Natural Refrigerant Applications in North American Supermarkets

Recent achievements with the application of CO2 secondary and cascade systems in North American supermarkets are presented. Practical information gained through start-up and operation of these systems as well as customer experiences is included. The results of a detailed analysis are presented which focus on impacts of distribution piping, material costs, and heat gain compared to conventional direct expansion systems using HFC refrigerants. An energy and TEWI comparison is made between several system types including CO2 secondary and cascade, as well as various primary refrigerants. Projects successfully  containing the refrigerant charge in the mechanical room renew the possibility of using ammonia on these systems—a discussion of the potential of commercial ammonia systems in the U.S. is added, highlighting needed developments for successful implementation in the future.