The warm water defrost is interesting. About how much water do you think was used during each defrost cycle? Over the last few months, I have gone back and forth about the merits of subcooling with a heat pump. Beyond the obvious use of pre-heating domestic water, I've wondered if defrosting could be done with some of the heat that can't be readily used to heat the indoor space. One way I thought of doing this is with a water spray or a cascade, similar to what you describe. I would want to do it with a separate water source, other than the heating loop, especially if I used any anti-freeze. I'd also like to catch the runoff and reuse it, as well as the condensate.
What kind of heat exchanger did you use for the water inside your home? Water loops in the floor aren't really an option for me right now, so I'm opting for a water to air heat exchanger and fan, for the RV here. I'm considering something like this:
12x12 Water to Air Heat Exchanger | eBay
Perhaps two of them in series, to produce a counter-flow with the air stream.
I'm 29, and although I did a little bit of hacking about 4 years ago, I also wish I would have gotten into this work when I was a kid. I can't get enough, and really desire more time to work on it. I lose track of time so easily, when I'm out there bending copper.
I truly need to slow down and begin analyzing the contraptions I build, but the empirical method is so much fun! An hour or two of running a machine, and I'm ready to hack it into something better.