How to Measure Superheat

  • Run the condensing unit until suction pressure and suction line temperature stabilize.
  • Read and record the suction pressure.
  • Place a digital temperature probe against the suction line near the suction gauge pressure port.  Read and record the temperature.
  • Reference the face of your suction gauge or use the temperature/pressure chart and convert the measured suction pressure to the corresponding evaporator coil saturation temperature for the refrigerant being used.  Round this value.
  • Next, subtract the saturation temperature from the measured suction line temperature.  The result is your actual suction vapor superheat.


  • R22
  • Suction Pressure: 70 PSIG
  • Corresponding evaporator saturation temperature: 41F
  • Suction line temperature: 51F
  • 51F -41F = Superheat
  • Superheat = 10F