Patent Publication Number: US-2023160615-A1

Title: Expansion Valve Performance Monitoring in Refrigeration System

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of and claims the benefit of priority to U.S. application Ser. No. 16/868,730, filed on May 7, 2020, the contents of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present disclosure relates generally to the field of refrigeration systems, including for refrigerated display cases. More specifically, the present disclosure relates to the field of controllers and diagnostic systems for refrigeration systems. 
     SUMMARY 
     At least one embodiment of the present disclosure relates a method of detecting electrical failure in a refrigeration system. The method includes determining whether a present superheat of the refrigeration system is between a maximum superheat and a minimum superheat for the refrigeration system. The maximum superheat and the minimum superheat define a normal operating range. The method also includes detecting an electrical property of an expansion valve assembly of the refrigeration system in response to the superheat of the refrigeration system being outside of the normal operating range, determining whether the expansion valve assembly has experienced an electrical failure based on at least the electrical property of the expansion valve assembly, and generating a first signal indicating that the expansion valve assembly has experienced the electrical failure in response to a determination that the expansion valve assembly has experienced the electrical failure. 
     Another embodiment of the present disclosure relates to a system (e.g., a refrigeration system). The system includes a housing defining a temperature controlled space and a thermal exchange system, coupled to the housing. The thermal exchange system is configured to selectively control a temperature of the temperature controlled space. The thermal exchange system includes an actuator and a controller. The controller is configured to determine whether a present superheat of the refrigeration system is between a maximum superheat and a minimum superheat for the refrigeration system. The maximum superheat and the minimum superheat define a normal operating range. The controller is also configured to detect an electrical property of an expansion valve assembly of the refrigeration system in response to the superheat of the refrigeration system being outside of the normal operating range, determine whether the expansion valve assembly has experienced an electrical failure based on at least the electrical property of the expansion valve assembly, and generate a first signal indicating that the expansion valve assembly has experienced the electrical failure in response to a determination that the expansion valve assembly has experienced the electrical failure. 
     Another embodiment of the present disclosure relates to a controller for diagnosing a refrigeration system. The controller configured to determine a present superheat of the refrigeration system and a maximum superheat and a minimum superheat for the refrigeration system. The maximum superheat and the minimum superheat define a normal operating range. The controller is also configured to detect, an electrical property of an expansion valve assembly of the refrigeration system responsive to the present superheat of the refrigeration system being outside of the normal operating range, determine whether the expansion valve assembly has experienced an electrical failure based on at least the electrical property of the expansion valve assembly, and generate a first signal indicating that the expansion valve assembly has experienced the electrical failure responsive to a determination that the expansion valve assembly has experienced the electrical failure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a refrigerated display case according to an exemplary embodiment. 
         FIG.  2    is a block diagram of a refrigeration system and associated components, according to an exemplary embodiment. 
         FIG.  3    is a detailed block diagram of the refrigeration system of  FIG.  2   , according to an exemplary embodiment. 
         FIG.  4    is a detailed block diagram of the refrigeration system of  FIG.  2   , according to an exemplary embodiment. 
         FIG.  5    is a block diagram of a controller for the refrigeration system of  FIG.  2    and associated components, according to an exemplary embodiment. 
         FIG.  6    is a flowchart of a process for monitoring and diagnosing an expansion valve of the refrigeration system of  FIG.  2   , according to an exemplary embodiment. 
         FIG.  7    is a flowchart of a process for failure mitigation controls of the refrigeration system of  FIG.  2   , according to an exemplary embodiment. 
         FIG.  8    is a chart of current vs time measured within the refrigeration system of  FIG.  2   , according to an exemplary embodiment. 
         FIG.  9    is a chart of current vs time measured within the refrigeration system of  FIG.  2   , according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring generally to the FIGURES, a refrigeration system and components thereof are shown, according to various exemplary embodiments. The refrigeration system may be a vapor compression refrigeration system. In some implementations, the refrigeration system may be used to provide cooling for temperature-controlled display devices in a supermarket or other similar facility. 
     In some embodiments, the refrigeration system includes a receiving tank (e.g., a flash tank, a refrigerant reservoir, etc.) containing refrigerant, a condenser assembly, a compressor assembly, an accumulator, a subcooler assembly, and a superheater assembly. The refrigeration system includes a controller for monitoring and controlling the pressure, temperature, and/or flow of the refrigerant throughout the refrigeration system. The controller can operate each of the assemblies (e.g., according to the various control processes described herein) to efficiently regulate the pressure of the refrigerant within the receiving tank. Additionally, the controller can interface with other instrumentation associated with the refrigeration system (e.g., measurement devices, timing devices, pressure sensors, temperature sensors, etc.) and provide appropriate control signals to a variety of operable components of the refrigeration system (e.g., compressors, valves, power supplies, flow diverters, etc.) to regulate the pressure, temperature, and/or flow at other locations within the refrigeration system. Advantageously, the controller may be used to facilitate efficient operation of the refrigeration system, reduce energy consumption, improve system performance, and diagnose problems within the system. 
     Before discussing further details of the refrigeration system and/or the components thereof, it should be noted that references to “front,” “back,” “rear,” “upward,” “downward,” “inner,” “outer,” “right,” and “left” in this description are merely used to identify the various elements as they are oriented in the FIGURES. These terms are not meant to limit the element which they describe, as the various elements may be oriented differently in various applications. 
     It should further be noted that for purposes of this disclosure, the term “coupled” means the joining of two members directly or indirectly to one another. Such joining may be stationary in nature or moveable in nature and/or such joining may allow for the flow of fluids, transmission of forces, electrical signals, or other types of signals or communication between the two members. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature. 
     Referring now to  FIG.  1   , a perspective view of a refrigerated display case  100  is shown, according to an exemplary embodiment. The refrigerated display case  100  includes a refrigeration body  101  which defines a temperature controlled space  103 . The refrigerated display case  100  may include a mechanical-compression refrigeration system, an absorption refrigerating system, an evaporative cooling system, or a thermoelectric refrigeration system configured to selectively control a temperature of the temperature controlled space  103 . In some embodiments, the refrigerated display case  100  may be a standalone unit. In other embodiments, the refrigerated display case  100  may be part of a larger refrigeration system. 
     Referring now to  FIG.  2   , a block diagram of a refrigeration system  105  is shown, according to an exemplary embodiment. The refrigeration system  105  is coupled to and configured to selectively control the temperature of the temperature controlled space  103 . The refrigeration system  105  includes a refrigerant disposed therein. The refrigerant is configured to facilitate thermal energy exchange throughout the refrigeration system  105 . The refrigeration system  105  also includes a condenser assembly  110  configured to facilitate thermal energy loss from the refrigerant. The condenser assembly  110  includes a fan  115  configured to assist in the thermal energy loss. The condenser assembly  110  is fluidly coupled to an expansion valve assembly  120  by liquid line  117 . 
     The expansion valve assembly  120  is configured to facilitate a pressure drop in the refrigerant. During the pressure drop, the refrigerant changes phase from a liquid to a vapor. The expansion valve assembly  120  is fluidly coupled to an evaporator assembly (e.g., a coil, etc.)  150  by fluid line  127 . Fluid line  127  includes an inlet sensor  310 . The inlet sensor  310  is configured to measure the temperature or the pressure of the refrigerant. In other embodiments, the inlet sensor  310  is part of the expansion valve assembly. 
     The evaporator assembly  150  is coupled to the temperature controlled space  103 . The evaporator assembly  150  is configured to facilitate thermal energy gain in the refrigerant. The evaporator assembly  150  includes a fan  155  configured to assist in the thermal energy gain. The evaporator assembly  150  is fluidly coupled to a compressor assembly  160  by vapor line  157 . Vapor line  157  includes outlet sensor  320 . The outlet sensor  320  is configured to measure the temperature or the pressure of the refrigerant. The compressor assembly  160  is configured to increase the pressure of the refrigerant. The compressor assembly is fluidly coupled to the condenser assembly  110  by a discharge line  167 . 
     The refrigeration system  105  also includes a power supply  190  and a controller  200 . The controller  200  is configured to send and receive control signals to each of the components of the refrigeration system  105 . As shown the controller is coupled to (1) the fan  115  by control line (e.g., conductive path, wire, cable, etc.)  307 , (2) the inlet sensor  310  by control line  317 , (3) the outlet sensor  320  by control line  327 , (4) the fan  155  by control line  357 , (4) the compressor assembly  160  by control line  367 , and (5) the expansion valve assembly  120  by control line  397 . In additional exemplary embodiments, the controller  200  may be coupled to each of the components of the refrigeration system  105  such that the controller can send and receive signals from each of the components of the refrigeration system  105 . Furthermore, the control lines may be configured to facilitate the exchange of data, signals (e.g., analog or digital), power, etc. 
     In some embodiments, the controller is also configured to facilitate power delivery to each of the components of the refrigeration system  105 . In the embedment shown in  FIG.  2   , the power supply  190  is directly electrically coupled to the controller by power line  195  and indirectly coupled to each of the other components of the refrigeration system  105  via the controller. In a different embodiment, the power supply  190  may be directly electrically coupled to each of the components of the refrigeration system  105 . In this embedment, the controller may control the power supply  190  to selectively provide power to each of the components of the refrigeration system  105 . 
     In other exemplary embodiments, the refrigeration system  105  may be configured as a thermal exchange system (e.g., refrigeration system, air conditioning system, heat pump, etc.) configured to facilitate thermal energy exchange. In these embodiments, the system may include the same or similar components, assemblies, and control logic as the refrigeration system  105 . 
     Now referring to  FIG.  3   , a detailed view of the block diagram of  FIG.  2    is shown, according to an exemplary embodiment. The controller  200  is shown as coupled to the expansion valve assembly  120  by control line  397 . The expansion valve assembly  120  is shown as including an expansion valve  121  and an actuator  125  (e.g., pneumatic actuator, hydraulic actuator, D/C motor, A/C motor, etc.). The actuator  125  is configured to receive a control signal from controller  200  via the control line  397  and actuate the expansion valve  121 . 
     In some embodiments, the actuator  125  may be configured as a D/C motor. More specifically, the actuator  125  may be configured as a stepper motor. In this configuration, the actuator  125  selectively actuates the expansion valve  121  in a plurality of positions. A first position may be a fully open position. A second position may be a fully closed position. Other positions may be disposed between the first position and the second position. 
     An actuator sensor  325  is coupled to the actuator  125  by control line  324 , as shown. The actuator sensor  325  is configured to continually collect data about the actuator  125 . The actuator sensor  325  is further configured to send the collected data to the controller by control line  326 . 
     In other embodiments, the actuator sensor  325  may be integrated with the actuator  125  such that the actuator sensor  325  and the actuator  125  are a single unit. Additionally, the control line  324  and control line  326  may be integrated with control line  397 . In one exemplary embodiment, the actuator sensor  325  may be configured to detect an electrical event at (e.g., within, along a path entering or exiting) the expansion valve assembly  120 . For example, the sensor may be configured to detect a voltage, a current, a power, or other electrical property (e.g., voltage spike, current spike, power spike, etc.) of the expansion valve assembly  120 . In another exemplary embodiment, the actuator sensor  325  is configured as an encoder configured to measure the displacement of the actuator  125 . 
     The expansion valve assembly  120  is fluidly coupled to the evaporator assembly  150  by fluid line  127 . The fluid line  127  includes an inlet sensor  310  (see  FIG.  2   ). The inlet sensor  310  includes an inlet temperature sensor  311  and an inlet pressure sensor  312  as shown in  FIG.  3   . The inlet temperature sensor  311  and the inlet pressure sensor  312  are coupled to the fluid line  127  by control line  317 . The inlet temperature sensor  311  is configured to continuously collect data about the temperature of the refrigerant at the fluid line  127  and send the data to the controller  200 . The inlet pressure sensor  312  is configured to continuously collect data about the pressure of the refrigerant at the fluid line  127  and send the data to the controller  200  by control line  317 . In other embodiments, the inlet temperature sensor  311  and the inlet pressure sensor  312  are integrated into the expansion valve assembly  120 . In a different embodiment, the inlet temperature sensor  311  and the inlet pressure sensor  312  are coupled directly to the fluid line  127 . 
     The evaporator assembly  150  is fluidly coupled to the compressor assembly  160  (see  FIG.  2   ) by vapor line  157 . The vapor line  157  includes an outlet sensor  320  (see  FIG.  2   ). The outlet sensor  320  includes an outlet temperature sensor  321  and an outlet pressure sensor  322  as shown in  FIG.  3   . The outlet temperature sensor  321  and the inlet pressure sensor  312  are coupled to the vapor line  157  by control line  327 . The outlet temperature sensor  321  is configured to continuously collect data about the temperature of the refrigerant at the vapor line  157  and send the data to the controller  200 . The outlet pressure sensor  322  is configured to continuously collect data about the pressure of the refrigerant at the vapor line  157  and send the data to the controller  200  by control line  327 . In a different embodiment, the inlet temperature sensor  311  and the inlet pressure sensor  312  are coupled directly to the vapor line  157 . 
     The controller  200  is configured to receive data from the actuator sensor  325 , the inlet temperature sensor  311 , the inlet pressure sensor  312 , the outlet temperature sensor  321 , and the outlet pressure sensor  322 . The controller  200  is further configured to send a control signal to the actuator  125  based on the data received from the actuator sensor  325 , the inlet temperature sensor  311 , the inlet pressure sensor  312 , the outlet temperature sensor  321 , and the outlet pressure sensor  322 . 
     Now referring to  FIG.  4   , a block diagram of another exemplary embodiment of the refrigeration system  105  of  FIG.  2    is shown. The embodiment shown in  FIG.  4    includes an ambient temperature sensor  361  and an ambient pressure sensor  362  coupled to the controller  200  by control line  367 . Ambient temperature sensor  361  is configured to measure ambient temperature (i.e. the temperature outside of the temperature controlled space  103  or the refrigerated display case  100 ). Ambient pressure sensor  362  is configured to measure ambient pressure (i.e. the pressure outside of the temperature controlled space  103  or the refrigerated display case  100 ). 
     In additional exemplary embodiments, the refrigeration system  105  may only include some of the temperature sensors or the pressure sensors shown in the embodiments of  FIGS.  2 - 4   . For example, the refrigeration system  105  may only include pressure sensors. Alternatively, the refrigeration system  105  may include any combination of temperature and pressure sensors. In these embodiments, the controller may be configured to determine a temperature based on the type of refrigerant and the pressure measured from a pressure sensor. Alternatively, the controller may be configured to determine a pressure based on the type of refrigerant and the temperature measured from a temperature sensor. Various combinations of sensors are within the scope of the present disclosure. 
     Now referring to  FIG.  5   , a block diagram of the controller  200  is shown, according to an exemplary embodiment. The controller  200  includes a processing circuit  400 . The processing circuit  400  includes a processor  405  and a memory device  410 . The processing circuit is communicably coupled (e.g., conductively linked) to various interfaces on the controller  200 . The processing circuit is configured to receive and transmit data from the interfaces on the controller  200 . 
     The controller  200  is shown as including a user interface  420 . The user interface  420  includes a signaling device  425 . The user interface  420  is configured to receive or provide signals from/to a control panel provided with the display case. The control panel may include digital or analog input/output devices for example a display (e.g., LCD, OLED, etc.), an audio device (e.g., speaker, etc.), or an indication device (e.g., LED, etc.) configured to present the data to the user. For example the user interface  420  may be configured to receive data from a user input such as ambient pressure, ambient temperature, desired superheat or subcooling conditions, or other parameters relevant to the operation of the refrigeration system  105  (see  FIG.  2   ). Additionally, the user interface  420  may be configured to provide information to the user such as data collected by various sensors of the refrigeration system  105 . The user interface  420  includes a signaling device  425  configured to provide a signal to the control panel. For example, the signaling device  425  may be configured to present operational data about the refrigeration system  105 . The signaling device  425  may be configured to notify the user that the refrigeration system  105  is operating within the specified parameters, or that the refrigeration system  105  has experienced a failure to one or more components. For example, the signaling device  425  may light up an LED indication light if certain conditions are meet. More specifically, the signaling device  425  may light up a green LED to indicate that the refrigeration system  105  is operating within the desired parameters set by the user, or the signaling device  425  may light up a red LED to indicate a problem within the refrigeration system  105 . In other embodiments, the signaling device  425  may be positioned on the controller  200  and configured to provide an indication of a problem within the refrigeration system  105 . For example the signaling device  425  may be a buzzer or alarm integrated with the controller  200  and configured to provide an audible signal indicating a problem within the refrigeration system  105 . 
     The controller  200  also includes a communication interface  430 . The communication interface  430  may be configured to send and receive data over a wired connection (e.g., Ethernet, thunderbolt, etc.) or a wireless connection (e.g., Wi-Fi, Bluetooth, etc.). The communication interface  430  may also be configured to interface with the user interface  420  such that the user interface  420  may send and receive data via the communication interface  430  (e.g., to a mobile device). 
     The controller  200  also includes a temperature interface  453  and a pressure interface  454 . The temperature interface  453  is configured to be communicably coupled to temperature sensors (e.g., inlet temperature sensor  311  of  FIG.  3   ) by a control line (e.g., control line  317  of  FIG.  3   ). The pressure interface  454  is configured to be communicably coupled to pressure sensors (e.g., inlet pressure sensor  312  of  FIG.  3   ) by a control line (e.g., control line  327  of  FIG.  3   ). The temperature interface  453  and the pressure interface  454  are each further configured facilitate communication between the sensors and the processing circuit  400 . 
     The controller  200  also includes a compressor interface  480  and an expansion valve interface  490 . The compressor interface  480  is configured to facilitate communication between the compressor assembly  160  of  FIG.  2    and the processing circuit  400  such that the processing circuit  400  may selectively facilitate the operation of the compressor assembly  160 . The expansion valve interface  490  is configured to facilitate communication between the actuator sensor  325  of  FIG.  3    and the processing circuit  400  by control line  326  of  FIG.  3   . Additionally the expansion valve interface  490  may be configured to facilitate communication between the actuator  125  of  FIG.  3    and the processing circuit  400  such that the processing circuit  400  may selectively facilitate the operation of the actuator  125  by control line  397  of  FIG.  3   . 
     The controller  200  is configured to execute the processes of  FIGS.  6 - 7   . The controller  200  is configured to determine if a component of the refrigeration system  105  (e.g., the actuator  125 ) has experienced an electrical failure. For example, the controller  200  may communicate with the inlet temperature sensor  311 , outlet temperature sensor  321 , ambient temperature sensor  361 , inlet pressure sensor  312 , outlet pressure sensor  322 , and ambient pressure sensor  362  by the respective control lines (e.g., control line  317 , control line  327 , and control line  367 ) to receive the temperature and pressure of the refrigerant at the inlet and the outlet of the evaporator assembly  150  and the ambient temperature and pressure. The controller  200  may then determine, by the processor, the superheat of the refrigeration system  105 . The controller  200  may also determine a maximum superheat and a minimum superheat based on the ambient temperature and the ambient pressure. The controller  200  may then determine whether the superheat is within specified parameters (e.g., the maximum superheat and the minimum superheat). Upon determining that the superheat is not within the specified parameters, the controller  200  may signal the actuator sensor  325  to begin collecting data about the actuator  125 . In some embodiments, the actuator sensor  325  is configured to detect the displacement of the actuator  125  (i.e., the actuator sensor  325  is configured as an encoder such that the controller  200  may determine if the actuator  125  is moving). In other embodiments, the actuator sensor  325  is configured to detect the electrical properties of the actuator  125  (e.g., current, voltage, power). In these embodiments, the controller  200  may determine if the actuator  125  is moving based on the electrical properties detected by the actuator sensor  325 . For example, the controller  200  may receive from the actuator sensor  325 , a high current spike indicating that the actuator  125  is moving. Alternatively, the controller  200  may receive, from the actuator sensor  325 , a low current spike indicating that the actuator  125  is not moving. The controller may determine, based on the actuator  125  not moving, that the actuator  125  has experienced a failure (e.g., an electrical failure, a mechanical failure, etc.). 
     Now referring to  FIGS.  6  and  7   , flowcharts of a method for detecting failure of an expansion valve (e.g., expansion valve  121 ) and responding to the failure are shown, according to exemplary embodiments. In an exemplary embodiment, the methods shown are performed by the controller  200  and connected components shown in  FIGS.  1 - 5   . Referring specifically to  FIG.  6   , a method  500  for detecting a valve failure is shown according to an exemplary embodiment. 
     At step  510 , the inlet temperature, the outlet temperature, the ambient temperature, the inlet pressure, the outlet pressure, and the ambient pressure are monitored. For example, the inlet temperature sensor  311  can measure the inlet temperature and provide the measurements to the controller. In some embodiments only one of the temperature or the pressure is monitored at each of the inlet sensors, outlet sensors, and ambient sensors. For example, step  510  may include receiving, by the controller  200 , data from the inlet pressure sensor  312 , the outlet pressure sensor  322 , and the ambient pressure sensor  362  and storing the data in the memory device  410 . It should be appreciated that other combinations of measuring temperature and pressure are possible. For example, the inlet pressure, the outlet pressure, and the ambient temperature may be measured. 
     At step  520 , a superheat of the refrigeration system  105  is calculated based on the measured values at step  510 . The superheat may be calculated using the type of refrigerant and only temperature data or pressure data stored in the memory device  410 . Additionally, the superheat of the refrigeration system  105  may be determined based on at least one of the inlet temperature or the inlet pressure, at least one of the outlet temperature or the outlet pressure, and, in some embodiments, the type of refrigerant. For example, the processor  405  retrieves a first temperature value from the memory device  410  originally received by the controller  200  from the inlet temperature sensor  311  at step  510 . The processor  405  may then retrieve a second temperature value from the memory device  410  originally received by the controller  200  from the outlet temperature sensor  321  at step  510 . The processor  405  may then calculate the superheat of the refrigeration system  105  based on the first temperature value and the second temperature value. For example, the first temperature value may be 35° F. and the second temperature value may be 42° F. The processor  405  calculates the superheat of the refrigeration system as 7° F., or the difference between the second temperature value and the first temperature value. The processor  405  may store this value in the memory device  410 . Alternatively, the processor  405  may determine the superheat by retrieving pressure values from the memory device  410  stored during step  510 . The processor  405  may also retrieve a saturated temperature pressure-temperature table stored in the memory device  410 . The processor  405  may determine the inlet temperature and the outlet temperature based on the table and the pressure values, and the superheat of the refrigeration system  105  thereafter. The processor  405  complete the calculation of the superheat and update the value stored in the memory device  410  at a predefined time interval (e.g., multiple times a second, ever second, every minute, etc.). 
     At step  525 , the maximum superheat and the minimum superheat are calculated and defined by the controller  200 . For example, the processor  405  may retrieve the ambient temperature or ambient pressure from the memory device  410 . In some embodiments, the maximum superheat and the minimum superheat are determined by comparing the ambient temperature or the ambient pressure with tabulated values for a particular refrigerant. 
     Step  530  may include performing a feedback control process (e.g., a PI control process, a PID control process) to generate control signals for the actuator based on values of the superheat calculated at step  520 . The feedback control process may be configured to generate control signals that drive the actual superheat value towards a setpoint. The setpoint is between the maximum and minimum values calculated at step  525 . Accordingly, when the system is well-controlled, the superheat value is at approximately the setpoint value and between the maximum and minimum values. For example, the controller  200  may generate a control signal for the expansion valve  121  allowing the pressure of the refrigerant at the evaporator assembly  150  inlet to further decrease based on the superheat of the refrigeration system  105  being too low (i.e., below or near the minimum superheat value). Alternatively, the controller  200  may generate a control signal for the expansion valve  121  to decrease the pressure drop based on the superheat of the refrigeration system  105  being too high (i.e., above or near the maximum superheat value.) 
     Step  540  may include determining, by the processor, that the superheat of the refrigeration system  105  is between the maximum superheat and the minimum superheat. If the superheat of the refrigeration system  105  is between the maximum superheat and the minimum superheat, the controller will continue to step  550 . If the superheat of the refrigeration system  105  is not between the maximum superheat and the minimum superheat, the controller  200  will continue to step  560  (i.e., this indicates a deviation from the controlled state and may correspond to a fault/error). 
     At step  550  the actuator  125  is identified as operating correctly by the controller. The controller may indicate that the actuator  125  is operating correctly to the user by the user interface  420  or the signaling device  425   
     At step  560 , the controller  200  will begin monitoring the actuator  125  at step. For example, the controller may begin monitoring a current supplied to the actuator  125  measured by actuator sensor  325 . 
     Step  570  includes determining, by the processor  405 , if the current supplied to the actuator  125  is varying. In an exemplary embodiment, the actuator  125  may receive current when the actuator  125  is not moving (e.g., idling). For example, the actuator  125  may be configured as a stepper motor. In this configuration, the actuator  125  will continuously or periodically draw power to maintain positional accuracy when idle. For example, a stepper motor may draw power with a current spike at approximately 2 amps (2 A) at every period (e.g., 60 or more times a second, 5 times a second, every second, every minute, etc.). When the actuator  125  begins to move, the actuator  125  draws power with a current spike at approximately 5 A. While moving, the actuator  125  continues to draw power with the current spike at approximately 5 A (see  FIG.  8   ). 
     If the controller  200  determines that the current is sufficiently varying (e.g., from 2 A to 5 A), the controller  200  continues to step  580 . 
     In the event of a failure (e.g., an electrical failure), the actuator  125  may not draw the necessary power to begin moving. For example, the actuator  125  may continue to draw power with current spikes at 2 A if the actuator  125  has failed (see  FIG.  9   ). If the controller  200  determines that the current is not sufficiently varying (e.g., the current spikes are not increasing from 2 A to 5 A) the controller  200  continues to step  590 . 
     At step  580 , the controller  200  determines that the actuator  125  is operating correctly. The controller may provide a signal by the user interface  420  or the signaling device  425  that the actuator  125  is operating correctly. The controller may return to step  510  or  530  to check for failures again. 
     At step  590 , the controller  200  determines that the actuator  125  is not operating correctly. The controller  200  may signal, by the user interface  420  or the signaling device  425 , that the expansion valve assembly  120  has experienced a failure. More specifically, the actuator  125  of the expansion valve assembly  120  has experienced an electrical failure. In other embodiments, the controller is configured to identify a valve failure based on a mathematical equation or lookup table. The controller may continue to method  600 , return to step  510  to recheck for failures, or both. 
     Now referring to  FIG.  7   , a flowchart of a method  600  of post-failure-identification procedures is shown. In some embodiments, the method  600  may be performed as a continuation of method  500  by the controller  200  as shown. At step  610 , the controller  200  signals to the devices that failure mitigation controls are enabled. At step  620 , the controller signals, by the signaling device  425 , an indication of valve failure. Step  620  may further include present data to the user that represents the failure mode identified by the controller  200 . At step  630 , the controller  200  prepares a shutdown signal for each of the system components. At step  640 , the controller  200  sends a shutdown signal to the compressor assembly  160 . At step  650 , the controller  200  sends a shutdown signal to the fans (e.g., fan  115  and fan  155 ). 
     The controller  200  advantageously signals a valve failure and, in some embodiments, begins failure mitigation controls such that the compressor assembly  160  is not damage by a high superheat or a low superheat. For example, the compressor assembly  160  may be damaged by a low superheat if the refrigerant is received by the compressor assembly  160  in a liquid state (i.e., the refrigerant did not take on enough thermal energy to remain a vapor). In this case, the liquid refrigerant may damage the compressor assembly  160 . Alternatively, the compressor assembly  160  may be damaged by a high superheat if the refrigerant is too hot when it is received by the compressor assembly  160 . In this case, the refrigerant may lead to the compressor assembly  160  overheating. 
     In one embedment, the failure mitigation controls may alternatively be performed by a user. For example the user may be notified, by the signaling device  425 , of a valve failure. The user may then shut down the refrigeration system  105  including the compressor assembly  160 , fan  115 , and fan  155 . 
     Now referring to  FIGS.  8  and  9   , a graph of current vs time supplied to the actuator  125  is shown, according to exemplary embodiments. Referring specifically to  FIG.  8   , a graph  800  of current  801  (Amps) vs time  802  (milliseconds) is shown. The graph shows a first region  810  in which the current  801  spikes up to about 2 A and a second region  850  in which the current  801  spikes up to about 5 A. The first region  810  is indicative of the actuator  125  of  FIG.  3    idling. The current  801  increase over the time  802  (e.g., the transition from the first region  810  to the second region  850 ) indicates that the actuator  125  is beginning to move. Due to the increase in the current  801  between the first region  810  and the second region  820 , the controller  200  may determine that the expansion valve assembly  120  is properly functioning. 
     Referring now to  FIG.  9    a graph  900  of current  901  (Amps) vs time  902  (milliseconds) is shown. The graph shows a region  910  where the current  901  spikes to about 2 A. The current  901  maximum, constant at 2 A, is indicative of the actuator  125  idling over the entire duration of the graph  900  (e.g., between the minimum and maximum values of time  902 ). Due to the constant spikes in the current  901 , the controller  200  may determine that the expansion valve assembly  120  is not functioning. 
     As utilized herein, the terms “approximately,” “about,” “substantially,” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims. It should be noted that the term “exemplary” and variations thereof, as used herein to describe various embodiments, are intended to indicate that such embodiments are possible examples, representations, or illustrations of possible embodiments (and such terms are not intended to connote that such embodiments are necessarily extraordinary or superlative examples). 
     The term “or,” as used herein, is used in its inclusive sense (and not in its exclusive sense) so that when used to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is understood to convey that an element may be either X, Y, Z; X and Y; X and Z; Y and Z; or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated. 
     The construction and arrangement of the elements of the refrigeration system and valve diagnostic system as shown in the exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure. 
     The hardware and data processing components (e.g., processing circuit  400 ) used to implement the various processes, operations, illustrative logics, logical blocks, modules and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, particular processes and methods may be performed by circuitry that is specific to a given function. The memory (e.g., memory, memory unit, storage device) may include one or more devices (e.g., RAM, ROM, Flash memory, hard disk storage) for storing data and/or computer code for completing or facilitating the various processes, layers and modules described in the present disclosure. The memory may be or include volatile memory or non-volatile memory, and may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present disclosure. According to an exemplary embodiment, the memory is communicably connected to the processor via a processing circuit and includes computer code for executing (e.g., by the processing circuit or the processor) the one or more processes described herein. 
     The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions. 
     Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps. 
     The background section is intended to provide a background or context to the invention recited in the claims. The description in the background section may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in the background section is not prior art to the description and claims and is not admitted to be prior art by inclusion in the background section. 
     It is important to note that the construction and arrangement of the systems and methods as shown in the various exemplary embodiments is illustrative only. Additionally, any element disclosed in one embodiment may be incorporated or utilized with any other embodiment disclosed herein. For example, the methods of the exemplary embodiment described in at least paragraph(s) [0039] may be incorporated with any of the components of the refrigeration system of the exemplary embodiment described in at least paragraph(s) [0018]. Although only one example of an element from one embodiment that can be incorporated or utilized in another embodiment has been described above, it should be appreciated that other elements of the various embodiments may be incorporated or utilized with any of the other embodiments disclosed herein.