So now, after I replace it, how can I protect the new unit? A camera and a motion detector are what I thought of first, but I am also interested in securing the unit to its concrete pad. Anyone have any ideas? How do I defend against bolt cutters?...
The guts of the HVAC were stolen from the house I'm buying as well (Dad and Uncle currently own it). My Uncle, after replacing the unit, had a cage fabricated that's a little bit larger than the unit, and still allows air flow. It's bolted to the pad the unit rests on.
It's technically not 100% secure, but it will take would-be robbers about 10x as long to get into it as before. I imagine you could do something similar with a chain link fence and locked gate, or something more decrotive (depending on how visible it is). Basically, make it so that the only way you could get "in" to it to service it or gut it would be to first open the gate(s) and/or remove a cage.
I had considered putting a decorative lattice work fence/gate system around the 2 outside units at my current home, just to hide their ugliness, but also to create a little shade (hot Texas Sun, heard you could boost effciency a tiny bit shading systems in the sun, and mine's positioned on the South side of the house) and provide a bit of security as well, but never got around to it. I think as long as you do it the right way you will not create any hinderance to air flow and still be able to access it for service.
Another alternative is to use a geothermal system, which will have everthing burried and out of sight (and I think efficiency get boosted BIG TIME, virtually free passive AC!!). DavidL, don't you have experience with these? They cost more to install, but have long-term savings. I'm considering using it when I get to the HVAC and water heating portion of my big project