An operator at a cold storage facility notices violent foaming in the compressor's oil sight glass immediately upon startup. This phenomenon quickly subsides. What is the most likely cause of this event?
-
A
Excessive superheat at the compressor suction.
-
B
Refrigerant migration into the crankcase during the off-cycle.
-
C
A malfunctioning high-pressure cut-out switch.
-
D
Non-condensables present in the refrigeration system.