Jeramy,
It is true that gas pressure can increase significantly with temperature and these are balanced systems in a sense. They rely on air flow to keep the pressure in check. The condenser, evaporator, and fan air flow are designed to work within the limits of the compressor capability and tolerances of the rest of the components. As air flow is restricted, either by dirt or bent fins, in the condensor, you work the system much harder with higher pressures and also reduce the overall cooling performance. There is a comb tool that the HVAC folks have that can straighten the condenser fins. While he has it out the fins should be straightened and you should be sure that the condenser has been cleaned. From what I saw in your photos the dirt level did not obscure the tubes so my guess is there should have been reasonable air flow. I have to assume that the other side of the condenser was similar in appearance but maybe not given that looks to be the side air flow eminates from.
From a failure analysis point of view, what one would expect if this was a pressure fail, is that the weakest pressure component in the system would fail. Usually in a HVAc system there is a means of excessive pressure relief, sometimes a metal plug in the dessicant container. If your weakest pressure point was the copper, it would have produced bulging and thinning walls at first, followed by the thinnest point giving way, blowing outward. I see none of that indication here in your photos. This looks like a metal fatigue fail due to the vibration of the compressor causing the metal to fatigue and fracture. Soft thick wall copper would be better a better choice and perhaps some means of tubing support at some distance above the compressor, to dampen the copper pipe amount of vibration would help. The photos show a tall vertical run of unsuspended copper tubing left to oscillate which can accelerate the metal fatigue fail. The compressor is the vibration generator but the moment arm of unsuspended piping can actually be the root cause. Hope this helps.
later Ed
