Refrigerant Charging
A measurement driven approach to charging, using the method the metering device calls for.
Procedure
Technician
#charging#superheat#subcooling#serviceSafety
Never vent refrigerant. Use certified recovery equipment and proper personal protective equipment. Refrigerant under pressure can cause serious injury.
Before you start
Charge is the last step, not the first
Airflow, coil condition, line set length and existing leaks all change the readings you are about to take. A system that leaks does not need charge - it needs the leak repaired.
- Confirm the refrigerant type on the data plate and use the matching pressure temperature reference.
- Verify indoor airflow: filter, coil, blower wheel and blower speed setting.
- Inspect the condenser coil and confirm unrestricted outdoor airflow.
- Record outdoor dry bulb and indoor wet bulb conditions.
Procedure
- 1Connect gauges or a digital manifold at the service ports with the system off.
- 2Start the system and allow it to run until pressures and temperatures stabilize.
- 3Attach accurate line temperature clamps at the suction line near the compressor and at the liquid line at the condenser outlet.
- 4Calculate superheat and subcooling from measured pressures and temperatures.
- 5For a fixed orifice system, compare superheat to the manufacturer charging chart for current conditions.
- 6For a system with a thermostatic or electronic expansion valve, charge to the manufacturer subcooling target.
- 7Add or recover refrigerant in small amounts, allowing the system to stabilize between adjustments.
- 8Record final readings and conditions on the service record.
Safety and compliance
Regulated work
Refrigerant recovery, charging and disposal are regulated. Use certified recovery equipment, keep refrigerant out of the atmosphere, and wear eye and hand protection when working with pressurized refrigerant.
Local Code Notice
Refrigerant handling, certification, recovery and record keeping requirements vary by jurisdiction and regulation. Verify the applicable local codes, regulations, permits and manufacturer instructions before performing this work.
Symptoms
Practice & Mastery
- Refrigerant Charging Troubleshooting Scenarios2
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