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Thread: Want to use my existing central A/C to chill water tanks

  1. #61
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    Chilling the water the way you want, for the use you want, won't be a thermal battery, more like a thermal capacitor.
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  2. #62
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    Quote Originally Posted by beenthere View Post
    Chilling the water the way you want, for the use you want, won't be a thermal battery, more like a thermal capacitor.
    I agree. I refer to "battery" and "capacitor" interchangeably, depending on context.

  3. #63
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    Quote Originally Posted by Gernby View Post
    I plan to achieve long cycles at part load by using a thermal battery.
    You are proposing to do it using an inherently inefficient method, with equipment that was not designed for the operating conditions that will be required though.
    The controls required to prevent damage to the equipment, at the evaporator temperatures you will need to get the air cold enough to cool the water enough to be useful, will be short cycling the equipment.

    I'm not saying it can't be done, it just won't gain you the energy savings you are after, will most likely require more energy, and will cost a lot of money to implement.

  4. #64
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    Quote Originally Posted by mark beiser View Post
    You are proposing to do it using an inherently inefficient method, with equipment that was not designed for the operating conditions that will be required though.
    The controls required to prevent damage to the equipment, at the evaporator temperatures you will need to get the air cold enough to cool the water enough to be useful, will be short cycling the equipment.

    I'm not saying it can't be done, it just won't gain you the energy savings you are after, will most likely require more energy, and will cost a lot of money to implement.
    It took at least 20 years for me to realize how valuable a "devil's advocate" is for a development project. They make it so much easier to refine a strategy (or abandon it). For that, I greatly appreciate your input! It helped me abandon the strategy I proposed in my first post. However, the refined strategy does not have the deficiencies or risk that you are talking about. I'm not going to bypass anything, or overload anything. I'm just going to pump water through a heat exchanger in the supply duct while the system is at medium or light load.

    Since my hybrid analogy wasn't convincing, another analogy would be driving an 18 wheeler through the mountains. A novice truck driver would let off the throttle while going down hill (engine brake), so they don't violate the speed limit, then they would stomp the gas once they hit the bottom of the hill, in a lame attempt to maintain an acceptable speed. However, a pro would build as much safe momentum as they could going down the hill, so that they can make it up the other side more efficiently. I think most would agree this strategy would also result in less wear on the truck's engine.

  5. #65
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    A Pro truck driver still leaves off the throttle(80,000 pounds comes down a hill fast). He just doesn't use the brakes as often. So not a good analogy.

    A better analogy is. You load up the back of a pick up truck with as many deep cycle batteries as it can hold. You then hitch up a toll able friction drive generator to the pick up. And have it set up that it only generates electric when your not driving up hill. The 15 MPG pick up now only gets 6 MPG. But once the batteries are fully charged(60 gallons of gas later), you have electric for 2 days.
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  7. #66
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    I think we all understand your idea...
    The problem lies in the implementation.

    You are planning to have a 1000 gallon storage tank of water...

    Then have a pump cycle the water into a heat exchanger to chill the water through the supply air in the home.

    You do understand that depending on how high the water flow is, the supply air trying to cool your home will dramatically raise in temp, causing your house to cool significantly slower... It may actually raise your home temp.

    Water has a lot of heat energy... and it transfers it rapidly.
    The TRUE highest cost system is the system not installed properly...

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  8. #67
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    I made a LOT of progress on my proof of concept this weekend! Below are some pictures, starting with the "before"...
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  9. #68
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    Once I add some additional support under the box for the blower, I will get that hooked up, then install the ducts. I ordered a air to water heat exchanger, but I haven't decided whether I should mount it before or after the blower. I have space for it on either side of the blower, so I'd really like to know whether there are any reasons to go one way or the other. Does the blower normally "push" through a coil, or does it sometimes "pull"?

  10. #69
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    Where are those ducts going out of the top of that box? Into the house?
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

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  11. #70
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  13. #71
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    Quote Originally Posted by rider77 View Post
    Where are those ducts going out of the top of that box? Into the house?
    There is one 12" return duct that will go to an upstairs bedroom, and two 10" supply ducts that will go to a downstairs hallway and an upstairs media room. The system will be sealed, and the air will be circulated by a Goodman MBVC1200 blower. I just need to figure out whether it would be better to push or pull the air through the air to water heat exchanger.

  14. #72
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    I also need to add some internal "air guides" or walls to optimize air flow across / through the mini-split. I want the mini-split to move its own air, so I do NOT plan to completely block air from bypassing it. I will control the speed of the MBVC blower, speed of the mini-split, and target temperature of the mini-split using a micro-controller (Arduino Tian), while monitoring multiple temperature sensors located inside the box. The same custom controller will monitor electrical load of the MBVC and mini-split (indoor and outdoor), in order to optimize efficiency.

  15. #73
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    Here is a sketch, showing the 2 locations I'm considering for the air to water heat exchanger. Obviously, I will need to build a water-tight drip pan under the coil.

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  16. #74
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    It is AGAINST CODE to move air into the living space from the garage. What your building there is illegal. And dangerous
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

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  17. #75
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    Quote Originally Posted by rider77 View Post
    It is AGAINST CODE to move air into the living space from the garage. What your building there is illegal. And dangerous
    Yeah. BeenThere pointed that out last week, but that's not going to stop me from proving the concept. I wouldn't do this in someone else's house, but I won't hesitate to build it in mine. If it works as well as I hope, then I'll either relocate the system, or build whatever around it to make it compliant.

  18. #76
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    BTW, if the air flowing through the system in the garage is not mixed with the air in the garage at all (completely air tight), would that still be a code violation? I know that I have AC ducts running above the garage ceiling, which are just separated by some sheet rock from the garage space.

  19. #77
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    Thread moved

    This is clearly not AOP but an experimental build therefor seems like Members Inventions would be a better match.

    Note: Per warnings posted by our membership there are critical code issues here and we (HVAC-Talk.com) do not condone this procedure.

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  21. #78
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    Quote Originally Posted by Dad View Post
    Thread moved

    This is clearly not AOP but an experimental build therefor seems like Members Inventions would be a better match.

    Note: Per warnings posted by our membership there are critical code issues here and we (HVAC-Talk.com) do not condone this procedure.
    Okay. Thanks! I didn't know there was a member inventions forum.

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  23. #80
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    Quote Originally Posted by joeysmith View Post
    That's a good find! Thanks for sharing it!

    It seems their product already proves the strategy I'm going for. However, it seems like their approach would be better if they offered an "ice battery" that could be stored inside the cooled space. The units they show on their site both have the ice battery incorporated into the outside unit, which has a huge footprint. It is insulated, but it will still absorb plenty of BTU's through the insulation. However, if the ice battery was stored inside the cooled space, any BTU's that leak through the insulation would just provide ultra-cheap cooling to the cooled space.

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