I'm a beginner at this, though I have a degree and the liscense, I am getting the "hands on experience" on my own with no instructor.
I changed out a 3/4 hp roof top condensing unit that was on a walk in cooler last week. It was an R12 unit, and I replaced it with an R22 unit of the same type. I was having a problem overcharging it, as I was trying to charge by reading the evap. temp on the low side guage. A friend of mine said the best way to charge this unit is "10 degrees subcooling". What does he mean, and exactly what are the steps you take to do this? Is it the best way to charge, and if not, what other methods are there?