Arkansas HVACR NewsMagazine May 2023

HVACR NewsMagazine May 2023

Tech News

Charging Procedures If the outdoor unit has a single speed or two speed compressor running in second speed and the unit is not a

If the metering device is a fixed orifice such as a piston or capillary tube, the refrigerant charge of the system can be checked with Total Superheat. If the metering device is a TXV then the refrigerant charge can be checked with Subcooling. If the unit has a TXV, check for the Target Subcooling posted at the outdoor unit. See the image below.

Micro-channel coil, then Total Superheat or Subcooling can be used to check the charge. To determine which one, view the indoor unit rating plate to see the metering device listed as installed. If the metering device cannot be determined by reading the indoor unit rating plate, verify the metering device by removing the front cover. The metering device that is listed may have been changed by the technician so it is best to visually verify the type of metering device. To determine the type of metering device, view the following image.

In order to check the refrigerant charge with Subcooling, measure the small liquid line pressure at the service valve port and convert the saturated pressure to temperature. Next, measure the actual temperature of the liquid line within 6” of the service valve and subtract it from the saturated temp. Add refrigerant to increase the subcooling and recover refrigerant to decrease the subcooling. Match the actual subcooling as close as you can to the target subcooling in order to attain an accurate refrigerant charge.