What is Superheat?
- Superheat refers to the number of degrees a vapor is above its saturation temperature (boiling point) at a particular pressure.
How to Measure Superheat
- Superheat is determined by taking the low side pressure gauge reading, converting that pressure to temperature using a PT chart, and then subtracting that temperature from the actual temperature measured (using an accurate thermometer or thermocouple) at the same point the pressure was taken.
Why is it important to know the superheat of a system?
- Superheat gives an indication if the amount of refrigerant flowing into the evaporator is appropriate for the load. If the superheat is too high, then not enough refrigerant is being fed resulting in poor refrigeration and excess energy use. If the superheat is too low, then too much refrigerant is being fed possibly resulting in liquid getting back to the compressor and causing compressor damage.
When should I check the superheat?
The superheat should be checked whenever any of the following takes place:
- System appears not to be refrigerating properly
- Compressor is replaced
- TXV is replaced
- Refrigerant is changed or added to the system
How do I change the superheat of a TXV?
Turning the adjustment stem on the TXV changes the superheat.
- Clockwise increases the superheat
- Counterclockwise decreases the superheat
- NOTE: You should not attempt this adjustment unless there are no other alternatives - TXV's are very touchy !!!