We have gotten a few quotes over the years, all too expensive to ever pay back. We don't have air vents upstairs, so we are going to go mini splits instead. I was told there are a few problems with heat exchangers in ponds:
1. Vinyl tubing will float up if air gets in the lines when you purge. Need to throw something over the top like chain link fence to keep it down and that is expensive.
2. Radiator-style heat exchangers get life and muck on them. If you have zebra mussels, they will clog it all up. You need to clean them often for best performance.
3. In our northern climes, they will get a pretty thick layer of ice on them depending on the weather. It takes a long time for the ice to melt when it is in the pond bottom. Enough ice will get it to float and potentially break lines when it merges with the surface ice and blows around.
They recommend trenches and wells instead.
In my case, the coil and trench length needed is about 30ft shy of reaching the pond. There is no point to go into the water.
If you can place the exchanger near flowing water, you may have better luck with freeze issues, or a massive area for heat exchange. Oversize it a fair bit.
