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A method of automatically detecting an anomalous condition relative to a nominal operating condition in a vapor compression system. An expected input power function in the form of a hyperplane is calculated based on three temperature readings: an intake temperature from an intake area of the condens

A method of automatically detecting an anomalous condition relative to a nominal operating condition in a vapor compression system. An expected input power function in the form of a hyperplane is calculated based on three temperature readings: an intake temperature from an intake area of the condenser unit, a return temperature from an intake area of an evaporator unit, and a supply temperature from a supply output area of the evaporator unit. The function produces an estimate of the expected input power consumed by the compressor unit, and this expected input power is compared with an actual input power measured from the compressor unit. If the expected input power deviates from the measured input power by more than a predetermined tolerance, an indication is stored and communicated that an anomalous condition, such as a refrigerant loss, condenser unit fouling, or a malfunctioning fan, exists in the vapor compression system.

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1. A method of automatically detecting an anomalous condition relative to a nominal operating condition in a vapor compression system, comprising: automatically calculating a measured input power function that includes a current measured from a compressor unit of the vapor compression system, which

1. A method of automatically detecting an anomalous condition relative to a nominal operating condition in a vapor compression system, comprising: automatically calculating a measured input power function that includes a current measured from a compressor unit of the vapor compression system, which includes a condenser unit coupled to the compressor unit;receiving a condenser temperature indicative of an intake temperature from an intake of the condenser unit;automatically calculating an expected input power function that includes the condenser temperature;responsive to the expected input power function deviating from the measured input power function by more than a predetermined tolerance, storing an indication that an anomalous condition exists in the vapor compression system. 2. The method of claim 1, wherein the condenser temperature is the intake temperature. 3. The method of claim 2, wherein the intake temperature is received from a first temperature sensor positioned in an intake area of the condenser unit. 4. The method of claim 1, further comprising receiving an interior temperature indicative of an indoor temperature of an indoor environment or a temperature of a closed managed thermal space within the indoor environment, wherein the expected input power function includes the interior temperature. 5. The method of claim 4, wherein the interior temperature is a thermostat setpoint temperature. 6. The method of claim 4, wherein the interior temperature is an ambient temperature of an indoor environment on which the vapor compression system operates. 7. The method of claim 4, wherein the interior temperature is a return temperature from a temperature sensor positioned in an intake area of an evaporator unit in the vapor compression system, and wherein the expected input power function includes the return temperature. 8. The method of claim 7, wherein the expected input power function includes a power offset constant, a first condenser temperature coefficient, and a second interior temperature coefficient, the power offset constant being expressed in the unit of the measured input power function, the first condenser temperature coefficient representing temperature sensitivity relating to the condenser temperature, and the second interior temperature coefficient representing temperature sensitivity relating to the return temperature, the first condenser temperature coefficient being multiplied by the condenser temperature, the second interior temperature coefficient being multiplied by the return temperature. 9. The method of claim 8, further comprising receiving a supply temperature at a supply output of the evaporator unit, wherein the expected input power function further includes the supply temperature and a third interior temperature coefficient representing temperature sensitivity to the supply temperature, the third interior temperature coefficient being multiplied by the supply temperature. 10. The method of claim 9, further comprising automatically deriving the power offset constant, the first condenser temperature coefficient, the second interior temperature coefficient, and the third interior temperature coefficient by a least-squares regression analysis. 11. The method of claim 7, wherein the vapor compression system includes a heat pump system, and wherein refrigerant for the heat pump system is evaporated in the condenser unit, and wherein high-pressure refrigerant vapor is compressed in the evaporator unit. 12. The method of claim 4, wherein the interior temperature is a supply temperature from a supply output area of an evaporator unit in the vapor compression system, wherein the expected input power function includes the supply temperature. 13. The method of claim 4, wherein the interior temperature is a return temperature from an intake area of an evaporator unit, wherein the receiving the condenser temperature and the return temperature is carried out at a sample rate interval, the method further comprising: delaying the automatically calculating the expected input power function by a predetermined number of cycles of a sample rate at which samples of the condenser temperature and the return temperature are received; andstoring each sample of the condenser temperature and the return temperature. 14. The method of claim 4, wherein the condenser temperature is the intake temperature and wherein the intake temperature is received from a first temperature sensor positioned in an intake area of the condenser unit. 15. The method of claim 4, wherein the interior temperature is of a liquid or a gas. 16. The method of claim 4, further comprising: automatically determining whether the compressor unit is in an ON state or an OFF state by comparing the measured input power function against a power threshold constant for a predetermined number of cycles as determined by a sampling rate of the current; andresponsive to the measured input power function exceeding the power threshold constant for the predetermined number of cycles, storing an indication that the compressor unit is in the ON statewherein the current corresponds to a line current to the compressor unit that is measured by a current transformer, the measured input power function includes a line voltage measured across a line conductor and a neutral conductor connected to the compressor unit, and automatically calculating the measured input power function is carried out in a power monitor coupled to the current transformer; andwherein the expected input power function is calculated independent of any pressure measurement relating to the vapor compression system. 17. The method of claim 1, wherein the expected input power function is independent of any pressure measurement relating to the vapor compression system. 18. The method of claim 1, wherein responsive to the measured input power function being less than the expected input power function by more than the predetermined tolerance, the anomalous condition indicates a loss of refrigerant in the vapor compression system. 19. The method of claim 18, further comprising automatically calculating the expected input power function as refrigerant is added to the vapor compression system and, responsive to the expected input power function being within the predetermined tolerance of the measured input power function, indicating that the vapor compression system has returned to the nominal operating condition. 20. The method of claim 1, wherein responsive to the expected input power function being less than the measured input power function by more than the predetermined tolerance, the anomalous condition indicates a fouling of the condenser unit in the vapor compression system or a malfunctioning fan in the vapor compression system. 21. The method of claim 1, responsive to the measured input power function being less than the expected input power function by more than the predetermined tolerance, the anomalous condition representing a loss of refrigerant in the vapor compression system, the method further comprising: automatically comparing the expected input power function with the measured input power function, in response to additional refrigerant being added to the vapor compression system, until the expected input power function falls within the predetermined tolerance of the measured input power function, and indicating to an operator that no additional refrigerant is required to be added. 22. The method of claim 1, wherein the current corresponds to a line current to the compressor unit measured by a current transformer, the measured input power function including a line voltage measured across a line conductor and a neutral conductor connected to the compressor unit, wherein the automatically calculating the measured input power function is carried out in a power monitor coupled to the current transformer. 23. The method of claim 1, wherein the vapor compression system includes an air conditioner system, a heat pump system, a chiller, or a refrigeration system. 24. The method of claim 1, further comprising: automatically determining whether the compressor unit is in an ON state or an OFF state by comparing the measured input power function against a power threshold constant for a predetermined number of cycles as determined by a sampling rate of the current; andresponsive to the measured input power function exceeding the power threshold constant for the predetermined number of cycles, storing an indication that the compressor unit is in the ON state. 25. The method of claim 24, further comprising deriving the power threshold constant by multiplying a nominal system voltage of the vapor compression system by a rated full-load current drawn by the compressor unit to produce a rated power, and multiplying the rated power by a percentage threshold. 26. The method of claim 25, further comprising, responsive to the measured input power function not exceeding the power threshold constant for a second predetermined number of cycles, storing an indication that the compressor unit is in an OFF state. 27. The method of claim 1, wherein the condenser temperature is of a gas or a liquid. 28. The method of claim 1, wherein the current measured from the compressor unit is an RMS current calculated from the measured current. 29. The method of claim 1, wherein the condenser temperature is an outdoor temperature of an outdoor environment.