compressor 1 this occurs as higher pressure tends to drive more refrigerant into the refrigerant oil mixture as a result the viscosity of the refrigerant oil mixture is reduced as the concentration of the refrigerant in the mixture is increased as a result both higher refrigerant mass flow and reduced oil viscosity make it easier to drag the oil along the tubes by the refrigerant thus the oil return to the compressor 11 is improved the continual running of the compressor with the increased mass flow of the refrigerant additionally decreases the super heat of the refrigerant as it leaves the evaporator as less suction throttling is required the lower super heat also plays an important role in reducing the viscosity of the oil in the superheated region of the evaporator and adjacent suction piping the reduced oil viscosity in this section of the system also contributes to better oil return to the compressor the reduction of oil viscosity in the superheated section occurs as a result of less refrigerant being boiled off from the oil mixture in this superheated region once again the reduced oil viscosity improves the oil return to the compressor 11 stated differently the heater can be pulsed in on off fashion to allow the unit to operate continuously without danger of logging oil in the evaporator or suction line located between the evaporator and compressor with reference to fig2 there is illustrated a logic diagram detailing.