Which is degree of overheating of the refrigerant. Why is it used?
The superheat of refrigerant at the outlet of the evaporator defined between the difference in suction temperature (Ts) and saturated evaporation temperature (Tev) can be measured by a manifold, bulb or electronic thermometer (with temperature sensor) Insulation and pressure-temperature conversion table for the refrigerant. To do this we must place the bulb in contact with the suction line. The surface must be clean and the measurement must be done at the top of the tube to avoid false readings. Isolate the bulb or sensor with the insulation in order to insulate it from ambient temperature. Install the manifold on discharge lines (high pressure gauge) and suction (low pressure gauge). After the operating conditions stabilize, read the pressure on the suction line manometer. From the R-22 table obtain the saturated evaporation temperature (Tve). Read the suction temperature (Ts) on the thermometer. Take several temperature readings. Subtract the saturated evaporation temperature (Tev) from the suction temperature, the difference is the overheating. If the superheat is between 4C and 6C, the expansion valve setting is within the standard. If below, a lot of coolant is being injected into the evaporator and the valve needs to be closed (turn adjusting screw clockwise clockwise). If overheating is high, little refrigerant is being injected into the evaporator and the valve must be opened (turn adjusting screw counterclockwise counterclockwise).
