Centrifugal compressor with reverse overhung volute

A centrifugal compressor for a chiller comprising:

• a first stage impeller arranged to receive refrigerant from an inlet;
• a first stage diffuser;
• a second stage impeller;
• a second stage diffuser;
• a second stage volute forming member defining a second stage volute, the second stage volute being disposed downstream of the second stage diffuser to receive the refrigerant after the refrigerant has been compressed, the second stage volute having a reverse overhung configuration;
• a compressor housing enclosing the first stage impeller and the second stage impeller;
• and
• an insert disposed around an outer periphery of the second stage impeller and interposed between the second stage volute forming member and the compressor housing,
• the insert including a diffuser defining wall surface that opposes an inner surface of the second stage volute forming member, and
• the second stage diffuser being defined between the second stage volute forming member and the diffuser defining wall surface of the insert.