A refrigerant circuit includes a first compressor connected to a first suction pipe and a first discharge pipe and configured to compress a refrigerant, a second compressor connected to a second suction pipe and a second discharge pipe and configured to compress the refrigerant discharged from the first compressor, a radiator, and a high-pressure passage connecting the second discharge pipe and the radiator. A first oil drain passage guides an oil in the second compressor to one of the first suction pipe and an intermediate port of the first compressor, without via the high-pressure passage.

Provided are a method and apparatus for controlling the operation of a compressor of an HVAC system in response to the refrigerant super heat value for refrigerant within the compressor. First and second signals are received for indicating one or more temperature values of refrigerant substantially at the first compressor sump and within the first distributor tube, respectively. A saturated suction temperature is estimated using at least the second signal. A first super heat value is calculated for refrigerant substantially at the first compressor sump using at least the saturated suction temperature and the one or more temperature values indicated by the first signal. A first control signal is generated for at least de-energizing the first compressor if the calculated first super heat value is below a tolerance value defining the minimum super heat value at which the first compressor may be operated.

A climate-control system may include a compressor, a condenser, an evaporator, a first sensor, a second sensor, a third sensor, and a control module. The compressor may include a motor and a compression mechanism. The condenser receives compressed working fluid from the compressor. The evaporator is in fluid communication with the compressor and disposed downstream of the condenser and upstream of the compressor. The first sensor may detect an electrical operating parameter of the motor. The second sensor may detect a discharge temperature of working fluid discharged by the compression mechanism. The third sensor may detect a suction temperature of working fluid between the evaporator and the compression mechanism. The control module is in communication with the first, second and third sensors and may determine whether a refrigerant floodback condition is occurring in the compressor based on data received from the first, second and third sensors.

In a refrigeration cycle apparatus, refrigerant circulates successively through a compressor, a condenser, an expansion valve, and an evaporator. The refrigeration cycle apparatus includes a detection unit, a heating unit, and a controller. The detection unit is configured to detect a temperature of refrigeration oil in the compressor. The heating unit is configured to heat the refrigeration oil. The controller is configured to operate the heating unit when the temperature detected by the detection unit is lower than a pour point of the refrigeration oil, and to stop the heating by the heating unit when the temperature detected by the detection unit reaches the pour point. Preferably, the heating unit includes a heater provided on an outer side of a compressor casing and at a lower portion of a motor unit.

A method of heating a component within a heating, ventilation and air conditioning (HVAC) system is provided. The method includes maintaining a non-heating condition of the HVAC system component when the HVAC system component is in a non-operational state. The method also includes determining when the HVAC system component will switch from the non-operational state to an operational state, the determination based on a threshold parameter being met. The method further includes operating a heating device from the non-heating condition to a heating condition to heat the HVAC system component from a temperature to a target temperature suitable for the operational state of the HVAC system component.

A climate-control system may include a compressor, a condenser, an evaporator, a first sensor, a second sensor, a third sensor, and a control module. The compressor may include a motor and a compression mechanism. The condenser receives compressed working fluid from the compressor. The evaporator is in fluid communication with the compressor and disposed downstream of the condenser and upstream of the compressor. The first sensor may detect an electrical operating parameter of the motor. The second sensor may detect a discharge temperature of working fluid discharged by the compression mechanism. The third sensor may detect a suction temperature of working fluid between the evaporator and the compression mechanism. The control module is in communication with the first, second and third sensors and may determine whether a refrigerant floodback condition is occurring in the compressor based on data received from the first, second and third sensors.

A method for managing and controlling a heat pump based on a compression/expansion thermodynamic cycle of an operating fluid including at least: first and second heat exchangers; an expansion valve; and a compressor. The compressor is able to suck and compress a wet operating fluid. A plurality of temperature sensors detects the delivery temperatures Tm of the compressor, an evaporation temperature SST in the first exchanger, and a condensation temperature SDT in the second exchanger. The temperature difference between the lubricating oil in the compressor and the operating fluid at the compressor delivery is kept equal to or greater than a safety threshold OIL_SH such that there is no condensation of the operating fluid in the lubricating oil.

A compressor assembly, a vapor compression system incorporating the same, and a method for operating the vapor compression system are provided. The compressor assembly includes a motor for driving a rotating shaft, a foil bearing for supporting the rotating shaft, a compression mechanism for increasing the pressure of a working fluid, a supply line in fluid communication with the compression mechanism, and a heating apparatus for heating the working fluid. The supply line is configured for injecting the working fluid (e.g., from downstream of the compression mechanism) toward the foil bearing. The method provides for the monitoring of the temperature of the working fluid. When the temperature of the working fluid is less than 3° F. of superheat it is heated prior to being injected toward the foil bearing. The heating of the working fluid prevents, or at least mitigates, liquid from being transferred to the foil bearing.

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.

In a refrigerant compressor for refrigeration plants, comprising a compressor unit driven by a drive unit, wherein at least one of these units is provided with a control unit which is controllable by means of a delivery rate control system in order to control the refrigerant compressor at different delivery rates, wherein an external delivery rate setpoint value is communicated to the delivery rate control system, in order to prevent critical operating states, it is proposed that the delivery rate control system acquires, by means of a sensor, a compressor reference temperature of the compressor unit, that the delivery rate control system ascertains an operating state value group for the acquisition of an operating state of the refrigerant compressor and, taking account of specified reference values, if the value of the ascertained operating state value group based upon the compressor reference temperature permits a critical operating state of the refrigerant compressor, specifies a delivery rate which has as its result an operation of the refrigerant compressor outside of the critical operating states.