got amazing results! The box started at 75 degrees and dropped down to 55 degrees in 25 minutes! I'm very impressed by this, and the temp kept dropping! I let it run for 2 hours and it stabilized at around 39 degrees. These are very good results and I couldn't have done it without the help of everyone on this forum, thank you! Pictures anyone?

[airefresco]

Good to hear it is working. What did you end up using?

[fiercedeity]

I used and old LGA 775 Heat sink from a PC. A 350 Watt PSU from another old PC. A Corsair Liquid cooling system. And 1 TEC1-12706 91.2W TEC unit. It looks good, need to work on the wires but I'll work on the cosmetics later tonight. I'll see if I can get some pics up later. Might have to do a couple bumps to get myself up to the 15 post minimum for URL uploads. :/

[fiercedeity]

Well the unit is working great. I had a hiccup along the way and the liquid cooling system cogged out on me. Apparently it was a faulty model. So I got another one and everything has been running smoothly since. Also, I promised some pics and so far I have failed to deliver. But here they are! I know I'm a few months late but I'm sure no one here will hold it against me.

Cooling unit with (makes a great condenser)


Radiator to pump heat out of tank


And the tank itself (yes I know it's a bit dark)


One of my plants


Another plant



Comments appreciated!

[Brian_UK]

Thanks for the update and the pictures, glad it's up and running.

[MikeGui]

Very nice set up fiercedeity! Could you share that with the folks at aquariacentral.com? There are a lot of vivarium keepers there who would be very interested in your DIY project!

[fiercedeity]

Very nice set up fiercedeity! Could you share that with the folks at aquariacentral.com? There are a lot of vivarium keepers there who would be very interested in your DIY project!

kk, posting now...

also, I made this to show the whole thing...

http://www.youtube.com/watch?v=M3LMnqslbXA