Patent Publication Number: US-9885507-B2

Title: Protection and diagnostic module for a refrigeration system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/776,879, filed on Jul. 12, 2007. which claims the benefit of U.S. Provisional Application No. 60/831,755, filed on Jul. 19, 2006. The disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to compressors, and more particularly, to a diagnostic system for use with a compressor. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Compressors are used in a wide variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system (generically referred to as “refrigeration systems”) to provide a desired heating and/or cooling effect. In any of the foregoing applications, the compressor should provide consistent and efficient operation to ensure that the particular refrigeration system functions properly. 
     Refrigeration systems and associated compressors may include a protection system that intermittently restricts power to the compressor to prevent operation of the compressor and associated components of the refrigeration system (i.e., evaporator, condenser, etc.) when conditions are unfavorable. The types of faults that may cause protection concerns include electrical, mechanical, and system faults. Electrical faults typically have a direct effect on an electrical motor associated with the compressor, while mechanical faults generally include faulty bearings or broken parts. Mechanical faults often raise a temperature of working components within the compressor, and thus, may cause malfunction of, and possible damage to, the compressor. 
     In addition to electrical faults and mechanical faults associated with the compressor, the compressor and refrigeration system components may also be affected by system faults attributed to system conditions such as an adverse level of fluid disposed within the system or to a blocked-flow condition external to the compressor. Such system conditions may raise an internal compressor temperature or pressure to high levels, thereby damaging the compressor and causing system inefficiencies and/or failures. To prevent system and compressor damage or failure, the compressor may be shut down by the protection system when any of the aforementioned conditions are present. 
     Conventional protection systems typically sense temperature and/or pressure parameters as discrete switches and interrupt power supplied to the electrical motor of the compressor should a predetermined temperature or pressure threshold be exceeded. Typically, a plurality of sensors are required to measure and monitor the various system and compressor operating parameters. With each parameter measured, at least one sensor is typically required, and therefore results in a complex protection system in which many sensors are employed. 
     Sensors associated with conventional protection systems are required to quickly and accurately detect particular faults experienced by the compressor and/or system. Without such plurality of sensors, conventional systems would merely shut down the compressor when a predetermined threshold mode and/or current is experienced. Repeatedly shutting down the compressor whenever a fault condition is experienced results in frequent service calls and repairs to the compressor to properly diagnose and remedy the fault. In this manner, while conventional protection devices adequately protect a compressor and system to which the compressor may be tied, conventional protection systems fail to precisely indicate a particular fault and often require a plurality of sensors to diagnose the compressor and/or system. 
     SUMMARY 
     A system is provided and may include a compressor functioning in a refrigeration circuit. An ambient temperature sensor may produce a signal indicative of an ambient temperature. Processing circuitry may calculate an energy efficiency rating of the refrigeration circuit and may generate a relationship of the calculated energy efficiency rating and ambient temperature. The processing circuitry may compare the calculated energy efficiency rating to a base energy efficiency rating to determine if a fault condition exists. 
     In another configuration, a system may include a compressor functioning in a refrigeration circuit. An ambient temperature sensor may produce a signal indicative of an ambient temperature. Processing circuitry may calculate an energy efficiency rating of the refrigeration circuit and may generate an efficiency index by dividing the calculated energy efficiency rating by the last stored value of the calculated energy efficiency rating for a particular ambient temperature to determine changes in efficiency of the refrigeration circuit over time. 
     A method is provided and may include producing a signal indicative of an ambient temperature, calculating by processing circuitry an energy efficiency rating of a refrigeration circuit, and generating by the processing circuitry a relationship of the calculated energy efficiency rating and ambient temperature. The method may also include comparing by the processing circuitry the calculated energy efficiency rating to a base energy efficiency rating and determining by the processing circuitry if a fault condition exists based on the comparison. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a perspective view of a compressor incorporating a protection system in accordance with the principles of the present teachings; 
         FIG. 2  is a cross-sectional view of the compressor of  FIG. 1 ; 
         FIG. 3  is a schematic representation of a refrigeration system incorporating the compressor of  FIG. 1 ; 
         FIG. 4  is a table illustrating various sensor combinations used to detect specific fault conditions; 
         FIG. 5  is a flow chart depicting a process for determining system energy efficiency; 
         FIG. 6  is a graph of current drawn by a compressor versus condenser temperature for use in determining condenser temperature at a given evaporator temperature; 
         FIG. 7  is a graph of discharge temperature versus evaporator temperature for use in determining an evaporator temperature at a given condenser temperature; 
         FIG. 8  is a graph of discharge superheat versus suction superheat to determine suction superheat at a given outdoor/ambient temperature; 
         FIG. 9  is a graph of energy efficiency versus outdoor/ambient temperature for use in diagnosing a compressor and/or refrigeration system; 
         FIG. 10  is a flowchart illustrating a procedure used to determine system load and energy consumption of a refrigeration system; 
         FIG. 11  is a table illustrating various sensor combinations used to detect specific fault conditions; 
         FIG. 12  is a graph depicting specific fault conditions at various discharge superheat conditions; 
         FIG. 13  is a flowchart depicting a process for installing and diagnosing a compressor and/or refrigeration system; 
         FIG. 14  is a flowchart depicting a compressor installation process; 
         FIG. 15  is a flowchart depicting a compressor installation and refrigerant-charge process; 
         FIG. 16  is a graphical representation of various system and compressor faults based on condenser temperature difference and discharge superheat progressions; 
         FIG. 17  is a graphical representation of subcooling, condenser temperature difference, discharge superheat, energy efficiency rating, and capacity for use in determining a charge level of a refrigeration system; 
         FIG. 18  is a flowchart illustrating a process for verifying air flow through an evaporator; and 
         FIG. 19  is a flowchart illustrating a process for verifying a refrigerant charge of a refrigeration system. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     With reference to the drawings, a compressor  10  is shown incorporated into a refrigeration system  12 . A protection and control system  14  is associated with the compressor  10  and the refrigeration system  12  to monitor and diagnose both the compressor  10  and the refrigeration system  12 . The protection and control system  14  utilizes a series of sensors to determine non-measured operating parameters of the compressor  10  and/or refrigeration system  12 . The protection and control system  14  uses the non-measured operating parameters in conjunction with measured operating parameters from the sensors to diagnose and protect the compressor  10  and/or refrigeration system  12 . 
     With particular reference to  FIGS. 1 and 2 , the compressor  10  is shown to include a generally cylindrical hermetic shell  15  having a welded cap  16  at a top portion and a base  18  having a plurality of feet  20  welded at a bottom portion. The cap  16  and the base  18  are fitted to the shell  15  such that an interior volume  22  of the compressor  10  is defined. The cap  16  is provided with a discharge fitting  24 , while the shell  15  is similarly provided with an inlet fitting  26 , disposed generally between the cap  16  and base  18 , as best shown in  FIG. 2 . In addition, an electrical enclosure  28  is fixedly attached to the shell  15  generally between the cap  16  and the base  18  and operably supports a portion of the protection and control system  14  therein. 
     A crankshaft  30  is rotatably driven by an electric motor  32  relative to the shell  15 . The motor  32  includes a stator  34  fixedly supported by the hermetic shell  15 , windings  36  passing therethrough, and a rotor  38  press-fit on the crankshaft  30 . The motor  32  and associated stator  34 , windings  36 , and rotor  38  cooperate to drive the crankshaft  30  relative to the shell  15  to compress a fluid. 
     The compressor  10  further includes an orbiting scroll member  40  having a spiral vein or wrap  42  on an upper surface thereof for use in receiving and compressing a fluid. An Oldham coupling  44  is disposed generally between the orbiting scroll member  40  and bearing housing  46  and is keyed to the orbiting scroll member  40  and a non-orbiting scroll member  48 . The Oldham coupling  44  transmits rotational forces from the crankshaft  30  to the orbiting scroll member  40  to compress a fluid disposed generally between the orbiting scroll member  40  and the non-orbiting scroll member  48 . Oldham coupling  44 , and its interaction with orbiting scroll member  40  and non-orbiting scroll member  48 , is preferably of the type disclosed in assignee&#39;s commonly owned U.S. Pat. No. 5,320,506, the disclosure of which is incorporated herein by reference. 
     Non-orbiting scroll member  48  also includes a wrap  50  positioned in meshing engagement with the wrap  42  of the orbiting scroll member  40 . Non-orbiting scroll member  48  has a centrally disposed discharge passage  52 , which communicates with an upwardly open recess  54 . Recess  54  is in fluid communication with the discharge fitting  24  defined by the cap  16  and a partition  56 , such that compressed fluid exits the shell  15  via discharge passage  52 , recess  54 , and fitting  24 . Non-orbiting scroll member  48  is designed to be mounted to bearing housing  46  in a suitable manner such as disclosed in assignee&#39;s commonly owned U.S. Pat. Nos. 4,877,382 and 5,102,316, the disclosures of which are incorporated herein by reference. 
     The electrical enclosure  28  includes a lower housing  58 , an upper housing  60 , and a cavity  62 . The lower housing  58  is mounted to the shell  15  using a plurality of studs  64 , which are welded or otherwise fixedly attached to the shell  15 . The upper housing  60  is matingly received by the lower housing  58  and defines the cavity  62  therebetween. The cavity  62  is positioned on the shell  15  of the compressor  10  and may be used to house respective components of the protection and control system  14  and/or other hardware used to control operation of the compressor  10  and/or refrigeration system  12 . 
     With particular reference to  FIG. 2 , the compressor  10  includes an actuation assembly  65  that selectively separates the orbiting scroll member  40  from the non-orbiting scroll member  48  to modulate a capacity of the compressor  10  between a reduced-capacity mode and a full-capacity mode. The actuation assembly  65  may include a solenoid  66  connected to the orbiting scroll member  40  and a controller  68  coupled to the solenoid  66  for controlling movement of the solenoid  66  between an extended position and a retracted position. 
     Movement of the solenoid  66  into the extended position separates the wraps  42  of the orbiting scroll member  40  from the wraps  50  of the non-orbiting scroll member  48  to reduce an output of the compressor  10 . Conversely, movement of the solenoid  66  into the retracted position moves the wraps  42  of the orbiting scroll member  40  closer to the wraps  50  of the non-orbiting scroll member  48  to increase an output of the compressor. In this manner, the capacity of the compressor  10  may be modulated in accordance with demand or in response to a fault condition. While movement of the solenoid  66  into the extended position is described as separating the wraps  42  of the orbiting scroll member  40  from the wraps  50  of the non-orbiting scroll member  48 , movement of the solenoid  66  into the extended position could alternately move the wraps  42  of the orbiting scroll member  40  into engagement with the wraps  50  of the non-orbiting scroll member  48 . Similarly, while movement of the solenoid  66  into the retracted position is described as moving the wraps  42  of the orbiting scroll member  40  closer to the wraps  50  of the non-orbiting scroll member  48 , movement of the solenoid  66  into the retracted position could alternately move the wraps  42  of the orbiting scroll member  40  away from the wraps  50  of the non-orbiting scroll member  48 . The actuation assembly  65  may be of the type disclosed in assignee&#39;s commonly owned U.S. Pat. No. 6,412,293, the disclosure of which is incorporated herein by reference. 
     With particular reference to  FIG. 3 , the refrigeration system  12  is shown to include a condenser  70 , an evaporator  72 , and an expansion device  74  disposed generally between the condenser  70  and the evaporator  72 . The refrigeration system  12  also includes a condenser fan  76  associated with the condenser  70  and an evaporator fan  78  associated with the evaporator  72 . Each of the condenser fan  76  and the evaporator fan  78  may be variable-speed fans that can be controlled based on a cooling and/or heating demand of the refrigeration system  12 . Furthermore, each of the condenser fan  76  and evaporator fan  78  may be controlled by the protection and control system  14  such that operation of the condenser fan  76  and evaporator fan  78  may be coordinated with operation of the compressor  10 . 
     In operation, the compressor  10  circulates refrigerant generally between the condenser  70  and evaporator  72  to produce a desired heating and/or cooling effect. The compressor  10  receives vapor refrigerant from the evaporator  72  generally at the inlet fitting  26  and compresses the vapor refrigerant between the orbiting scroll member  40  and the non-orbiting scroll member  48  to deliver vapor refrigerant at discharge pressure at discharge fitting  24 . 
     Once the compressor  10  has sufficiently compressed the vapor refrigerant to discharge pressure, the discharge-pressure refrigerant exits the compressor  10  at the discharge fitting  24  and travels within the refrigeration system  12  to the condenser  70 . Once the vapor enters the condenser  70 , the refrigerant changes phase from a vapor to a liquid, thereby rejecting heat. The rejected heat is removed from the condenser  70  through circulation of air through the condenser  70  by the condenser fan  76 . When the refrigerant has sufficiently changed phase from a vapor to a liquid, the refrigerant exits the condenser  70  and travels within the refrigeration system  12  generally towards the expansion device  74  and evaporator  72 . 
     Upon exiting the condenser  70 , the refrigerant first encounters the expansion device  74 . Once the expansion device  74  has sufficiently expanded the liquid refrigerant, the liquid refrigerant enters the evaporator  72  to change phase from a liquid to a vapor. Once disposed within the evaporator  72 , the liquid refrigerant absorbs heat, thereby changing from a liquid to a vapor and producing a cooling effect. If the evaporator  72  is disposed within an interior of a building, the desired cooling effect is circulated into the building to cool the building by the evaporator fan  78 . If the evaporator  72  is associated with a heat-pump refrigeration system, the evaporator  72  may be located remote from the building such that the cooling effect is lost to the atmosphere and the rejected heat experienced by the condenser  70  is directed to the interior of the building to heat the building. In either configuration, once the refrigerant has sufficiently changed phase from a liquid to a vapor, the vaporized refrigerant is received by the inlet fitting  26  of the compressor  10  to begin the cycle anew. 
     With particular reference to  FIGS. 2 and 3 , the protection and control system  14  is shown to include a high-side sensor  80 , a low-side sensor  82 , a liquid-line temperature sensor  84 , and an outdoor/ambient temperature sensor  86 . The protection and control system  14  also includes processing circuitry  88  and a power-interruption system  90 , each of which may be disposed within the electrical enclosure  28  mounted to the shell  15  of the compressor  10 . The sensors  80 ,  82 ,  84 ,  86  cooperate to provide the processing circuitry  88  with sensor data for use by the processing circuitry  88  in determining non-measured operating parameters of the compressor  10  and/or refrigeration system  12 . The processing circuitry  88  uses the sensor data and the determined non-measured operating parameters to diagnose the compressor  10  and/or refrigeration system  12  and selectively restricts power to the electric motor of the compressor  10  via the power-interruption system  90 , depending on the identified fault. 
     The high-side sensor  80  generally provides diagnostics related to high-side faults such as compressor mechanical failures, motor failures, and electrical component failures such as missing phase, reverse phase, motor winding current imbalance, open circuit, low voltage, locked rotor current, excessive motor winding temperature, welded or open contactors, and short cycling. The high-side sensor  80  may be a current sensor that monitors compressor current and voltage to determine and differentiate between mechanical failures, motor failures, and electrical component failures. The high-side sensor  80  may be mounted within the electrical enclosure  28  or may alternatively be incorporated inside the shell  15  of the compressor  10  ( FIG. 2 ). In either case, the high-side sensor  80  monitors current drawn by the compressor  10  and generates a signal indicative thereof, such as disclosed in assignee&#39;s commonly owned U.S. Pat. No. 6,615,594, U.S. patent application Ser. No. 11/027,757 filed on Dec. 30, 2004 and U.S. patent application Ser. No. 11/059,646 filed on Feb. 16, 2005, the disclosures of which are incorporated herein by reference. 
     While the high-side sensor  80  as described herein may provide compressor current information, the protection and control system  14  may also include a discharge pressure sensor  92  mounted in a discharge pressure zone and/or a temperature sensor  94  mounted within or near the compressor shell  15  such as within the discharge fitting  24  ( FIG. 2 ). The temperature sensor  94  may additionally or alternatively be positioned external of the compressor  10  along a conduit  103  extending generally between the compressor  10  and the condenser  70  ( FIG. 3 ) and may be disposed in close proximity to an inlet of the condenser  70 . Any or all of the foregoing sensors may be used in conjunction with the high-side sensor  80  to provide the protection and control system  14  with additional system information. 
     The low-side sensor  82  generally provides diagnostics related to low-side faults such as a low charge in the refrigerant, a plugged orifice, an evaporator fan failure, or a leak in the compressor  10 . The low-side sensor  82  may be disposed proximate to the discharge fitting  24  or the discharge passage  52  of the compressor  10  and monitors a discharge-line temperature of a compressed fluid exiting the compressor  10 . In addition to the foregoing, the low-side sensor  82  may be disposed external from the compressor shell  15  and proximate to the discharge fitting  24  such that vapor at discharge pressure encounters the low-side sensor  82 . Locating the low-side sensor  82  external of the shell  15  allows flexibility in compressor and system design by providing the low-side sensor  82  with the ability to be readily adapted for use with practically any compressor and any system. 
     While the low-side sensor  82  may provide discharge-line temperature information, the protection and control system  14  may also include a suction pressure sensor  96  or a low-side temperature sensor  98 , which may be mounted proximate to an inlet of the compressor  10  such as the inlet fitting  26  ( FIG. 2 ). The suction pressure sensor  96  and low-side temperature sensor  98  may additionally or alternatively be disposed along a conduit  105  extending generally between the evaporator  72  and the compressor  10  ( FIG. 3 ) and may be disposed in close proximity to an outlet of the evaporator  72 . Any or all of the foregoing sensors may be used in conjunction with the low-side sensor  82  to provide the protection and control system  14  with additional system information. 
     While the low-side sensor  82  may be positioned external to the shell  15  of the compressor  10 , the discharge temperature of the compressor  10  can similarly be measured within the shell  15  of the compressor  10 . A discharge core temperature, taken generally at the discharge fitting  24 , could be used in place of the discharge-line temperature arrangement shown in  FIG. 2 . A hermetic terminal assembly  100  may be used with such an internal discharge temperature sensor to maintain the sealed nature of the compressor shell  15 . 
     The liquid-line temperature sensor  84  may be positioned either within the condenser  70  or positioned along a conduit  102  extending generally between an outlet of the condenser  70  and the expansion valve  74 . In this position, the temperature sensor  84  is located in a position within the refrigeration system  12  that represents a liquid location that is common to both a cooling mode and a heating mode if the refrigeration system  12  is a heat pump. 
     Because the liquid-line temperature sensor  84  is disposed generally near an outlet of the condenser  70  or along the conduit  102  extending generally between the outlet of the condenser  70  and the expansion valve  74 , the liquid-line temperature sensor  84  encounters liquid refrigerant (i.e., after the refrigerant has changed from a vapor to a liquid within the condenser  70 ) and therefore can provide an indication of a temperature of the liquid refrigerant to the processing circuitry  88 . While the liquid-line temperature sensor  84  is described as being near an outlet of the condenser  70  or along a conduit  102  extending between the condenser  70  and the expansion valve  74 , the liquid-line temperature sensor  84  may also be placed anywhere within the refrigeration system  12  that would allow the liquid-line temperature sensor  84  to provide an indication of a temperature of liquid refrigerant within the refrigeration system  12  to the processing circuitry  88 . 
     The ambient temperature sensor or outdoor/ambient temperature sensor  86  is located external from the compressor shell  15  and generally provides an indication of the outdoor/ambient temperature surrounding the compressor  10  and/or refrigeration system  12 . The outdoor/ambient temperature sensor  86  may be positioned adjacent to the compressor shell  15  such that the outdoor/ambient temperature sensor  86  is in close proximity to the processing circuitry  88  ( FIG. 2 ). Placing the outdoor/ambient temperature sensor  86  in close proximity to the compressor shell  15  provides the processing circuitry  88  with a measure of the temperature generally adjacent to the compressor  10 . Locating the outdoor/ambient temperature sensor  86  in close proximity to the compressor shell  15  not only provides the processing circuitry  88  with an accurate measure of the surrounding air around the compressor  10 , but also allows the outdoor/ambient temperature sensor  86  to be attached to or within the electrical enclosure  28 . 
     The processing circuitry  88  receives sensor data from the high-side sensor  80 , low-side sensor  82 , liquid-line temperature sensor  84 , and outdoor/ambient temperature sensor  86 . As shown in  FIGS. 4 and 5 , the processing circuitry  88  may use the sensor data from the respective sensors  80 ,  82 ,  84 ,  86  to determine non-measured operating parameters of the compressor  10  and/or refrigeration system  12 . 
     The processing circuitry  88  determines the non-measured operating parameters of the compressor  10  and/or refrigeration system  12  based on the sensor data received from the respective sensors  80 ,  82 ,  84 ,  86  without requiring individual sensors for each of the non-measured operating parameters. The processing circuitry  88  is able to determine a condenser temperature (T cond ), subcooling of the refrigeration system  12 , a temperature difference between the condenser temperature and outdoor/ambient temperature (TD), and a discharge superheat of the refrigeration system  12 . 
     The processing circuitry  88  may determine the condenser temperature by referencing compressor power on a compressor map. The derived condenser temperature is generally the saturated condenser temperature equivalent to the discharge pressure for a particular refrigerant. The condenser temperature should be close to a temperature at a mid-point of the condenser  70 . Using a compressor map to determine the condenser temperature provides a more accurate representation of the overall temperature of the condenser  70  when compared to a condenser temperature value provided by a temperature sensor mounted on a coil of the condenser  70  as the condenser coil likely includes many parallel circuits having different temperatures. 
       FIG. 6  is an example of a compressor map showing compressor current versus condenser temperature at various evaporator temperatures (T evap ). As shown, current remains fairly constant irrespective of evaporator temperature. Therefore, while an exact evaporator temperature can be determined by a second degree polynomial (i.e., a quadratic function), for purposes of control, the evaporator temperature can be determined by a first degree polynomial (i.e., a linear function) and can be approximated as roughly 45, 50, or 55 degrees Fahrenheit. The error associated with choosing an incorrect evaporator temperature is minimal when determining the condenser temperature. While compressor current is shown, compressor power and/or voltage may be used in place of current for use in determining condenser temperature. Compressor power may determined based on the current drawn by motor  32 , as indicated by the high-side sensor  80 . 
     Once the compressor current is known and is adjusted for voltage based on a baseline voltage contained in a compressor map ( FIG. 6 ), the condenser temperature may be determined by comparing compressor current with condenser temperature using the graph shown in  FIG. 6 . The above process for determining the condenser temperature is described in assignee&#39;s commonly-owned U.S. patent application Ser. No. 11/059,646 filed on Feb. 16, 2005, the disclosure of which is herein incorporated by reference. 
     Once the condenser temperature is known, the processing circuitry  88  is then able to determine the subcooling of the refrigeration system  12  by subtracting the liquid-line temperature as indicated by the liquid-line temperature sensor  84  from the condenser temperature and then subtracting an additional small value (typically 2-3° F.) representing the pressure drop between an outlet of the compressor  10  and an outlet of the condenser  70 . The processing circuitry  88  is therefore able to determine not only the condenser temperature but also the subcooling of the refrigeration system  12  without requiring an additional temperature sensor for either operating parameter. 
     The processing circuitry  88  is also able to calculate a temperature difference (TD) between the condenser  70  and the outdoor/ambient temperature surrounding the refrigeration system  12 . The processing circuitry  88  is able to determine the condenser temperature by referencing either the power or current drawn by the compressor  10  against the graph shown in  FIG. 6  without requiring a temperature sensor to be positioned within the condenser  70 . Once the condenser temperature is known (i.e., derived), the processing circuitry  88  can determine the temperature difference (TD) by subtracting the ambient temperature as received from the outdoor/ambient temperature sensor  86  from the derived condenser temperature. 
     The discharge superheat of the refrigeration system  12  can also be determined once the condenser temperature is known. Specifically, the processing circuitry  88  can determine the discharge superheat of the refrigeration system  12  by subtracting the condenser temperature from the discharge-line temperature. As described above, the discharge-line temperature may be detected by the low-side sensor  82  and is provided to the processing circuitry  88 . Because the processing circuitry  88  can determine the condenser temperature by referencing the compressor power against the graph shown in  FIG. 6 , and because the processing circuitry  88  knows the discharge-line temperature based on information received from the low-side sensor  82 , the processing circuitry  88  can determine the discharge superheat of the compressor  10  by subtracting the condenser temperature from the discharge-line temperature. 
     As described above, the protection and control system  14  receives sensor data from the high-side sensor  80 , low-side sensor  82 , liquid-line temperature sensor  84 , and outdoor/ambient temperature sensor  86 , and derives non-measured operating parameters of the compressor  10  and/or refrigeration system  12  such as condenser temperature, subcooling of the refrigeration system  12 , a temperature difference between the condenser  70  and outdoor/ambient temperature, and discharge superheat of the refrigeration system  12 , without requiring individual sensors for each of the derived parameters. Therefore, the protection and control system  14  not only reduces the complexity of the compressor and refrigeration system, but also reduces costs associated with monitoring and diagnosing the compressor  10  and/or refrigeration system  12 . 
     Once the processing circuitry  88  has received the sensor data and determined the non-measured operating parameters, the processing circuitry  88  can diagnose the compressor  10  and refrigeration system  12 . As shown in  FIGS. 4 and 5 , the processing circuitry  88  is able to categorize a fault based on specific information received from the individual sensors and calculated non-measured operating parameters. 
     As shown in  FIG. 4 , once the processing circuitry  88  receives the sensor data and determines the non-measured operating parameters, the processing circuitry  88  can differentiate between specific low-side and high-side faults experienced by the compressor  10  and/or refrigeration system  12 . Low-side faults may include a low charge condition, a low evaporator air flow condition, and/or a flow restriction at either or both of the condenser  70  and evaporator  72 . A high-side fault may include a high-charge condition, a non-condensible condition (i.e., air in the refrigerant), and a low condenser air flow condition. 
     By way of example, the processing circuitry  88  may be able to determine that the compressor  10  and/or refrigeration system  12  is experiencing a low-charge condition if the discharge superheat of the refrigeration system  12  is increasing relative to a predetermined target stored within the processing circuitry  88  while both the subcooling and the condenser temperature difference (i.e., condensing temperature minus outdoor/ambient temperature) are decreasing relative to a predetermined target stored in the processing circuitry  88 . 
     By way of another example, the processing circuitry  88  may be able to determine that the compressor  10  and/or refrigeration system  12  is experiencing a high-side fault such as a high charge condition if the subcooling of the refrigeration system  12  and the temperature difference (i.e., condensing temperature minus outdoor/ambient temperature) are each increasing relative to a predetermined target stored in the processing circuitry  88  while the discharge superheat of the refrigeration system  12  remains relatively unchanged relative to a predetermined target stored in the processing circuitry  88  for a thermal expansion valve/electronic expansion valve flow control system or decreases relative to a predetermined target stored in the processing circuitry  88  for an orifice flow control system. 
     High-efficiency systems tend to employ larger condenser coils, which tend to require less subcooling (i.e., less liquid in the condenser coil, in percentage, when compared to a smaller condenser coil) relative to the condenser temperature difference to deliver optimum charge, therefore both subcooling and condenser temperature difference can be used for a more precise charge verification. Therefore, the ratio of subcooling over condenser temperature difference may be used to check both subcooling and condenser temperature difference. This ratio may be pre-programmed as a target value in processing circuitry  88 . The ratio of subcooling over condenser temperature difference is a function of efficiency and may be used to verify charge ( FIGS. 16 and 17 ). For example, the efficiency for a standard refrigeration system may be 0.6, the efficiency for a mid-level refrigeration system may be 0.75, and the efficiency for a high-efficiency refrigeration system may be 0.9. Such target ratios may be programmed into the processing circuitry  88  to confirm proper operation of the refrigeration system ( FIG. 19 ). 
     The various other low-side faults and high-side faults that may be determined by the processing circuitry  88  are shown in  FIG. 4 , where increasing parameters are identified by an upwardly pointing arrow, decreasing parameters are identified by a downwardly pointing arrow, and constant (i.e., unchanged) parameters are identified by a horizontal arrow. 
     While the protection and control system  14  is useful in diagnosing the compressor  10  and/or refrigeration system  12  by differentiating between various low-side faults and high-side faults during operation of the compressor  10  and refrigeration system  12 , the protection and control system  14  may also be used during installation of the compressor  10  and/or refrigeration system  12 . As noted in  FIG. 4 , the protection and control system  14  may be used to diagnose each of the low-side faults and high-side faults with the exception of a low condenser air-flow condition at installation. Such information is valuable during installation to ensure that the compressor  10  and respective components of the refrigeration system  12  are properly installed and functioning within acceptable limits. 
     As indicated in  FIG. 4 , each of the low-side faults are monitored by the protection and control system  14  on an on-going basis, while the only high-side fault monitored by the protection and control system  14  on an on-going basis is the low condenser-air-flow condition. The high-charge condition is typically not measured on an on-going basis by the protection and control system  14 , as the charge of the system is generally set at installation. In other words, the charge of the refrigeration system  12  cannot be increased without physically supplying the system  12  with additional refrigerant. Therefore, the need for monitoring a high-charge condition after installation is generally unnecessary except when additional refrigerant is added to the refrigeration system  12 . The protection and control system  14  does not typically monitor the non-condensibles high-side fault on an on-going basis because air is not usually injected into the refrigerant once the refrigerant is added to the refrigeration system  12 . Air is only added into the refrigeration system  12  when a supply of refrigerant used to charge the refrigeration system  12  is contaminated with air. 
     While monitoring the high-charge condition and non-condensibles condition are described as not being monitored on an on-going basis, each parameter may be monitored on an on-going basis by the protection and control system  14  to continually monitor the condition of the refrigerant disposed within the compressor  10  and/or refrigeration system  12 . 
     Once the processing circuitry  88  has received the sensor data and has derived the non-measured operating parameters, the processing circuitry  88  can use the sensor data and non-measured operating parameters to derive performance data regarding operation of the compressor  10  and/or refrigeration system  12 . With reference to  FIG. 5 , a flow chart is provided detailing how the processing circuitry  88  can derive a coil capacity of the evaporator  72  and an efficiency of the refrigeration system  12 . 
     The processing circuitry  88  first receives sensor data from the high-side sensor  80 , low-side sensor  82 , liquid-line temperature sensor  84 , and outdoor/ambient temperature sensor  86 . Once the sensor data is received, the processing circuitry  88  uses the sensor data to derive the non-measured operating parameters such as subcooling of the refrigeration system  12 , discharge superheat, and condenser temperature at  83 . 
     The processing circuitry  88  can determine the condenser temperature by referencing an approximated evaporator temperature (i.e., at 45 degrees F., 50 degrees F., or 55 degrees F.) against the current drawn by the compressor, as previously described. A plot of current versus condenser temperature may be used to reference an approximated evaporator temperature against current information received from the high-side sensor  80  ( FIG. 6 ). By using a plot as shown in  FIG. 6 , the processing circuitry  88  can determine the condenser temperature by referencing current information received from the high-side sensor  80  against the approximated evaporator temperature values to determine the condenser temperature. 
     Once the condenser temperature is determined, the processing circuitry  88  can then reference a plot as shown in  FIG. 7  to determine the exact evaporator temperature based on discharge temperature information received from the low-side sensor  82 . Once both the condenser temperature and the evaporator temperature are known, the processing circuitry  88  can then determine the compressor capacity and flow. 
     The discharge superheat may be determined by subtracting the condenser temperature from the discharge-line temperature, as indicated by the low-side sensor  82 . Once the discharge superheat is determined, the processing circuitry  88  can determine the suction superheat by referencing a plot as shown in  FIG. 8 . Specifically, the suction superheat may be determined by referencing the discharge superheat against the ambient temperature as indicated by the outdoor/ambient temperature sensor  86 . 
     In addition to deriving the condenser temperature, evaporator temperature, subcooling, discharge superheat, compressor capacity and flow, and suction superheat, the processing circuitry  88  may also measure or estimate the fan power of the condenser fan  76  and/or evaporator fan  78  and derive a compressor power factor for use in determining the efficiency of the refrigeration system  12  and the capacity of the evaporator  72 . The fan power of the condenser fan  76  and/or evaporator fan  78  may be directly measured by sensors  85  associated with the fans  76 ,  78  or may be estimated by the processing circuitry  88 . 
     Once the non-measured operating parameters are determined, the performance of the compressor  10  and refrigeration system  12  can be determined at  87 . The processing circuitry  88  uses compressor capacity and flow and suction superheat to determine a coil capacity of the evaporator  72  at  89 . Because the processing circuitry  88  uses the fan power of the condenser fan  76  and/or evaporator fan  78  in determining the capacity of the evaporator  72 , the processing circuitry  88  is able to adjust the capacity of the evaporator  72  based on an estimated heat of the condenser fan  76  and/or evaporator fan  78 . In addition, because the compressor capacity and flow is determined using the suction superheat, the capacity of the evaporator  72  may also be adjusted based on suction-line heat gain. 
     Once the capacity of the evaporator  72  is determined, the efficiency of the refrigeration system  12  can be determined using the capacity of the evaporator  72  along with the fan power and compressor power factor at  91 . Specifically, the processing circuitry  88  divides the capacity of the evaporator  72  by the sum of the compressor power and fan power. Dividing the capacity of the evaporator  72  by the sum of the fan power and compressor power provides an indication of the energy efficiency of the refrigeration system  12 . 
     The energy efficiency of the refrigeration system  12  may be used to diagnose the compressor  10  and/or refrigeration system  12  by plotting the determined energy efficiency rating for the refrigeration system  12  against a base energy efficiency rating to determine a fault condition ( FIG. 9 ). If the determined energy efficiency rating of the refrigeration system  12  deviates from the base energy efficiency rating, the processing circuitry  88  can determine that the refrigeration system  12  is operating outside of predetermined limits. Because operation of the refrigeration system  12  varies with changing outdoor/ambient temperatures, the energy efficiency rating is plotted against the outdoor/ambient temperature to account for changes in the outdoor/ambient temperature and its affect on the refrigeration system  12 . 
     In addition to driving the energy efficiency of the refrigeration system  12 , the processing circuitry  88  can also determine the load experienced by the refrigeration system  12  (i.e., kilowatt hours per day). As shown in  FIG. 12 , the processing circuitry  88  can determine the house load based on the capacity of the evaporator  72  and the run time of the compressor  10  (i.e., BTU per hour multiplied by run time (in hours) equals BTU load). This information, in combination with the run time of the compressor  10 , may be used by the processing circuitry  88  to determine the overall load of the refrigeration system  12 , and can be used by the processing circuitry  88  to diagnose the compressor  10  and/or refrigeration system  12 . 
     Once the capacity is derived, the processing circuitry  88  may then also derive the evaporator air flow (i.e., air flow through the evaporator  72 ) as shown in  FIG. 18  based on a pre-determined table located in non-volatile memory of the processing circuitry  88 . The processing circuitry  88  relates the capacity or evaporator temperature to air flow as a function of outdoor ambient and indoor room dry-bulb and wet-bulb temperatures (i.e., humidity). 
     Specifically, the processing circuitry  88  may receive the outdoor temperature from the outdoor temperature sensor  86  and may receive the wet-bulb and/or room humidity from a thermostat. The thermostat may communicate the wet-bulb temperature and/or room humidity to the processing circuitry  88  through digital serial communication. Alternatively, the wet-bulb temperature and room humidity can be manually input by a user. Once the outdoor ambient temperature and indoor wet-bulb temperatures are known, the processing circuitry  88  can reference the outdoor temperature and wet-bulb temperature on a performance map stored in the processing circuitry  88  to determine the air flow through the evaporator  72 . The performance map may include pre-programmed capacity and/or evaporator temperature information as it relates to outdoor ambient temperature, wet-bulb temperature, and air flow. Verifying evaporator air flow may be used to confirm proper installation and system capacity. 
     As described, the protection and control system  14  uses the various sensor data and derived non-measured operating parameters to monitor and diagnose operation of the compressor  10  and/or refrigeration system  12 . The sensor data received from the high-side sensor  80 , low-side sensor  82 , liquid-line temperature sensor  84 , and outdoor/ambient temperature sensor  86  may be used by the processing circuitry  88  to differentiate between various fault areas to diagnose the compressor  10  and/or refrigeration system  12 .  FIG. 11  details various fault areas and diagnostics that the processing circuitry  88  can differentiate between based on sensor data received from the high-side sensor  80 , low-side sensor  82 , liquid-line temperature sensor  84 , and outdoor/ambient temperature sensor  86 . 
     For example, the processing circuitry  88  relies on information from the high-side sensor  80  and low-side sensor  82  to determine compressor faults such as a locked rotor, a motor failure, or insufficient pumping, while the processing circuitry  88  relies on information from the high-side sensor  80 , low-side sensor  82 , and liquid-line temperature sensor  84  to distinguish between high-side system faults such as cycling on protection (i.e., cycling under a tripped condition), low air-flow through the condenser  70 , and an overcharged condition. 
       FIG. 12  further illustrates how the processing circuitry  88  is able to distinguish between high-side faults and low-side faults using discharge superheat. As described above, the discharge superheat is a derived parameter and is calculated based on information received from the high-side sensor  80  and low-side sensor  82 . The processing circuitry  88  compares the discharge superheat with the condenser temperature difference to differentiate between various high-side faults such as an overcharged condition or a non-condensible condition and various low-side faults such as low air-flow through the evaporator  72  or a low-charge condition. The processing circuitry  88  is not only able to derive non-measured operating parameters, but is also able to use the non-measured operating parameters and the sensor data to diagnose the compressor  10  and refrigeration system  12 . 
     Receiving sensor data and deriving non-measured operating parameters allows the protection and control system  14  to monitor and diagnose the compressor  10  and refrigeration system  12  during operation. In addition to diagnosing the compressor  10  and refrigeration system  12  during operation, the protection and control system  14  can also use the sensor data and the non-measured operating parameters during installation of the compressor and individual components of the refrigeration system  12  (i.e., condenser  70 , evaporator  72 , and expansion device  74 ) to ensure that the compressor  10  and individual components of the refrigeration system  12  are properly installed. 
     With reference to  FIG. 13 , an exemplary flow chart is provided detailing an installation check used by the protection and control system  14  during installation of the compressor  10  and/or components of the refrigeration system  12 . Once the compressor  10  is installed into the refrigeration system  12 , the compressor  10  is stabilized at  104 . Once the compressor  10  is stabilized, the processing circuitry  88  receives sensor data from the high-side sensor  80 , low-side sensor  82 , liquid-line temperature sensor  84 , and outdoor/ambient temperature sensor  86  at  106 . As described above, the processing circuitry  88  uses the sensor data from the high-side sensor  80 , low-side sensor  82 , liquid-line temperature sensor  84 , and outdoor/ambient temperature sensor  86  to derive non-measured operating parameters at  108 . The non-measured operating parameters include, but are not limited to, condenser temperature, subcooling of the refrigeration system  12 , condenser temperature difference (i.e., condenser temperature minus outdoor/ambient temperature), and discharge superheat of the refrigeration system  12 . This information is used at an installation check  110  to determine whether the compressor  10  and various components of the refrigeration system  12  are property installed. 
     Original equipment manufacturing data (OEM Data) such as size, type, condenser coil pressure drop, compressor maps, and/or subcooling targets for refrigeration system components such as the expansion device  74  are input into the processing circuitry  88  to assist with the installation check  110 . For example, tables of capacity as a function of indoor air flow (i.e., air flow through the evaporator  72 ) and indoor and outdoor temperatures may also be pre-programmed into the processing circuitry  88 . The processing circuitry  88  can use this information, for example, to adjust a subcooling calculation made by reading a pressure at an outlet of the condenser  73  to account for a pressure drop through the condenser  73 . This information is used by the processing circuitry  88  to determine whether the components of the refrigeration system  12  are operating within predetermined limits. 
     With reference to  FIG. 14 , the processing circuitry  88  first calculates the energy efficiency rating of the refrigeration system  12  and plots the energy efficiency rating versus the outdoor/ambient temperature as provided by the outdoor/ambient temperature sensor  86  at  114 . The processing circuitry  88  compares the calculated energy efficiency rating versus a base energy efficiency rating ( FIG. 9 ) to determine if a fault exists at  116 . If the energy efficiency rating is within an acceptable range such that the energy efficiency rating is sufficiently close to the base efficiency rating, the processing circuitry stores the value of the energy efficiency rating at  118 . If the processing circuitry  88  determines a fault condition exists, the processing circuitry  88  calculates a new energy efficiency rating after the fault started at  120 . 
     The processing circuitry  88  is able to track the energy efficiency of the refrigeration system  12  by generating an efficiency index at  122 . The processing circuitry  88  generates the efficiency index by dividing the current efficiency by the last stored reference at the same outdoor/ambient temperature. This way, the processing circuitry  88  is able to track the change in efficiency of the refrigeration system  12  over time at the same outdoor/ambient temperature. 
     Once the installation check  110  is complete, the protection and control system  14  then determines the refrigerant charge within the refrigeration system  12 , as well as the air flow through the condenser  70  and evaporator  72 . With reference to  FIG. 15 , a flowchart detailing a process for determining the refrigerant charge is provided. The processing circuitry  88  first determines the initial charge within the refrigeration system  12  and the air flow through the condenser  70  and evaporator  72  at  124 . Once the initial charge and air flow are determined, the processing circuitry  88  then calculates the capacity and energy efficiency rating of the refrigeration system  12  at  126 . 
     The capacity and energy efficiency rating are compared to baseline values to determine whether the refrigeration system  12  contains a predetermined amount of refrigerant. If the capacity and/or energy efficiency rating indicates that the refrigeration system  12  is either undercharged or overcharged, the processing circuitry  88  indicates that either more charge or less charge is required at  128 . Once the capacity and energy efficiency rating indicate that the refrigeration system  12  is properly charged, the level of refrigerant and airflow through the condenser  70  and evaporator  72  is verified by the processing circuitry  88  at  130 . 
     Once the compressor  10  and components of the refrigeration system  12  are properly installed and the charge and air flow are verified, the protection and control system  14  is able to diagnose the compressor  10  and/or refrigeration system  12  at  132 . The protection and control system  14  ensues active protection of the compressor  10  and/or refrigeration system  12  at  134 , indicating that the installation is complete at  136 . During operation of the compressor  10  and refrigeration system  12 , the protection and control system  14  provides alerts and data at  138  indicative of operation of the compressor  10  and/or refrigeration system  12 . 
     The protection and control system  14  is able to receive sensor data and determine non-measured operating parameters of a compressor and/or refrigeration system to reduce the overall number of sensors required to adequately protect and diagnose the compressor and/or refrigeration system. In so doing, the protection and control system  14  reduces costs associated with monitoring and diagnosing a compressor and/or a refrigeration system and simplifies such monitoring and diagnostics by driving virtual sensor data from a limited number of sensors.