Patent ID: 7073344

Claim:
A refrigeration system for a cooling a space comprising: a compressor to compress a refrigerant gas; a reversing valve connected to said compressor; a condenser connected to said reversing valve which receives the hot pressurized refrigerant gas provided by said compressor; wherein said condenser functions as a heat exchanger to allow the refrigerant gas to dissipate the heat of pressurization such that the refrigerant condenses into a liquid; an electric expansion valve connected to said condenser wherein the refrigerant passing through said expansion valve expands and evaporates; a controller electrically connected to said electric expansion valve and to said reversing valve further comprising: a cooling space temperature sensor that indicates the temperature in the cooled space so that said controller can control the cooling cycle of said refrigeration system; a first evaporator temperature sensor positioned adjacent to the evaporator on the connection between said evaporator and said electric expansion valve; a second evaporator temperature sensor positioned on the connection between said evaporator and said compressor wherein said second evaporator temperature sensor is adjacent to said evaporator but outside the cooled space; wherein the superheat of said evaporator is determined by said controller by measuring said first evaporator temperature sensor and said second evaporator temperature sensor; and wherein said controller modulates the superheat of said evaporator until the predetennined temperature is reached; and wherein once said controller is set to defrost cycle, said controller causes said reversing valve to reverse, said electrical expansion valve is further opened, and said refrigeration system enters a defrost mode; and wherein if said second evaporator temperature sensor indicates to said controller that the temperature is greater than or equal to a defrost termination temperature set in said controller, said controller ends the defrost cycle and causes said refrigeration system to enter a drip mode.