Abstract: Novel non-flammable refrigerants having a GWP of less than 750 and containing R-32, R-125, R-134a and R-1234yf, and novel air conditioning systems (including heat pumps) which use such refrigerants, and method of retrofitting standard single refrigerant vapor compression air conditioning systems using said refrigerants, including especially residential heat pumps and residential split direct expansion air conditioning systems.

Abstract: Disclosed are refrigerants and refrigeration systems, including cascade refrigeration sysemsar comprising: a plurality of refrigeration units, each refrigeration unit containing a first refrigeration circuit, each first refrigeration circuit comprising an evaporator and a heat exchanger; and a second refrigeration circuit; wherein each first circuit heat exchanger is arranged to transfer heat energy between its respective first refrigeration circuit and the second refrigeration circuit.

Abstract: Methods for forming an improved, centralized refrigeration systems comprising: (a) providing an existing refrigeration circuit with an existing high GWP refrigerant; (b) disconnecting the fluid connection between the existing liquid refrigerant from the condenser and the evaporators; (c) disconnecting the fluid connection between the existing refrigerant vapor from the evaporators and the compressor suction; (d) establishing a new first refrigeration circuit comprising the compressor and the condenser; (e) establishing a new second refrigeration circuit comprising the evaporators by removing existing refrigerant from the evaporators and the disconnected conduits and replacing the removed refrigerant with a second refrigerant comprising at least 50% of R1234ze(E) and being Class A1 and having an OEL greater than 400 and a GWP of about 150 or less; and thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with an inter-circuit heat exchanger.