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  1. #1
    Join Date
    Oct 2008
    Location
    Northeast PA
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    257

    Geothermal Parallel well installation

    Thanks for reading.

    I am a licensed water operator with plenty of experience with wells and piping. I am building a house and hired a contractor to install my HVAC system using a loop configuration consisting of two wells, each well is 300 feet deep. My system is a 4-ton system.

    My question is about head loss. The two wells are 15 feet apart and the 1.25 inch pipes from one are mated to the other in parallel and then two pipes enter the house using the same size 1.25 inch pipe. In the parallel connection they used two T connections and two elbow connections. They placed the straight side of the both T connections on the same well making it a straight shot from house to the first well. They then used the side out of the two T connections followed by two elbows to the second well. In simplest form this means the first well has a straight shot to the house and the second well has 4 elbows.

    I would think a balanced flow is important in this type of situation and if they had used one sideout T on one well 1 and one on well 2 they would have achieved balanced flow from both wells.

    Can someone please tell me if this should be an issue or not? Will the flow rate differ between both wells? Since the ditch is still open should it be changed?

    I spent a lot of money on this system to achieve a efficient system and I don’t want to see it not work as well as it should just because of this.

    Thanks,
    John

  2. #2
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    Parallel wells is common. The major point is to have the correct circulator flow. The well tubing should be the same length and and diameter. Fitting losses are most likely insignificant in your case.

    paul

  3. #3
    Join Date
    Oct 2008
    Location
    Northeast PA
    Posts
    257

    Important to be right.

    Thanks for the post but I really need a definitive answer. I’ve attached a picture. Some of my reading suggests that the flow being the same among the wells is important. I may have to sit down and do some math but I don’t know enough about these systems and the pipe to make a lot of sense from the math.
    Attached Images Attached Images  

  4. #4
    Join Date
    May 2005
    Posts
    161
    Those lines coming off the "T" going vertical in the picture......... do they both go into the same well? If so that's wrong. If they go to seperate wells then you'll get equal pressure drop through each well.

    My concern is the fact that you used 1 1/4" for your two loops. To get peak efficiency you'll need to push 18 gpm through your loop to get proper turbulence in each parallel loop (9 gpm each). Your heat pump probably only needs 10-12 gpm though. What kind of flow center are you using?

  5. #5
    Join Date
    Oct 2008
    Location
    Northeast PA
    Posts
    257
    2 lines from the sideout T and through the elbows go to one well. The other well has a straight shot.

  6. #6
    Join Date
    Oct 2008
    Location
    Northeast PA
    Posts
    257

    Pictures

    Here is another picture which shows the piping and the wells as the pipe goes into them.

    I'm very tempted to have them run all 4 pipes into the basement and then header them into the pump. It seems since I'm so close to the house it might be nice to monitor temperature from both wells.

    Thoughts please!

    John
    Attached Images Attached Images  

  7. #7
    Join Date
    Oct 2008
    Location
    Northeast PA
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    257
    Quote Originally Posted by crash11 View Post
    Those lines coming off the "T" going vertical in the picture......... do they both go into the same well? If so that's wrong. If they go to seperate wells then you'll get equal pressure drop through each well.

    My concern is the fact that you used 1 1/4" for your two loops. To get peak efficiency you'll need to push 18 gpm through your loop to get proper turbulence in each parallel loop (9 gpm each). Your heat pump probably only needs 10-12 gpm though. What kind of flow center are you using?
    Just the information I'm looking for.

    The flow center is a black module looking thing which is just two pumps mounted together with barbed fittings. I didn't get the pump info but I will. As I recall them saying that the pumps are attached going out and comming in to the house, push/pull configuration.

    Even if you're right and I need 18 GPM there can not be equal flow through both wells due to the piping.

    Can someone that knows this pipe do the head loss math and let me know the difference?

    Thanks,

    John

  8. #8
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    After seeing the picture, you're fine. Since the majority of the pressure drop is in the actual vertical loops, any small pressure drop difference from the main line to the bore hole is insignificant. The sizes step down from the main header to two equal sized lines.

    paul

  9. #9
    Join Date
    Oct 2008
    Location
    Northeast PA
    Posts
    257

    Pipes are all the same size

    Quote Originally Posted by tecman View Post
    After seeing the picture, you're fine. Since the majority of the pressure drop is in the actual vertical loops, any small pressure drop difference from the main line to the bore hole is insignificant. The sizes step down from the main header to two equal sized lines.

    paul
    The picture does look as though the pipes are smaller going into the wells.

    The pipes are smaller from the T to the wells. it drops down to 1 inch.
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  10. #10
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,375
    I,ve looked at your picture.
    I prefer to see a header instead, but it still can work with what you got!
    Question:
    are the loops the same length?

    If so, you should had one tee on each side, not the same side; like a reverse connection! This will make sure you get the same amount of resistance and water flow!

  11. #11
    Join Date
    May 2005
    Posts
    161
    This is true (in response to tecman). The flow rates through each loop will only differ by 10% at the most I'm guessing. Also, with a 2 pump flow center you should be able to get the flowrate you need (do you know if they are Grundfos up26-116 or up26-99 pumps?), but the problem may be that to get good heat transfer in your loop you won't be able to get good heat transfer in your unit. Does your unit have 1" fpt ports? I have a 4 ton Florida Heat Pump unit and it came with 1" ports. Flowing that much (~18 gpm) through those ports is risky because of erosion.

    If you do plan to bring the 4 lines into your basement, you may as well cut those t-fittings out and re-route them while you're at it. However, it's not imperative.

  12. #12
    Join Date
    Oct 2008
    Location
    Northeast PA
    Posts
    257

    Update and MY mistake.

    I had to get in the ditch and measure the pipe and the pipe to/from the house is 1.25" and the pipe from the T connections is 1". As was said earlier this makes it a much better situation. I still would have rather seen the pipes run differently but this certainly is acceptable.

    My unit is a 4 ton unit with 1.25" connections. I didn't note what the circulators were but I will and let you know.

    The unit gets turned on tomorrow and I'm sure it will work just fine.

    After all the money I've spent on this I really want low monthly bills to make up for the extra cost. My wife was never completly on board with the extra money and I sure would like to show that it was worth it.

    Thanks,

    John

  13. #13
    Join Date
    May 2005
    Posts
    161
    Quote Originally Posted by jongig View Post
    I had to get in the ditch and measure the pipe and the pipe to/from the house is 1.25" and the pipe from the T connections is 1". As was said earlier this makes it a much better situation. I still would have rather seen the pipes run differently but this certainly is acceptable.

    My unit is a 4 ton unit with 1.25" connections. I didn't note what the circulators were but I will and let you know.

    The unit gets turned on tomorrow and I'm sure it will work just fine.

    After all the money I've spent on this I really want low monthly bills to make up for the extra cost. My wife was never completly on board with the extra money and I sure would like to show that it was worth it.

    Thanks,

    John
    Now we're talking. Now the ideal flow rates for the unit and the loop match (~12 gpm) so all you have to do is set up your valves to achieve that 12 gpm (I may go a touch higher just because of the slight difference you'll have between each loop........maybe 13 gpm). Does your unit have pressure curves? Mine came with a little table that tells you what pressure drop you get at various flowrates through the condenser. I plotted the data in Excel to form a curve. Then I hooked up some pressure gauges on either side of the unit to read my pressure drop so I could back-figure what kind of flowrate I had.

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