Conference Year



Variable Refrigerant Flow, Occupancy emulated building, HVAC field performance evaluation


VRF systems are touted for their superior part-load performance compared to conventional systems. This study compares both the full and part-load performance of a VRF system with a conventional RTU VAV system in a multi-zone office building with emulated occupancy. To accomplish this, full and part-load conditions (i.e., 100%, 75% and 50% loads) in the building are maintained alternately by conditioning either the entire building or selected zones, and emulating the occupancy, accordingly. During the study period, each system is operated alternately under each of the three load conditions for 2-3 days, and the system parameters, indoor and outdoor conditions, loads, and energy use are monitored.  The cooling season performance and energy use of both systems was monitored during the summer of 2015. System performance is compared in terms of weather-normalized HVAC energy consumption and seasonal average COP. In addition, the ability of each system to maintain the indoor temperature in the conditioned zones is also evaluated. Based on the analysis, the energy savings for the VRF system compared with the RTU system for the cooling season are estimated to be 29%, 36%, and 46% under the 100%, 75%, and 50% load conditions, respectively. The average cooling COP was ~4.0-4.5, 3.9, and 3.7 for the VRF system and 3.1, 2.9, 2.5 for the RTU system under the 100%, 75% and 50% load conditions. Both systems maintained the indoor temperature very well. However, the VRF system maintained the indoor temperature in a slightly tighter range compared to the RTU system.