Abstract: A method for defrosting an evaporator of a refrigeration system includes providing a refrigeration system including a low temperature (LT) compressor, a medium temperature (MT) compressor, a low temperature evaporator, and a medium temperature evaporator. The method includes initiating a defrost cycle for the refrigeration system by closing a return valve to shut off refrigerant return to the LT compressor from an outlet of the low temperature evaporator and opening a defrost supply valve to define a fluid flow path between a suction side of the MT compressor and an outlet of the low temperature evaporator. The method includes operating the LT compressor and the MT compressor such that warm refrigerant from the suction side of the MT compressor is provided through the low temperature evaporator and returned to a suction side of the LT compressor through a hot gas tank.

Abstract: A method for controlling a three-way valve that diverts return refrigerant from a first compressor to a second compressor or a third compressor, the second and third compressor in parallel includes obtaining a temperature of the return refrigerant indicating a degree of superheat of the return refrigerant. The method also includes determining if the three-way valve should be transitioned into a first position, transitioned into a second position, or maintained in a current one of the first position or the second position. The method also includes transitioning the three-way valve into the first position or the second position, or maintaining the three-way valve in the first position or the second position. In the first position, the first compressor provides the return refrigerant to the second compressor through the three-way valve and in the second position, the first compressor provides the return refrigerant to the third compressor through the three-way valve.