A refrigeration cycle apparatus includes a refrigerant circuit in which a compressor, a first heat exchanger, an expansion mechanism, and a second heat exchanger are connected by pipes. The first heat exchanger includes a first refrigerant passage and a second refrigerant passage that share a plurality of fins with each other and provided in parallel in the refrigerant circuit. The apparatus further includes a high-and-low-pressure switching mechanism which is located on an inlet side of the second refrigerant passage of the first heat exchanger in flowing of refrigerant in an operation in which the first heat exchanger functions as a condenser, and which performs switching between flow directions of the refrigerant. The apparatus further includes a refrigerant blocking mechanism located on an outlet side of the second refrigerant passage of the first heat exchanger in the flowing of the refrigerant in the operation, and which blocks the flowing of the refrigerant.

A refrigeration cycle apparatus in which a compressor, a heat-source-side heat exchanger, a decompressor, and a use-side heat exchanger are connected by pipes to allow refrigerant to be circuited as a refrigeration cycle. The refrigeration cycle apparatus includes a controller which controls an operation of each of devices. The controller sets an operation mode to a specific operation mode for determining where abnormality occurs based on states of the compressor, the heat-source-side heat exchanger, the decompressor and the use-side heat exchanger in the case where an operating state of one of a plurality of element devices to be controlled by the controller is changed from a first state to a second state, the element devices being included in the compressor, the heat-source-side heat exchanger, the decompressor and the use-side heat exchanger.

In one embodiment, an HVAC system includes an indoor unit having a furnace, an outdoor heat pump unit having a compressor and an outdoor coil, a refrigerant line coupled to the indoor unit and the outdoor heat pump unit, and an EEV coupled to the refrigerant line. The HVAC system further includes one or more controllers operable to determine an occurrence of a first event, initiate a closure of the EEV, initiate operation of the compressor at a completion of the air conditioning cycle to pump down a refrigerant to the outdoor coil, and cease operation of the compressor when a low-pressure switch is tripped.

Disclosed is a four-way valve including a housing having a refrigerant filling chamber formed therein, a high pressure pipe hole formed on a bottom surface of the housing and coupled to a high pressure pipe through which refrigerant discharged from the compressor flows, a first pipe hole formed on an upper surface of the housing and coupled to a first pipe extending to a first heat exchanger, a second pipe hole formed on the upper surface of the housing and coupled to a second pipe extending to a second heat exchanger, a low pressure pipe hole formed on the upper surface of the housing and configured to allow the refrigerant to be collected to the compressor, and a switching guide configured to rotate to allow the low pressure pipe hole to selectively communicate with the first pipe hole or the second pipe hole.

When a controller receives an instruction for a heating operation, the controller switches an operation mode of a refrigeration cycle apparatus between a heating operation mode and an oil recovery operation mode. The heating operation mode is a mode to circulate refrigerant in a refrigerant circuit such that the refrigerant flows through a gas extension pipe in a gas phase state. The oil recovery operation mode is a mode to circulate the refrigerant in the refrigerant circuit such that the refrigerant flows in the gas extension pipe in a gas-liquid two-phase state. The direction in which the refrigerant flows in the gas extension pipe in the oil recovery operation mode is opposite to that in which the refrigerant flows in the gas extension pipe in the heating operation mode.

A heat exchanger includes a plurality of heat transfer tubes arranged at predetermined intervals in a vertical direction, a tubular header that has a plurality of connection portions where the heat transfer tubes are connected to a side portion of the header and that communicates with each of the heat transfer tubes, a refrigerant pipe that communicates with the header at a middle portion of the header in the vertical direction, and a first bypass pipe having ends one of which communicates with a lower portion of the header and the other of which communicates with a middle portion of the refrigerant pipe. A distance between a communication position at which the first bypass pipe and the refrigerant pipe communicate with each other and an inner wall of the header is not more than double an inside diameter of the refrigerant pipe.

An air-conditioning apparatus includes a refrigeration circuit, a first shut-off device provided at a pipe connecting a heat-source-side heat exchanger and an expansion device, a refrigerant leak detection device, and a controller. The controller controls a flow switching device to switch a connection state between a first connection state in which a discharge side of a compressor is connected to the heat-source-side heat exchanger, and a second connection state in which a suction side of the compressor is connected to the heat-source-side heat exchanger via an accumulator. When a refrigerant leak is detected, the controller performs a refrigerant retrieval operation and a refrigerant transfer operation.

A pressure spike prevention assembly for use in a heat pump system includes a thermostatic expansion valve that includes a first port and a second port. The first port is designed to be fluidly coupled to an indoor coil, and the second port is designed to be coupled to an outdoor coil. The pressure spike prevention assembly further includes a multi-way valve that includes an inlet port, an output port, and a liquid line port. The inlet port is fluidly coupled to the first port. The output port is fluidly in communication with the second port. The liquid line port is configured to be fluidly coupled to a charge compensator of the heat pump system via a liquid line of the heat pump system.

A method of defrosting an indoor coil in a refrigeration system including, while the system is operating in the refrigeration mode, with a controller of the refrigeration system, determining a defrost commencement time at which the refrigeration system is to commence operating in the defrost mode. With the controller, one or more defrost energy conservation processes are initiated prior to the defrost commencement time, to decrease a rate at which thermal energy is transferred from the refrigerant in the outdoor coil to ambient air around the outdoor coil. The defrost energy conservation process continues until a defrost energy conservation termination criterion is satisfied, at which time the defrost energy conservation process is terminated. Upon termination of the defrost energy conservation process, operation of the refrigeration system in the defrost mode is commenced.

An air conditioner system is disclosed. The air conditioner system includes: a compressor; a four-way valve configured to provide a refrigerant circulation path depending on an operation mode of the air conditioner system; a blocking valve disposed between the compressor and the four-way valve; a circulation line configured to provide a path for introducing a refrigerant discharged from the compressor back into the compressor, when the blocking valve is in a closed state; and a controller configured to control the blocking valve based on a pressure of the refrigerant discharged from the compressor.