A system (200; 250) comprising: a first compressor; a heat rejection heat exchanger coupled to the first compressor to receive refrigerant compressed by the first compressor; a first ejector having: a primary inlet coupled to the heat rejection heat exchanger to receive refrigerant; a secondary inlet; and an outlet; a first separator having: an inlet coupled to the outlet of the first ejector to receive refrigerant from the first ejector; a gas outlet coupled to the first compressor to return refrigerant to the first compressor; and a liquid outlet coupled to the secondary inlet of the first ejector to deliver refrigerant to the first ejector; a heat absorption heat exchanger between the liquid outlet of the first separator and the first ejector secondary inlet; and a second compressor between the heat absorption heat exchanger and the first ejector secondary inlet, characterised in that the system further comprises: a second separator having: an inlet; a gas outlet coupled to the secondary inlet of the first ejector via the second compressor; and a liquid outlet; and a second ejector having: a primary inlet coupled to the liquid outlet of the first separator to receive refrigerant; a secondary inlet coupled to the outlet of the heat absorption heat exchanger; sand an outlet coupled to the inlet of the second separator. a first compressor; a heat rejection heat exchanger coupled to the first compressor to receive refrigerant compressed by the first compressor; a first ejector having: a primary inlet coupled to the heat rejection heat exchanger to receive refrigerant; a secondary inlet; and an outlet; a primary inlet coupled to the heat rejection heat exchanger to receive refrigerant; a secondary inlet; and an outlet; a first separator having: an inlet coupled to the outlet of the first ejector to receive refrigerant from the first ejector; a gas outlet coupled to the first compressor to return refrigerant to the first compressor; and a liquid outlet coupled to the secondary inlet of the first ejector to deliver refrigerant to the first ejector; an inlet coupled to the outlet of the first ejector to receive refrigerant from the first ejector; a gas outlet coupled to the first compressor to return refrigerant to the first compressor; and a liquid outlet coupled to the secondary inlet of the first ejector to deliver refrigerant to the first ejector; a heat absorption heat exchanger between the liquid outlet of the first separator and the first ejector secondary inlet; and a second compressor between the heat absorption heat exchanger and the first ejector secondary inlet, a second separator having: an inlet; a gas outlet coupled to the secondary inlet of the first ejector via the second compressor; and a liquid outlet; and an inlet; a gas outlet coupled to the secondary inlet of the first ejector via the second compressor; and a liquid outlet; and a second ejector having: a primary inlet coupled to the liquid outlet of the first separator to receive refrigerant; a secondary inlet coupled to the outlet of the heat absorption heat exchanger; sand an outlet coupled to the inlet of the second separator. a primary inlet coupled to the liquid outlet of the first separator to receive refrigerant; a secondary inlet coupled to the outlet of the heat absorption heat exchanger; sand an outlet coupled to the inlet of the second separator.