Refrigeration Systems and Components
Refrigeration cycle
The vapor-compression cycle has four basic components: compressor, condenser, metering device, and evaporator. The metering device controls superheat; the condenser controls subcooling. Diagnose with pressures, line temperatures, and airflow-not pressure alone. A restriction, low airflow, and low charge can look similar on gauges.
Refrigerant rules
EPA Section 608 certification is required to handle regulated refrigerants. Recover refrigerant; do not vent. Evacuate to 500 microns and hold to confirm no moisture or leaks. A recovery cylinder must not exceed 80% fill by weight; use a scale. A2L refrigerants such as R-32 and R-454B are mildly flammable; follow ASHRAE 15 and manufacturer charge limits.
Worked example
A walk-in cooler has low superheat and a frosted suction line. Check for a stuck-open TXV or overcharge. If superheat is high, check for undercharge, restriction, or a failed TXV. Confirm evaporator airflow before adding refrigerant.
Traps
Adding refrigerant without finding the leak; charging by gauge pressure only; skipping evacuation; and ignoring recovery cylinder fill limits.