Experimental study on multi-split air conditioner with digital scroll compressor

A set of 10 horse powers (HP) multi-split air conditioner with a digital scroll compressor and a standard compressor was designed. The control strategy of compressor switching and the control model of compressor output capacity were presented. The output ratio of the digital compressor was determined in the control strategy. Furthermore, in the control model of compressor output capacity, considering the pressure disturbance, a certain suction pressure range was used as the pressure control target to adjust the output capacity. Experiments show that the system ran unstably, the standard compressor frequently appeared on–off phenomenon, and some operation parameters such as the output ratio of the digital compressor, the opening of electric expansive valve (EEV), the cooling capacity and the air outlet temperature fluctuated. A new control model of the output capacity was proposed, in which the average suction pressure in an adjustment period was taken as the current pressure to regulate the output capacity. Experimental results demonstrate that the control model can be used to solve the frequent on–off phenomenon of the standard compressor and oscillation of the operation parameters, realize control accuracy of less than 0.2 °C deviation of the air outlet temperature. ► A set of 10 HP VRF AC with a digital scroll compressor has been designed. ► The control strategy of compressor switching and control model of compressor output capacity have been presented. ► The average suction pressure in a period can be taken as the current pressure to regulate the output capacity. ► The control strategy can realize reliable running, high control accuracy of air outlet temperature.