A method of operating a heat pump system is provided, the heat pump system having at least a controller and configured to operate at least two defrost cycles. The method comprises receiving, at the controller, weather data for a defined geographic area proximate to an installed location of the heat pump system; and selecting, based on said weather data, one of the at least two defrost cycles.

A refrigeration cycle apparatus includes a refrigeration cycle in which refrigerant circulates, the refrigeration cycle including a compressor, an outdoor heat exchanger, expansion valves, and indoor heat exchangers, which are connected to each other via a refrigerant pipe, a heat source unit accommodating the outdoor heat exchanger, use-side units accommodating the indoor heat exchangers, and a control unit that controls at least turning on and off of the refrigeration cycle. The control unit detects abnormality of the refrigeration cycle based on the pressure or temperature of the refrigeration cycle in an off time of the refrigeration cycle.

In a case of a heating operation in which the use side heat exchanger functions as a condenser when an outside temperature is a predetermined low temperature, a low-outside-temperature heating operation start-up mode in which, while a refrigerant discharged from the compressor is caused to flow into the use side heat exchanger, a refrigerant is supplied to the injection port of the compressor via the injection pipe and part of the refrigerant that has transferred heat in the heat source side heat exchanger is supplied to the compressor, is followed by a low-outside-temperature heating operation mode in which the refrigerant discharged from the compressor is supplied to the injection port of the compressor via the injection pipe while the refrigerant being caused to flow into the use side heat exchanger.

A channel on an upstream side of a third expansion device and a channel on an upstream side of a second expansion device are connected during a heating operation, and medium pressure refrigerant generated by the third expansion device during the heating operation is introduced on a suction side of a compressor via the second expansion device and a suction injection pipe.

A multi-connected heat recovery air conditioning system and a control method thereof. The multi-connected heat recovery air conditioning system includes an indoor unit, an outdoor unit and a hydraulic module, wherein the outdoor unit comprises a compressor, an outdoor heat exchanger, a first four-way valve and a second four-way valve. The multi-connected heat recovery air conditioning system further comprises an indoor unit temperature unit, a water temperature unit, a high-pressure sensor and a low-pressure sensor. The indoor unit temperature unit is arranged in the indoor unit for detecting and obtaining the outlet temperature value of the indoor unit, the water temperature unit is arranged at a heat exchange water tank for detecting and obtaining water temperature, and the high-pressure sensor and the low-pressure sensor are arranged at the output end and the air return end of the compressor respectively.

A heat pump system including a charge compensator having a liquid line port for an inflow of a refrigerant into the charge compensator and for an outflow of the refrigerant from the charge compensator. The heat pump system further includes an isolation valve configured to control flows of the refrigerant to and from the charge compensator through a liquid line piping of the heat pump system based on whether the heat pump system is operating in a cooling mode, a defrost mode, or a heating mode, where the liquid line port is fluidly coupled to the liquid line piping of the heat pump system.

A defrost cycle control assembly includes a first sensor that is configured to measure a temperature adjacent a top portion of an outdoor heat exchanger of a heat pump, a second sensor that is configured to measure a temperature adjacent a bottom portion of the outdoor heat exchanger, and a third sensor that is configured to measure an ambient temperature. Further, the defrost cycle control assembly includes a controller that is configured to initiate a defrost cycle of the heat pump based on the temperature adjacent the top portion and the ambient temperature when said temperatures indicate formation of frost at the top portion of the outdoor heat exchanger where the first sensor is disposed. The controller is configured to terminate the defrost cycle when the temperature at the bottom portion reaches a termination temperature which indicates that the frost on the outdoor heat exchanger has melted.

An air-conditioning device including multiple outdoor units and an indoor unit through a pipe includes a control section that obtains a degree of subcooling at an outlet of a subcooling circuit of each outdoor unit based on a temperature detected by a temperature sensor that detects the temperature of refrigerant having passed through the subcooling circuit of each outdoor unit, obtain a target value of the degree of subcooling based on the obtained multiple degrees of subcooling, and perform the control of increasing the rotation speed of a compressor of an outdoor unit having a higher degree of subcooling than the target value and decreasing the rotation speed of a compressor of an outdoor unit having a lower degree of subcooling than the target value such that a difference in the degree of subcooling at the outlet of the subcooling circuit of each outdoor unit is decreased.

An air-conditioning apparatus includes a refrigerant circuit, a heat medium circuit, and a controller. In the refrigerant circuit, a compressor, a heat-source-side heat exchanger, an expansion unit, and a load-side heat exchanger are connected by refrigerant pipes, and refrigerant flows. The heat-source-side heat exchanger causes heat exchange to be performed between the refrigerant and a heat-source heat medium. The load-side heat exchanger causes heat exchange to be performed between the refrigerant and a load heat medium, and refrigerant flows. In the heat medium circuit, a flow control valve that regulates the flow rate of the heat-source heat medium and the heat-source-side heat exchanger are connected by a heat medium pipe, and the heat-source heat medium flows. The controller includes a storage unit that stores data indicating a defined maximum flow rate and a defined minimum flow rate of the heat-source heat medium that flows in the heat medium circuit.

In a power converter, an inductance L of a reactor and a capacitance C of a capacitor satisfy a condition of the expression (1) below. In the power converter, a current-limiting circuit between an AC power source and the capacitor is unnecessary. Herein, αm ([A.Math.s]) is a value of a ratio of a maximum rated current squared time product to a maximum rated output current of diodes of a rectifier circuit, Pmax is a maximum power consumption of the motor, Vac is a voltage value of a three-phase AC voltage, and a value of a constant a is 4.3

[00001]$\begin{array}{cc}a.C.\sqrt{\frac{C}{L}}.Math.\frac{{\mathrm{Vac}}^3}{P_{\max }}\le {\alpha }_m.& \left(1\right)\end{array}$