Brought to you by: Ted's Aquarium
This chiller is made from a used dehumidifier. It works by keeping a small tank (the insulated box) of freshwater cold and then circulating the cold water through a heat exchanger in the sump as needed to cool the aquarium. In my case, I have used a coil of 1/2" Polyethylene hose as the heat exchanger in the sump. There are other (more reasonable) variations to this if you don't mind spending a little more money. I will discuss variations at the end of this documentation.
My unit has been working perfectly since April, 2002 and can produce 2300 BTU (about 1/6HP). With the amount of hose I have in the sump, I can utilize about 1/2 of the full capacity. It would take 35' of hose in the sump for full capacity (assuming 55 degree chiller water temperature). The insulated tank works well, and even though the unit is always on, it only runs when it is needed - in other words, there is not a lot of waste in keeping the water cold all of the time.
If you decide to attempt this project or need more information,
email me - I would love to hear how
your system works. I am also interested in any ideas you may have for
Why a Dehumidifier?
I browsed the web for a long time looking for ideas, and I could not find any DIY chillers that made sense for my tank. Using a small refrigerator is one idea that you can find, but it is not powerful enough to cool anything but a small tank with a small heat load. I also found ideas about converting a window air-conditioner, but that would take me about 4 years to complete. I literally tripped over this idea in my workshop one evening when I walked into my basement dehumidifier - I still have the bruise to prove it. A dehumidifier is basically an air-conditioner that reheats the air after it is cooled. Normally, a 25Qt/Day unit is equipped with a compressor that operates around 1/6HP. The construction and refrigeration circuit design are perfectly suited to this project.
Dehumidifiers are readily available, cheap ($140 Bran'-spankin'-new), and are very easy to convert to a chiller. My project cost me about $60 in addition to the dehumidifier and was up and running with about 6 hours of work.
The down-side is that it is somewhat large, and probably a little less electrically efficient than a commercial chiller. Its not the sort of thing you want sitting around in your living room. There is also a small amount of maintenance (keeping the tank filled with water and an occasional cleaning. I have other ideas below that solve these problems, but I do not know if they will work as well. If you try one, please let me know how it turns out.
Unfortunately, if you want the tank temperature to be stable, you will STILL need a relatively expensive temperature controller to operate this unit and your heater . There is a possibility that you can tweak the snot out of this setup allowing the pump to run constantly and using your heater to make up the difference, but it would take a long time, a lot of experimentation and would not be electrically efficient. If you would like to try, I recommend setting the chiller thermostat to just below your water temperature, and if needed, shorten the tubing in the sump until the chiller can not quite keep up with the load (in other words, the aquarium temperature starts to drift up). Then, turn down the chiller water temperature a little more until the aquarium water remains cool. You will be able to tweak the chiller water temperature as need throughout the year to try to minimize the time that your heater is on. Personally, I like the controller idea better.
Finally, if you are lucky (and weathly) enough to have more than one tank, you can use one chiller for multiple systems. This obviously assumes that your chiller has the capacity to handle the total load of all of the tanks. You would do this by using a pump and sump coil for each tank that you wish to cool.
When you need to find anything I have used or recommend using on this page, please check McMaster-Carr Supply at www.mcmaster.com. They are a wealth of DIY hardware at great prices. If you don't like mail-order, chances are that there is a McMaster branch store within reasonable driving distance of your home.
(1) Dehumidifier - a 25Qt/Day unit will operate at about 2300BTU or 1/6 HP.
(1) Water Cooler Thermostat - http://www.mcmaster.com part number 30045K99 (I paid $12.00).
(1) 7-1/2 Gallon Vinyl Wastepaper basket.
(1) Smallest powerhead you can find.
(1) Powerhead or Pump capable of about 100GPH at 5' head (I recommend RIO 2100 or 2500 or equivalent).
35' of 1/2" OD polyethylene tubing or black garden irrigation tubing.
-OR- 2' of 1/2" OD Titanium tubing - McMaster Part #89835K63.
Foil covered Insulation board.
Aluminum Foil Tape.
Pipe, 1/2" ID vinyl hose, hose clamps and 1/2" pipe insulation to suit your setup.
Titanium heat exchanger:
In order to make the system more efficient in the sump, 18 inches of 1/2" Titanium tubing will do the same job as 35' of plastic tubing. Titanium tubing is expensive ($35 for 5'), but it would obviously be nice for small sumps. You could theoretically cut the tube into a few (or many) pieces and use hose to connect them together as needed to fit into the sump. If you do this, you will need to be very careful to make tight joints to prevent the chiller water from leaking into the sump. Definitely do not use any chemicals in the chiller water if you plan to try this - unless you can make all joints outside of the sump.
You can use a much smaller pump with this variation because there is less pressure loss through the much shorter run. The object is to get about 100gph for maximum efficiency.
I have found that you can use a standard tubing bender (for steel or copper tubing) to bend Titanium tubing. This picture shows a shape that I bent using a 1/2" tubing bender rented at a local rental center. The coil hangs over the side of the sump, with the connections on the outside. The tubing is pretty tough, but with a little muscle, you can bend it to any shape that will fit into the sump. For full chiller capacity you need about 18" submersed in the sump. My design is overkill, but I did not want to cut the tube which came in a 5' length.
Conceivably, you could pump the aquarium water through many small (6" ?) pieces of Titanium tubing, interconnected with hose and strapped to the cooling coils of the dehumidifier. I suppose you could also bend a single piece as an alternative.
You would have to try to find a way to maximize contact between them by running the Titanium tubing in parallel with the aluminum dehumidifier coils (typically up and down). I would recommend trying to bend the aluminum tubes slightly so that two or four of them could be strapped around one Titanium tube with wire ties. The entire cooling coil would have to be fully insulated without restricting air flow to the condenser (hot) coils. To maximize efficiency, you would want to have the aquarium water start at the warm end of the cooling coil and work its way to the cold side. (the cold side is the side with the small copper capillary connected to it). I have no idea how efficiently this would work. If you do not transfer enough heat, the dehumidifier will shut down on low pressure.
The nice things about this scenario are that there is no cooling water to maintain, and you do not need to replace the humidistat with a thermostat - just turn it all the way up or short it out.
You will definitely need to use an aquarium temperature controller to start and stop the chiller in this method. The pump can run continuously or turn on and off with the chiller.
I am really interested to know if anyone tries this! Please email me with results or information!
Thanks for visiting!