Refrigeration equipment began its move away from HCFCs to HFCs before the air conditioning sector started its switchover. Supermarket systems have been using such HFCs as 404A and 507 for more than a decade. Even the refrigerated equipment that was designed for and installed with HCFC-22 is being targeted for retrofitting with a number of HFCs specifically designed to work in R-22 refrigerated systems. But even as all that goes on, new refrigerated equipment is being designed to run on so-called natural refrigerants such as ammonia, hydrocarbons, and CO2.
The biggest natural player in refrigeration, especially for supermarkets, is R-744 (CO2). It initially came into cooling and freezing applications in subcritical configurations. They often included HFCs in the design, but at much lower amounts than might have been needed in more conventional supermarket systems. This reduced the carbon footprint of a store and allowed owners to promote environmental awareness to customers who could be positively influenced by such claims.