A refrigeration cycle apparatus including a refrigerant circuit including a compressor, an indoor heat exchanger, an expansion device, an outdoor heat exchanger, an outside air temperature sensor, and a controller configured to perform a hot gas defrosting operation and a reverse-defrosting operation based on a temperature obtained by the outside air temperature sensor. In the hot gas defrosting operation, hot gas discharged from the compressor without passing through the indoor heat exchanger is supplied to the outdoor heat exchanger. In the reverse-defrosting operation, refrigerant passing through the indoor heat exchanger is supplied from the compressor to the outdoor heat exchanger. The controller has at least a mixed defrosting operation mode in which the hot gas defrosting operation and the reverse-defrosting operation are performed in sequence. The controller is configured to start the mixed defrosting operation mode when the temperature obtained by the outside air temperature sensor satisfies a preset condition.

An air conditioner includes first and second refrigerant circulation systems each including an indoor unit including an indoor heat exchanger and an indoor throttle device, an outdoor unit including a compressor and an outdoor heat exchanger, an exhaust pipe arranged at an exhaust port of the compressor, an intake pipe arranged at an intake port of the compressor, a liquid-side piping connecting the exhaust pipe, the outdoor heat exchanger, the indoor throttle device, and the indoor heat exchanger in sequence, and a gas-side piping connecting the indoor heat exchanger and the intake pipe. The air conditioner further includes a heat circulation device configured to convey heat energy or cold energy of at least one of the indoor heat exchanger of the first refrigerant circulation system or the indoor heat exchanger of the second refrigerant circulation system into a room.

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 heat pump system for conditioning regeneration air from a space is provided. The heat pump system is operable in a winter mode and/or a summer mode, and may be selectively operated in a defrost mode or cycle. During a defrost mode, hot refrigerant may be used to directly and sequentially defrost the regeneration air heat exchanger. A compressor may be configured to be overdriven during a defrost cycle.

Stress to be imposed on a compressor in reverse cycle operation is reduced. A cycle controller causes an outdoor heat exchanger to function as a condenser and an indoor heat exchanger to function as an evaporator when a reverse cycle executing condition is met, so that a refrigerant circulates in reverse of a heating cycle. A rotation speed controller adjusts a rotation speed of a compressor in a reverse cycle, depending on an index correlated with an amount of frost on the outdoor heat exchanger at a start of the reverse cycle. The rotation speed controller decreases the rotation speed of the compressor in the reverse cycle as the index at the start of the reverse cycle indicates that the amount of the frost on the outdoor heat exchanger is smaller.

An apparatus using a heat pump includes a refrigerant circuit and a heat medium circuit. The refrigerant circuit is capable of performing a first operation, in which a load-side heat exchanger is used as a condenser, and a second operation, in which the load-side heat exchanger is used as an evaporator. A main circuit of the heat medium circuit has a branching part and a joining part. An overpressure protection device and a refrigerant leakage detecting device are connected to the main circuit. The overpressure protection device is connected to a connection part located between the load-side heat exchanger and one of the branching part and the joining part, or at the load-side heat exchanger. When leakage of refrigerant is detected, the state of a refrigerant flow switching device is set to a second state, an expansion device is set to a closed state, and a compressor is operated.

A refrigerant circuit includes a compressor operable to compress a refrigerant, an expansion valve, an outdoor heat exchanger, an indoor heat exchanger in a fresh air inlet to a conditioned space, a recovery heat exchanger in an extracted air outlet from the conditioned space, and a reversing valve operable to direct a direction of refrigerant flow between a cooling mode and a heating mode.

An air conditioning apparatus includes, a first heat exchanger, a second heat exchanger configured to exchange heat between a first heat medium and a second heat medium, flow rate control valves, and a pump. In a heating mode, a controller is configured to open the flow rate control valve corresponding to a heat exchanger, of the third heat exchangers, to which a request for air conditioning has been made, and to close the flow rate control valve(s) corresponding to a heat exchanger(s), of the third heat exchangers, to which the request for air conditioning has not been made. In a defrosting mode, when a temperature of the second heat medium is lower than a first determination temperature, the controller is configured to open at least one of the flow rate control valve(s) corresponding to the heat exchanger(s) to which the request for air conditioning has not been made.

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.