An air conditioning apparatus suppresses an increase in power consumption associated with a reduction in start-stop frequency of a compressor. The air conditioning apparatus includes an outdoor unit equipped with a compressor and a plurality of indoor units connected with the outdoor unit and has a control device that performs thermo-off and thermo-on control such that a suction air temperature of the indoor unit falls within a predetermined temperature range with a set temperature defined as a reference. The control device detects the suction air temperatures of the indoor units, and, in a case where a sum total of air conditioning capacities of the indoor units, the suction air temperatures of which are between the set temperature and the thermo-off temperature, is at least a predetermined value, makes at least one indoor unit, the suction air temperatures of which are between the set temperature and the thermo-off temperature, forcedly thermo-off.

A sound level control system for a heating, ventilation, and air conditioning (HVAC) system is provided. The sound level control system comprises an outdoor unit with a compressor, an outdoor fan, and an outdoor controller and a communication device located at a predefined distance from the outdoor unit. The communication device measures sound levels in response to operating the outdoor unit. The outdoor controller is configured to receive a first noise level limit for a predefined time period, receive an instruction related to selective control of the outdoor unit, selectively control both of the compressor to rotate at a first compressor speed and the outdoor fan to rotate at a first fan speed based on the noise level limit for the predefined time period, and receive information related to whether a sound pressure level at a predefined location exceeds the first noise level limit for the predefined time period.

In various implementations, frost in a vapor compression system may be controlled. A property of a fan may be determined. A determination may be made whether a frost event and/or a nonfrost event has occurred based at least partially on the determined fan property.

An air-conditioning apparatus is configured to melt a large amount of adhering frost while maintaining an appropriate operation of a compressor by setting a defrosting operation time period depending on a low pressure of the compressor. The air-conditioning apparatus includes a refrigerant circuit including the compressor, a refrigerant flow switching device, a heat source-side heat exchanger, an expansion device, and a use-side heat exchanger, which are connected via a refrigerant pipe to form a refrigeration cycle, a pressure sensor configured to detect a pressure on a suction side of the compressor, and a controller configured to control, in a defrosting operation, the refrigerant flow switching device to supply compressed refrigerant from the compressor to the heat source-side heat exchanger, compare a value detected by the pressure sensor with a first threshold value, and change the defrosting operation time period based on a result of the comparison.

A target condensing temperature and a target evaporating temperature are changed in accordance with a load of each load side unit obtained by using load detection means, and an operating frequency of a compressor and a rotation speed of a fan are controlled such that a condensing temperature obtained by using temperature detection means coincides with the target condensing temperature and an evaporating temperature obtained by using the temperature detection means coincides with the target evaporating temperature.

A heat pump apparatus includes an outdoor heat exchanger, a fan configured to introduce outdoor air into the outdoor heat exchanger, and a control device configured to control a defrosting operation of the outdoor heat exchanger. The fan rotates at a first rotational speed within a first period, after the defrosting operation is finished and the fan starts rotating. The fan rotates at the first rotational speed within a second period, after a non-defrosting operation is finished and the fan starts rotating. The first period is shorter than the second period.

An outdoor unit for an air conditioner, and an air conditioner are provided. The outdoor unit has a housing and a draught fan. The housing is provided with a first air exchange port and a second air exchange port. The draught fan is arranged in the housing and located between the first air exchange port and the second air exchange port. The draught fan has an electric motor, a first fan, and a second fan. The electric motor has two rotors which rotate independently of each other, and a first output shaft and a second output shaft connected to the two rotors respectively. The first output shaft and the second output shaft are respectively fixedly connected to the first fan and the second fan for driving the first fan and the second fan to rotate independently of each other.

An air conditioner includes: a refrigerant circuit including a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger, the refrigerant circuit being configured to circulate refrigerant; a blower configured to send air to the outdoor heat exchanger; and a controller configured to control at least one actuator that is one of the compressor, the expansion valve, and the blower. One of the indoor heat exchanger and the outdoor heat exchanger is configured to function as a condenser. The controller is configured to calculate a parameter used for controlling the at least one actuator in a state in which a degree of subcooling of refrigerant having passed through the condenser is equal to or greater than a threshold value.

A failure diagnosis system diagnoses the state of an air-conditioning apparatus having a refrigerant circuit in which refrigerant circulates. The failure diagnosis system has an abnormality diagnosis unit that performs normal-operation abnormality diagnosis for determining whether or not there is an abnormality in the air-conditioning apparatus by using state data and control data during normal operation of the air-conditioning apparatus. If the abnormality diagnosis unit determines that there is an abnormality, it changes a control value for an actuator of the air-conditioning apparatus and acquires state data and control data. Then, the abnormality diagnosis unit performs abnormality-cause identification diagnosis for identifying the cause of the abnormality in the air-conditioning apparatus by using the state data and the control data acquired before the change of the control value and the state data and the control data acquired after the change of the control value.

A controller in a refrigeration cycle apparatus performs a refrigerant recovery operation when switching an operation mode from a defrosting mode to a heating mode. During the refrigerant recovery operation, by rotating a fan of a blower while monitoring a pressure at a discharge side of the compressor, the controller is configured to perform feedback control to cause a high-pressure side pressure to be close to a high-pressure side target pressure value. During the refrigerant recovery operation, by controlling a driving frequency of the compressor while monitoring a pressure at a suction side of the compressor, the controller is configured to perform feedback control to cause a low-pressure side pressure to be close to a low-pressure side target pressure value.