First, experimental tests were conducted without vapor injection. In such a case the heat pump system works as a conventional single-stage vapor compression cycle. Figure 4 shows capacity comparison between R410A and R32 at different operating conditions without vapor injection. The dotted line divides the ambient temperatures into cooling mode and heating mode results on the left and right, respectively. The capacity improvement was observed to be 3.4% to 9.7%. However, it is noticed that there was no improvement at the ambient temperature condition of -18ºC. Figure 5 shows the COP comparison between R410A and R32 at different ambient temperatures. The improvement was found to be 2.0% to 9.0% comparing R32 to R410A. It is also noticed that there was no improvement for COP at the low ambient temperature heating condition of -18ºC and cooling condition of 28ºC.