An apparatus includes a first compressor, a first load, a second compressor, a second load, and a heat exchanger. The first compressor compresses a first refrigerant. The first load uses the first refrigerant to remove heat from a space proximate the first load. The first load sends the first refrigerant to the first compressor. The second compressor compresses a second refrigerant. The second load uses the second refrigerant to remove heat from a space proximate the second load. The second load sends the second refrigerant to the second compressor. The heat exchanger receives the first refrigerant from the first compressor and receives the second refrigerant from the second compressor. The heat exchanger transfers heat from the first refrigerant to the second refrigerant. The heat exchanger discharges the first refrigerant to the first load and discharges the second refrigerant to the second compressor.