Compressor control for refrigeration system

Claim 1

In a refrigeration unit including a compressor (12) with a first heat exchange coil (14) joined to the discharge side of said compressor, expansion means (18) and a second heat exchange coil (20) joined to the suction side of said compressor, the improvement comprising: a. a combination equalizer and over-pressure control (10) having passage means adapted to communicate said compressor discharge side with said compressor suction side bypassing said other components of said unit, said passage means including a first piston-like member (60) having a first relief port therethrough, said member when in a first position preventing any flow of fluid through a second relief port (28); b. means for closing said first relief port including a second piston-like member (45), said second piston-like member being disposed upstream of said first piston-like member, said first and second members being movable relative to one another; c. control means including first means (49) providing a force to maintain said second member in spaced relationship relative to said first member, said second member moving into sealing abutment with said first member to close said first relief port when fluid pressure acting on said second member exceeds a predetermined value, second means (56) providing a force to maintain said first and second members in position relative to said second relief port to prevent any fluid flow therethrough, said first and second members moving jointly at a predetermined over-pressure condition to open said second relief port; and d. said first force supplying means moving said second member relative to said first member when the compressor becomes inoperable thereby opening said first relief port, said second member including abutment means (52) to maintain said passage means in an open state when said first relief port is opened to relatively quickly equalize pressures between the discharge side and the suction side of said compressor.