Supco May 13, 2019 - Sealed Unit Parts Co., Inc. (SUPCO), a global manufacturer and distributor of HVACR and Appliance parts, announced today that they have become a national Master Distributor for Kulthorn aftermarket air conditioning and refrigeration compressors and condensing units. How to Wire a Supco 3 in One | eHow How to Wire a Supco 3 in One. Your refrigerator's built-in compressor unit functions as both a motor and a pump that moves liquid refrigerant throughout the unit. The compressor is powered by a relay box. When the relay loses power, the compressor stops working and keeps your refrigerator from staying cool. Supco RCO 3 'n 1 is a relay box that can..