An apparatus (100, 200) comprising: a high side heat exchanger configured to remove heat from a refrigerant; a heat exchanger; a flash tank configured to store the refrigerant from the heat exchanger; a first expansion valve; a second expansion valve; a valve (135, 205); a load; a first compressor; a second compressor; and software or hardware logic, wherein, during a first mode of operation, the software or hardware logic is configured to: close the first expansion valve; open the second expansion valve to direct refrigerant from the flash tank to the load, the load arranged to use the refrigerant from the second expansion valve to cool a space proximate the load; turn off the first compressor; open the valve (135, 205) to direct the refrigerant from the load to the heat exchanger, bypassing the first compressor; operate the heat exchanger to transfer heat from the refrigerant from the high side heat exchanger to the refrigerant from the load, the heat exchanger being arranged to direct the refrigerant from the load to the second compressor after heat from the refrigerant from the high side heat exchanger is transferred to the refrigerant from the load; and operate the second compressor to compress the refrigerant from the heat exchanger; and wherein, during a second mode of operation, the software or hardware logic is configured to: open the first expansion valve to direct refrigerant from the flash tank to the load; close the second expansion valve, the load arranged to use the refrigerant from the first expansion valve to cool the space; operate the first compressor to compress the refrigerant from the load; and operate the second compressor to compress the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high side heat exchanger. a high side heat exchanger configured to remove heat from a refrigerant; a heat exchanger; a flash tank configured to store the refrigerant from the heat exchanger; a first expansion valve; a second expansion valve; a valve (135, 205); a load; a first compressor; a second compressor; and software or hardware logic, wherein, during a first mode of operation, the software or hardware logic is configured to: close the first expansion valve; open the second expansion valve to direct refrigerant from the flash tank to the load, the load arranged to use the refrigerant from the second expansion valve to cool a space proximate the load; turn off the first compressor; open the valve (135, 205) to direct the refrigerant from the load to the heat exchanger, bypassing the first compressor; operate the heat exchanger to transfer heat from the refrigerant from the high side heat exchanger to the refrigerant from the load, the heat exchanger being arranged to direct the refrigerant from the load to the second compressor after heat from the refrigerant from the high side heat exchanger is transferred to the refrigerant from the load; and operate the second compressor to compress the refrigerant from the heat exchanger; close the first expansion valve; open the second expansion valve to direct refrigerant from the flash tank to the load, the load arranged to use the refrigerant from the second expansion valve to cool a space proximate the load; turn off the first compressor; open the valve (135, 205) to direct the refrigerant from the load to the heat exchanger, bypassing the first compressor; operate the heat exchanger to transfer heat from the refrigerant from the high side heat exchanger to the refrigerant from the load, the heat exchanger being arranged to direct the refrigerant from the load to the second compressor after heat from the refrigerant from the high side heat exchanger is transferred to the refrigerant from the load; and operate the second compressor to compress the refrigerant from the heat exchanger; and wherein, during a second mode of operation, the software or hardware logic is configured to: open the first expansion valve to direct refrigerant from the flash tank to the load; close the second expansion valve, the load arranged to use the refrigerant from the first expansion valve to cool the space; operate the first compressor to compress the refrigerant from the load; and operate the second compressor to compress the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high side heat exchanger. open the first expansion valve to direct refrigerant from the flash tank to the load; close the second expansion valve, the load arranged to use the refrigerant from the first expansion valve to cool the space; operate the first compressor to compress the refrigerant from the load; and operate the second compressor to compress the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high side heat exchanger.