Closed Loop with Temperature Dump?

Discussion in 'Hybrid Systems' started by OceanStateTuning, Feb 25, 2018.

  1. OceanStateTuning

    OceanStateTuning New Member

    SO I have a house that I had sized for a Geothermal (3 ton) by a reputable company. I have 2 wells on my property. They wanted to drill a 3rd for $5000 to drill it, plus pump setup and I do the trench. Okay let me think about this, got to be a easier option. One of my wells is a 26' Dug well that we were planning on using as a reinjection well (well more of a dump location) and he wanted to use a new well as a supply. Sounds good but this is expensive.
    My other well I have provides about 15gpm and I have not been able to run it dry yet, I run irrigation and stuff off of it. Installer wanted to install a new well to prevent any future issues, My current well is 200', installer wanted to go 4-500' as long as he got required GPM.
    Alright so I have a backhoe and was going to trench water out to my barn this summer (About 150'), Was only planning to go down about 2' BUT in the meantime of thinking about what to do I went and bought a Fujitsu Mini split 15k btu. Went through 2 winters with this so far, I supplement it with my pellet stove on the very cold nights. I also picked up a console Geothermal unit (12k btu) used I was thinking of putting on the other side of my house from the Fujitsu. I figured when I would install my water line to my barn that I could go down 7' or so and put a slinky loop or a second run of pipe spaced in the same trench to supply this 1 ton console Geo unit - 150'x2=300' in a straight run back and forth, I could probably make this a bit longer taking a non direct route with my machine... Maybe add another 25 or 50' or so? I would think this would be fine for my 1 ton geo in works with my fujitsu.
    Well thinking about all this it made me think back about my whole house Geo Idea I was planning a few years ago and I had a thought. Why not dig as deep and as long as I can to my barn for water, Put as much HDPE in the trench. Get my 4 ton Geo (Or maybe 3 ton geo and keep Fujitsu 15RLS3H), sell the console WSHP. Install it as a closed loop system BUT put an auto fill valve in the loop (with backflow of course) and put a temperature dump. Maybe use a slightly smaller tubing size on the tempature dump than the fill (say 3/4 fill, 1/2 on dump, I think 1/2 flows around 5gpm) So basically the system would run with what it can in my ground loop, when temps start heating up too much or getting too cold, set the dump to open, will auto fill.
    I think this would waste less water (Good for my well). Reduce short cycling of pump and stuff during small temp changes. Potentially get a higher efficiency at times over a regular ground loop (closer to open loop).
    Downsides I see is I could not fill with antifreeze so I would need to dump around 33* or so during heating season. Possibly would run open all the time anyway. Possible contaminants sitting in the closed loop, though they would of went through HP in open loop anyway.

    Any thoughts on this guys? I am a DIY guy and love to get involved. I think with my unit, tubing, duct work I could be out of this for around 10k doing it this way with no more destruction of property than I was planning on doing anyway. I do not have the space for the required ground loops on a 3-4 ton system. I do not think I will run my 200' well dry with this method but I can install my irrigation off the loop so it will have new water introduced during the summer months when watering my lawn and garden to keep loops more stable. I could also instead run irrigation off my injection well instead (don't currently use as my water table dropped drastically years ago so will run dry after 15 minutes or so) My installer wanted about 40k for a full system installed. I have been very happy with my Fujitsu but using duct work would greatly help my air distribution as I do not have an open floor plan on my 2 floor house.

  2. OceanStateTuning

    OceanStateTuning New Member

    Scratch the 3 ton on the top, He wanted to do a 4 ton system, that was a type-o.
  3. ChrisJ

    ChrisJ Active Member Forum Leader

    Welcome Kyle, I am in North RI as well.

    Most any open loop use needs to be very clean water. When water temp of open loop approaches high 30's you would need to dump.

    Could you fit 3 trenches 10' apart going out towards barn?
  4. OceanStateTuning

    OceanStateTuning New Member

    My well I would like to use is 140PPM. Return well is actually 40PPM BUT That one would never be able to keep up with supply.

    I could probably do 3 trenches but I would have to cut a few a little bit short and return in the same trench. I do have a few massive rocks in my yard that may cause some issues with multiple runs.

    Planning to use my skid's backhoe it has a 7' reach and I have a 2' or 1' bucket with it. I have a full size backhoe with 14' reach and 2' bucket but that machine is pretty unreliable.
  5. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    I am running 4 tons in 6 trenches. Six feet deep 500 feet of pipe each. 250' out and straight back on either side of a 2' wide trench. Works well in m Maryland soil.
  6. Krush

    Krush New Member

    I like this approach of mitigating water quality and quantity concerns of open loop systems by making it partially closed. Maybe keep that mitigation going by figuring out a control that would keep your air source running when its over 30f or so? if your surviving as is why not experiment! and let me know how it goes:) / went?

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