sizing question for loop field

Discussion in 'Vertical and Horizontal Loops' started by eternallearner, Jul 13, 2014.

  1. eternallearner

    eternallearner New Member

    Have been learning a lot lately about Geo loops and decided to design one for my home while I had the need to destroy my yard anyways for some other projects.

    Ran a manual J on my home and from the best I know of it and the internals it is showing me with a heating load of 29514 and a cooling load of 20362.

    But am looking to expand the home and add some additional square footage as well as heat the 2 car garage partially. Which has led me to want to size this system to approx 4 tons to ensure adequate coverage for the new areas. ( I realize this basically throws the manual J out the window) but figured it would be a decent idea as to the current loads. The expansion will increase the house by a third or more depending on some design elements.

    Would like to use this for hot water as well so there is that to consider on top of the rest.

    I live in Eastern Tennessee with a semi moist clay. All the digging I have done that is the only soil type I have run across on my lot.

    My thought for the loop is 7 300' runs of 3/4 hpde pipe set in a trench configuration sort of. I could not find an exact configuration of what I am thinking but from all I have seen and read I think it should work.

    Basically would be a down and back 2 times for each loop stacked with 1' between each run. Then a second loop set on the other wall of the trench 16" apart.That would repeat twice then the last run would be the same as the first two but a loop ran in between. Making a sort of 6 pipe configuration.

    Deepest pipes at 8-9'.

    distance between trenches 2'. Could possibly go 3 I think if it will help it out.

    Is the loop a feasible design and layout with enough support for what I want to do?

    Going to put the manifold inside the house so can cut zones easily. Would also like to be able to monitor each zone just to see how it functions. Yeah I like all the detail stuff and saving data. Might help me down the road. Or someone else.

    What pump size would you recommend for a system with this setup? Once inside the loop will run to a 1 1/4 manifold and travel either 3' to the heat pump or 10'. Either configuration will use 6 fittings. The system will reside in the basement and will be more or less on level with the system + or - 1 ft with the loop.

    Debated 1 1/4" pipe but the cost difference for the efficiency seemed lacking. Not sure if it would make the pump end of things better or not. Have not really worked on that end a whole lot yet.

    Been a lot of learning to configure one. More than I originally anticipated for sure. Thank you for all your help in this. Interesting to learn for sure.
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    The gross rule of thumb is once you exceed 200' the cost differance for 1" pipe vs. 3/4" pipe is off set by the gains you will see in pumping costs as it relates to " feet of head and friction loss ". Also for a DIY install I strongly recomend a non pressurised flow center.
  3. eternallearner

    eternallearner New Member

    Thanks for the tip on that. I was wondering at what point that point would break over. I have done a lot of different things with plumbing but never has there been a reason to worry about the efficiency of it. Just hook it up and make it work. Learning to tweak a system for maximum efficiency throughout is definitely new. Really liking this process.

    Why would you recommend a non pressurized system? Just due to the possibilities of leaks? Or is there more involved in the math?

    I know more pressure=more flow but also equals more power to drive it. Plus the ground will only absorb so much so fast per given length of pipe no matter the speed. Plus faster= less transfer time. So give and take I suppose. Is that why?
  4. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    A non pressurised system is more forgiving of DIY errors in your connections that may occur. The industry standard for closed loop circulation is 3GPM per ton. That is the speed at which it must travel. The pressure that is maintained during that trip is not important.
  5. eternallearner

    eternallearner New Member

    What are the benefits of pressurized vs non pressurized?
    like you said non pressure is less prone to leakage as the fittings arent stressed as much.
    Is a pressurized system more efficient despite needing a stronger pump to maintain the pressure?

    That is one of the parts I am trying to learn about. How to find that balance. I know I can get water through it and get the required flow but doing it efficiently is different.

    As far as the rest of my op how close am I with sizing and will that configuration be feasible?

    Thabks a ton for your replies. Definitely helped a ton.
  6. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Non pressurized is easier to add brine to if needed and to some degree burps it's own air out. They are definately more user friendly, but both work
  7. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Your pipes seem to be too close together, try to keep them spaced at least 2' apart.It can support 30 kbtu/h load, but that load suggests more a 3 ton rather than a 4 ton system. If you want to leave room for expansion, than your loop should also sized larger, to support a 4 ton load in the future.
  8. eternallearner

    eternallearner New Member

    Hmm will have to do some rethinking on the system in that case. I was going by some designs I had seen from various sites and software demos. That and going by how close the slinky design is I figured a foot would be ok.

    what calculations did you use to arrive at that? So I can work to resize this thing.

    why is slinky so close and ok but straight needs so much room?

    Sorry for all the questions but this is as much academic for me as practical. I really want to understand this as I think I must be missing something that will just make me go duh at the end and get it.

    Again thank you all for the help actually talking to people rather than just researching does help answer some questions I have been pondering.

    Been looking at your site and love looking at the systems you have installed. Very informative. Also make me miss NY. Grew up there on the St. Lawerence. Lovely area up there.
    Last edited: Jul 18, 2014
  9. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Slinkies usually have at least 18" pitch, that means the majority of the pipe is 12-18" apart. But you still need 30% more pipe in order to compensate for the overlapping of the slinky. then after 3' you keep some space between the slinkies, allowing some heat to travel upwards between the trenches.

    I did not calculate this particular design, but I am doing this for a while...

    Why don't you run 6 trenches, 2' wide, 8' deep, 300' long, 10' O.C., running 0.75" or 1" pipe out there and back (600' pipe per circuit). Then you have enough pipe in the ground for 4 tons, and a you get the 11-12 GPM of flow recommended with a single grundfos 26-99 circulation pump.

    For me, the oat important advantage of non-pressurized flow centers is the lack of pressure fluctuations due to different temps between heating and cooling operation. No pressure fluctuation, no dissolved gasses participate out of the water, no bubbles form, no loops get air locked, happy home owner happy installer who does not have to come back an re-purge the loop. Plus if micro bubbles participate out, the micro bubbles get all purged out by the canister before they can accumulate.

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