Patent ID: 8393169

Claim:
A system comprising: a compressor having a motor; a refrigeration circuit including an evaporator and a condenser fluidly coupled to said compressor; a first sensor producing a signal indicative of one of current and power drawn by said motor; a second sensor producing a signal indicative of a saturated condensing temperature; and processing circuitry processing said current or power signal to determine a derived condenser temperature and comparing said derived condenser temperature to said saturated condensing temperature received from said second sensor, said processing circuitry determining an overcharge condition or an undercharge condition if said saturated condensing temperature varies from said derived condenser temperature by a predetermined amount and determining an adequate-charge condition if said saturated condensing temperature varies from said derived condenser temperature less than said predetermined amount, said processing circuitry controlling at least one of said compressor and said refrigeration circuit based on information received from said second sensor only when said adequate-charge condition is determined.