Superheat is suction-line temperature minus evaporator saturation temperature at suction pressure; subcooling is condenser saturation temperature at liquid pressure minus liquid-line temperature. TXV systems charge to 8 to 12 F subcooling per the data plate; fixed-orifice systems charge to target superheat from indoor wet-bulb and outdoor dry-bulb.
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Superheat and Subcooling Guide
Charge by numbers, not by feel. EPA 608 applies.