Quote:
Originally Posted by Vern2
If periods of time the ground source is depleted, can the ground source be used for summer cooling. Then during summer cooling the ground source can be replenished for the winter heating.
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This is absolutely the case. The only gotcha is that if there is water flowing through the loop field it will carry away heat stored during the summer... on the other hand, it will also carry away any cold stored during the winter.
Quote:
Originally Posted by Vern2
I would think, but have no idea... If the ground source is depleted at a fast rate that might mean the ground loops are working very well (removing heat). Then you might jump to the conclusion that replenishing the ground source might be very successful as well.
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My knowledge is incomplete, but I have seen that heat in the ground moves very, very slowly.
To help me understand it, I imagine it to be like cold molassas flowing in from surrounding sand. When you first start extracting the stuff, it comes out pretty easily. But then the 'make-up heat' (molassas) flows in from slightly more distant sand (tales longer), and so on and so forth.
If your heat pump's extraction rate is matched by the long term heat-flow rate of the heat soil (molassas sand) then you should see a temperature decline which finally levels off and your heat extraction is matched by the migration of heat to the boreholes, for the duration of the winter.
If the decline rate is fast it means that the heat pump is removing heat faster than it can "ooze in". So then you need either more loopfield, or less heat extraction (possibly conservation through auxillary fuel or better insulation, or perhaps wiser use of the heat produced).
So the proceedure is
Dig a test hole, or test trench, and test it to see what it's steady-state heat production rate is per foot.
Next you need to find out what the heat load is for your house or shop or water heater or whatever.
Then you divide the heat load by the heat produced per foot, and you will know what the minimum amount of borehole is required to do the trick. More than that is gravy.
-AC_Hacker