A reheat system of an air conditioning unit includes a bypass line that fluidly couples an outlet of a reheat coil to an input end of a metering device. Further, the reheat system includes a reheat exit line that fluidly couples the outlet of the reheat coil to an input of a condenser. A bypass valve is disposed in the bypass line and a reheat valve is disposed in the reheat exit line. A controller is configured to control the bypass valve and the reheat valve such that a refrigerant from the outlet of the reheat coil is routed to the metering device via the bypass line when an ambient temperature is greater than or equal to a cut-off temperature value that is indicative of a high ambient temperature condition at which the condenser begins operating as an evaporator.

A system for measuring oil circulation ratio in a vapor-compression refrigeration system (VCRS) is provided. The system may include an oil separator configured to receive the refrigerant and oil flow from the low-pressure line of the VCRS and output a oil flow and a refrigerant flow. The system may further include an oil collector configured to receive the separated oil flow provided by the oil separator. A valve may control an oil flow from the oil collector to the low-pressure line. A level sensor may measure oil level in the oil collector. The system may close, in response to the oil being at or less than a first level, the valve to collect oil in the oil collector. The system may open, in response to the oil being at or greater than a second level, the valve to release oil from the oil collector to the low-pressure line.

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 system includes a heat exchanger configured to provide superheat control for the low temperature low pressure gas refrigerant flowing out of the evaporator and through the first side of the heat exchanger by transferring heat from the high pressure high temperature superheated gas refrigerant flowing through a second side of the heat exchanger. A modulating solenoid valve is located at the inlet of the second side of the heat exchanger and configured to modulate the flow of high pressure high temperature superheated gas refrigerant flowing through the second side of the heat exchanger. A temperature sensor is located in such a way as to measure the temperature of the gas refrigerant flowing out of the evaporator and through the first side of the heat exchanger. A controller is configured to calculate the superheat of the gas refrigerant based on the measured temperature and measured pressure of the gas refrigerant and may compare the calculated superheat to a superheat threshold. If the calculated superheat is less than the superheat threshold, the controller will modulate the flow the high pressure high temperature gas refrigerant flowing through the second side of the heat exchanger. The refrigeration system may be activated in a variety of methods by appropriate control of the valves and other system components.

A refrigeration cycle apparatus causes refrigerant to circulate through a compressor, an indoor heat exchanger, an outdoor heat exchanger, a heat storage body, a first expansion valve, and a second expansion valve. The refrigeration cycle apparatus includes a bypass path and a first on-off valve provided in the bypass path. The bypass path branches off from a first portion that connects the indoor heat exchanger and the first expansion valve in a first refrigerant pipe, and leads to a fourth refrigerant pipe that connects a suction port of the compressor and a four-way valve. The first on-off valve is opened in a defrosting operation.

Provided is a measure against a refrigerant leak. A heat load processing system has a plurality of refrigerant circuits and includes a plurality of device units, a casing that collectively houses the plurality of device units configuring the different refrigerant circuits, a refrigerant leak detector that individually detects a refrigerant leak in the respective refrigerant circuits, and a controller. The device units include a heat exchanger that is connected to a refrigerant pipe and a heat medium pipe as a device configuring one of the refrigerant circuits. When the refrigerant leak detector detects the refrigerant leak, the controller performs refrigerant leaking circuit identification processing for identifying a refrigerant circuit in which the refrigerant leak is occurring and a refrigerant leak third control for changing an operating state of a predetermined refrigerant circuit based on a result of the refrigerant leaking circuit identification processing.

A method for operating a heat pump (20; 300) includes operating in a cooling mode wherein heat is absorbed by refrigerant in the indoor heat exchanger (26) and rejected by refrigerant in the outdoor heat exchanger (24). The heat pump switches to operation in a heating mode wherein heat is rejected by refrigerant in the indoor heat exchanger, heat is absorbed by refrigerant in the outdoor heat exchanger, and there is an ejector (60) motive flow and ejector secondary flow. In the heating mode a refrigerant pressure (PH) or temperature (TL) is measured and, responsive to the measured refrigerant pressure or temperature, at least one of a fan speed is changed and a needle (132) of the ejector is actuated.

A CO.sub.2 based refrigeration system and a method of operating the CO.sub.2 based refrigeration system. The system includes a condenser configured to transfer heat from a CO.sub.2 refrigerant of the refrigeration system to an air stream. The system also includes an indirect evaporative cooler arranged to cool an ambient air stream without changing its moisture content and to supply the cooled ambient air to the condenser to facilitate the transfer of heat from the CO.sub.2 refrigerant.

An HVAC system includes a compressor, condenser, and evaporator. A sensor measures a value associated with the refrigerant in the condenser or the evaporator, and a controller is communicatively coupled to the compressor and the sensor. The controller determines, based on an operational history the compressor, that pre-requisite criteria are satisfied for entering a sensor validation mode. After determining the pre-requisite criteria are satisfied, an initial sensor measurement value is determined. Following determining the initial sensor measurement value, the compressor is operated according to a sensor-validation mode. Following operating the compressor according to the sensor-validation mode for at least a minimum time, a current sensor measurement value is determined. The controller determines whether validation criteria are satisfied for the current sensor value. In response to determining that the validation criteria are satisfied, the controller determines that the sensor is validated.

A method for estimating refrigerant charge for an HVACR system is provided. The method includes obtaining one or more system parameters during operation. The one or more system parameters include at least one of compressor suction superheat, system mass flow, expansion device mass flow or opening degree, compressor suction saturated temperature, and compressor discharge saturated temperature. The method also includes conducting a regression analysis on the one or more system parameters to determine one or more predictive parameters for estimating the refrigerant charge. The method further includes determining a predictive model based on regression analysis. The predictive model establishes a relationship between the refrigerant charge and the one or more predictive parameters. Also the method includes estimating the refrigerant charge based on the predictive model.