Just move up to grand Junction and am working for a outfit that does alot of commrercial refrigeration, Anyway I have run across at least 3 systems walk in freezers that are running 404a. Problem I'm seeing is high head pressures and or compressors out on internal over load. Usually when I check them they are running low superheat 3-9 and high subcoolng 40+. When I start to adjust charge it willl not keep temp inside box. Only happens when ambients reach over 105. I suspect the systems are undersized and the tech before me is overcharging the system. Also does 404 usaully run at such hi pressures, 350 to 370 with 105 to 111 outside.one more question where is the best place to check sub cooling? at evap, liquid line or at condensor liquid line? And I have always checked superheat at evap, and used pressure at compressor suction port, is this correct. These systems are measured in ounces and I'm use to working on large ac systems, It's been a good learning experience and i've really had to study up on all the new freons and such.