Refrigeration Cycle, Refrigerants, and Charging

Identify the four major components: evaporator (absorbs heat), compressor (raises pressure), condenser (rejects heat), and metering device (drops pressure).

Recognize that the discharge line carries hot high-pressure vapor and the suction line carries cooler low-pressure vapor.

Understand that the metering device creates the pressure drop that lets refrigerant boil at low temperature in the evaporator.

Calculate superheat as suction line temperature minus saturation temperature at the suction pressure.

Calculate subcooling as condensing saturation temperature minus liquid line temperature.

Charge TXV systems by subcooling and fixed-orifice systems by target superheat.

Use a pressure-temperature chart for the specific refrigerant to find saturation temperatures.

Evacuate with a vacuum pump and confirm depth with a micron gauge to remove moisture and non-condensables before charging.

Locate leaks with electronic detectors, bubble solution, or UV dye and repair before recharging.

Diagnose high head pressure from poor condenser airflow, dirty coils, non-condensables, or overcharge.

Recover refrigerant with certified equipment before opening a system; do not knowingly vent regulated refrigerants.

Hold the appropriate EPA Section 608 certification for the equipment being serviced.

Stay current on the phasedown of high-GWP HFC refrigerants and approved alternatives.