Patent ID: 7921660
Filing Date: 2011-04-12
Classification: F25B

Abstract:
1. A method of defrosting a refrigeration unit having a compressor, a defrost heater and an evaporator, the method comprising: a) deriving a total wasted energy parameter of the compressor for at least one time interval; b) at a time determined at least in part by said derived total wasted energy of the compressor issuing a defrost command to the defrost heater, wherein said deriving of said total wasted energy includes: i) choosing a reference runtime; ii) estimating an expended energy parameter of the compressor during said reference runtime; and iii) for a plurality of later runtimes, incrementing said total wasted energy parameter by a difference between an expended energy parameter of the compressor during said later runtime and said expended energy parameter of the compressor during said reference runtime and wherein said reference runtime is chosen to be a minimum energy runtime after a previous defrosting of the refrigeration unit.