The refrigerant charge of a refrigeration system is critical to the operation of the system. Insufficient charging will result in insufficient evaporation of the evaporator, too low suction pressure of the compressor, reduced cooling capacity, and even overheating of the compressor. Overcharging will cause the condenser exhaust pressure to be too high, liquid refrigerant to flow back, and even damage the compressor. Most systems have reasonable limits on the charge amount, but small systems have extremely strict requirements on the charge amount. The following are eight common refrigerant charging methods and their advantages and disadvantages.
Method 1: Liquid filling
Operation steps:
1. Place the refrigerant bottle upside down on the scale, connect the filling pipe and the filling valve, and remove the gas in the pipeline.
2. Open the refrigerant bottle valve and the filling valve, and use the system vacuum to suck the refrigerant.
3. Close the liquid receiver outlet valve, start the compressor, and let the liquid refrigerant flow into the system.
4. Observe the system pressure. When the specified pressure is reached, close the filling valve and open the liquid receiver outlet valve.
Note:
The liquid receiver stop valve is used for throttling to facilitate the flow of refrigerant into the system.
The system needs to be evacuated to a high vacuum when installed for the first time.
The rapid rise in exhaust pressure indicates that the condenser is full of refrigerant.
Advantages and disadvantages:
Advantages: Applicable to most refrigeration systems.
Disadvantages: The refrigerant filling amount needs to be accurately mastered, and the filling amount provided by the manufacturer is usually required.
Method 2: Gas filling
Operation steps:
1. Weigh the weight of the refrigerant bottle.
2. Connect the pressure gauge valve pipe to the suction and exhaust inspection valves to remove the gas in the pipeline.
3. Open the steam valve of the refrigerant bottle, start the compressor, and adjust the filling amount through the pressure gauge.
Note:
After filling, close the refrigerant bottle valve, observe the system operation, and decide whether to continue filling.
Advantages and Disadvantages:
Advantages: Suitable for small systems with high filling accuracy.
Disadvantages: Only suitable for small amounts of refrigerant filling (usually no more than 12kg).
Method 3: Weighing method
Operation steps:
Weigh the weight of the refrigerant added to the system directly.
Note:
Applicable to the situation where the required charging amount of the system is known and needs to be fully charged.
When the charging amount is small, the refrigerant in the system must be released first, and then recharged after repair.
Advantages and disadvantages:
Advantages: Suitable for integrated equipment and simple operation.
Disadvantages: The accurate charging amount of the system must be known in advance.
Method 4: Current method
Operation steps:
1. Install a clamp ammeter at the power input end of the air conditioner.
2. Connect the refrigerant bottle to the low-pressure end liquid filling port to remove the gas in the pipeline.
3. Start the compressor, open the refrigerant bottle valve, observe the ammeter, and stop charging when the current reaches the rated value.
Note:
The current is affected by many factors, such as voltage fluctuations, ambient temperature, etc.
Advantages and disadvantages:
Advantages: Easy to operate.
Disadvantages: The current is easily disturbed by external factors and has low accuracy.
Method 5: Mirror method
Operation steps:
Observe the flow of refrigerant through the sight glass in the liquid pipe. The flow of transparent liquid refrigerant indicates proper charging.
Note:
Bubbles or flashes usually indicate insufficient refrigerant.
Liquid pipe pressure loss may also cause bubbles, which needs to be combined with system performance analysis.
Advantages and disadvantages:
Advantages: intuitive and easy to observe.
Disadvantages: cannot rely entirely on the sight glass to judge, and other methods need to be combined.
Method 6: Pressure method
Operation steps:
1. Install pressure gauges in high and low pressure sections and connect the liquid filling pipeline.
2. Start the compressor, observe the indications of the high and low pressure gauges, and judge the charging amount.
Note:
Insufficient condensing air volume and evaporating air volume will affect the pressure test results.
Before testing, it is necessary to ensure that the system air volume meets the requirements.
Advantages and disadvantages:
Advantages: more accurate through pressure judgment.
Disadvantages: greatly affected by external conditions, it is necessary to ensure the normal operation of the system.
Method 7: Calculation of superheat method
Operation steps:
Calculate the superheat by measuring the suction temperature and pressure of the evaporator suction pipe.
Note:
The superheat of the capillary system is affected by pressure and resistance.
The expansion valve system is prone to overcharging, and the superheat needs to be controlled at 58℃.
Advantages and disadvantages:
Advantages: Applicable to expansion valve system with high control accuracy.
Disadvantages: Complex operation and requires precise measurement.
Method 8: Liquid level meter method
Operation steps:
Open the liquid level test port of the liquid receiver to observe whether there is liquid refrigerant flowing out.
Note:
Large liquid receivers may be equipped with float indicators to facilitate observation of the liquid level.
Advantages and disadvantages:
Advantages: Intuitive and easy to judge the filling amount.
Disadvantages: Only applicable to systems equipped with liquid level test ports.
Summary:
Each filling method has its applicable scenarios and advantages and disadvantages. Choosing the appropriate method requires comprehensive consideration of system type, filling volume requirements and operating conditions. For small systems, gas filling and weighing methods are more commonly used; while for large systems, liquid filling and pressure methods are more applicable. Regardless of which method is used, the system operation must be closely observed to ensure that the filling volume is accurate and to avoid damage to the system.
Post time: Apr-02-2025
