Arkansas HVACR NewsMagazine May 2023

HVACR NewsMagazine May 2023

Tech News

If the system has a fixed orifice instead of a TXV then the Total Superheat Method must be used. In order to determine the Target Superheat. Measure the indoor WB (wet bulb) temperature and the outdoor DB (Dry Bulb temperature. Input these temperatures in a superheat chart, calculation, app, or digital manifold set to determine the target superheat for that moment in time. See the image below.

temperature measured on the large vapor line near the service valve. In order to match the actual superheat to the total superheat, add refrigerant to decrease the actual total superheat or recover refrigerant to increase the total superheat. To see videos on total superheat and subcooling view these- If you want to learn more about refrigerant charging methods, procedures, and tro ubleshooting, read the “Refrigerant Charging and Service Procedures” book by Craig Migliaccio. When looking for cool stuff, go to Craig’s site. Read the articles provided there. Also cruise through Craig’s book offerings. You’ll find them thorough but made for a tech or student to use. Hands on versus just theory. His calculators are also fun and valuable. https://www.acservicetech.com/articles

The image above shows an indoor WB of 64° F and an outdoor DB of 85° F. These temperatures are input in a target superheat chart to determine the target superheat.

In order to read the actual total superheat on the system, measure the pressure on the large vapor line service valve at the outdoor unit and convert this pressure to saturated temperature. Subtract this from the actual