A refrigerant cycle apparatus includes a main refrigerant circuit, a bypass circuit, and a controller. The main refrigerant circuit includes a compressor, a heat source-side heat exchanger, a heat source-side expansion valve, and a utilization-side heat exchanger. The controller performs a second operation of opening a hot gas bypass valve in a state in which the compressor is driven before performing a first operation in which the heat source-side heat exchanger serves as a heat absorber for the refrigerant and the utilization-side heat exchanger serves as a radiator for the refrigerant. In the first operation or the second operation, when a difference between a pressure of the refrigerant on the discharge side of the compressor and a pressure of the refrigerant on the suction side of the compressor becomes larger than a first predetermined value, the controller decreases the number of revolutions of the compressor.

An apparatus for staged startup of air-cooled low charged packaged ammonia refrigeration system includes motorized valves on condenser coil inlets, a main compressor discharge motorized valve, a bypass pressure regulator valve in the main compressor piping, and check valves on the condenser outlets. The condenser inlet motorized valves provide precise control of gas feed to the condensers, so pressure can build without collapsing oil pressure. The condenser outlet contains check valves to prevent liquid backflow during coil isolation. The compressor discharge line contains a motorized valve for regulating discharge pressure at start-up. The motorized valve in the compressor discharge piping includes a bypass with a pressure regulator for precise regulation at minimum discharge pressure. Once discharge pressure rises above the setpoint, the condenser inlet solenoid coils open one at a time. The discharge pressure regulating motorized valve simultaneously regulates the discharge pressure until the condenser maintains discharge pressure.

In a method for operating a compressor (22) having an inlet (26) and an outlet (28), the method includes: running the compressor to compress a fluid; shutting down (422) the compressor; determining (420) a condition-dependent threshold restart pressure difference (threshold) across the compressor; relieving the pressure difference to reach the threshold; and, after the threshold is reached, restarting (434) the compressor.

Systems and methods for providing lubricant from a first compressor to a second compressor are provided. A control module receives a start command for a climate-control system having the first and second compressors, allows lubricant from the first compressor to flow into an inlet of the second compressor, turns the second compressor to an ON-mode, and prevents lubricant from the first compressor from flowing into the inlet of the second compressor after the second compressor has been in the ON-mode for a predetermined time period.

A multi-air conditioner for cooling and heating is provided to remove latent heat and sensible heat by using a single outdoor unit. The multi-air conditioner includes: at least one indoor unit installed in a room, that comprises an indoor heat exchanger and an indoor expansion valve; an outdoor unit connected to the indoor unit via a refrigerant pipeline, that comprises an outdoor heat exchanger, a plurality of compressors, an outdoor expansion valve, and a four-way valve; and a dedicated outdoor air ventilation unit connected to the indoor unit and the outdoor unit via the refrigerant pipeline, that dehumidifies and ventilates outdoor air and supplies the outdoor air to the room, wherein the outdoor unit provides a refrigerant to both the dedicated outdoor air ventilation unit and the indoor unit by controlling the compressors depending on an operation mode of the dedicated outdoor air ventilation unit and the indoor unit. Accordingly, it is possible to run an air conditioner for cooling and heating and a dedicated outdoor air conditioner simultaneously by using a single outdoor unit. Moreover, the handling of sensible and latent heats can be controlled by a single outdoor unit, thereby minimizing facility costs and enhancing control reliability.

A method of controlling a refrigeration system including a medium temperature refrigeration load and a low temperature refrigeration load. The method includes selectively bypassing refrigerant between a medium temperature suction group and a low temperature suction group via a bypass line using an electronic valve positioned in the bypass line. The method also includes controlling flow of refrigerant between the medium temperature suction group and the low temperature suction group via a controller communicatively coupled to the valve, and modulating the valve at any position between a closed position and a full open position to vary an amount of refrigerant flow between the medium temperature suction group and the low temperature suction group in response to determining, via the controller, one or both of a state of the medium temperature suction group and a state of the low temperature suction group.

An air conditioner includes a use-side unit, a heat source-side unit, refrigerant connection pipes, cutoff valve provided in the refrigerant connection pipes, a refrigerant leakage detector, and a controller control. When the refrigerant leakage detector detects a refrigerant leakage, the controller performs pressure reduction control to lower the pressure of the refrigerant in the use-side unit, and thereafter puts the cutoff valves into a cutoff state.

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 fresh-air air conditioning system and control method, the system comprising an interior unit (1) and an exterior unit (2). The interior unit (1) comprises a first interior heat exchanger (11) and a second interior heat exchanger (13). The exterior unit (2) comprises a compressor (21), intake bypass circuit, first accumulator (22) and second accumulator (23). The intake bypass circuit comprises a first electromagnetic valve (24), second electromagnetic valve (25), and third electromagnetic valve (26). A first end of the first electromagnetic valve (24) is connected to a first end of the first interior heat exchanger (11), and a second end of the first electromagnetic valve (24) is connected via the first accumulator (22) to a first intake end of the compressor (21) and a first end of the third electromagnetic valve (26). The second end of the third electromagnetic valve (26) is connected via the second accumulator (23) to a second intake end of the compressor (21) and a first end of the second electromagnetic valve (25). The second end of the second electromagnetic valve (25) is connected to a first end of the second interior heat exchanger (13). When one of the first interior heat exchanger (11) or second interior heat exchanger (13) is closed, the third electromagnetic valve (26) opens so that the first accumulator (22) and second accumulator (23) simultaneously communicate with the open interior heat exchanger, avoiding poor oil return as a result of prolonged single-cylinder operation of the compressor, and ensuring the reliability of the compressor as well as interior comfort.

An apparatus includes a high side heat exchanger, a heat exchanger, a flash tank, a first expansion valve, a second expansion valve, a load, a first compressor, and a second compressor. During a first mode of operation, the second expansion valve directs refrigerant from the flash tank to the load. The refrigerant from the load bypasses the first compressor. The heat exchanger transfers heat from the refrigerant from the high side heat exchanger to the refrigerant from the load. The second compressor compresses the refrigerant from the heat exchanger. During a second mode of operation, the first expansion valve directs refrigerant from the flash tank to the load. The first compressor compresses the refrigerant from the load and the second compressor compresses the refrigerant from the first compressor before the refrigerant from the first compressor reaches the high side heat exchanger.