Quote Originally Posted by mytekcontrols View Post
If the discharge pressure gets too high during start-up/cool-down, it dumps some of the refrigerant gas into the expansion tank to lower the amount of refrigerant circulating in the system. This reduces the discharge pressure, and then slowly meters the refrigerant back into the system via the expansion tank captube. Since the gas source is taken after the 1st phase separator, we leave the bulk of the highest boiling refrigerants (as separated condensates), to continue the work of cooling the succeeding stages, so that eventually enough of a phase change has occurred in the other circulating refrigerants to keep the discharge at a more reasonable pressure.
I love explainations like these. Well said.

I knew why you used the valve, but not how or where. Great idea.