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  1. #1

    Homebrew ground source hydronic cooling

    I bought a house last year that has forced air heat but no A/C. It does however, have a well. I'm in MN where the annual temperature average is 40-45, therefore so is the groundwater. In the past I've heard a lot about home made well water powered cooling. Farmers running water through an old truck radiator with a fan behind it, etc. Strangely though I can find little to no info about such projects on the net.

    Anyways, I got my hands on the 4-4.5 ton evap coil seen in the picture below (cased). I plan to install this on top of my upflow furnace and run water through it at whatever rate needed to about maintain geo temp. The liquid line is of course the bottle neck, but in this size coil it's 3/8" which should be good.

    Now, here's the question. I think my furnace is a two speed, and I could just set the thermostat to FAN: ON (which will be the lower speed, I assume) and run downstairs and turn the water on until my house is cold. But I don't seem like the kind of guy that would be happy with that, do I? Rather, I'd like to wire in a 24v solenoid valve to the PCB on my furnace so I can set the temp on my thermostat, so the water goes on, and the fan goes on high, when it's time to cool.

    As shown in the pictures, there's only three wires running from the thermostat to my furnace and I understand I need to run another for from the Y post to the Y post on the furnace PCB.

    Then were do can I hook up the solenoid?

    I see this forum discourages DIYers doing standard HVAC projects, but hey this is not a project for a HVAC profession so hopefully this isn't inappropriate here. Any help would be much appreciated.
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  2. #2
    Join Date
    Jun 2011
    Location
    Hammond,La.
    Posts
    1,176
    You will probably have better luck with that here

  3. #3
    Didn't see that, thanks. I was going to repost there and delete this one but I see I can't post file attachments in that forum for some reason. Maybe an admin can move it?
    Last edited by tartrazine; 07-10-2011 at 02:57 AM.

  4. #4
    Join Date
    Jun 2011
    Location
    Hammond,La.
    Posts
    1,176
    They may move it.
    I have two wells I have been thinking about trying to do some geothermal cooling tests with myself. Maybe one day I will actually have some time to do it.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,058
    Sorry, but wiring still falls under the no DIY rules. It doesn't matter if its something that is normal for HVAC or not.



    Moved to Residential geo/water source forum.
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    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Mar 2007
    Location
    Cedar Rapids, Iowa
    Posts
    121
    That coil will not work. It is designed for refrigerant, not water. You will have to find a water coil for your experiment.

    Bergy

  7. #7
    Join Date
    Jun 2011
    Location
    Hammond,La.
    Posts
    1,176
    I was going to play around with a few compact car radiators. lol

  8. #8
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    Quote Originally Posted by Bergy View Post
    That coil will not work. It is designed for refrigerant, not water. You will have to find a water coil for your experiment.

    Bergy
    I concur. The coil needs to have more rows and a much lower pressure drop. A well study needs to be performed if you are planning to draw and return to the well. Unlike a true geothermal which can have COP s of 3 to 5 plus, you are limited to the direct exchange. The hp of the pump and hp of the blower needed to push air across a coil with much higher static is the kicker which makes this idea not so attractive.

  9. #9
    your water temp prolly isnt cold enuff to do any dehumidifying either.

  10. #10
    Hey you guys should really rename this forum the No Fun Club.

    Ok naysayers:

    "It won't work"
    Did you miss the part where I'm running 45 degree water through a 4.5 ton coil? This is in a 1500 sq ft house. So I need about 1.5 tons of cooling for this to work great. And as I said, I'm not reinventing the wheel here. Lots of people do the same thing, I've heard about it numerous times since I was a kid. I'm in MN remember where we have hot humid summers but cold well water and plenty of industrious farmers. I just didn't find much info googling this.

    "That coil wasn't made for water"
    Did I seem unaware of that? That's why I'm using a coil 3x the size I would need on a split system. It's an r22 coil btw with a 3/8 liquid line as the bottleneck. Also, hydronic coils are expensive and uncommon used, and all the ones I've seen are designed for hot water only and so won't direct water from condensation to a drip tray.

    "Needs more passes"
    That is a valid consideration. It's a four pass coil though so I should work pretty well. I may add a second stage if necessary. I figure I can use something flat like a radiator or oil cooler even as I can mount it horizontally above the A coil and the condesation would just drip onto the A coil below.

    "It won't dehumidify".

    It's my understanding that an evap coil in a typical split system operates at about 40 degrees. So if I can get mine to close to the geo temp, let's say the coil is at 50 degrees (with a lot more surface area). If my house is at 72 and I get to a dewpoint of 50 degrees that's 45% humidity.

    But...since you guys aren't interested in this project, I'll assume you won't want me to post any updates with my results, right?

  11. #11
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    I can not speak for all of the others here but it is wrong to jump on the defense. There are a lot of very smart people on this forum.We are all here to learn. If your idea works for your application, then more power to you. We are all interested in your findings.

  12. #12
    Join Date
    Mar 2007
    Location
    Cedar Rapids, Iowa
    Posts
    121
    Quote Originally Posted by tartrazine View Post
    "That coil wasn't made for water"
    Did I seem unaware of that? That's why I'm using a coil 3x the size I would need on a split system. It's an r22 coil btw with a 3/8 liquid line as the bottleneck. Also, hydronic coils are expensive and uncommon used, and all the ones I've seen are designed for hot water only and so won't direct water from condensation to a drip tray.
    The 3/8 inch is NOT your bottleneck... The eight 1/8 inch lines are!!

    Bergy

  13. #13
    Join Date
    Jul 2011
    Location
    Minn
    Posts
    9

    your coil

    I am in Minn too,back in the 60s i seen a system like what you are working on. It was made with a 5ton coil You need to remove the cap tubes and replace with 3/8s to a 3/4 header for water flow. a little work. temp from your vents 65 to 70 deg. last week it would have worked good. about 200 gal. per hour down the drain. good luck ed

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