Quote Originally Posted by digerious View Post
i was taught in college that when a system has run, not slightly short, or nearly empty of gas, but roughly at half charge, the mixture has the capacity to cut away at the orifice seat and allow more refrigerant through than is required, causing flooding to comp.
What they taught you at college is indeed correct. I had this happen in a system that had been undercharged and ran for a long time. The system was a blast freezer running R502. At the end of the cycle when there was little load we started to get flood back. That was an easy one to figure. The process is called wiredrawing. It seems to be more pronounced on ammonia systems. Steam does this as well. Anytime you have a mixture of liquid and gas this can occur.