Air conditioner

An air conditioner comprising:

• use-side units that are each switchable between a cooling operation and a heating operation;
• and
• a heat-source-side unit comprising:
• a lower-stage compressor and a higher-stage compressor;
• a discharge pipe to which a refrigerant is discharged after being compressed by the higher-stage compressor;
• a first main heat-source-side flow path and a second main heat-source-side flow path that branch off from the discharge pipe;
• a first heat-source-side heat exchanger;
• a second heat-source-side heat exchanger;
• a first economizer heat exchanger;
• and
• a second economizer heat exchanger, wherein
• the first heat-source-side heat exchanger is connected to the first economizer heat exchanger in series in the first main heat-source-side flow path,
• the second heat-source-side heat exchanger is connected to the second economizer heat exchanger in series in the second main heat-source-side flow path,
• the heat-source-side unit further comprises:
• a first economizer pipe that branches off from the first main heat-source-side flow path and extends toward the lower-stage and higher-stage compressors;
• and
• a second economizer pipe that branches off from the second main heat-source-side flow path and extends toward the lower-stage and higher-stage compressors,
• the first economizer heat exchanger exchanges heat between the refrigerant flowing in the first main heat-source-side flow path and the refrigerant flowing in the first economizer pipe,
• the second economizer heat exchanger exchanges heat between the refrigerant flowing in the second main heat-source-side flow path and the refrigerant flowing in the second economizer pipe,
• the heat-source-side unit further comprises a common part,
• the common part is disposed:
• between the first main heat-source-side flow path and the first economizer heat exchanger in the first economizer pipe, and
• between the second main heat-source-side flow path and the second economizer heat exchanger in the second economizer pipe, and
• the common part comprises an expansion valve that is common to the first economizer pipe and the second economizer pipe.