An apparatus comprising: a compressor having an inlet and an outlet and at least a first port between the inlet and outlet; a condenser having an inlet coupled to the compressor outlet to receive refrigerant and having an outlet; a first evaporator having an inlet coupled to the condenser to receive refrigerant and having an outlet coupled to the compressor inlet; a second evaporator having an Inlet coupled to the condenser to receive refrigerant and having an outlet coupled to the first port to return refrigerant to the compressor, bypassing a compression path between the compressor inlet and first port; and a bypass conduit extending between: a first location between the first evaporator and the compressor inlet; and a second location between the second evaporator and the first port; a first valve positioned to directly control flow through the bypass conduit; and characterised by further comprising: a second valve positioned to directly control flow between the second location and the first port; a first heat exchanger exchanging heat from refrigerant discharged by the compressor to refrigerant discharged by the first evaporator; and a second heat exchanger exchanging heat from refrigerant discharged by the compressor to refrigerant discharged by the second evaporator, and wherein: a refrigerant flowpath portion extending downstream from the compressor branches into: a first branch through a donor conduit of the first heat exchanger, the first evaporator, and a recipient conduit of the first heat exchanger, a first expansion valve being arranged in said first branch; and a second branch through a donor conduit of the second heat exchanger the second evaporator and a recipient conduit of the second heat exchanger a second expansion valve being arranged in said second branch. a compressor having an inlet and an outlet and at least a first port between the inlet and outlet; a condenser having an inlet coupled to the compressor outlet to receive refrigerant and having an outlet; a first evaporator having an inlet coupled to the condenser to receive refrigerant and having an outlet coupled to the compressor inlet; a second evaporator having an Inlet coupled to the condenser to receive refrigerant and having an outlet coupled to the first port to return refrigerant to the compressor, bypassing a compression path between the compressor inlet and first port; and a bypass conduit extending between: a first location between the first evaporator and the compressor inlet; and a second location between the second evaporator and the first port; a first location between the first evaporator and the compressor inlet; and a second location between the second evaporator and the first port; a first valve positioned to directly control flow through the bypass conduit; and characterised by further comprising: a second valve positioned to directly control flow between the second location and the first port; a first heat exchanger exchanging heat from refrigerant discharged by the compressor to refrigerant discharged by the first evaporator; and a second heat exchanger exchanging heat from refrigerant discharged by the compressor to refrigerant discharged by the second evaporator, and wherein: a second valve positioned to directly control flow between the second location and the first port; a first heat exchanger exchanging heat from refrigerant discharged by the compressor to refrigerant discharged by the first evaporator; and a second heat exchanger exchanging heat from refrigerant discharged by the compressor to refrigerant discharged by the second evaporator, and wherein: a refrigerant flowpath portion extending downstream from the compressor branches into: a first branch through a donor conduit of the first heat exchanger, the first evaporator, and a recipient conduit of the first heat exchanger, a first expansion valve being arranged in said first branch; and a second branch through a donor conduit of the second heat exchanger the second evaporator and a recipient conduit of the second heat exchanger a second expansion valve being arranged in said second branch. a first branch through a donor conduit of the first heat exchanger, the first evaporator, and a recipient conduit of the first heat exchanger, a first expansion valve being arranged in said first branch; and a second branch through a donor conduit of the second heat exchanger the second evaporator and a recipient conduit of the second heat exchanger a second expansion valve being arranged in said second branch.