Hill Phoenix’s carbon dioxide technology is now including what the company calls Second Nature Low Temperature Direct Expansion Cascade (SNLTX2). The company describes the approach as “the next level in CO2 refrigeration.”

Features in the system include, according to the company:

• An energy efficient design that saves on operating costs;

• Use of low-cost natural refrigerant that is widely available;

• Smaller copper piping that requires less material;

• System components accessible for maintenance;

• Low global warming impact.


The system uses CO2 as a direct expansion (DX) refrigerant. The CO2 removes heat from display cases and walk-in freezers through copper piping that is smaller than what is found in traditional HFC-based DX systems. The HFC refrigerant is confined to the primary system located in the machine room and condenser. The HFC refrigerant charge is reduced by 70 percent of what would be needed in systems with only HFCs.

The modified-loop copper piping system is one to two sizes smaller than traditional DX piping. The system uses CO2 subcritical compressors. The material compatibility of CO2 allows most commercial refrigeration equipment to be used, the manufacturer said.


The manufacturer outlined several system options for use with the SNLTX2:

• Can be used with either Copeland CO2 compressors or Bitzer recips;

• HFC system can be further minimized by using water-cooled condensers and hydronic heat-reclaim loops;

• HFC system can also be used to refrigerate other medium-temperature loads including Second Nature medium temperature secondary systems;

• Low-temperature display cases and freezers can be equipped with the Hill Phoenix Smart Value™ system with electronic expansion valves for automatic control of superheat leaving the evaporators;

• System is available as a stand-alone rack or installation in a mechanical center or WeatherPac enclosure;

• Optional glycol-cooled CO2 condensers can be used to allow smaller systems to be packaged for modular systems;

• Multiple CO2 suction groups on low-temperature systems to improve efficiency.

For more information, visit www.hillphoenix.com.

Publication date:08/02/2010