Abstract: An apparatus for summing capacities of outdoor units in a multiple air conditioner comprises self-capacity storage devices mounted in outdoor units, respectively, for storing self-capacities of the outdoor units and outputting the self-capacities of the outdoor units when necessary, an outdoor unit capacity summing part mounted in one outdoor unit of the outdoor units for receiving the capacities of the outdoor units outputted from the respective self-capacity storage devices to calculate the total capacity of all the outdoor units, and a control device for receiving the result of the calculation performed by the outdoor unit capacity summing part to control the operation of the multiple air conditioner. The possibility of incorrect input of the capacities of the outdoor units is eliminated, and therefore, more accurate control of the multiple air conditioner is accomplished.

Abstract: Disclosed herein are a multi-air conditioner and a group-unit control method thereof, wherein a plurality of indoor units can be controlled on a group basis. The method comprises the step of grouping the indoor units into a plurality of groups, the step of if an air conditioning operation condition of a specific one of the indoor units is changed, sending, by the specific indoor unit, the changed operation condition to all the other indoor units according to a predefined communication protocol, and the step of by each of the indoor units, receiving an air conditioning operation condition sent from a different one of the indoor units in the same group and performing an air conditioning operation based on the received operation condition. According to the invention, the plurality of indoor units can be more efficiently controlled on a group basis through inter-indoor unit data communication. Further, the group-unit control is not restricted by whether a controller is used or not.