Heat transfer compositions and methods of retrofitting heat transfer systems

A method of retrofitting an existing MAC system containing R-134a and existing PAG lubricant with a refrigerant comprising HFO-1234yf, said retrofitting methods comprising:

• (a) ensuring that the existing MAC system is essentially free of the existing R134a refrigerant without taking steps to remove any existing PAG lubricant that remains in the system after said R134a removal;
• (b) after said ensuring step (a), introducing into the system refrigerant comprising at least about 50% by weight of HFO-1234yf and (c) either before, after, and/or simultaneous with said introducing step (b), introducing into the system a supplemental PAG lubricant composition, wherein the amount of said supplemental PAG lubricant introduced is from about 5% to about 20% of the design lubricant load of the system, wherein the supplemental PAG lubricant composition comprises a dispersing agent which enhances the miscibility of said existing PAG lubricant and said HFO-1234yf.

A method of retrofitting an existing MAC system that contains R-134a refrigerant and an existing PAG lubricant, said method comprising:

• a. removing at least a portion of the existing R-134a refrigerant from said existing system;
• and
• b. after said removing step, introducing into said existing system a lubricant package composition comprising supplemental PAG lubricant and a dispersing agent, wherein said dispersing agent comprises one or more polyalkylsuccinamide-polyamine based agents and/or one or more polyalkylsuccinimide-polyamine based dispersing agents and/or one or more ethoxylated amine dispersing agents, wherein said dispersing agent is present in the lubricant package in an amount of from about 20% by weight to about 80% by weight based on the weight of said supplemental PAG lubricant and said dispersant.