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With the widespread use of variable refrigerant flow (VRF) systems in various commercial and residential buildings, the performance and efficiency of VRF systems have attracted considerable attention in recent years. Although the compressor set energy conservation (CSEC) method exhibits a high accuracy in most cases of VRF performance measurement, several problems limit its accuracy. To improve the accuracy of the CSEC method for performance measurement, two methods are proposed to resolve the measurement difficulty of two-phase suction. The accuracies of the proposed methods are experimentally validated using three VRF configurations. In the experiments, the relative errors for the compressor isentropic efficiency-based method range from ±15%, ±17%, and ±18% for the three configurations. For the compressor volumetric efficiency-based method, the relative errors of the three configurations range from ±15%, ±16%, and ±16%, respectively. The capacity distribution and heat loss of the VRF system are measured and analyzed in the experiment. Heat losses from closed indoor units range from 0% to 21.5% in different cases in the cooling mode and from 0% to 31.1% in the heating mode. Additionally, an estimation method for the temperature measurement deviation is proposed to improve the precision of performance measurement.

In variable refrigerant flow (VRF) systems with multiple indoor units, individual energy metering (IEM) not only contributes to a fair charge for the tenants, thus avoiding their complaints on the charging fee, but also shows the actual allocation of capacity for IUs. However, it is extremely challenging to measure the accurate capacity of each IU directly according to current researches though total capacity can be measured. In this paper, methods of individual energy metering for VRF systems were reviewed, and three new methods, based on the electronic expansion valve (EEV), machine learning model (MLM), and throttling model (TM), were proposed. The accuracy and applicability of the three methods were investigated and analyzed according to experiments on a water-cooled VRF system. In the experiments, the maximum deviation factors of the EEV-, MLM-, and TM-based methods were ±7.8%, ±6.0%, and ±6.9%, respectively. In addition, coefficients of variation of the root-mean-square error of the above methods were ±4.4%, ±3.3%, and ±4.4%, respectively. Considering the practicability and feasibility in real projects, the TM-based method was applied to an air-cooled VRF system, showing superior accuracy in cooling conditions.