Dual compressor heat pump

A method for operating a vapor compression system (20;

• 120;
• 220), the vapor compression system comprising:
• a first compressor (22A;
• 122A;
• 222A);
• a second compressor (22B;
• 122B;
• 222B);
• a first heat exchanger (40);
• a second heat exchanger (46);
• and
• one or more expansion devices (52);
• the method comprising:
• running the system in a first mode wherein:
• the first compressor compresses refrigerant;
• the compressed refrigerant is cooled in the first heat exchanger;
• the cooled refrigerant is expanded in at least one of the one or more expansion devices;
• the expanded refrigerant absorbs heat in the second heat exchanger and returns to the first compressor;
• and
• the second compressor is offline;
• and
• running the system in a second mode wherein:
• the second compressor compresses refrigerant;
• the compressed refrigerant is cooled in the second heat exchanger;
• the cooled refrigerant is expanded in at least one of the one or more expansion devices;
• the expanded refrigerant absorbs heat in the first heat exchanger and returns to the second compressor;
• and
• the first compressor is offline,
• wherein:
• the first compressor has a suction flowpath merging with a discharge flowpath of the second compressor at a first junction (34);
• the first compressor has a discharge flowpath merging with a suction flowpath of the second compressor at a second junction (36);
• a first control valve (32A) is along the first compressor discharge flowpath;
• and
• a second control valve (32B) is along the second compressor discharge flowpath;
• in the first mode, the first control valve is open and the second control valve is closed;
• and
• in the second mode, the first control valve is closed and the second control valve is open.

A vapor compression system (20;

• 120;
• 220) comprising:
• a first compressor (22A;
• 122A;
• 222A);
• a second compressor (22B;
• 122B;
• 222B);
• a first heat exchanger (40);
• a second heat exchanger (46);
• one or more expansion devices (52);
• and
• means (32A, 32B;
• 32A, 32B, 126A, 126B;
• 32A, 32B, 232A, 232B) for switching the system between operation in:
• a first mode wherein:
• the first compressor compresses refrigerant;
• the compressed refrigerant is cooled in the first heat exchanger;
• the cooled refrigerant is expanded in at least one of the one or more expansion devices;
• the expanded refrigerant absorbs heat in the second heat exchanger and returns to the first compressor;
• and
• the second compressor is offline;
• and
• a second mode wherein:
• the second compressor compresses refrigerant;
• the compressed refrigerant is cooled in the second heat exchanger;
• the cooled refrigerant is expanded in at least one of the one or more expansion devices;
• the expanded refrigerant absorbs heat in the first heat exchanger and returns to the second compressor;
• and
• the first compressor is offline,
• wherein:
• the first compressor has a suction flowpath merging with a discharge flowpath of the second compressor at a first junction (34);
• the first compressor has a discharge flowpath merging with a suction flowpath of the second compressor at a second junction (36);
• a first control valve (32A) is along the first compressor discharge flowpath;
• and
• a second control valve (32B) is along the second compressor discharge flowpath.