Check refrigerant charge accuracy
Superheat measures how much the refrigerant vapor is heated above its boiling point. It's the primary method to check if a system has the correct refrigerant charge.
What is Superheat? The difference between the actual suction line temperature and the saturation temperature (boiling point) at the measured pressure.
Formula: Superheat = Suction Line Temp - Saturation Temp
Target Superheat: Varies based on indoor/outdoor conditions. Typically 8-12°F for residential fixed orifice systems. Lower outdoor temps = higher superheat target.
What the results mean:
• Too Low (under 5°F): Overcharged or restricted airflow
• Normal (±3°F of target): Correct charge
• Too High (10°F+ over target): Undercharged or restriction
Important: This calculator works for fixed orifice/piston systems. TXV systems should use subcooling method instead.
How to use: Measure wet bulb indoor temp, outdoor temp, suction line temp and pressure. Calculator shows target superheat and diagnoses charge status.