Patent ID: 7275377

Claim:
A monitoring system for monitoring the operation of a refrigerant-cycle system, comprising: a plurality of condenser unit sensors configured to measure operating characteristics of a condenser unit, said plurality of condenser unit sensors comprising a sensor to sense when a compressor in said condenser unit is drawing electrical power, said plurality of condenser unit sensors further comprising at least a first temperature sensor, said condenser unit comprising a condenser and a compressor; one or more evaporator unit sensors configured to measure one or more operating characteristics of an evaporator unit, said one or more evaporator unit sensors comprising at least a second temperature sensor configured to measure an output air temperature of said evaporator, said evaporator unit comprising an evaporator and an air-handler fan; one or more ambient sensors configured to measure one or more ambient conditions; at least one current sensor configured to measure current provided to a motor connected to a fan; and a processing system configured to calculate an efficiency of said refrigerant-cycle system using at least a portion of the data from each of said plurality of condenser unit sensors, at least a portion of the data from each of said one or more evaporator unit sensors, at least a portion of the data from said one or more ambient sensors, and at least a portion of the data from the at least one current sensor.