Power monitor for vapor compression equipment diagnostics

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.