Air Conditioner Refrigerant Repair Guide

This guide applies to the entire process of repairing household split air conditioners and conventional commercial central air conditioning systems, including refrigerant (refrigerant) testing, leak detection, leak repair, vacuuming, charging, and troubleshooting. It standardizes repair operation standards, safety requirements, and maintenance points, avoiding air conditioning malfunctions, equipment damage, and safety hazards caused by blindly adding refrigerant or improper operation, and provides standardized practical guidance for repair personnel.

I. Basic Knowledge of Refrigerants

1. Commonly Used Refrigerant Types and Compatible Models

Air conditioning refrigerants must never be mixed or used incorrectly. Different types of refrigerants have completely different pressures, boiling points, and compatible equipment. This is a core fundamental principle of maintenance. The compatibility rules for mainstream models are as follows:

• R22 : Traditional Freon, mostly used in older fixed-frequency air conditioners, gradually being phased out. It has a lower pressure and is highly versatile in maintenance. It is only suitable for older models and is prohibited from being used in newer environmentally friendly air conditioners.
• R410A : An environmentally friendly mixed refrigerant, compatible with most inverter air conditioners and high-end fixed-frequency air conditioners. It has high operating pressure and excellent cooling efficiency. It must be charged using the liquid charging method.
• R32 : A new type of low-carbon refrigerant, energy-efficient and highly effective, but flammable and explosive. It is currently the mainstream model for new household air conditioners, and repairs must strictly adhere to explosion-proof safety regulations.

The standard refrigerant type and rated charge amount for all air conditioner models are based on the nameplate on the unit. These must be checked before maintenance, and it is strictly forbidden to add refrigerant arbitrarily based on experience.

2. Core Manifestations of Refrigerant Abnormalities

When an air conditioner is not cooling or cooling poorly, in over 89% of cases, the problem is not a lack of refrigerant. Instead, it's often due to issues like clogged filters, poor heat dissipation, or a malfunctioning fan. These problems need to be checked first before determining the refrigerant status. Typical symptoms of refrigerant abnormalities include:

• Insufficient refrigerant: High air outlet temperature, frost on indoor unit evaporator, low low pressure in pipeline, and compressor operating current below standard value;
• Excessive refrigerant: poor cooling effect, excessively high pipeline pressure, compressor overheat protection, abnormal heat dissipation of outdoor unit, and soaring energy consumption;
• Refrigerant leakage: The air conditioner's cooling performance has been slow and declining over a long period of time, and there are oil stains on the pipe joints and welds (refrigerant leakage accompanied by refrigeration oil leakage).

II. Pre-maintenance preparations and safety regulations

1. Essential tools and equipment

Refrigerant repair is a professional operation. It is forbidden to operate without tools or qualifications. Required tools include: high and low pressure combined pressure gauge, vacuum pump, refrigerant recovery machine, special refrigerant charging hose, electronic leak detector, soapy water, ammeter, infrared thermometer, wrench, welding equipment, and sealing accessories.

2. General Safety Guidelines

• Before maintenance, disconnect the air conditioner power supply and let it stand for more than 5 minutes to release residual electricity in the circuit. Never operate while the circuit is live.
• When repairing units using R32 refrigerant, open flames and smoking are prohibited on-site. Good ventilation should be maintained to avoid the risk of explosion.
• Direct release of refrigerant into the air is strictly prohibited; it must be collected using a recycling machine in accordance with environmental protection standards.
• Before disassembling or assembling pipelines, clean the interfaces of dust and oil. After disconnecting the pipelines, immediately seal the ports to prevent moisture and impurities from entering the system.
• Wear protective gloves and goggles when working to avoid frostbite caused by refrigerant coming into contact with the skin.

III. Standardized Maintenance Process

Complete refrigerant repair process: troubleshooting → system pressure testing → precise leak detection → leak repair → refrigerant recovery → system vacuuming → pressure holding test → quantitative charging → operating condition retest. It is strictly forbidden to skip the leak detection and vacuuming steps and directly add refrigerant.

1. Initial troubleshooting

Run the air conditioner in cooling mode for more than 15 minutes to allow it to reach a stable operating condition. Then, check the following steps in order: clean the indoor unit filter, check if the outdoor unit heat sink is blocked, check if the fan is running normally, and check if the temperature difference between the inlet and outlet is normal. After ruling out heat dissipation and mechanical faults, then test the refrigerant system.

2. System pressure and operating condition monitoring

Connect the pressure gauge set to the high and low pressure inspection ports of the air conditioner to read the static and dynamic pressures. At the same time, use an ammeter to detect the compressor's operating current and a thermometer to detect the temperature difference between the inlet and outlet air vents. Cross-reference these three sets of data to determine the system status: Under standard operating conditions with an ambient temperature of around 30℃, the low-pressure operating pressure of R22 is 0.4–0.5MPa, R410A is 0.8–1.0MPa, and R32 is 0.7–0.9MPa. If the low-pressure is too low, the current drops by more than 15%, or the temperature difference between the inlet and outlet air vents is less than 8℃, it can be determined that the refrigerant is abnormal or there is a leak.

3. Precise leak detection operation

Leak detection is the core step in repair. Adding refrigerant without first checking and repairing leaks will lead to a recurrence of refrigerant deficiency in a short period of time. There are three common leak detection methods:

• Oil stain observation method : Refrigerant leaks will bring out refrigeration oil. Focus on checking pipe joints, welds, and valve interfaces. The location of oil stains is likely the leak point. This method is suitable for initial troubleshooting.
• Soap water leak detection method : Apply concentrated soap water evenly to pipe joints and welds. The location where bubbles appear is the leak point. It is low-cost, simple to operate, and suitable for large leak detection and re-inspection.
• Electronic leak detector detection : Turn on the leak detector and slowly scan along the pipeline. The alarm location of the device is the micro-leak point. It has the highest accuracy and is suitable for troubleshooting small leaks. It is the first choice for professional maintenance.

Pressure holding criteria: If the pressure drops by more than 0.02 MPa after the system is filled with dry nitrogen and held for 24 hours, a leak can be identified.

4. Leak Repair

• Loose joints or aging seals: Tighten the joints again, replace the sealing gaskets with new ones, and reinforce the seals.
• Pipeline pinholes and weld cracks: We use oxygen-free welding process to repair the welds, ensuring that the welds are flat and seamless.
• Severely damaged pipelines: Replace the corresponding pipelines directly to prevent secondary leaks after repair.

After repair, leak detection and pressure testing are required again. Only after confirming that there are no leaks can the next step of the operation be carried out.

5. Refrigerant recovery and system cleaning

For old refrigerant systems, use a refrigerant recovery machine to recover the remaining refrigerant in the system, record the amount recovered as a reference for subsequent quantitative charging; at the same time, clean the pipes of residual impurities and oil stains to avoid clogging the throttling components.

6. Vacuuming operation

After leak repair and refrigerant recovery, a vacuum must be evacuated to remove moisture and air from the system, preventing ice blockage, abnormal pressure, and reduced cooling performance. For standard household air conditioners, the vacuuming time should be no less than 15 minutes; for commercial central air conditioning systems and high-capacity models, no less than 30 minutes. A vacuum level of -0.1 MPa is considered合格 (qualified). After vacuuming, maintain the pressure for 5 minutes to confirm that there is no pressure rebound.

7. Quantitative refrigerant charging

Strictly adhere to the model and weight specifications indicated on the air conditioner's nameplate when filling; avoid relying on estimations based on experience.

• R410A and R32 mixed refrigerant: must be added vertically in liquid form to prevent refrigerant ratio imbalance;
• R22 refrigerant: can be added in gaseous form, the addition speed should be slow, and the addition should be done in increments, while observing the operating conditions.
• The pressure, current, and outlet temperature are monitored in real time during the filling process, and minor adjustments are made when the temperature approaches the standard value to avoid overfilling.

8. Re-measurement of completed work conditions

After charging is complete, run the air conditioner continuously for 20-30 minutes. After the operating conditions stabilize, retest the following: high and low pressure, compressor operating current, inlet and outlet temperature difference, and evaporator condensation status. Ensure there is no frost, no high-pressure alarm, the cooling and heating effect meets the standards, and there are no leaks in the pipeline. This indicates that the maintenance is qualified.

IV. Troubleshooting and Rectification Plans for Common Faults

V. Maintenance Taboos and Common Misconceptions

• Do not add refrigerant without checking for leaks: 90% of recurring refrigerant shortages are caused by not repairing leaks, and simply adding refrigerant only treats the symptoms, not the root cause.
• Do not omit the vacuuming step: Direct charging will cause air to mix into the system, resulting in unstable pressure, poor cooling, and shortened compressor life;
• Mixing or misusing refrigerants is prohibited: Different types of refrigerants have different physical properties, and mixing them will lead to system failure and equipment failure.
• Do not overfill refrigerant: Too much refrigerant will increase the compressor load, causing problems such as overheating protection, increased power consumption, and pipe bursts.
• It is forbidden to judge the amount of fuel to be added based on feel or experience: the amount must be determined by the nameplate readings, pressure, current, and temperature difference data.

VI. Key Points for Daily Maintenance and Leak Prevention

• Clean the air conditioner filter and outdoor unit heat exchanger every 3–6 months to ensure smooth heat dissipation, reduce system load, and slow down refrigerant loss.
• Before using the air conditioning system each year, check the joints and valves for oil stains and looseness, and check for potential leaks in advance.
• Air conditioner relocation must be carried out in a standardized manner with refrigerant recovery. Arbitrary venting is strictly prohibited. After relocation, the refrigerant must be re-vacuumed, pressurized, and recharged in a measured amount.
• When the machine is not in use for an extended period, close the high and low pressure valves and seal the pipelines to prevent air and moisture from entering and causing slow leakage.

VII. Maintenance and Acceptance Standards

• The system has no leaks: the pressure holding test showed stable pressure with no pressure drop, and the pipeline had no oil stains or air bubbles;
• Stable operating conditions: The high and low pressure and operating current of the air conditioner meet the model standards and there are no abnormal fluctuations;
• Cooling performance meets standards: Under normal operating conditions, the temperature difference between the indoor unit's inlet and outlet air vents is ≥10℃, and the evaporator condenses evenly without frost.
• The equipment is operating normally: there is no abnormal noise from the compressor and fan, and no frequent start-stop, overheat protection, or other malfunctions.