Notice in Figure 3 at the higher ou

Notice in Figure 3 at the higher outdoor temperatures greater than 23°C that the VRF, REF, and HP curves produce very similar resultsThis means that each of these systems will provide similar capacity, at nearly the same energy use, which in and of itself is not extraordianry since these are all DX compression systems. It does mean that the results for these simulations, when operating in this outdoor temperature region, are driven more by other aspects of the model than the performance curve selected for each AC system(i.e., impacts of duct heat gain, fan energy, etc.).At lower outdoor temperatures, these performance curves do show differences. The VRF system transitions from an uncontrolled to a controlled mode where the control system maintains internal set points and both capacity and power remain relatively constant. This is possible because as outdoor temperature decreases, additional capacity is available via refrigerant subcooling and the control system is able to regulate capacity and, as a result, the operating energy is also nearly constant. Realize here that the VRF performance curve is the only curve not allowing extrapolation across the entire range of outdoor temperatures.