We need a calibrated thermometer to calculate the overheating of the system. We installed the thermometer sensor on the suction line. Then we insulate with thermal insulation to avoid reading errors. We turn on the equipment, the superheat calculation is used to have the highest possible performance of the equipment with an acceptable safety range for its full operation.
The superheat calculation must be done after 20 minutes of initial equipment operation. First we write down the system low pressure and use the saturation pressure versus temperature table to obtain the saturation temperature of the fluid in the evaporator. Then we write down the temperature read on the sensor.
Note that the degree of overheating is obtained from the difference between the temperature read at the compressor suction and the temperature converted by the saturation table.
Example: our overheating is 9 degrees Celsius. The ideal superheat range is 5 to 7 degrees Celsius. Therefore, we should add a little more coolant. As the amount of fluid increases, there will be a reduction in the degree of overheating.
Try to obtain saturation tables for different refrigerants. This will be essential for calculating the degree of overheating. We must measure overheating again. We measure the current of the equipment with clamp meters and compare it with the rated current (see manufacturer's catalog). Then we remove the pressure gauge and place the nuts on the service valves.
