System and method for operation of variable geometry diffuser as check valve

A heating, ventilation, air conditioning, and refrigeration (HVAC&R) system, comprising;

• a compressor configured to pressurize refrigerant within a refrigerant circuit, wherein the compressor comprises a diffuser passage configured to receive the refrigerant from an impeller of the compressor;
• a variable geometry diffuser of the compressor, wherein the variable geometry diffuser is configured to be positioned within the diffuser passage and is configured to adjust a dimension of a refrigerant flow path through the diffuser passage;
• an actuator configured to adjust a position of the variable geometry diffuser within the diffuser passage;
• and a controller configured to regulate operation of the actuator, wherein the controller is configured to control the actuator to position the variable geometry diffuser within the diffuser passage and against a compressor discharge plate during stoppage of the compressor.

A heating, ventilation, air conditioning and refrigeration (HVAC&R) system controller comprising a tangible, non-transitory, computer-readable medium comprising computer-executable instructions that, when executed, are configured to cause processing circuitry to:

• control an actuator to position a variable geometry diffuser in a diffuser passage of a compressor within a first range of positions during operation of the compressor;
• control the actuator to position the variable geometry diffuser in the diffuser passage of the compressor within a second range of positions during stoppage of the compressor;
• and
• control the actuator to maintain a position of the variable geometry diffuser within the diffuser passage and against a compressor discharge plate of the compressor during stoppage of the compressor.