A refrigerant circuit includes a compressor, a high-pressure side heat exchanger, a decompressor, and a low-pressure side heat exchanger, which are annularly connected by a refrigerant pipe, and is configured to circulate refrigerant. The refrigerant circuit is configured to perform an oil recovery operation based on an operation history of the compressor during a normal operation of the refrigerant circuit and a property of the refrigerant circuit. The property of the refrigerant circuit includes at least one selected from the group of a length of the refrigerant pipe, a height difference of the refrigerant pipe, and an outside air temperature.

The present disclosure provides a multi-air conditioner for heating/cooling operation including: at least one of indoor units for heating/cooling operation including an indoor heat exchanger respectively; and an outdoor unit for heating/cooling operation including a compressor, an outdoor heat exchanger, and a switching unit configured to be disposed in a discharge side of the compressor to switch a flow of refrigerant, wherein the outdoor unit for heating/cooling operation includes a receiver which selectively stores refrigerant or oil according to a cooling or heating operation mode and provides the stored refrigerant or oil to the compressor. Accordingly, in the accumulator of the multi-air conditioner for heating/cooling operation using the receiver, the receiver that is not used in the heating mode can be converted and used for oil storage, thereby preventing oil burnout without adding a structure.

A compressor (31a, 31b) and an oil separator (35a, 35b) are provided in a refrigerant circuit (20). A flow-rate regulating valve (41a, 41b) is provided in an oil return pipe (40a, 40b) for returning a refrigerating-machine oil in the oil separator (35a, 35b) to the compressor (31a, 31b). A temperature sensor (42a, 42b) is provided downstream of the flow-rate regulating valve (41a, 41b) in the oil return pipe (40a, 40b). The oil-amount determiner (71a, 71b) determines whether an oil shortage state in which the amount of the refrigerating-machine oil held by the compressor (31a, 31b) is insufficient is present, on the basis of a measured value obtained by the temperature sensor (42a, 42b).

A cooling system uses P-traps to address the oil return issues that result from a vertical separation between the compressor and the high side heat exchanger. Generally, the vertical piping that carries the refrigerant from the compressor to the high side heat exchanger includes P-traps installed at various heights to capture oil in the refrigerant and to prevent that oil from flowing back to the compressor. T-connections are coupled to the P-traps to allow the oil to drain out of the P-traps. The oil may then be collected and returned to the compressor.

A cooling system uses P-traps to address the oil return issues that result from a vertical separation between the compressor and the high side heat exchanger. Generally, the vertical piping that carries the refrigerant from the compressor to the high side heat exchanger includes P-traps installed at various heights to capture oil in the refrigerant and to prevent that oil from flowing back to the compressor. As oil collects in the P-traps, the refrigerant begins to push the oil upwards until the oil reaches the high side heat exchanger. Multiple piping of different sizes may be used depending on a discharge pressure of the compressor. When the discharge pressure is higher, a larger piping may be used direct the oil and refrigerant to the high side heat exchanger.

A refrigeration cycle apparatus refrigeration cycle apparatus in which refrigerant circulates in an order of a compressor, an oil separator, a condenser, an expansion valve, an evaporator, and an accumulator. The refrigeration cycle apparatus includes: an oil returning path extending from the oil separator to the compressor; a first electromagnetic valve provided on the oil returning path; an oil returning path extending from the accumulator to the compressor; a second electromagnetic valve provided on the oil returning path; and a controller configured to control a degree of opening of the first electromagnetic valve and a degree of opening of the second electromagnetic valve.

A device management system having a device having a structural component and a terminal connected to the device via a network includes a feature value detection unit provided in the device and for detecting a feature value of the structural component, a storage device storing in time series the feature value detected by the feature value detection unit, a lifespan estimation unit for estimating a lifespan of the structural component from the feature value stored in the storage device, a determination unit for determining whether a remaining period that is a time period from a time at which estimation is performed to an end of the lifespan is less than or equal to a set scheduled period, and a notification unit provided in the terminal and for sending a notification indicating that the remaining period is less than or equal to the set scheduled period.

Systems and methods are provided and include an optical sensor configured to be disposed on a sight glass. The optical sensor is configured to generate signals based on a light reflectivity associated with a liquid of the refrigeration system. An optical sensor control module that includes a processor that is configured to execute instructions stored in a nontransitory memory, and the instructions include (i) generating a set of data based on the signals, and (ii) determining an amount of liquid of the refrigeration system based on the set of data.

A cooling system uses P-traps to address the oil return issues that result from a vertical separation between the compressor and the high side heat exchanger. Generally, the vertical piping that carries the refrigerant from the compressor to the high side heat exchanger includes P-traps installed at various heights to capture oil in the refrigerant and to prevent that oil from flowing back to the compressor. T-connections are coupled to the P-traps to allow the oil to drain out of the P-traps. The oil may then be collected and returned to the compressor.

A cooling system uses P-traps to address the oil return issues that result from a vertical separation between the compressor and the high side heat exchanger. Generally, the vertical piping that carries the refrigerant from the compressor to the high side heat exchanger includes P-traps installed at various heights to capture oil in the refrigerant and to prevent that oil from flowing back to the compressor. As oil collects in the P-traps, the refrigerant begins to push the oil upwards until the oil reaches the high side heat exchanger. Multiple piping of different sizes may be used depending on a discharge pressure of the compressor. When the discharge pressure is higher, a larger piping may be used direct the oil and refrigerant to the high side heat exchanger.