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Window AC to water chiller conversion

Discussion in 'Heating or Cooling of your AP system.' started by Ronald Lao, Apr 2, 2015.

  1. Ronald Lao

    Ronald Lao Member

    Joined:
    Mar 19, 2015
    Messages:
    38
    Country:
    Philippines
    State:
    Not Applicable
    City:
    Pasig City
    Hi All,

    For my AP system, I found myself in need of a water chiller. But commercial chillers that are available in my area are too small for me. The largest I've seen is for around 200 gallons. So I decided to make my own chiller from an old AC unit and some other spare parts.

    This conversion is not for everybody because it might not be economical for small systems and it needs skilled ref technician to do the conversion. But I'm outlining how I did it and if you want you can follow what I did and just hired my friendly neighborhood Refrigerator Technician to do the other parts of the build for me. Total build time is about 3 hours.

    [​IMG]
    Start with an old thermal bucket or the like. I used an old 18L thermal bucket.

    [​IMG] [​IMG]
    Look for a matching stainless steel tub that will fit inside the thermal bucket.

    [​IMG] [​IMG]
    Make an inlet hole near the bottom where your aquaponic water will go in. Then put a piece of connector for easy attachment to your AP system. I used a 1/2-inch PVC pipe as the inlet and used a bigger sized clear tubing as the connector.

    [​IMG] [​IMG] [​IMG]
    Make an outlet hole near the top. Ideally, the hole should be opposite your inlet so that the water will be forced to travel around the stainless tub to maximize the time your water is kept in contact with the cool stainless tub. For the outlet I used a 1-1/4" PVC, it is important that your outlet be a lot bigger than your inlet. The reason is that you use a pump for the inlet so it's pressurized while the outlet only acts as an overflow and you will allow only gravity to dictate the outflow of the water. Another thing to consider is that the outlet height should be lower than the stainless steel tub as it sits inside the thermal bucket. This is to ensure that there is a separation between the liquid inside the Stainless steel tub and the water from your AP. I used an A+B Epoxy to secure the PVC on the side of the thermal bucket.

    [​IMG]
    Next you need to form the copper tubing into a coil inside the stainless steel tub. This is just done manually and carefully. If you need more info on this just google "Wort Chiller" for more detailed instructions. In my case I used up 32 feet of copper tubing. Try to form the copper tubing as close to the sides of the stainless steel tub.

    WARNING: For the next section, I highly advice that you seek professional help in disassembly and assembly of the AC and cooling parts since you are going to be dealing with pressurized gasses that can go as high as a couple hundred PSI.
    As I'm not a Refrigeration Technician, some of the words I use may be more descriptive in nature rather than the proper terminology. I apologize for that.

    [​IMG] [​IMG]
    Take your old window-type AC and remove the blower section. This includes the housing, the plastic face, the controller and even the blower fan. You will have to cut the blower from the fan motor. This will leave a barebones of only the condenser unit, the condenser fan and fan motor.

    [​IMG] [​IMG]
    Next it's time to connect your "wort chiller" copper coil into the compressor. I don't have a closeup picture but if you look closely on the 2nd picture you will notice a smaller copper coil that connects to your wort chiller copper tubing. I was told that this acts like a pressure builder valve before the expansion of the gas where it absorbs heat (hence the cooling effect). The 2nd pic was taken when the technician was charging the system with the refrigerant gas.

    Sorry no pics for these but let me just describe the wiring. The fan motor is directly connected in parallel with the compressor. This means that my fan will run when the compressor runs just to make things simple. If you want some sort of control, you can plug the whole unit into an electronic on-off timer. Another way is to buy a thermostat controller and just connect it in series with the compressor/fan motor. I plan to use both, the On-off timer will control what time the cooler should be operating (say 11am to 3pm). I will also have a thermostat to control the temp of the stainless steel tub.

    [​IMG]
    This is the final product. I used the empty space left when I removed the blower section of the aircon to put my thermal bucket. So now, everything fits the original AC base.

    NOTE on Refrigerants:
    Some might notice that the compressor of my final build is not the same as the compressor found in my aircon. I decided to change the compressor and use the one from an old freezer that I'm not using anymore. The reason is that the window AC I have was using R22 as the refrigerant while the freezer unit was using 134a as the refrigerant. Although according to what I read, R22 can be as much as 40% better than 134a in cooling efficiency it is not an earth friendly refrigerant like 134a. Hence, I decided to use 134a.

    NOTE on Copper Tubing:
    Copper coils are generally not good to be in contact with your AP water. I am told this is because as your system becomes acidic your copper will corrode and it will kill your fish. Hence, this design compartmentalizes the copper tubing inside the stainless tub. HOWEVER, if you are able to find somebody who can make stainless steel tubing and turn it into the "wort chiller" coil style, you can directly cool your AP water. Just remove the stainless steel tub and put the stainless steel tubing directly inside the thermal bucket.

    INITIAL TESTING:
    [​IMG]
    I put in some water into the stainless steel tub enough to cover at least 85% of the copper coil. The water is just to help the thermal conduction between the copper coil and the stainless tub. Turned on the compressor and after 15 minutes, the water went from an ambient temp of 30 deg Celsius to 18.6 degrees celsius (65 deg F). WOOT!

    For the final installation, I'm planning to use a water/coolant mixture of 8:2. According to what I've read so far, 20% coolant mix will be enough to deter corrosion in the copper coils but still maintain a good thermal conduction. This mixture will also give some anti-freeze property to the tune of -12 deg celsius (10.4 deg F).

    I'll probably have the whole system integrated into my AP in a day or two. I need to do a little carpentry work to make a table for the chiller. I'll send an update when I'm done.
     
    Last edited: Apr 2, 2015
    Asia-Off-Grid and kissweld like this.
  2. Simonb

    Simonb New Member

    Joined:
    Mar 19, 2016
    Messages:
    1
    Country:
    Indonesia
    State:
    Sulawesi
    City:
    Bitung
    Take a look at some of the Scuba Diving Compressor shops in Manila or Cebu and find where they get their 1/4" Stainless High Pressure Tube from. This can take 300bar and will not kill the fish :)

    I'm just about to put my system online and may consider something like this for times of the day when we have 'spare electricity.' Would you mind letting me know how big your system is and how many watts the compressor is? i can't see it being viable for my system size but curious to follow what you discover.
     
  3. Murray

    Murray Site Admin Staff Member

    Joined:
    Jun 4, 2009
    Messages:
    7,635
    Country:
    Australia
    State:
    Queensland
    City:
    Brisbane
    Great post Ronald.
    Keep us posted. Most of us could not do that because we do not have access to the gas pumping gear. Pity. The idea is really good.
     

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