Steps an AC Repair Technician Follows to Test and Add R-22 Refrigerant
Preparation and Safety
- Confirm the system uses R-22 by checking the manufacturer’s label or service manual.
- Ensure you have the correct tools: R-22 manifold gauge set, R-22 refrigerant cylinder, digital scale, thermometer, and PPE (gloves, goggles, respirator).
- Work in a well-ventilated area and follow all EPA regulations regarding R-22 handling, as it is now banned for production/import and only recycled/reclaimed R-22 is allowed15.
- Turn off the air conditioner and set the thermostat to its lowest setting14.
Inspection and Diagnosis
- Inspect for signs of refrigerant leaks (oil residue, hissing sounds, ice on lines) and confirm low refrigerant symptoms (warm air from vents, ice on coils)5.
- Repair any leaks before adding refrigerant—never add refrigerant to a leaking system.
Connecting Equipment
- Remove the service port caps from the R-22 valves on the outdoor unit14.
- Connect the blue (low side) hose of the manifold gauge to the larger suction line port.
- Connect the red (high side) hose to the smaller liquid line port.
- Connect the yellow hose to the R-22 refrigerant cylinder.
- Purge air from the hoses by briefly opening each manifold valve to release trapped air until you hear a change in sound, then close the valve127.
System Operation and Baseline Readings
- Open the refrigerant cylinder valve with the container upright for vapor charging (common for topping off; for large charges, liquid may be added but must be metered slowly to avoid compressor damage)12.
- Turn the AC system back on and let it run for 3–5 minutes to stabilize1.
- Observe the initial pressure readings on the manifold gauges.
Measuring and Charging
- Use a thermometer to measure the temperature at the suction line (about 6 inches from the service port)1.
- Compare the suction line temperature and pressure to a pressure/temperature (P/T) chart to determine superheat (for fixed orifice systems) or subcooling (for TXV systems)12.
- For superheat:
- Calculate superheat: Suction line temp – Saturation temp (from low-side gauge).
- Target superheat is typically 8–18°F; 12°F is often optimal1.
- If superheat is too high, slowly add R-22 vapor into the low side while monitoring the readings.
- If superheat is too low (below 7°F), the system may be overcharged.
- For subcooling (TXV systems):
- Calculate subcooling: Saturation temp (high-side gauge) – Liquid line temp.
- Add refrigerant slowly if subcooling is below manufacturer specs; stop when correct subcooling is reached2.
- Add refrigerant in small increments, allowing the system to stabilize between additions.
- Always monitor the amount of refrigerant added using a scale for accuracy2.
Final Checks
- Once the correct charge is achieved, let the system run for several more minutes to ensure stable operation and correct readings.
- Check for abnormal noises, vibrations, or continued signs of leaks.
- Close the refrigerant cylinder valve and the manifold valves.
- Recover any refrigerant from hoses back into the system to minimize loss.
- Disconnect the manifold hoses and replace all service port caps tightly12.
Cleanup and Documentation
- Restore all panels and clean the work area.
- Record the amount of R-22 added, final pressure/temperature readings, and any repairs performed for future reference.
Key Points and Differences from Modern Refrigerants
- R-22 uses 1/4″ SAE flare fittings, while R-410A uses 5/16″ fittings.
- R-22 can be charged as vapor or liquid (if liquid, always meter slowly into the suction side).
- Topping off is allowed with R-22, but not with R-410A or blends.
- R-22 is now only available as recycled or reclaimed refrigerant due to environmental regulations15.
Summary Table: R-22 Charging Steps
| Step | Details |
|---|---|
| Safety/Prep | Confirm R-22, PPE, tools, system off, area ventilated |
| Inspection | Leak check, repair leaks, confirm low refrigerant symptoms |
| Connect Gauges | Blue to suction, red to liquid, yellow to cylinder, purge hoses |
| System On, Stabilize | AC on, run 3–5 min, observe pressures |
| Measure/Charge | Superheat (fixed orifice) or subcooling (TXV), add refrigerant as needed |
| Final Checks | Confirm readings, system stable, no leaks, close valves |
| Disconnect/Cleanup | Recover refrigerant from hoses, remove gauges, replace caps |
| Documentation | Record refrigerant added, readings, repairs |