An apparatus using a heat pump includes a refrigerant circuit and a heat medium circuit. The refrigerant circuit is allowed to perform 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 container is provided to a suction pipe provided between a refrigerant flow switching device and a compressor. To the heat medium circuit, an overpressure protection device and a refrigerant leakage detecting device are connected. When leakage of refrigerant into the heat medium circuit is detected, the refrigerant flow switching device is switched to a second state, an expansion device is set to a closed state, and the compressor is made in operation. When a requirement for ending the operation of the compressor is satisfied after the leakage of the refrigerant into the heat medium circuit is detected, the compressor is set to a stopped state, and the refrigerant flow switching device is switched to a first state.

An air conditioning system and a control method are provided. The air conditioning system includes: at least one heat exchanger (1, 2); and at least one control mechanism. Each control mechanism is connected to one of the at least one heat exchanger (1, 2) and is configured to control the corresponding heat exchanger to switch between a first working state and a second working state. The heat exchanger (1, 2) drains liquid when in the first working state and stores liquid when in the second working state.

Systems and methods are provided and include a variable-capacity compressor operable in a first capacity mode and in a second capacity mode that is higher than the first capacity mode. A control module is configured to switch the variable-capacity compressor between the first capacity mode and the second capacity mode based on a demand signal from a thermostat and an indoor relative humidity sensed by an indoor relative humidity sensor. The control module determines whether the indoor relative humidity is greater than a predetermined humidity and operates the variable-capacity compressor in the second capacity mode in response to receiving the demand signal from the thermostat and the indoor relative humidity exceeding the predetermined humidity.

An exemplary heat pump includes: a compressor configured to compress a refrigerant; a first heat exchanger configured to condense the compressed refrigerant; a flow rate adjustment valve configured to adjust a flow rate of the condensed refrigerant; an expansion valve having an adjustable opening and configured to decompress the refrigerant having passed the flow rate adjustment valve; a second heat exchanger configured to cool a temperature control target by using the refrigerant decompressed by the expansion valve; and a control device configured to control the opening of the expansion valve based on a difference between the temperature of the refrigerant flowing into the second heat exchanger and the temperature of the refrigerant flowing out from the second heat exchanger, and to control the opening of the flow rate adjustment valve based on the flow rate of the refrigerant to be supplied to the second 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.

In an air-conditioning system, a gaseous refrigerant remaining in a reservoir can be discharged from the reservoir even when a cooling operation has started and the reservoir is being filled with a liquid refrigerant. Therefore, the reservoir can be filled with the liquid refrigerant at a faster speed.

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 refrigeration cycle apparatus includes an outdoor unit including a compressor, a first heat exchanger, and a first expansion valve, an indoor unit including a second expansion valve and a second heat exchanger, and a first pipe and a second pipe connected between the outdoor unit and the indoor unit. In a cooling operation, refrigerant delivered from the compressor sequentially passes through the first heat exchanger, the first expansion valve, the first pipe, the second expansion valve, the second heat exchanger, and the second pipe and returns to the compressor, and in the cooling operation, the first expansion valve converts refrigerant from a liquid-phase state to a two-phase state and sends two-phase refrigerant to the first pipe.

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.

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