Abstract: Primarily-conditioned air is discharged from a heat source, and distributed into a plurality of rooms through a duct. The duct has a plurality of air passages connected to the rooms, and a damper is provided in each air passage for adjusting the flow of the primarily-conditioned air. Further, a heat exchanger is provided in each air passage, and connected to a refrigerating cycle for the heat source. The thermal load in each room is detected, and the required air flow in the room is determined based on the thermal load. The opening degree of a damper corresponding to the room is controlled on the basis of the required air flow. Each damper has an allowable minimum opening degree. When the opening degree of any damper becomes equal to the allowable minimum value, refrigerant flows into a heat exchanger corresponding to the damper, thereby correcting the temperature of the primarily-conditioned air.

Abstract: A central air conditioning system includes a compensating control function in which the prescribed target temperature Tfs of the conditioned air supplied from the air conditioning apparatus to a main duct is changed from the original value to a prescribed value of a modified target temperature Tfm to establish the target temperature Tfs when the actual room temperature Ta in each room does not achieve a corresponding desired room temperature Ts even though the damper of the corresponding air volume control unit is positioned at either the fully opened position or the closed position. The temperature of the conditioned air from the air conditioning apparatus is controlled in accordance with the target temperature Tfs, and the target temperature Tfs of the conditioned air is further changed to successive values of the modified target temperature Tfm until the actual room temperature Ta in each room achieves the corresponding desired room temperature Ts.

Abstract: A central air conditioning system includes an air conditioning apparatus having a system controller and a variable air volume controller having a damper which controls the amount of conditioned air fed from the air conditioning apparatus into each room to be air-conditioned. Each room is provided with a room remote controller for controlling the operation of the air volume controller. The room remote controller outputs a start/stop command signal to control the operation of both the air conditioning apparatus and the air volume controller. The temperature of conditioned air fed from the air conditioning apparatus is maintained at a prescribed value determined on the basis of the desired room temperature in each room.

Abstract: A rapid increase in the static pressure in the air duct which occurs while the damper is moving to the fully closed position is avoided by maintaining the damper at a preclosed position between fully opened and fully closed positions for a prescribed period and by simultaneously reducing the amount of conditioned air supplied to the air duct while the damper is positioned at the pre-closed position to regulate the static pressure in the air duct to a desirable level. Thus, air leakage noise which occurs in the air duct when the static pressure in the air duct rapidly increases for a short time can be avoided.

Abstract: An air conditioning apparatus includes two different refrigerating circuits in one central unit for supplying a conditioned air into a defined space through an air duct. Each refrigerating circuit has an air exhausting damper for exhausting internal air from the defined space, and an external air intake damper for taking the external air into the defined space through the central unit. One of the refrigerating circuits forcibly carries out the heating operation, and the external air intake damper thereof is maintained in a closed state while the other refrigerating circuit carries out the defrosting operation to prevent temperature of the conditioned air fed from the central unit into the defined space from decreasing below a desirable level.