A method of controlling an HVAC circuit, comprises allowing refrigerant to circulate within the HVAC circuit, wherein the HVAC circuit comprises an evaporator coil, a condenser coil, at least one fan configured to provide airflow to the condenser coil, at least one expansion valve, and at least one compressor. The method continues by receiving a temperature measurement and determining based on the temperature measurement, a minimum fan speed configured to avoid pressure spikes within the condenser coil. The method concludes by sending a signal to the at the least one fan to direct the at least one fan to spin at a rate greater than or equal to the minimum fan speed when the measured temperature is less than a predetermined temperature, wherein, when the refrigerant circulates through the condenser coil, the minimum fan speed is greater than zero rotations per minute.

A refrigeration system includes a receiver, a gas bypass valve, a parallel compressor, and a controller. The gas bypass valve and the parallel compressor are fluidly coupled to an outlet of the receiver in parallel and configured to control a pressure of a gas refrigerant in the receiver. The controller is configured to switch from operating the gas bypass valve to operating the parallel compressor to control the pressure of the gas refrigerant in the receiver in response to a value of a process variable crossing a switchover setpoint. The value of the process variable depends on an amount of the gas refrigerant produced by the refrigeration system. The controller is configured to automatically adjust the switchover setpoint in response to the amount of the gas refrigerant produced by the refrigeration system being insufficient to sustain operation of the parallel compressor.

A performance degradation diagnosis system includes a determining unit, and control unit. A refrigeration cycle apparatus includes a refrigerant circuit having a compressor, heat-source-side heat exchanger, and use-side heat exchanger. The determining unit determines, based on an index indicating an operation state of the refrigeration cycle apparatus, performance degradation of the refrigeration cycle apparatus with respect to each of a plurality of performance degradation factors. In a case in which the determining unit determines performance degradation, the control unit grasps an operation condition of the refrigeration cycle apparatus which is operating. In a case in which the operation condition of the refrigeration cycle apparatus is not suitable to determine performance degradation with respect to a performance degradation factor of a determination target, the control unit controls the operation condition of the refrigeration cycle apparatus so that the operation condition of the refrigeration cycle apparatus becomes an appropriate operation condition.

A refrigerant leakage determination system capable of detecting leakage of refrigerant without requiring complicated processing is provided. A refrigerant leakage determination system is a refrigerant leakage determination system of a refrigeration cycle apparatus that includes a refrigerant circuit including a heat-source-side heat exchanger and has, as operating modes, a normal mode in which the heat-source-side heat exchanger is caused to function as an evaporator and a defrosting mode in which the heat-source-side heat exchanger frosted during a normal operation is defrosted. The refrigerant leakage determination system includes a processor configured to acquire defrosting information regarding a relationship between a normal operation period and the number of defrosting operations, and memory that stores the defrosting information. The processor is further configured to determine, based on the acquired defrosting information, leakage of refrigerant in the refrigerant circuit.

A refrigeration apparatus (1) includes a heat-source-side unit (10) using a refrigerant that works in a supercritical region. The heat-source-side unit (10) includes a compression element (20) configured to compress the refrigerant, a heat-source-side heat exchanger (24), an expansion valve (26) provided downstream of the heat-source-side heat exchanger (24), a receiver (25) provided downstream of the expansion valve (26), and a control unit (101). The control unit (101) performs a first operation for evaluating the amount of the refrigerant based on a high-pressure-side pressure, on a first condition that the internal pressure of the receiver (25) be equal to or less than a supercritical pressure.

A variable refrigerant flow (VRF) air conditioning system, a control method thereof, and a computer-readable storage medium are provided. When the VRF air conditioning system is cooling, indoor units in an operating state are obtained. Indoor units with humidity demand and indoor units without humidity demand in the operating state are obtained. A ratio of humidity demand is determined according to an output nominal value of each indoor unit in the operating state. The ratio can include a ratio of a total output nominal value of indoor units with humidity demand to a total output nominal value of indoor units without humidity demand When the ratio is greater than a preset ratio, a rotation speed of an outdoor fan can be adjusted according to an outdoor environment temperature.

A refrigerant leakage notifying device includes a refrigerant sensor, a determination unit, a notification unit, and an output unit. The refrigerant sensor detects a refrigerant and outputs a detection signal according to a detection result. The determination unit receives the detection signal outputted from the refrigerant sensor and determines leakage of the refrigerant in accordance with the detection signal received. The notification unit notifies leakage of the refrigerant with at least one of sound and light in a case in which the determination unit has determined that the refrigerant is leaking. The output unit is provided separately from the refrigerant sensor. The output unit outputs a test signal to the determination unit. The test signal is a signal that the determination unit has determined that the refrigerant is leaking in a case in which the determination unit receives the signal.

A refrigeration cycle system includes a refrigeration cycle apparatus, an operation signal transmitter, a detection unit, a notification unit, and a processing unit. The refrigeration cycle apparatus includes a refrigerant circuit. The operation signal transmitter transmits an operation signal for the refrigeration cycle apparatus. The detection unit detects leakage of a refrigerant. The notification unit notifies of leakage of the refrigerant by emitting at least one of sound and light in a case in which the detection unit has detected leakage of the refrigerant. The processing unit causes the notification unit to execute test behavior of emitting at least one of sound and light in a case in which the operation signal transmitter transmits the operation signal to the refrigeration cycle apparatus.

A heat exchanger connected to a refrigerant pipe includes: heat transfer tubes; and a header that connects the refrigerant pipe and the heat transfer tubes, and that forms a refrigerant flow path between the refrigerant pipe and the heat transfer tubes. The header includes a first member that includes a first plate-shaped portion, and a second member that includes a second plate-shaped portion that is stacked on a heat transfer tubes side of the first plate-shaped portion. The first plate-shaped portion has a first opening that forms the refrigerant flow path. The second plate-shaped portion has a second opening that forms the refrigerant flow path. When viewed in a stacking direction of the first plate-shaped portion and the second plate-shaped portion, the second opening and the first opening overlap each other at a first region and at a second region that is different from the first region.

A heat pump is provided that may include an indoor unit including an indoor heat exchanger; an outdoor unit including an outdoor heat exchanger and a compressor that compresses a refrigerant; a housing that forms an outer shape of the outdoor unit and provides an internal space in which the outdoor heat exchanger and the compressor are disposed; a partition wall that is disposed in the internal space of the housing, and divides the internal space into a flow path space in which the outdoor heat exchanger is disposed and a cycle space in which the compressor is disposed; an outdoor fan disposed in the flow path space to cause an air flow; and a controller that controls an operation of the compressor and the outdoor fan. The housing may include a hole that communicates with the cycle space, and the partition wall may include a barrier hole that communicates the flow path space and the cycle space.