AC Cooling Unit for Highland Nepenthes Terrarium

Essentially I've just taken a 6000 btu a/c (I got for free off kijiji), opened it up, removed the evaporation fan (the one that looks like a hamster wheel), moved the temp sensor off the cooling rad. Then I bent out the front cooling radiator so that I can insert it into my terrarium. I didn't modify the wiring or anything else on the a/c so it's not that hard to do if you're interested in a nice cooling system. I ran the a/c for 10 minutes with no insulation, just open in my room (23 Celsius); I got temps of 5 Celsius off the rad, and the whole rad was frosted. I'm going to hook the a/c up to my hygrotherm temperature control device so that it can turn it off and on when needed. Here's some pics:

On the left is the front cooling rad from the a/c I pulled out of the box. And on the right is the ac after i put it back together.
http://img141.imageshack.us/img141/2162/img2739c.th.jpghttp://img143.imageshack.us/img143/7956/img2738w.th.jpg


Last thing to do is insulate a section of my tank, and then drop the rad in. I'm going to place some cpu fans on the rad as well to stop it from frosting. Also I need to insulate the copper piping that runs from the compressor to the cooling rad. I'll post some more pics soon. I get a couple of the frosted over rad, it looks really cool (no pun intended)
Smile

I'm going to move all my plants out of my tank and into another temporary one so that I can run some tests. I'll post all my info here.

I chose an a/c because they are made to be run for long periods of time, unlike fridges which run off and on. So I shouldnt have any problem with burning out the compressor.

Here are some more pics I just took.

A/C Running for 2 minutes - you can see the frost beginning to build up and the temp went from 23 celcius to 7.

http://img341.imageshack.us/img341/3319/img2741j.th.jpghttp://img706.imageshack.us/img706/4554/img2742wv.th.jpg


Here's is the a/c after running for about 6 minutes or so - more frost, and cooler temps Smile.

http://img716.imageshack.us/img716/227/img2743j.th.jpghttp://img24.imageshack.us/img24/2158/img2744k.th.jpghttp://img535.imageshack.us/img535/8912/img2745of.th.jpg



And here is a rough design I drew up in mspaint. pink is insulation.
http://img638.imageshack.us/img638/7674/designl.jpg

I bought some pipe insulation and insulated the copper piping that runs from the compressor to the rad. Ran the a/c and didnt get any frost build up on the pipes, except for the parts that were exposed. I also got some insulation for the tank.

Here's some pics of the tube after I put the insulation on. Tests are pending me getting my tank insulated at the moment.

http://img810.imageshack.us/img810/5470/img2765q.th.jpg

 

Update:

I'm currently rewiring my a/c so that the compressor and fan come on when i plug the unit in. Currently the unit goes to a standby mode when power reaches it, which is not what i want; i need the unit to come on when it gets power. All I'm doing is inserting a toggle switch between the fan/compressor and the power outlet and bypassing the whole digital control unit.

Here's is what the wiring diagram looked like originally:

 

And here is what it looks like after I bypass the whole control unit. Also note that I didnt have to use the fuse as my AC's power cord already has a breaker in it.

You really don't need high fan speed so just cap it with a wire nut or nylon wire joint. If you plan to use a SCR type speed controller then use the high speed winding and cap the low speed (this is only if you want to control the speed of the fan on the AC, I opted not to do it). If you ever want to quiet it down then put a ceiling fan speed controller on the high speed winding. Note that those are SCR and not dimmer.  A junction box would make the wiring much safer and neater. You can drill a hole in the cover for the toggle switch. Run the power in through a strain relief connector. The inline fuse holder and all wire connections inside the box.

For the switch, get a 3/4hp SPST switch (Single Pole, Single Throw). They're like 5 bucks at CAnadian Tire, see here: http://www.canadiantire.ca/AST/browse/3/HouseHome/2/Electrical/LightSwitches/PRD~0528329P/Gardner-Bender%252BGSW-11%252BSwitch%25252C%252B0.75%252BHP.jsp?locale=en


Essentially I'd suggest that if you want to do this modification it would be best to use an a/c that uses knobs and turns on automatically when power reaches the unit so that you do not have to rewire the thing like i have to. If you use a digital one, make sure it has an auto start feature.

I'll update once I finish up the wiring.

Update:

I've completed the rewiring. It was fairly easy and straight forward.

I just had to take the low fan speed wire and the compressor power wire, join them and then attach them to one end of my switch. Then I took the power wire and hooked it to the other end. Now the A/C turns on and off with the flick of a switch and I was able to bypass the whole standby feature. I'll post some pics tonight.

I plugged it into my hygrotherm temp and humidity control unit and it works great
Smile. I then ran the A/C for about 5 minutes and the whole rad was covered in frost. Temps on the rad were about 5 degrees celcius. I then placed a fan behind the rad and the temps dropped down to -8 in about 2 minutes. Now I just need to finish insulating the tank and I'll be able to run some tests. Looks promising Smile.

I'm on the fence on how to setup my fan system for the rad though. Anyone have any ideas? I was thinking I would either place the fans directly on the rad but the temps get quite cold, or box the rad in with insulation and then have one fan blow air out and one blowing into the box (like i showed in my crappy mspaint diagram).

 

I have a plastic cover which protected the evap fan from hitting the rad. I'm thinking of mounting it back on and putting a high CFM computer fan on it. see the pics below.

http://img227.imageshack.us/img227/3379/raddesignfanoptions.th.jpghttp://img37.imageshack.us/img37/2115/img2776n.th.jpg


I'm thinking of using either 2 of these:
http://www.sohodiffusion.com/prod/16138/SCYTHE-ULTRA-KAZE-120MM-HIGH-STATIC-PRESSURE-FAN-3.html

or one of these:
http://www.sohodiffusion.com/prod/15319/ANTEC-TRICOOL-BIG-BOY-200-CASE-FAN.html

 

Update:

I went with the Skythe Ultra Kaze I got the fan and spliced the wires and soldered them to a DC 12v adapter, and covered the soldered connections with shrink wrap. The fan spins at 3000 RPM and pushes 133 CFM, it's so fast that I accidentally got my finger in the way and it cut me twice before I could move it lol.

Anyway, I mounted the fan on the shroud and ran the A/C for 30 minutes. I got temps of about -3C in my room which was about 25-27C and I got NO FROST on the rad! So it's all good to go into the tank now for some tests
Smile.

 

Update:

Silicon came loose and fell out of the shroud. I suspect that the plastic I used to fit into the shroud is slightly too malleable and warps and bends with temperature changes. I now took a hard plastic bucket, shoved it into the hole and then cut around the hole. Then I siliconed the hell out of both sides, let it dry and then applied another layer. It seems to be holding strong now. I also fashioned a stand to place the AC on next to my terrarium. All is a go for tests once I have some spare time, which should be soon I hope  :). Here's some pics of the finshed shroud.

 

Update:
I got the fan and spliced the wires and soldered them to a DC 12v adapter. The fan spins at 3000 RPM and pushes 133 CFM, it's so fast that I accidentally got my finger in the way and it cut me twice before I could move it lol.

Anyway, I mounted the fan on the shroud and ran the A/C for 30 minutes. I got temps of about -3C in my room which was about 25-27C and I got NO FROST on the rad! So it's all good to go into the tank now for some tests
Smile. I'll post some pics tonight Smile.

Build complete!

http://farm6.static.flickr.com/5062/5603904076_468e4445f4.jpg
Cooling System COMPLETE! by robthered, on Flickr

http://farm6.static.flickr.com/5306/5603320951_e73c3a8d4f.jpg
Cooling system by robthered, on Flickr

So far so good. When i run the system the humidity drops but the fogger quickly comes on and compensates. I only tried it for a bit but it seems to work great. Doesnt come on too often once the desired temperature is reached. I'm not running it at the moment as the temperatures are still cool enough for me to cool the tank by opening a window. So the summer will be the true test. Will update when I start using it more.

 

Update:

My current settings are:

Day: @ 26c the AC comes on and cools the tank down to about 21-22c. Rise and repeat.

Night: @ 15c the AC comes on and cools the tank down to 13c.

You can find these pics in my photo album as well with comments and whatnot.  

http://farm4.static.flickr.com/3440/5819683258_f18cbda78f_m.jpg

Above: I ditched the old shroud I made cause i was afraid of losing too much humidity while the AC was running. It takes my temp controller about a minute to realize the humidity is dropping before it turns on the fogger. So I put the whole rad in a plastic box and shoved the fan behind it between the two. I then cut a hole for the fan to pull in air and another in the other side to push out. Works really well this way and the lowest the RH drops is to about 65% now.

http://farm3.static.flickr.com/2559/5819683122_77cdfab2a5_m.jpg
Above: I put a cardboard box on the back of the AC so that I could vent out the warm air that the AC emits when it's running. I was going to mount it directly in the window like a normal AC, but I cant move my setup cause it's too heavy and would be more work.


http://farm3.static.flickr.com/2483/5819120869_383785f488_m.jpg
Above: another shot from a different angle.


http://farm4.static.flickr.com/3248/5819682884_bc90660dcc_m.jpg

Above: Another shot.

 

If you have any questions about how to make a setup like this or are just curious about it, you can find me on the OCPS website and send me a PM there.