Patent ID: 7650758

Claim:
A method for automatically defrosting a refrigeration plant evaporator, based on the evaluation of a non-measured operating variable in a refrigeration plant which variable is derivable from at least one signal, which signal is sensed at predetermined time points, wherein for the evaluation a failure indicator is formed by way of the following steps: a) setting the failure indicator at a first point of time to a first pregiven value, b) forming a sum from the failure indicator of a predetermined earlier time point and a first value derived from an estimated value of the operating variable, under consideration of at least one signal dependent value, c) setting the failure indicator to the value of the sum if the sum is larger than the first pregiven value and setting the failure indicator to the first pregiven value if the sum is smaller than or equal to the first pregiven value, and d) starting an evaporator defrost based on comparison of the failure indicator to a second pre-given value.