Just want some thoughts from this forum on the topic of using a Thermal expansion valve vs a piston or orfice in residential central a/c unit. I came across a study that was done on the amount of refrigerant charge that was in completed installs. And the results showed that the vast majority of installs were undercharged. Now from what I believe, a txv valve will be better in a unit that is not properly charged. The performance will be effected by about 5% decrease . However in a fixed orfice system, an inaccurate charge will result in a 15-20% loss of performance. So the real trick is to get the charge right in fixed orfice system and it will perform comparably to a txv equipped system. Your thoughts please. stiz