The Sub-Zero 3211 (must be at least 20 years old) has one sealed system. It has a single compressor that pumps to a condensor and from the condensor into cap tube to the refer evap. From the refer evap to another cap tube into the the freezer evap. When freon is low it effects the freezer first. There is a freezer defrost circuit, the refer uses off cycle defrost. Air is not exchaned between the refer and freezer. Modern Sub-Zero's use 2 seperate sealed systems to acomplish this. |