The search for replacements for HCFC and HFC based refrigerants such as R-22 and R-404A, being phased out globally due to stratospheric ozone depletion and global warming potential issues, has led to the development of low GWP HFO blend alternatives, such as R-449A. This presentation includes the retrofit procedure for HFO refrigerants in low and medium temperature commercial refrigeration systems that were originally designed for HCFC and HFC refrigerants. Also, data obtained during actual system conversions, including compatibility with seals/lubricants as well as operational and energy performance is reported.