Abstract: Due to the difference of heat exchanger in split air-source heat punp, it is difficult to give consideration to refrigerant charging amount of both cooling throttling by indoor unit and heating throttling by outdoor unit. This problem can be solved by adjusting the size of piping connection between indoor unit and outdoor unit, and throttling by outdoor unit in both cooling and heating conditions, without adding other refrigerant receivers. According to the experiment and calculation of 8kW unit using R32, the optimal refrigerant amount in indoor unit and outdoor unit can be obtained. Then the correlation between the refrigerant amount in piping connection and length of piping connection were carried out, and optimal refrigerant charging amount can be determined. Finally, the optimal piping connection and refrigerant charging amount were verified by experiment, which were suitable for both cooling and heating.

Key words: Air-source heat pump, Throttle method, Piping connection, Optimal charging amount