Using a pond

Discussion in 'General Discussions' started by Rob McDaniel, May 4, 2018.

  1. Rob McDaniel

    Rob McDaniel New Member

    I’m looking to build on a lot with a pond. It is 160’ diameter and 22’ deep and at least 20’ deep across almost 100’ of the width. I’m still learning and need some advice as to whether this volume of water is enough for a 6 ton system? I may not need that much but I want to over figure and see what is realistic. I’m in the Saint Louis Missouri area.
  2. Rob McDaniel

    Rob McDaniel New Member

    These measurements are actual measurements NOT estimates. I went to the pond and measured carefully with a weight and tape measure for depth.
  3. mtrentw

    mtrentw Member Industry Professional Forum Leader

    Here is an extract for some numbers i ran a couple years ago when discussing a 1/4 acre pond at 12 foot depth. Since your pond is closer to 1/2 acre and 20 feet, I'd say your probably gonna be OK. You may get notable ice buildup around the loop so ensure it is well weighted down with nearly a ton of weight or otherwise anchored so you don't float the loop.


    Just to play with numbers:

    Assume it is a ¼ acre. Average depth of twelve feet. That would be a total of 3 Acre Feet of water, or 1 million gallons.

    To freeze 32 degree water requires 1,200 BTU per gallon.

    To freeze the pond solid requires 1.2 billion BTU, or 100,000 ton-hours. Or 4 ton of continuous cooling for 120 days.

    What gets complicated is the heat loss from the surface and heat gain from the earth below.

    I can’t imagine you’d freeze it solid, and I am assuming heat gain from below would be greater than heat loss from surface. In effect, you have 10,000 square feet of heat exchanger (water) in contact with earth below and the HDPE pipes are a secondary heat exchanger from pond water to heat pump. I’ve kinda accounted for the heat loss from above, by using an average depth of 12 feet in order to discount the 1 to 2 feet of ice present due to natural heat loss.

    Also need to think when heating, maybe 25% of your heat is from the electric to run the heat pump.
  4. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    You are good for 6 tons.

    Heat from the ground will replenish what you take out.
    At the bottom, the pond will maintain 39F due to stratification (convection). You can't freeze the pond with a 6 ton heat pump, even when running 24/7/365 in heating mode.

    We are burying 6 ton horizontal loop field in a lesser area, with not convection of water.

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