Conference Year



VRF, Air-conditioning, Performance rating, Dummy Unitary System, SPLV


A multi-split air-conditioner is a refrigeration system that consists of one outdoor unit and multiple indoor units and the indoor units can be controlled independently. The capability to turn on and off the multiple indoor units independently distinguishes a multi-split air-conditioner from a typical unitary system. This characteristic makes it possible to practice energy-saving through modulating the load request via turning on or off indoor units. Today, multi-split systems have been widely used for centralized air-conditioning applications, including domestic, commercial and offices as well. This study starts with a survey on the operation of typical centralized air-conditioning systems to understand the end user’s operating behaviour and a series of modeling follows to build up a new performance rating approach. In the process, a one-to-four system (i.e. one outdoor unit connected to four indoor units) is used as an example. The study can serve as a new direction for future discussion and practice in the discipline of multi-split system performance rating. In this paper, the following areas are discussed: - 1) The general turned-ON probability of the indoor unit generated through the survey - 2) The calculation of the probabilities to have one, or two, or three or all-four indoor units on for a one-to-four multi-split system - 3) The introduction of 4 dummy unitary systems to functionally replace the one-to-four multi-split system - 4) The calculation of the ratio (weightings) of the capacity delivered by each dummy unitary system to the total capacity from the multi-split system - 5) The Construction of a mathematical model to calculate the performance rating of the multi-split system Steps 2) and 3) build up a strong link between a complicated multi-split VRF system and the well-understood unitary system, thus SEER (seasonal cooling efficiency) and SCOP (seasonal heating performance) developed for the unitary system can be plug-and-used for the rating of a VRF system. (3500 words, 8 figures, 8 tables)

3361_presentation.pdf (520 kB)
A Study on a New Performance Rating Approach for a Multi-Split (VRF) Air-Conditioning System