Superheat is a very important measurement to take as it confirms how much liquid is in the evaporator. From an efficiency perspective, keep the evaporator fully flooded with liquid refrigerant allowing it to absorb as much heat as possible.
However, be careful not to have too much liquid flooding back to the compressor as it will cause severe damage.
Make sure there is as much liquid in the evaporator as possible, but ensure it is completely boiled off before it enters the compressor. This can be seen by measuring the superheat.
To measure evaporator superheat:
- Record the actual temperature at the TXV bulb with a probe.
- Record the evaporating pressure at the TXV bulb. (Low side gauge pressure)
- Convert the evaporating pressure to temperature by using a pressure/temperature comparator.
- Subtract the temperature converted on the pressure/temperature Comparator from the actual temperature recorded at the TXV bulb.
- The difference is the actual evaporator superheat.
The superheat value should be 4-8K (Kelvin).
If the Superheat value is too high then the evaporator is not fully flooded with cold liquid refrigerant causing the evaporator to be inefficient.
If the superheat value is too small of even 0K (Kelvin) this means that liquid is coming out of the evaporator and back to the compressor. As mentioned above this can cause damage to the compressor.