An oil return control method of a multi-functional multi-split system with double four-way valves. The multi-functional multi-split system includes an outdoor unit, at least one set of hydraulic modules and at least one set of indoor modules. When the multi-split system is switched from a normal operation mode to an oil return mode, a first four-way valve and a second four-way valve are powered down, and operation modes of each set of indoor modules and each set of hydraulic modules, the on/off state of fans of an indoor heat exchanger and a hydraulic heat exchanger, opening degrees of a first electronic expansion valve of the indoor heat exchanger and a first electronic expansion valve of the hydraulic heat exchanger, and the on/off state of a first electromagnetic valve and a second electromagnetic valve are correspondingly adjusted based on the previous operation modes.

A compressor may include a shell, a first scroll, and a second scroll. The shell may include a first inlet, a second inlet, and an outlet. The first scroll may include a first end plate and a first spiral wrap. The second scroll may include a second end plate and a second spiral wrap, the first and second spiral wraps cooperating to define a series of moving compression pockets therebetween. The moving compression pockets decrease in volume as the moving compression pockets move from a radially outer position to a radially inner position. The moving compression pockets may receive working fluid from the first inlet at the radially outer position and provide working fluid to the outlet at the radially inner position. The second end plate may include a fluid cavity receiving working fluid from the second inlet and fluidly isolated from working fluid within the moving compression pockets.

A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system operates in three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.

A vapor compression system includes a compressor configured to circulate a refrigerant through a refrigerant loop, a sump configured to receive a mixture of lubricant and the refrigerant from the compressor, and a controller having a memory and a processor. The processor is configured to receive a first signal indicative of a temperature of the mixture within the sump, receive a second signal indicative of a pressure of the mixture within the sump, determine a relative amount of the refrigerant in the mixture based on the first signal and the second signal, and output a control signal in response to the relative amount of the refrigerant in the mixture exceeding a threshold value.

An air conditioning system includes a main circuit having a multi-stage compressor, a condenser, a throttling element and an evaporator connected by pipelines; and a cooling branch, the inlet of which is connected to the main circuit between the condenser and the throttling element, and the outlet of which is connected to at least one of the first-stage suction port and the intermediate-stage suction port of the multi-stage compressor, wherein the cooling branch flows through the drive motor of the multi-stage compressor, and a regulating valve for controlling the opening of the cooling branch is provided on the cooling branch; and a control module that controls the opening of the regulating valve on the cooling branch based on the temperature of the outlet downstream of the drive motor on the cooling branch and the intermediate suction pressure of the intermediate-stage suction port of the multi-stage compressor.

The present invention relates to an air conditioner. A first invention according to the present embodiment is an air conditioner which has a refrigeration capacity of 16 kW to 28 kW, inclusive, and uses a mixed refrigerant R134a as a refrigerant, and in which a refrigerant pipe includes a ductile stainless steel pipe having 1% or less of a delta-ferrite matrix structure with respect to the grain size area thereof.

A refrigeration cycle apparatus includes: a refrigerant circuit; an oil reservoir; a first pipe that connects the oil separator and the oil reservoir, the first pipe being configured to send the refrigeration oil separated by the oil separator to the oil reservoir; a first valve provided at the first pipe; a second pipe that connects the oil reservoir and a suction side of the compressor; a second valve provided at the second pipe; a third pipe that connects the oil reservoir and the suction side of the compressor at a position lower than a position at which the second pipe is connected to the oil reservoir; and a third valve provided at the third pipe. The first to third valves are closed in a non-operational period of the compressor.

A heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system includes a refrigerant loop having a compressor configured to circulate a refrigerant therethrough, a motor configured to drive rotation of the compressor, wherein the motor is a permanent magnet assisted synchronous reluctance (PMASR) motor, and a motor cooling system configured to direct a portion of the refrigerant from the refrigerant loop and through a housing of the PMASR motor to place the portion of the refrigerant in thermal communication with components of the PMASR motor.

This disclosure relates to a compressor having a shaft, wherein the shaft is hollow to define a fluid passage extending along the shaft and a motor arranged along the shaft. A motor cooling line is configured to convey a cooling fluid to the motor, wherein the motor cooling line is fluidly connected to the fluid passage. The compressor may be a refrigerant compressor used in a heating, ventilation, and air conditioning (HVAC) chiller system.

The present invention relates to heat transfer compositions comprising refrigerant, lubricant and stabilizer, wherein the refrigerant comprises 39 to 45% by weight difluoromethane (HFC-32), 1 to 4% by weight pentafluoroethane (HFC-125), and 51 to 57% by weight trifluoroiodomethane (CF.sub.3I), and wherein said lubricant comprises polyol ester (POE) lubricant and/or polyvinyl ether (PVE) lubricant, and wherein said stabilizer comprises an alkylated naphthalene and optionally but preferably an acid depleting moiety.