How to Diognose Low System Refrigerant Charge, TXV

When a system is undercharged and equipped with a TXV metering device, the TXV may open enough to maintain adequate suction pressure and suction vapor superheat.  The condensing pressure will be low along with low subcooling.  If the system charge is very low, the system will appear with the same symptoms as a fixed metering device.

  • Leak test the system
  • Charge to OEM requirements.
  • If OEM requirements are not available, a subcooling target of 10F can be used until specs are found.

When charging R-410A systems always charge in a liquid state only.