With SNAP rules dictating a transition to low-GWP refrigerants, efficiency, safety, environmental impact, chemical properties and economic factors all influence refrigerant choices in various applications. Some commercial refrigeration applications (ice makers and freezers) currently rely heavily on HFCs, such as R404A. The recent SNAP proposals would largely encourage the transition of these applications to hydrocarbon propane (R290), which can improve equipment performance. Hydrocarbons are more efficient than HFCs, but are also highly flammable and, depending on the application, may require implementing additional safety measures, including revisions to fire and building codes.
Carbon dioxide has been proven as a very effective refrigerant substitute in applications like supermarkets because it is chemically inert and environmentally benign. Furthermore, CO2 is nonflammable, toxic only in high concentrations and comparatively inexpensive. Its high pressure profile, however, makes it suitable only for certain applications. In subcritical systems in which pressures are lower, CO2 is used in concert with another refrigerant. These are typically applications in which HFCs or ammonia is used as the primary refrigerant and CO2 is used as a secondary refrigerant. In higher pressure transcritical systems, CO2 can function as a standalone refrigerant. Under SNAP, EPA lists it as an alternative for transportation, vending machines and food retail refrigeration.
Ammonia is traditionally used in industrial applications of the cold/food chain, such as food processing and warehousing. It is also SNAP-approved for some commercial uses, including refrigeration and stationary air-conditioning applications. With higher toxicity and flammability than other refrigerants, however, installations using ammonia are nationally regulated to ensure safety and are subject to further pressure to reduce charge levels, especially for systems located in populated areas. One emerging solution is to use ammonia in combination with CO2 (for medium or high temperatures) or in cascade applications (for low temperatures), as previously mentioned.
The Future of the Food Chain
The low-GWP refrigerant transition is driving rapid changes to the food cold chain. FDA’s FSMA and EPA’s SNAP play significant roles in driving these changes, while new technologies are shaping how these regulations are implemented. At the heart of change, however, will be the convergence of policy, technology and training. It is critical that installing and servicing contractors stay informed of the regulatory landscape and seek training for the newest technologies.