Depends on age of unit, SEER rating, manufacturers specs etc. Usually if you can find the chart that came with the outdoor condensor unit/on the back of the elec box cover use it or take a good refrig course and train as an apprentice for a few years and understand airflows/thermodynamics/pyschrometerics and the fundamentals of refrigeration/AC and airflows/humidity effect on a unit etc. Takes at least 5 years to make a half decent tech and the best ones have over 10-30 yrs experience.
On fixed metering devices you can use that formula. Written mathematically, its ((3*IDWB)-80-ODDB)/2
On a TXV that formula has no bearing, and some manufacturers are not using 10 to 12 for the TXV's SH. Along with many are printing the SC they need on the condensers data label. So you have to look at newer units.
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