Oil management system for heating, ventilation, air conditioning, and refrigeration applications

Abstract

A method for monitoring and managing oil migration in a heating, ventilation, air conditioning, and refrigeration (HVACR) system includes establishing reference benchmarks for oil weight, volume, and differential pressure in a compressor and oil separator. Differential pressure sensors continuously measure real-time oil levels, with temperature and pressure compensation applied. The quantity of migrated oil is calculated by comparing real-time differential pressure data to predefined benchmark ranges. When migrated oil exceeds a defined threshold, an oil return process is initiated by adjusting compressor speed and electronic expansion valve (EXV) aperture using a proportional-integral-derivative (PID) control algorithm. The process maintains system stability by regulating leaving water or air temperature deviations within a preset limit. A Compressor Health Index (CHI) is generated based on oil migration trends and system operating parameters, enabling predictive maintenance and preventive actions in response to compressor performance degradation.

Description

Attorney Docket No.: NESFE-002WQ1Oil Management System for Heating, Ventilation, Air Conditioning, and Refrigeration ApplicationsCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority to and incorporates by reference the entire disclosure of U.S. Provisional Patent Application No. 63 / 777,770, filed on March 26, 2025, and titled “Oil Management System for Heating, Ventilation, Air Conditioning, and Refrigeration Applications”.BACKGROUND

[0002] The following description relates to an oil management system for heating, ventilation, air conditioning, and refrigeration applications.

[0003] Heating, ventilation, air conditioning, and refrigeration (HVACR) systems are used to regulate environmental conditions within an enclosed space. Typically, HVACR systems have a circulation system that pulls fluid from the enclosed space through ducts and pushes the conditioned fluid back into the enclosed space through additional ducts after conditioning the fluid (e.g., heating, cooling, humidifying, or dehumidifying the air). To direct operation of the circulation system and other components, HVACR systems include a controller. In addition to directing operation of the HVACR system, the controller may be used to monitor various components, (i.e. equipment) of the HVACR system to determine if the components are functioning properly.DESCRIPTION OF DRAWINGS

[0004] FIG. 1A is a schematic diagram of an example heating, ventilation, air conditioning, and refrigeration ("HVACR") system having an air-cooled condenser.

[0005] FIG. IB is a schematic diagram of an example HVACR system having a water-cooled condenser.

[0006] FIG. 2 is a schematic diagram of an example compressor.Attorney Docket No.: NESFE-002WQ1

[0007] FIG. 3 is a schematic diagram of an example oil separator.

[0008] FIG. 4 is a schematic diagram of an example HVACR system illustrating a location of temperature sensors, pressure sensors, and differential pressure sensors.

[0009] FIG. 5 is a schematic diagram of an example HVACR system illustrating a location of fluid level sensors.

[0010] FIG. 6 is a schematic diagram of an example HVACR system illustrating communication with a controller.

[0011] FIG. 7 is a flow diagram of an example process for operating an HVACR system.

[0012] FIG. 8 is a flow diagram of an example process for operating an HVACR system to return migrated lubricating oil to a compressor or oil separator.

[0013] FIG. 9 is a flow diagram of an example process for monitoring health of a compressor and an oil separator in an HVACR system.DETAILED DESCRIPTION

[0014] In some aspects of what is described here, an oil management system for heating ventilation, air conditioning, and refrigeration (HVACR) applications includes an HVACR system that utilizes a compressor and an oil separator. In various embodiments, the HVACR system may be, for example, a vapor compression system in which cyclic compression and expansion of a fluid refrigerant facilitates the absorption and discharge of heat to or from a conditioned space. In other implementations, the HVACR system may be another type of system such as, for example, a gas cycle system, or a Stirling cycle system. Each of these refrigeration systems relies on compression of a refrigerant. Thus, the HVACR system includes a compressor and an oil separator. During operation, lubricating oil present in the compressor may be drawn by the refrigerant into other components of the HVACR system. Such migration of lubricating oil reduces the quantity of lubricating oil present in the compressor, which can place the compressor at risk of damage. Additionally, migrated lubricating oil can foul heat exchange coils making heat transfer more difficult and reducing the efficiency of the HVACR system.Attorney Docket No.: NESFE-002WQ1

[0015] In some aspects, the oil management system includes a controller that receives signals that correspond to measured fluid parameters from sensors disposed in various components of the HVACR system. In various implementations, these fluid parameters may include, for example, lubricating oil temperature, refrigerant temperature, refrigerant pressure, lubricating oil fluid levels, and mixture of lubricating oil and refrigerant. In various implementations, the controller may control one or more operational parameters of the HVACR system. In various implementations, the operational parameters of the HVACR system include, for example, a compressor speed, a metering device aperture size, an evaporator fan speed, and a condenser fan speed, a condenser water pump speed, a compressor power consumption, or power consumption of the evaporator fan or the condenser fan.

[0016] In some aspects, responsive to the measured fluid parameters, the control system quantifies an amount of lubricating oil that has migrated away from the compressor and the oil separator. The control system then adjusts the operational parameters of the HVAC system to induce migration of the lubricating oil to the compressor. For example, in some implementations, the control system may increase a speed of the compressor, increase opening of an aperture of a metering device, or some combination thereof.

[0017] In some aspects, the oil management system is operable to provide an indication of the health of the compressor and other components of the HVACR system. For example, recurrent migration of lubricating oil away from the compressor and the oil separator may be a symptom of a mechanical defect within the compressor or the oil separator. In some implementations, the oil management system may provide an alert of recurrent migration of lubricating oil or recurrent lubricating oil levels in the compressor that are below a threshold. By inducing the migration of lubricating oil to the compressor, the oil management system maintains the lubricating oil levels within the compressor at proper levels, preserves equipment life, and maintains heat transfer efficiency of the HVACR system.

[0018] FIG. 1A is a schematic diagram of an example HVACR system 100 utilizing an aircooled condenser 104. The HVAC system 100 includes a refrigerant evaporator coil 102, a condenser coil 104, a compressor 106, an oil separator 108, and a metering device 110. In various implementations, the metering device 110 is, for example, an electronic expansionAttorney Docket No.: NESFE-002WQ1valve, a thermostatic expansion valve or a throttling valve. In various implementations, the compressor 106 may be, for example a variable speed compressor having, for example, a variable frequency drive. The refrigerant evaporator coil 102 is fluidly coupled to the compressor 106 via a suction line 112. The compressor 106 is fluidly coupled to the oil separator 108 via a first discharge line 114. The oil separator 108 is fluidly coupled to the condenser coil 104 via a second discharge line 116. The condenser coil 104 is fluidly coupled to the metering device 110 via a liquid line 118.

[0019] Still referring to FIG. 1A, during operation, low-pressure, low-temperature refrigerant is circulated through the refrigerant evaporator coil 102. The refrigerant is initially in a liquid / vapor state. In various implementations, the refrigerant is, for example, a chlorofluorocarbon (CFG) refrigerant such as R-22, R-134a, R-410A, or R-744, a hydochlorofluorcarbon (HCFC) refrigerant, a hydrofluorocarbon (HFC) refrigerant, a hydrofluoroolefin (HFO) refrigerant, or any other suitable type of refrigerant. Air from within a conditioned space 101, which is typically warmer than the refrigerant, is circulated around the refrigerant evaporator coil 102 by an evaporator circulation fan 120. By way of example, air flowthrough the evaporator coil 102 is illustrated in FIG. 1A by arrow 121. In various implementations, the evaporator circulation fan 120 may be, for example, a variablespeed fan having a variable frequency drive. The refrigerant evaporator coil 102 conducts heat from the air from the conditioned space into the liquid / vapor refrigerant. The refrigerant absorbs the conducted heat and changes state to a low-pressure, low-temperature, super-heated vapor refrigerant. Saturated vapor, saturated liquid, and saturated fluid refer to a thermodynamic state where a liquid and its vapor exist in approximate equilibrium with each other. Super-heated fluid and super-heated vapor refer to a thermodynamic state where a vapor is heated above a saturation temperature of the vapor. Sub-cooled fluid and sub-cooled liquid refers to a thermodynamic state where a liquid is cooled below the saturation temperature of the liquid.

[0020] The low-pressure, low-temperature, super-heated vapor refrigerant is received into the compressor 106 via the suction line. In a typical embodiment, the compressor 106 increases the pressure of the low-pressure, low-temperature, super-heated vapor refrigerant and, by operation of the ideal gas law, also increases the temperature of the low-Attorney Docket No.: NESFE-002WQ1pressure, low-temperature, super-heated vapor refrigerant to form a high-pressure, high-temperature, superheated vapor refrigerant. The high pressure, high temperature, superheated vapor refrigerant enters the oil separator 108 via the first discharge line 114. In operation, lubricating oil that is present in the compressor 106 may be drawn into the first discharge line 114 along with the high-pressure, high-temperature, superheated refrigerant. Such migration of lubricating oil from the compressor 106 can reduce the amount of lubricating oil present in the compressor 106 causing the compressor 106 to be at greater risk of damage. Additionally, migration of lubricating oil from the compressor 106 and the oil separator 108 may cause the lubricating oil to accumulate in one or both of the evaporator coil 102 or the condenser coil 104. Accumulation of lubricating oil in the evaporator coil 102 or the condenser coil 104 interferes with heat transfer, making the HVACR system less efficient, and can cause damage to one or more of the evaporator coil 102 and the condenser coil 104. In the oil separator 108, lubricating oil that has migrated from the compressor 106 is separated from the high-pressure, high-temperature, superheated refrigerant and returned to the compressor 106. This flow of lubricating oil from the oil separator 108 to the compressor 106 is illustrated in FIG. 1A by oil return line 122. Upon leaving the oil separator 108, the high-pressure, high-temperature, superheated vapor refrigerant enters the condenser coil 104 via the second discharge line 116.

[0021] In various implementations, an oil control valve 111 controls a volume of lubricating oil that passes from the oil separator 108 to the compressor 106. In various implementations, the oil control valve 111 is an electronically actuated valve that can be selectively adjusted in order to maintain a predetermined oil level in the compressor oil sump and in the oil separator 108. A non-return valve 113 is disposed in the oil return line 122. In various implementations, the non-return valve 113 prevents backflow of the lubricating oil into the oil separator 108.

[0022] Outside air is circulated around the condenser coil 104 by a variable-speed condenser fan 124. The outside air is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant present in the condenser coil 104 Thus, heat is conducted from the high-pressure, high-temperature, superheated vapor refrigerant, through the condenser coil 104, to the outside air. By way of example, air flow through theAttorney Docket No.: NESFE-002WQ1condenser coil 104 is illustrated in FIG. 1A by arrow 125. This transfer of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state. The high-pressure, high-temperature, sub-cooled liquid refrigerant leaves the condenser coil 104 via the liquid line 118 and enters the metering device 110.

[0023] In the metering device 110 , the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant is abruptly reduced. In various embodiments where the metering device 110 is, for example, an electronic expansion valve, the metering device 110 includes a stepper motor that selectively adjusts a size of the metering device aperture. Adjustment of the metering device aperture size changes the amount of refrigerant that is able to pass through the metering device 110 thereby changing the pressure drop created by the metering device 110. The metering device 110 reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant by regulating an amount of refrigerant that travels to the refrigerant evaporator coil 102. Abrupt reduction of the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant causes rapid evaporation of a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant, commonly known as flash evaporation. The flash evaporation lowers the temperature of the resulting liquid / vapor refrigerant mixture to a temperature lower than a temperature of the air in the conditioned space 101. The liquid / vapor refrigerant mixture leaves the metering device 110 and returns to the refrigerant evaporator coil 102.

[0024] FIG. IB is a schematic diagram of an example HVACR system 150 having a water-cooled condenser 154 and a water cooled evaporator 152. Other components of the HVACR system 150, with the exception of the water cooled condenser 154 and the water cooled evaporator 152 are the same as those illustrated in FIG. 1A. Upon leaving the oil separator 108, the high-pressure, high-temperature, superheated vapor refrigerant enters the condenser coil 154 via the second discharge line 116. Chilled water is circulated around the condenser coil 104 by a water pump 156. The chilled water is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant present in the condenser coil 104 Thus, heat is conducted from the high-pressure, high-temperature, superheatedAttorney Docket No.: NESFE-002WQ1vapor refrigerant, through the condenser coil 104, to the chilled water. By way of example, flow of the chilled water is illustrated in FIG. 1A by arrow 158. The chilled water exchanges heat with the refrigerant in the condenser coil 154. The heat absorbed by the chilled water is then exhausted to an exterior environment in a cooling tower 160. In various implementations, the chiller 160 maybe located, for example, on a building rooftop or other exterior space. This transfer of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state. The high-pressure, high-temperature, sub-cooled liquid refrigerant leaves the condenser coil 154 via the liquid line 118 and enters the metering device 110. In various implementations, the HVACR system 100 and the HVACR system 150 may be reversible in order to function as a heat pump.

[0025] In the water-cooled evaporator 152, the refrigerant is initially in a liquid / vapor state. The evaporator 152 functions as a heat exchanger and facilitates energy transfer between a refrigerant and water. In cooling mode, the evaporator 152 produces chilled water and in heating mode, the evaporator 152 produces heated water. The conditioned water is circulated by a water pump 164 to the space 101. The conditioned water then passes through fan coil units or air handling units to control the climate within the space 101. In various implementations, the evaporator water pump 164 may be, for example, a variablespeed pump having a variable frequency drive. In various implementations, aspects of the HVACR system 100 and the HVACR 150 may be combined. For instance, an HVACR system may include a water cooled condenser and an air cooled evaporator and vice versa.

[0026] FIG. 2 is a cross-sectional view of an example compressor 200. In various implementations, the compressor 200 may be the compressor 106 illustrated in FIGS.1A and IB or another compressor. By way of example, the compressor 200 illustrated in FIG. 2 is a reciprocating piston compressor; however, in various implementations, other types of compressors such as, for example, scroll compressors, rotary compressors, screw compressors, and centrifugal compressors. In various implementations, the compressor 200 may be the compressor 106 illustrated in FIGS. 1A-1B or another compressor. The compressor 200 includes an upper compartment 202 and an oil sump 204. The upperAttorney Docket No.: NESFE-002WQ1compartment 202 receives refrigerant from the suction line 112 and discharges pressurized refrigerant into the first discharge line 114. The upper compartment 202 also includes a motor 205, which drives a reciprocating piston 206. The piston 206 directs the refrigerant through the first discharge line 114. In various implementations, a discharge valve 203 is disposed between the first discharge line 114 and the upper compartment 202 so as to prevent backflow of refrigerant into the upper compartment 202.

[0027] The oil sump 204 is disposed below the upper compartment 202 and contains lubricating oil for moving compressor components. In various implementations, the lubricating oil may be, for example, a mineral oil, a synthetic oil, a blended oil, or another type of oil. During idle periods, the lubricating oil accumulates in the oil sump; however, during periods with the compressor 106 is active, the lubricating oil may be drawn into low pressure areas of the upper compartment 202 where the lubricating oil can mix with the refrigerant passing through the compressor. The lubricating oil that mixes with the refrigerant may then migrate out of the compressor 106 via the first discharge line 114.

[0028] FIG. 3 is a cross-sectional view of an example oil separator 300. In various implementations, the oil separator 300 may be the oil separator 108 illustrated in FIGS. 1A and IB or another oil separator. The oil separator 300 receives gaseous refrigerant mixed with lubricating oil from the compressor 106 via the first discharge line 114. In various implementations, the oil separator 300 may be, for example, the oil separator 108 illustrated in FIG. 1A or another oil separator. Due to the difference in densities between the lubricating oil and the refrigerant, the increased cross sectional area of the oil separator 300 causes the lubricating oil to collect at the bottom of the oil separator 300. The collected oil is then returned to the compressor 106 via a return line 302. The gaseous refrigerant then moves to the condenser via the second discharge line 116.

[0029] FIG. 4 is a schematic diagram of an example HVACR system 400 illustrating a location of temperature sensors, pressure sensors, and differential pressure sensors. In various implementations, the HVACR system 400 may be the HVACR system 100 illustrated in FIG. 1A, the HVACR system 150 illustrated in FIG. IB, or another HVACR system. A first differential pressure sensor 404 is located within a compressor 402 and measures a pressure difference between an oil sump of the compressor 402 and a suction line, such as the suctionAttorney Docket No.: NESFE-002WQ1line 112, connected to an upper cavity of the compressor 402. A second differential pressure sensor 406 is disposed within the compressor 402 and measures a pressure difference between an inlet of an oil pump in the compressor 402 and an outlet of the oil pump in the compressor 402. A third differential pressure sensor 407 is disposed in an oil separator 408 and measures a pressure difference between a lower cavity of the oil separator 408 and a discharge line, such as the second discharge line 116 that is connected to an upper cavity of the oil separator 408. A fourth differential pressure sensor 409 is disposed in an oil filter 410 in an oil return line 412 and measures a pressure difference between in the return line 412 before the oil filter 410 and after the oil filter 410. In various implementations, the first differential pressure sensor 404, the second differential pressure sensor 406, the third differential pressure sensor 407, and the fourth differential pressure sensor 409 may be, for example, a resistive type differential pressure sensor, a piezoelectric type differential pressure sensor, an optical type differential pressure sensor, a micromechanical differential pressure sensor, a piezoresistive differential pressure sensor, a magnetic differential pressure sensor, a capacitive differential pressure sensor, a fiber optic differential pressure sensor, or another type of differential pressure sensor. In various other implementations, the first differential pressure sensor 404, the second differential pressure sensor 406, the third differential pressure sensor 407, and the fourth differential pressure sensor 409 may each include two pressure sensors in order to obtain a value for differential pressure.

[0030] Still referring to FIG. 4, a first pressure sensor 416 is located at the inlet of the compressor 402 and measures the gauge pressure within a suction line 414. A second pressure sensor 418 is disposed at a discharge outlet of the compressor 402 and measures a gauge pressure in the discharge line 420 of the compressor 402. A first temperature sensor 422 is disposed in the oil sump of the compressor 402 and measures a temperature of lubricating oil in the oil sump. A second temperature sensor 424 is disposed in a lower cavity of the oil separator 408 and measures an oil temperature in the oil separator. In various implementations, the first pressure sensor 416 and the second pressure sensor 418 may be, for example, a strain gauge pressure sensor, a piezoelectric pressure sensor, a piezoresistive pressure sensor, a sealed pressure sensor, a vacuum pressure sensor, a Bourdon tube pressure sensor, a manometer pressure sensor, or another type of pressure sensor. InAttorney Docket No.: NESFE-002WQ1various implementations, the first pressure sensor 416 and the second pressure sensor 418 may be a pressure transducer, a pressure transmitter, or another type of device. In various implementations, the first temperature sensor 422 and the second temperature sensor 424 may be, for example, a resistive temperature device, a thermistor, a thermocouple, a semiconductor based sensor, or another type of temperature sensor.

[0031] Still referring to FIG. 4, the first differential pressure sensor 404, the second differential pressure sensor 406, the third differential pressure sensor 407, and the fourth differential pressure sensor 409 communicate with a controller (shown in FIG.6). In various implementations, the first differential pressure sensor 404, the second differential pressure sensor 406, the third differential pressure sensor 407, and the fourth differential pressure sensor 409 communicate with a controller via a wired connection such as, for example, a parallel connection, a serial connection, a PS2 connection, a USB connection, a firewire connection, or another type of wired connection. Alternatively, the first differential pressure sensor 404, the second differential pressure sensor 406, the third differential pressure sensor 407, and the fourth differential pressure sensor 409 communicate with a controller via a wireless protocol such as, for example IEEE 801.22 or another protocol. Additionally, the first pressure sensor 416, the second pressure sensor 418, the first temperature sensor 422, and the second temperature sensor 424 are also in communication with the controller. In various implementations, the first pressure sensor 416, the second pressure sensor 418, the first temperature sensor 422, and the second temperature sensor 424 communicate with a controller via a wired connection such as, for example, a parallel connection, a serial connection, a PS2 connection, a USB connection, a firewire connection, or another type of wired connection. Alternatively, the first temperature sensor 422, and the second temperature sensor 424 are also in communication with the controller. In various implementations, the first pressure sensor 416, the second pressure sensor 418, the first temperature sensor 422, and the second temperature sensor 424 communicate with a controller via a wireless protocol such as, for example IEEE 801.22 or another protocol.

[0032] FIG. 5 is a schematic diagram of an example HVACR system 500 illustrating a location of fluid level sensors. In various implementations, the HVACR system 500 may be the HVACR system 100 illustrated in FIG. 1A, the HVACR system 150 illustrated in FIG. IB,Attorney Docket No.: NESFE-002WQ1or another HVACR system. A first fluid level sensor 502 is disposed in the compressor 504 and measures a level of lubricating oil within the compressor 504. A second fluid level sensor 506 is disposed in the oil separator 508 and measures a level of the lubricating oil in the oil separator 508.

[0033] FIG. 6 is a schematic diagram of an example HVACR system illustrating communication with a controller 602. In various implementations, the HVACR system 600 may be the HVACR system 100 illustrated in FIG. 1A, the HVACR system 150 illustrated in FIG. IB, or another HVACR system. In various implementations, the controller 602 may be, for example, a proportional controller, an integral controller, a derivative controller, a proportional, integral, derivative (PID) controller, or another type of controller. In various implementations, the controller 602 may be embodied on one or more microprocessors or other similar device. The controller 602 collects data from all sensors and processes it to generate values that indicate the amount of migrated oil inside and outside the compressor and oil separator.

[0034] In various implementations, the controller 602 continuously measures and logs oil quantities in the compressor and in the oil separator. With the logged data, the processor determines a quantity of lubricating oil that has migrated outside of the oil separator and the compressor. In various implementations, a moving average of differential pressure is computed over a time window (N). In such implementations, this moving average reduces transient errors such as, for example, sensor noise, oil foaming, and other transient effects. The moving average is calculated according to the equation

[0035] Where Pavg is the averaged differential pressure, N is the number of time steps in the averaging window, and Pt is the instantaneous differential pressure at time (t).

[0036] In various implementations, a mass and volume of migrated lubricating oil is determined. In various implementations, the mass of migrated lubricating oil is computed according to the equation^migrated = (Mc +—(Wc,t +Ms,t)Attorney Docket No.: NESFE-002WQ1Where Me is the mass of lubricating oil in the compressor at time t=0, Ms is the mass of lubricating oil in the oil separator at time t=0, Mc,t is the mass of lubricating oil in the compressor at time (t), and Ms,t is the mass of lubricating oil in the oil separator at time (t). In various implementations, the volume of migrated lubricating oil is computed according to the equation^migrated = (Vc + K) - (Vc,t + ^s,t)

[0037] Where Vc is the mass of lubricating oil in the compressor at time t=0, Vs is the mass of lubricating oil in the oil separator at time t=0, Vc,t is the mass of lubricating oil in the compressor at time (t), and Vs,t is the mass of lubricating oil in the oil separator at time (t). In various implementations, a temperature-adjusted oil density lookup table or other mathematical model is utilized to correlate oil density changes with oil temperature and refrigerant pressure values.

[0038] This data helps maintain targeted minimum and maximum oil levels. The controller regulates the opening and closing of electrical oil valves based on pre-set thresholds determined by the minimum logged values of the oil levels in the compressor and the oil separator. The logged oil values are measured in mass and volume and are correlated with a differential pressure reading ensuring stable operation within these working values. In various implementations, the thresholds are the minimum logged values of the oil levels in the compressor and the oil separator, which is the data collected in the manual oil filings. These values are measured in mass and volume and is correlated with the differential pressure reading.

[0039] In various implementations, the controller 602 dynamically manages the return of migrated oil to the compressor and oil separator. In various implementations, increasing the refrigerant velocity assists in returning the migrated oil to the compressor and oil separator. Low refrigerant velocity can cause oil to separate and accumulate in other parts of the refrigerant circuit. This method addresses this issue by optimizing refrigerant flow to support efficient oil recovery. The controller adjusts compressor speed and metering device positioning in real time to maximize oil return. In some implementations, a speed of the compressor is adjusted based on real-time values of refrigerant pressures, oil pumpAttorney Docket No.: NESFE-002WQ1pressures, power consumption, and temperatures. This real-time adjustment is accomplished by receiving feedback about the quantity over a unit of time of returned oil from the condenser and evaporator circuit to the compressor and oil separator. Based on this feedback the compressor speed and the metering device opening will be determined by, for example, a proportional, integral, derivative (PID) control scheme to optimize the compressor speed and expansion value opening. To operate this logic preset conditions are established. First, water or air temp should not go exceed, for example, + / - 1°C of the set temperature. This value is set depending on the load requirement. Second, the factory set working parameters for the HVAC asset. In some implementations, an aperture size of the metering device is adjusted to control refrigerant velocity. Regulation of the metering device aperture helps to keep oil mixed with the refrigerant and avoiding separation in the refrigerant pipes, condenser, or evaporator. For example, rapid release of pressure within the HVACR system may create a "bullet effect" which induces forced return of the migrated lubricant oil to the compressor.

[0040] In various implementations, the controller uses data obtained from the sensors to monitor the health and performance of the compressor and oil separator, continuously comparing real-time values to pre-set performance benchmarks. In various implementations, a reference benchmark is established for near-zero migration of lubricating oil. In various implementations, the reference benchmark is established by correlating an oil weight (kg / lb) initially filled in the compressor and an oil volume (cc / mm3 / in3) initially filled in the compressor to a differential pressure between the compressor sump and the compressor suction line. This process is repeated for the oil separator. In various implementations, the measurements are normalized to unity where 1.0 represents a reference benchmark of lubricating oil levels in the compressor and the oil separator. 0.0 - 1.0 represents near-zero lubricating oil level in the compressor or in the oil separator. >1.0 represents excess oil return to the oil separator or the compressor. Thus, the reference benchmark in the compressor may be expressed as:Woc=Kc= =unity reference valueAttorney Docket No.: NESFE-002WQ1Where Woe represents the weight of oil initially filled in the compressor, Voc represents the volume of oil initially filled in the compressor, and Ap represents the differential pressure between the compressor sump and the compressor suction line.

[0041] the reference benchmark in the oil separator may be expressed as:Wos=Os=P=unity reference valueWhere Wosrepresents the weight of oil initially filled in the oil separator, Vos represents the volume of oil initially filled in the oil separator, and Ap represents the differential pressure between the oil separator sump and the discharge line.

[0042] In various implementations, the system assesses the condition of the compressor and oil separator by tracking parameters such as pressure, temperature, and oil quantity. The controller compares these readings against predefined standards. In various implementations, deviations from targeted values trigger alarms and operational adjustments. These alerts facilitate real-time corrective actions, ensuring consistent system performance and enabling predictive maintenance.

[0043] FIG. 7 is a flow diagram of an example process 700 for operating an HVACR system. In various implementations, the HVACR system may be the HVACR system 100 illustrated in FIG. 1A, the HVACR system 150 illustrated in FIG. IB, or another HVACR system. The HVACR system can measure a quantity of lubricating oil that has migrated away from a compressor and an oil separator. Additionally, the HVACR system can adjust operational parameters of the HVACR system to encourage flow of the migrated lubricating oil back to the compressor and the oil separator. Operations of the example process 700 may be performed by a remote computer system (e.g., a server in the cloud), a wireless communication device (e.g., one or more of the wireless communication devices), or another type of system. For example, one or more operations in the example process 700 may be performed by one or more of the example controllers 602, or by a cloud-based computer system.

[0044] The example process 700 may include additional or different operations, and the operations may be performed in the order shown or in another order. In some cases, one or more of the operations shown in FIG. 7 can be implemented as a process that includesAttorney Docket No.: NESFE-002WQ1multiple operations, sub-processes, or other types of routines. In some cases, operations can be combined, performed in another order, performed in parallel, iterated or otherwise repeated, or performed in another manner.

[0045] At 710, refrigerant is removed from the HVACR system. In various implementations, vacuum evacuation is utilized to remove refrigerant from the HVACR system. In various implementations, 710 is performed before other components of the HVACR system are installed or verified. Evacuation of the HVACR system ensures a controlled environment for accurate assessment of lubricating oil levels within the HVACR system.

[0046] At 720, the oil separator is installed and the sensors are mounted. In various implementations, the oil separator may be, for example, the oil separator 108 illustrated in FIGS. 1A and IB or another oil separator. In various implementations, the oil separator may be integrated into the compressor. All sensors, actuators, and related components are mounted in the oil separator. For example, the sensors and related components could be the sensors described above relative to FIG. 4, the sensors described above relative to FIG. 5 or other sensors.

[0047] At 730, lubricating oil is initially filled in the compressor and the initial oil level is checked. In various implementations, the compressor may be, for example, the compressor 106 illustrated in FIGS. 1A and IB or another compressor. In various implementations, the compressor is filled with manufacturer recommended quantity and type of lubricating oil. In various implementations, a sight glass, level sensor, or level switch may be utilized to verify the level of lubricating oil within the compressor.

[0048] At 740, a baseline level of lubricating oil is established in the oil separator. In various implementations, the oil separator is filled with the same type of oil that is utilized in the compressor. The oil level in the oil separator is maintained at a required minimum oil level. In various implementations, the required minimum oil level maybe, for example, zero in some types of HVACR systems. In various implementations, a sight glass, a level sensor, or a level switch may be utilized to verify the level of lubricating oil within the oil separator. At 750, the HVACR system is charged with the correct type and quantity of refrigerant.Attorney Docket No.: NESFE-002WQ1

[0049] At 760 a first soft start is performed to establish baseline sensor readings under minimal system load. In various implementations, the compressor is gradually started and the RPM is increased from 0% until the oil pump differential pressure reaches the minimum required value. During this time, sensor readings are logged and the compressor power consumption is measured. At 762, the HVACR system is stopped and the lubricating oil is allowed to settle.

[0050] At 770, levels of lubricating oil are rechecked and adjusted. In various implementations, the levels of lubricating oil in the compressor and the oil separator are recorded and compared with the initial measurements taken in 730 and 740. If the lubricating oil levels drop below a minimum threshold, additional lubricating oil may be injected into the compressor and / or the oil separator to restore the minimum required levels.

[0051] At 780, a second soft start is performed to ensure stable oil levels under controlled operational conditions. In various implementations, the compressor is gradually started and the RPM is increased from 0% until the oil pump differential pressure reaches the minimum required value. During this time, sensor readings are logged and the compressor power consumption is measured. At 782, the HVACR system is stopped and the lubricating oil is allowed to settle.

[0052] At 790, a reference benchmark is established for near-zero migration of lubricating oil. In various implementations, the oil quantity values determined in 780 are used as a benchmark for near-zero oil migration. In various implementations, the oil quantity values include oil weight in the compressor, oil volume in the compressor, the differential pressure between the compressor suction line and the compressor oil sump, and a unity reference value described below. In various implementations, the oil quantity values also include the oil weight in the oil separator, the oil volume in the oil separator, the differential pressure between the oil separator sump and the oil separator discharge, and the unity value described below. In various implementations, the measurements are normalized to unity where 1.0 represents a reference benchmark of lubricating oil levels in the compressor and the oil separator.0.0 - 1.0 represents near-zero lubricating oil level in the compressor or inAttorney Docket No.: NESFE-002WQ1the oil separator. >1.0 represents excess oil return to the oil separator or the compressor. Thus, the reference benchmark in the compressor may be expressed as:Woc— Kc — — unity reference valueWhere Woe represents the weight of oil initially filled in the compressor, Voc represents the volume of oil initially filled in the compressor, and Ap represents the differential pressure between the compressor sump and the compressor suction line.

[0053] the reference benchmark in the oil separator may be expressed as:Wos== Ap = unity reference valueWhere Wosrepresents the weight of oil initially filled in the oil separator, Vos represents the volume of oil initially filled in the oil separator, and Ap represents the differential pressure between the oil separator sump and the discharge line.

[0054] At 795 real-time monitoring and quantification of migrated oil is established. In various implementations, the HVACR system continuously measures and logs oil quantities in the compressor and in the oil separator. In particular, the logged quantities include the values described in 790. With the logged data, the processor determines a quantity of lubricating oil that has migrated outside of the oil separator and the compressor. In various implementations, a moving average of differential pressure is computed over a time window (N). In such implementations, this moving average reduces transient errors such as, for example, sensor noise, oil foaming, and other transient effects. The moving average is calculated according to the equationWhere Pavg is the averaged differential pressure, N is the number of time steps in the averaging window, and Pt is the instantaneous differential pressure at time (t).

[0055] At 797 a mass and volume of migrated lubricating oil is determined. In various implementations, the mass of migrated lubricating oil is computed according to the equation^migrated = (Wc+ — (Mc t+ Ms t)Attorney Docket No.: NESFE-002WQ1Where Me is the mass of lubricating oil in the compressor at time t=0, Ms is the mass of lubricating oil in the oil separator at time t=0, Mc,t is the mass of lubricating oil in the compressor at time (t), and Ms,t is the mass of lubricating oil in the oil separator at time (t). In various implementations, the volume of migrated lubricating oil is computed according to the equation^migrated = (Vc + K) - (Vc,t + ^s,t)Where Vc is the mass of lubricating oil in the compressor at time t=0, Vs is the mass of lubricating oil in the oil separator at time t=0, Vc,t is the mass of lubricating oil in the compressor at time (t), and Vs,t is the mass of lubricating oil in the oil separator at time (t). In various implementations, a temperature-adjusted oil density lookup table or other mathematical model is utilized to correlate oil density changes with oil temperature and refrigerant pressure values.

[0056] FIG.8 is a flow diagram of an example process 800 for operating an HVACR system to return migrated lubricating oil to a compressor or oil separator. In various implementations, the HVACR system may be the HVACR system 100 illustrated in FIG. 1A, the HVACR system 150 illustrated in FIG. IB, or another HVACR system. The HVACR system can measure a quantity of lubricating oil that has migrated away from a compressor and an oil separator. Additionally, the HVACR system can adjust operational parameters of the HVACR system to encourage flow of the migrated lubricating oil back to the compressor and the oil separator. Operations of the example process 800 may be performed by a remote computer system (e.g., a server in the cloud), a wireless communication device (e.g., one or more of the wireless communication devices), or another type of system. For example, one or more operations in the example process 800 may be performed by one or more of the example controllers 602, or by a cloud-based computer system.

[0057] The example process 800 may include additional or different operations, and the operations may be performed in the order shown or in another order. In some cases, one or more of the operations shown in FIG. 7 can be implemented as a process that includes multiple operations, sub-processes, or other types of routines. In some cases, operations canAttorney Docket No.: NESFE-002WQ1be combined, performed in another order, performed in parallel, iterated or otherwise repeated, or performed in another manner.

[0058] At 810, real-time monitoring and quantification of migrated oil is established. In various implementations, the HVACR system continuously measures and logs oil quantities in the compressor and in the oil separator. With the logged data, the processor determines a quantity of lubricating oil that has migrated outside of the oil separator and the compressor. In various implementations, the real-time measurements are compared with the reference benchmark values determined in 790 to determine migration of lubricating oil. In various implementations, the process 800 is initiated in response to a determination that a real-time migrated oil quantity as determined in 790 exceeds a predefined threshold. In various implementations, the comparison includes a weight and volume of the oil, a percentage of the total oil charge, oil temperature and refrigerant pressure compensation, and compressor speed.

[0059] At 820, a controller dynamically adjusts a speed of the compressor and the metering device opening to return the migrated lubricating oil to the compressor and the oil separator. In various implementations, the controller may be the controller 602 illustrated in FIG. 6 or another controller. In various implementations, in response to a determination that a quantity of lubricating oil that has migrated away from the compressor and the oil separator exceeds a predefined threshold, the controller may direct the compressor to increase operating speed and may additionally direct the metering device to reduce an opening size. In various implementations, the controller may utilize a proportional, integral, derivative (PID) feedback loop. In various implementations, increasing the operating speed of the compressor and reducing the opening size of the metering device increases a high-side refrigerant pressure while maintaining the compressor’s maximum allowable current limit and the refrigerant’s maximum allowable working pressure. In various implementations, the compressor speed and the metering device opening size are regulated by the controller in order to maintain an output temperature of the HVAC system within, for example, + / - 1°C. In various implementations, if the output temperature deviates from this range, the process 800 is paused in order to prevent disruption of heating or cooling performance.Attorney Docket No.: NESFE-002WQ1

[0060] At 830, when the maximum allowable compressor RPM and the minimum allowable metering device opening are reached, these parameters are maintained for a predetermined duration to facilitate return of lubricating oil to the compressor and the oil separator. In various, implementations, the predetermined duration may be, for example, in the range of a few seconds to approximately 1 minute or more.

[0061] At 833, the metering device opening is gradually increased in order to reduce the high-side refrigerant pressure to the minimum allowable level based on ambient temperature. At 835, the metering device opening is decreased again to restore the high-side refrigerant pressure and the amount of lubricating oil that is returned to the compressor and the oil separator is monitored. The cycle of 830-835 is repeated until a target amount of migrated oil is returned. In various implementations, if the target lubricating oil level is not reached, the process 820-835 is repeated in such a way that the output water or air temperature is withing approximately 1 degree of the set temperature. At 837, once the target level of lubricating oil return has been reached, the HVACR system returns to normal operation.

[0062] At 840, return of lubricating oil to the compressor and oil separator is confirmed. In various implementations, the oil quantity in the compressor and the oil separator is measured and compared with the reference benchmarks determined in 790 to confirm that the return is complete.

[0063] At 850, the operational parameters of the HVACR system are adjusted for stability. In various implementations, the compressor speed and metering device settings are adjusted to align with system requirements.

[0064] FIG. 9 is a flow diagram of an example process 900 for monitoring health of a compressor and an oil separator in an HVACR system. In various implementations, the HVACR system may be the HVACR system 100 illustrated in FIG. 1A, the HVACR system 150 illustrated in FIG. IB, or another HVACR system. The HVACR system can measure a quantity of lubricating oil that has migrated away from a compressor and an oil separator. Additionally, the HVACR system can adjust operational parameters of the HVACR system to encourage flow of the migrated lubricating oil back to the compressor and the oil separator.Attorney Docket No.: NESFE-002WQ1Operations of the example process 900 may be performed by a remote computer system (e.g., a server in the cloud), a wireless communication device (e.g., one or more of the wireless communication devices), or another type of system. For example, one or more operations in the example process 900 may be performed by one or more of the example controllers 602, or by a cloud-based computer system.

[0065] The example process 900 may include additional or different operations, and the operations maybe performed in the order shown or in another order. In some cases, one or more of the operations shown in FIG. 9 can be implemented as a process that includes multiple operations, sub-processes, or other types of routines. In some cases, operations can be combined, performed in another order, performed in parallel, iterated or otherwise repeated, or performed in another manner.

[0066] At 910, the amount of lubricating oil that has migrated from the compressor to the oil separator is quantified. In various implementations, the compressor may be the compressor 106, illustrated in FIG. 1A and IB or another compressor and the oil separator may be the oil separator 108 illustrated in FIGS. 1A and IB or another oil separator. In various implementations, the migrated oil mass over time is computed according to the below equation:fldMcdMsM Migrated^') J I.... dMr . r , r , r, r Whereis the rate of oil mass loss from the compressor at time ft) and is the rate of oil mass accumulation in the oil separator at time (t). Additionally, the migrated oil volume over time is computed according to the equationdVcdVs^Migrated + —dt dtWhere is the rate of oil volume loss from the compressor at time (t) andis the rate of oil volume accumulation in the oil separator at time (t).

[0067] At 920, the lubricating oil migration information calculated in 910 is correlated with operational parameters. In various implementations, migration of lubricating oil isAttorney Docket No.: NESFE-002WQ1tracked relative to compressor speed (RPM or Hz), the compressor oil pump differential pressure, the temperature of the compressor and of the lubricating oil, the refrigerant suction and discharge pressures, the current load of the compressor (A), and the compressor energy efficiency (Kwh or TRh). In various implementations, this information is stored over a time span and is correlated with changing operational conditions.

[0068] At 930, data is stored and trends are analyzed continuously. In various implementations, this action creates a long-term record of migration of lubricating oil and indicators of compressor health. In various implementations, machine learning models may be utilized to refine predictions for lubricating oil migration and to correlate anomalies with possible failure risks in the compressor.

[0069] At 940, a compressor health deterioration index (CHI) is computed. This computation yields a weighted deterioration index that is indicative of compressor health and is based on operational parameters. The CHI is computed according to the equation CHI = + W2f(bRPM} + W3f^Pollpump) + W4 / (AAMP) + W5 / (AKW / I) Where f(x) is a normalized scaling function and Wi, W2, W3, W4, and W5 are adaptive weights.

[0070] At 950 an oil return efficiency index is computed to quantify the effectiveness of oil return actions. The oil return efficiency index is computed according to the equation Mr1)=M — -^‘retainedX 100Where Mr is the mass of lubricating oil successfully returned to the compressor and oil separator. Mm is the mass of lubricating oil initially determined as migrated and Mretained is the mass of lubricating oil retained in HVACR system tubing and other components

[0071] At 960 a wear rate per total working hours is determined as a way to quantify compressor longevity. This calculation normalizes the compressor wear rate per total working hours to standardize comparisons across different systems. The wear rate per total working hour (WRH) is calculated according to the equationtotal working hoursAttorney Docket No.: NESFE-002WQ1Where CHI is the health deterioration index computed at 940. In various implementations, the computation facilitates early failure detection by tracking CHI trends over operational time.

[0072] At 970, automated system responses are generated based on the health trends. In various implementations, an alert is generated when a minimum level of compressor lubricating oil is reached, CHI exceeds a predefined threshold, oil return efficiency drops below acceptable limits, a significant increase in compressor power consumption. In various implementations, the alert may be for, example a visual alert or an auditory alert. Additionally, in other implementations, the controller may transmit a text alert to a remote processor such as, for example, a mobile telephone, a handheld device, or a computer.

[0073] Some of the subject matter and operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Some of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage medium for execution by, or to control the operation of, data-processing apparatus. A computer storage medium can be, or can be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

[0074] Some of the operations described in this specification can be implemented as operations performed by a data processing apparatus on data stored on one or more computer-readable storage devices or received from other sources.

[0075] The term "data-processing apparatus" encompasses all kinds of apparatus, devices, and machines for processing data, including by way of example a programmableAttorney Docket No.: NESFE-002WQ1processor, a computer, a system on a chip, or multiple ones, or combinations, of the foregoing. The apparatus can include special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). The apparatus can also include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of them.

[0076] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing environment.. A computer program may, but need not, correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0077] Some of the processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform actions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0078] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random-access memory or both. Elements of a computer can include a processor that performs actions in accordance with instructions, and one or more memoryAttorney Docket No.: NESFE-002WQ1devices that store the instructions and data. A computer may also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic disks, magneto optical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a phone, an electronic appliance, a mobile audio or video player, a game console, a Global Positioning System (GPS) receiver, or a portable storage device (e.g., a universal serial bus (USB) flash drive). Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices (e.g., EPROM, EEPROM, flash memory devices, and others), magnetic disks (e.g., internal hard disks, removable disks, and others), magneto optical disks , and CD ROM and DVD-ROM disks. In some cases, the processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0079] To provide for interaction with a user, operations can be implemented on a computer having a display device (e.g., a monitor, or another type of display device) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse, a trackball, a tablet, a touch sensitive screen, or another type of pointing device) by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user’s client device in response to requests received from the web browser.

[0080] A computer system may include a single computing device, or multiple computers that operate in proximity or generally remote from each other and typically interact through a communication network. Examples of communication networks include a local area network ("LAN") and a wide area network ("WAN"), an inter-network (e.g., the Internet), a network comprising a satellite link, and peer-to-peer networks (e.g., ad hoc peer-to-peerAttorney Docket No.: NESFE-002WQ1networks). A relationship of client and server may arise by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

[0081] In a first example, a method of operating a HVACR system includes operating the HVACR system in a first mode of operation with a first set of operational parameters. By operation of a processor, a plurality of fluid parameters are measured. Based on the first set of operational parameters and the plurality of fluid parameters, a quantity of oil that has migrated from a compressor and an oil separator is determined. Responsive to the calculation, operation of the HVACR system is changed to a second mode of operation with a second set of operational parameters so as to induce migration of the oil into the compressor and oil separator.

[0082] According to aspects of the first example, the compressor may be a variable speed compressor and the first set of operational parameters may include a compressor speed and a metering device aperture.

[0083] According to aspects of the first example, changing the operation of the HVACR system to a second set of operational parameters may include increasing a speed of the compressor and adjusting a metering device aperture to a more open position.

[0084] According to aspects of the first example, the metering device may be an electronic expansion valve and changing operation of the HVACR system may include increasing a refrigerant velocity.

[0085] According to aspects of the first example, the plurality of fluid parameters may include differential fluid pressure, fluid temperature, and fluid pressure. Such aspects of the first example may include determining a refrigerant velocity from the plurality of fluid parameters.

[0086] According to aspects of the first example, the plurality of fluid parameters may include a fluid level in at least one of the compressor and the oil separator. In such aspects of the first example, a refrigerant velocity may be determined from the plurality of fluid parameters.

[0087] In a second example, an HVACR system includes a compressor and an oil separator coupled to the compressor. A condenser is coupled to the oil separator and a metering deviceAttorney Docket No.: NESFE-002WQ1is coupled to the condenser. An evaporator is coupled to the metering device. A plurality of sensors are disposed in the compressor and the oil separator. The plurality of sensors are operable to measure a plurality of fluid parameters. A processor is coupled to the plurality of sensors and is operable to control the compressor and the metering device based on the plurality of fluid parameters.

[0088] According to aspects of the second example, the compressor is a variable speed compressor and the metering device is an electronic expansion valve.

[0089] According to aspects of the second example, the plurality of sensors may include a plurality of differential pressure sensors. The plurality of differential pressure sensors may include a first differential pressure sensor disposed between a lower cavity of the compressor and an upper cavity of the compressor, a second differential pressure sensor disposed between an oil pump inlet and an oil pump outlet of the compressor, a third differential pressure sensor disposed between a lower cavity of the oil separator and an upper cavity of the oil separator, and a fourth differential pressure sensor disposed between a lower cavity of the oil separator and an upper cavity of the oil separator.

[0090] According to aspects of the second example, the plurality of sensors may include a plurality of pressure sensors. The plurality of pressure sensors may include a first pressure sensor disposed at a suction inlet of the compressor and a second pressure sensor disposed at a discharge outlet of the compressor.

[0091] According to aspects of the second example, the plurality of sensors may include a plurality of temperature sensors. The plurality of temperature sensors may include a first temperature sensor disposed in a lower cavity of the compressor and a second temperature sensor disposed in a lower cavity of the oil separator.

[0092] According to aspects of the second example, the plurality of sensors may include a plurality of fluid level sensors. The plurality of fluid level sensors may include a first fluid level sensor disposed in a lower cavity of the compressor and a second fluid level sensor disposed in a lower cavity of the oil separator.

[0093] According to aspects of the second example, the processor may be coupled to the variable frequency drive of the compressor and the motor of the metering device. In suchAttorney Docket No.: NESFE-002WQ1aspects, the processor directs operation of the variable frequency drive and the actuator so as to control a speed of the compressor and an aperture size of the metering device responsive to input received from the plurality of sensors.

[0094] In a third example, a method of operating an HVACR system includes operating the HVACR system in a first mode of operation. A volume of oil that has migrated away from a compressor and an oil separator is quantified. In response to the quantifying, the HVACR system is operated in a second mode of operation to induce migration of oil into at least tone of the compressor and the oil separator.

[0095] According to aspects of the third example, the compressor may be a variable speed compressor.

[0096] According to aspects of the third example, the first mode of operation includes a compressor speed and a metering device aperture.

[0097] According to aspects of the third example, changing operation of the HVACR system to the second mode of operation may include at least one of increasing the speed of the compressor and adjusting the aperture of the metering device to a more open position.

[0098] According to aspects of the third example, quantifying the volume of oil that has migrated away from the compressor and the oil separator may include determining a refrigerant velocity. In such aspects, determining the refrigerant velocity may include measuring differential fluid pressure, fluid temperature, and fluid pressure. In such aspects, determining the refrigerant velocity may also include measuring a fluid level in at least one of the compressor and the oil separator.

[0099] In a fourth example, a method for quantifying migrated oil in an HVACR system includes filling the compressor and the oil separator with a predetermined quantity of oil and recording the initial oil weight and volume. A differential pressure is measured within the compressor and the oil separator using differential pressure sensors positioned to detect pressure differences between a lower cavity of the compressor and a suction line of the compressor and a lower cavity of the oil separator and a discharge line of the compressor. A reference benchmark range is established for oil levels in the compressor and the oil separator by correlating electronically measured differential pressure values with manuallyAttorney Docket No.: NESFE-002WQ1recorded oil weight and volume values. The benchmark range defining threshold levels corresponding to minimum, nominal, and maximum oil quantities within the compressor and oil separator sumps. The benchmark range is expressed in multiple measurement units, including differential pressure units (adjusted for temperature and pressure compensation), oil weight units, and oil volume units. Temperature and pressure compensation factors are applied to adjust oil density and correct benchmark values. A unity reference value (1.0) is assigned to standardize the benchmark measurements across all monitored parameters. Real-time differential pressure values are continuously monitored in the compressor and the oil separator. Deviations from the benchmark are calculated to determine the quantity of oil migrated from the compressor and the oil separator. An averaging algorithm is utilized to minimize transient errors caused by oil foaming, refrigerant turbulence, and sensor fluctuations. The calculated oil migration quantities is logged over time in correlation with compressor speed (RPM / Hz), oil pump differential pressure, compressor current (AMP), and refrigerant suction and discharge pressures for trend analysis. Programmable alarms are automatically triggered and actions when predefined threshold values of migrated oil are reached.

[0100] According to a fifth example, aspects of the disclosure relate to a method for returning migrated oil to a compressor and an oil separator in an H VACR system. The method includes initiating an oil return process when the calculated migrated oil quantity exceeds a predefined threshold. The threshold is dynamically adjusted based on a percentage of the total oil charge, operating temperature and refrigerant pressure conditions, and compressor speed and system load. Compressor speed is increased within manufacturer-defined operational limits to enhance refrigerant velocity and oil transport. An electronic expansion valve (EXV) is dynamically adjusted to decrease the valve aperture, increasing high-side refrigerant pressure to promote oil return. Compressor speed and EXV position are controlled through a proportional-integral-derivative (PID) feedback algorithm based on real-time oil migration data, refrigerant pressures, and temperatures. The oil return process is regulated to maintain leaving water or air temperature deviation within a preset range (±1°C) from the system setpoint, pausing the process if the deviation exceeds the preset range, and resuming when stability is restored. Oil return efficiency is verified by comparingAttorney Docket No.: NESFE-002WQ1post-process oil levels in the compressor and oil separator against their respective reference benchmarks. An Oil Return Efficiency Index (OREI) is calculated representing the percentage of migrated oil successfully returned during the cycle. Operational data is logged, including compressor speed, EXV position, oil migration quantities, refrigerant pressures, leaving water / air temperatures, and cycle duration. Alarms are triggered and adaptive control responses are initiated if the OREI falls below a predefined efficiency threshold.

[0101] In a sixth example, aspects of the disclosure relate to a method for monitoring the health of a compressor in an HVACR system. The method includes tracking oil migration trends by continuously logging migrated oil quantities from the compressor to the oil separator over time. Oil migration data is correlated with system operational parameters, including: compressor speed (RPM / Hz), oil pump differential pressure, compressor current (AMP), refrigerant suction and discharge pressures, compressor energy efficiency measured in kilowatt-hours per ton-hour (kWh / TRh). A Compressor Health Index (CHI) is generated by applying a weighted scoring model to historical data, identifying trends indicative of compressor wear, oil pump degradation, or abnormal energy consumption. Predictive maintenance alerts and alarms are triggered when the CHI exceeds a predefined threshold, indicating deterioration in compressor health. Preventive actions, including system diagnostics, maintenance scheduling, and alerts are automatically initiated for critically low oil levels in the compressor or oil separator. Data from compressor operations, oil return efficiency (OREI), and CHI values are logged for continuous system health monitoring and optimization.

[0102] While this specification contains many details, these should not be understood as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features that are described in this specification or shown in the drawings in the context of separate implementations can also be combined. Conversely, various features that are described or shown in the context of a single implementation can also be implemented in multiple embodiments separately or in any suitable subcombination.

[0103] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particularAttorney Docket No.: NESFE-002WQ1order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single product or packaged into multiple products.

[0104] A number of embodiments have been described. Nevertheless, it will be understood that various modifications can be made. Accordingly, other embodiments are within the scope of the following claims.

Claims

Attorney Docket No.: NESFE-002WQ1CLAIMSWhat is claimed is:

1. A method of operating a HVACR system, the method comprising:operating the HVACR system in a first mode of operation with a first set of operational parameters;by operation of a processor, measuring a plurality of fluid parameters; based on the first set of operational parameters and the plurality of fluid parameters, calculating a quantity of oil that has migrated from a compressor and an oil separator; andresponsive to the calculation, changing operation of the HVACR system to a second mode of operation with a second set of operational parameters so as to induce migration of the oil into the compressor and oil separator.

2. The method of claim 1, wherein the compressor is a variable speed compressor.

3. The method of claim 2, wherein the first set of operational parameters comprises a compressor speed and a metering device aperture.

4. The method of claim 3, wherein changing operation of the HVACR system to the second set of operational parameters comprises at least one of:increasing the speed of the compressor; andadjusting the metering device aperture to a more open position.

5. The method of claim 4, wherein the metering device is an electronic expansion valve.

6. The method of claim 4, wherein changing operation of the HVACR system comprises increasing a refrigerant velocity.Attorney Docket No.: NESFE-002WQ17. The method of claim 1, wherein the plurality of fluid parameters comprises differential fluid pressure, fluid temperature, and absolute fluid pressure.

8. The method of claim 7, comprising determining a refrigerant velocity from the plurality of fluid parameters.

9. The method of claim 1, wherein the plurality of fluid parameters comprises fluid level in at least one of the compressor and the oil separator.

10. The method of claim 9, comprising determining a refrigerant velocity from the plurality of fluid parameters.

11. An HVACR system comprising:a compressor;an oil separator coupled to the compressor;an condenser coupled to the oil separator;a metering device coupled to the condenser;an evaporator to the metering device and the compressor;a plurality of sensors disposed in the compressor and the oil separator, the plurality of sensors operable to measure a plurality of fluid parameters; anda processor coupled to the plurality of sensors, the processor being operable to control the compressor and the metering device based on the plurality of fluid parameters.

12. The HVACR system of claim 11, wherein the compressor is a variable speed compressor having a variable frequency drive.

13. The HVACR system of claim 12, wherein the metering device is an electronic expansion valve that is operatively coupled to an actuator.Attorney Docket No.: NESFE-002WQ114. The HVACR system of claim 13, wherein the plurality of sensors comprises a plurality of differential pressure sensors, the plurality of differential pressure sensors comprising:a first differential pressure sensor disposed between a lower cavity of the compressor and an upper cavity of the compressor;a second differential pressure sensor disposed between an oil pump inlet and an oil pump outlet of the compressor; anda third differential pressure sensor disposed between a lower cavity of the oil separator and an upper cavity of the oil separator.

15. The HVAC system of claim 14, wherein the plurality of differential pressure sensors further comprises a fourth differential pressure sensor disposed between an inlet of an oil filter and an outlet of the oil filter.

16. The HVACR system of claim 14, wherein the plurality of sensors comprises a plurality of pressure sensors, the plurality of pressure sensors comprising:a first pressure sensor disposed at a suction inlet of the compressor; and a second pressure sensor disposed at a discharge outlet of the compressor.

17. The HVACR system of claim 16, wherein the plurality of sensors comprises a plurality of temperature sensors, the plurality of temperature sensors comprising:a first temperature sensor disposed in the lower cavity of compressor; and a second temperature sensor disposed in the lower cavity of the oil separator.

18. The HVACR system of claim 13, wherein the plurality of sensors comprises a plurality of fluid level sensors, the plurality of fluid level sensors comprising:a first fluid level sensor disposed in a lower cavity of the compressor; and a second fluid level sensor disposed in a lower cavity of the oil separator.Attorney Docket No.: NESFE-002WQ119. The HVACR system of claim 13, wherein:the processor is operatively coupled to the variable frequency drive of the compressor and a motor of the metering device; andresponsive to input received from the plurality of sensors, the processor directs operation of the variable frequency drive and the actuator so as to control a speed of the compressor and an aperture size of the metering device.

20. A method of operating an HVACR system, the method comprising:operating the HVACR system in a first mode of operation;quantifying a volume of oil that has migrated away from a compressor and an oil separator in the first mode of operation; andresponsive to the quantifying, operating the HVACR system in a second mode of operation to induce migration of the oil into at least one of the compressor and the oil separator.

21. The method of claim 20, wherein the compressor is a variable speed compressor.

22. The method of claim 21, wherein the first mode of operation comprises a compressor speed and a metering device aperture.

23. The method of claim 22, wherein changing operation of the HVACR system to the second mode of operation comprises at least one of:increasing the speed of the compressor; andadjusting the metering device aperture to a more open position.

24. The method of claim 22, wherein quantifying the volume of oil that has migrated away from the compressor and the oil separator comprises determining a refrigerant velocity.

25. The method of claim 24, wherein determining the refrigerant velocity comprises measuring differential fluid pressure, fluid temperature, and fluid pressure.Attorney Docket No.: NESFE-002WQ126. The method of claim 24, wherein determining the refrigerant velocity comprises measuring fluid level in at least one of the compressor and the oil separator.

27. A method of quantifying migrated oil in an HVACR system, the method comprising:determining a weight and a volume of oil added to a compressor; determining a weight and a volume of oil added to an oil separator; measuring a differential pressure in the compressor and in the oil separator; based on the measured weight, volume, and differential pressure, establishing a reference oil migration benchmark for the compressor and the oil separator;actively monitoring oil migration based on real time measurement of differential pressure; andquantifying an amount of oil that has migrated from the compressor and the oil separator.

28. A method of mitigating oil migration, the method comprising:monitoring and quantifying an amount of migrated oil in real time; adjusting a speed of a compressor responsive to the amount of migrated oil; adjusting an opening of a metering device responsive to the amount of migrated oil;returning the HVACR system to normal operation;confirming the return of migrated oil to the compressor and oil separator; andadjusting HVACR system operating parameters for stability.

29. A method for measuring compressor health, the method comprising:monitoring and quantifying an amount of migrated oil in real time; correlating the amount of migrated oil to operational parameters of the HVACR system;compute a health deterioration index of the compressor;Attorney Docket No.: NESFE-002WQ1compute a wear rate of the compressor; andgenerate responses of the HVACR system based on at least one of the wear rate and the compressor health deterioration index.

30. A method for quantifying migrated oil in an HVACR system comprising a compressor and an oil separator, the method comprising:filling the compressor and the oil separator with a predetermined quantity of oil and recording the initial oil weight and volume;measuring differential pressure within the compressor and the oil separator using differential pressure sensors positioned to detect pressure differences between:a lower cavity of the compressor and a suction line of the compressor; anda lower cavity of the oil separator and a discharge line of the compressor;establishing a reference benchmark range for oil levels in the compressor and the oil separator by correlating electronically measured differential pressure values with manually recorded oil weight and volume values, the benchmark range defining threshold levels corresponding to minimum, nominal, and maximum oil quantities within the compressor and oil separator sumps, the benchmark range expressed in multiple measurement units, including differential pressure units (adjusted for temperature and pressure compensation), oil weight units, and oil volume units;applying temperature and pressure compensation factors to adjust oil density and correct benchmark values;assigning a unity reference value (1.0) to standardize the benchmark measurements across all monitored parameters;continuously monitoring real-time differential pressure values in the compressor and the oil separator;calculating deviations from the benchmark to determine the quantity of oil migrated from the compressor and the oil separator;Attorney Docket No.: NESFE-002WQ1utilizing an averaging algorithm to minimize transient errors caused by oil foaming, refrigerant turbulence, and sensor fluctuations;logging the calculated oil migration quantities over time in correlation with compressor speed (RPM / Hz), oil pump differential pressure, compressor current (AMP), and refrigerant suction and discharge pressures for trend analysis;automatically triggering programmable alarms and actions when predefined threshold values of migrated oil are reached.

31. A method for returning migrated oil to a compressor and an oil separator in an HVACR system, the method comprising:initiating an oil return process when the calculated migrated oil quantity exceeds a predefined threshold, wherein the threshold is dynamically adjusted based on:a percentage of the total oil charge;operating temperature and refrigerant pressure conditions;• Compressor speed and system load;increasing compressor speed within manufacturer-defined operational limits to enhance refrigerant velocity and oil transport;dynamically adjusting an electronic expansion valve (EXV) to decrease the valve aperture, increasing high-side refrigerant pressure to promote oil return; controlling compressor speed and EXV position through a proportionalintegral-derivative (PID) feedback algorithm based on real-time oil migration data, refrigerant pressures, and temperatures;regulating the oil return process to maintain leaving water or air temperature deviation within a preset range (±1°C) from the system setpoint, pausing the process if the deviation exceeds the preset range, and resuming when stability is restored;verifying oil return efficiency by comparing post-process oil levels in the compressor and oil separator against their respective reference benchmarks;calculating an Oil Return Efficiency Index (ORE1), representing the percentage of migrated oil successfully returned during the cycle;Attorney Docket No.: NESFE-002WQ1logging operational data, including compressor speed, EXV position, oil migration quantities, refrigerant pressures, leaving water / air temperatures, and cycle duration;triggering alarms and initiating adaptive control responses if the OREI falls below a predefined efficiency threshold.

32. A method for monitoring the health of a compressor in an HVAC / R system, the method comprising:tracking oil migration trends by continuously logging migrated oil quantities from the compressor to the oil separator over time;correlating oil migration data with system operational parameters, the operational parameters comprising:compressor speed (RPM / Hz);oil pump differential pressure;compressor current (AMP);refrigerant suction and discharge pressures;compressor energy efficiency measured in kilowatt-hours per ton- hour (kWh / TRh);generating a Compressor Health Index (CHI) by applying a weighted scoring model to historical data, identifying trends indicative of compressor wear, oil pump degradation, or abnormal energy consumption;triggering predictive maintenance alerts and alarms when the CHI exceeds a predefined threshold, indicating deterioration in compressor health;automatically initiating preventive actions, including system diagnostics, maintenance scheduling, and alerts for critically low oil levels in the compressor or oil separator;logging data from compressor operations, oil return efficiency (OREI), and CHI values for continuous system health monitoring and optimization.

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