Bring the lake to the house?

Discussion in 'Surface Water Loops' started by graydon, Sep 26, 2012.

  1. graydon

    graydon New Member

    I have read lots and lots and so far have seen noone do this. I am thinking about bringing the water from the bottom of our lake through a 2" pipe up to my house. In the house, I'll have a heat exchanger to transfer the heat from the lake water to a process fluid (antifreeze) which will then go through my Waterfurnaces. I'll use a big Grundfos pump to pump the water from the lake and through the heat exchanger. Calculations from the Grundfos spec sheet indicate I should be able to flow at least 200 gpm through this 2" pipe. I'll use a VFD to control the speed of the pump according to inlet and outlet temperatures in the heat exchanger. As the outlet gets too cold, I'll speed up the pump. The process fluid will run through a coil of copper tubing in the heat exchanger (a basic shell and tube heat exchanger) thus delivering the lake's heat to the Waterfurnace.

    My question is this, if one were to run your pond loops with copper tubing with water constantly flowing past the loops (which is essentially what is happening in my heat exchanger), how many feet of copper tubing would I need per ton? What do I need to figure out in order to make this prediction?

    Any ideas?
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    You only need to figure out how cold the outlet water can get to. That is why this doesn't work in northern climates (don't know where you are).

    If you have water coming in at 36F in the middle of winter, it gets pretty difficult to pull heat out of it without freezing everything up. Of course you can just pump like hell to keep a temperature drop down to only 1C. But still...

    Anyway, your best bet is to use delta t's as a flow control.
  3. graydon

    graydon New Member

    Agreed on the freezing. We're in Michigan. I expect best case the water from the lake will be about 39 deg F and at low flows, I need to pump it back to the lake before it goes below 32 degF. I can control the pump with thermocouples in the water to make sure the pump turns on when the water approaches 32 degF. Also, the water will pick up a little heat in the ground on the way back to the lake because the plumbing is all well below the frost line. So, best case, I should have a 7 deg delta T and over 200 gpm heat source. That should work out to roughly 700k BTU/H. Correct?

  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    Yes about 700 kbtu's. But that is a lot of pumping. More like a placer mining operation:)

    You won't pick up much ground heat at those flows. If you did, it would quickly cool the ground anyway.

    You will want to be a few degrees above freezing for your shutoff.

    I do know a diy who did this in my area. He proudly told me how he only has to switch to wood heat for a few months in winter:( Not really a system I can recommend to my clients, but you seem prepared.
  5. Howard Ek

    Howard Ek Member

    I have done it with a well. If you are interested, PM with your email address.

    Howard J. Ek, PE

    You can have it with quality; You can have it fast; You can have it cheap. Pick any one. :D
  6. graydon

    graydon New Member

    Thanks, I would like to hear what you did. My email is graydon at gdsamps dot com I couldn't find the link to PM on this site.

  7. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    The coldest point is not at the end of the discharge line but inside the heat exchanger, where you need a certain delta t differential to transfer heat!
    Similar in closed loops, the loop never freezes, it is always the end (exit) of the heat exchanger!
  8. jrh

    jrh Member

    How are you going to keep the fish out?
  9. graydon

    graydon New Member

    My youngest son is a great fisherman. I am going to station him by the inlet with his baddest fishing pole. :)

    Seriously, I put well points on the ends of both pipes. I don't think I really needed it on the discharge back to the lake, but if I ever wanted to switch pipes, or use both as suction lines, I could do so.
  10. zacmobile

    zacmobile Guest

    I shudder to think how much it would cost to move that volume of water, is there a reason why you don't want to put the heat exchanger in the lake?
  11. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader


    Or just go pump and dump
  12. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I have mentioned this before about biologics. do not underestimate the ability of bilogic beings or material from fouling a well screen/point. Everything from tad polls to the green and brown algae blooms on the intake and discharge. Useing raw water here from a surface supply was tried and abandoned more than once.
  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    I've come to understand the lake is not one we can put pond loops in.
  14. tugguy

    tugguy New Member

    What is meant by the statment the lake is not one we can put pond loops in?
  15. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    I visited the project. The lake was not the sole property of the original poster.
  16. tugguy

    tugguy New Member

    Ahh sooo Bummer well I own mine so that hurdle is jumped now for the huge rock and dam between my basement and the pond!

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