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The most commonly consumed materials in York refrigeration units are lubricating oil and refrigerant. Usually, customers need to have these substances refilled; if the work is done by the manufacturer or a maintenance service provider, the cost can exceed 1,000. Before refilling, engineers must evacuate the unit of air. If customers have basic knowledge of refrigeration unit maintenance, they should be able to save on the costs associated with refilling lubricating oil and refrigerant by reading this article. Today, Gonglenghui will use ammonia-free refrigeration units as an example to explain the process of evacuating units and how to refill York refrigeration units. To bring the refrigeration unit to a dry state, the evacuation equipment should achieve a pressure of 3 mmHg Abs (4 mBar A). To achieve this effect, engineers need to set aside two to three times of their time. A single-stage vacuum pump should be used here, capable of achieving a vacuum level of 1 mm Hg (1.3 mBar). An inflation/evacuation pipeline set should be provided, complete with the necessary valves. The specific evacuation process for the refrigeration unit is as follows: 1. First, ensure that all components within the unit are at atmospheric pressure and that all liquid water has been removed. Open all valves, including those on the gauge and in the piping (except for those that lead to the atmosphere or to equipment that could be damaged by vacuum). All components should be heated to 70-85°F (20-30°C). It is important to note this requirement when the ambient temperature reaches 32°F (0°C); if you are unsure, you can use cold welding. 2. Connect the vacuum pump to the unit’s filling valve, and install a pressure gauge on the unit away from the vacuum pump. Check the water content in the vacuum pump oil and observe whether it is milky; if so, the pump must be separated from the system and run idle for 30 minutes or the oil must be replaced. 3. After the vacuum pump is operating properly, open the exhaust valve. 4. At this point, the pressure in the unit decreases, then remains constant; once the moisture evaporates, the pressure in the unit continues to drop. The time required to evacuate the unit is determined by the size of the unit, the ambient temperature of the vacuum pump, and the humidity in the unit. 5. The vacuum pump must not be turned off before the filling valve is closed; otherwise, the vacuum pump oil will flow back and contaminate the unit. The power supply should also be checked regularly; if there is any leakage, the affected area must be addressed immediately. 6. During the first vacuum pumping process of the unit, leaks may occur; it is sufficient to locate the leak and repair it. As for how to carry out the repair, private cold welding can be used. 7. The areas where leaks occur in the unit include the compressor shaft seal, valve bodies, vacuum pump connections, and situations where the stop valves cannot be closed properly. 8. After repairing all leaks, continue to reduce the pressure to 3 mmHg Abs (4 mBar A). Once this pressure is reached, the vacuum pump should be isolated. 9. If there is a large amount of moisture inside the unit, it will take at least two attempts to achieve a vacuum; otherwise, there is a risk of freezing inside the unit. 10. During vacuum pumping, if the pressure remains unchanged for an extended period, it indicates that there is a large amount of moisture inside the unit; in such cases, the vacuum pump should be isolated and nitrogen should be injected. 11. It should be noted that the vacuum level in the unit must reach 3 mmHg Abs; if this level is not achieved, nitrogen should be introduced, followed by further vacuuming until the required standard is reached. II. Check the dryness and airtightness of the unit. 1. Isolate the vacuum pump and maintain the pressure for at least 4 hours; during this time, the system pressure must not rise above 3.75 mHg (5 m bar). 2. If the ambient temperature is below 5°C, the system must be divided into sections, the components must be heated, and the components must be evacuated one by one using the aforementioned method. 3. The unit has been evacuated and dried; now refrigerant filling begins. 4. Vacuum testing must be carried out in the presence of a professional engineer; it is not recommended for beginners, as it may pose risks to both people and equipment. III. Lubricant filling: Before filling, we must ensure that the unit is properly insulated and safely grounded. Next, we check whether the compressor and oil pump are running; once the motor starts the compressor, then the lubricant is filled into the screw compressor unit. 1. Evacuate the oil separator and isolate it from the unit. 2. Connect a suitable filling hose at the oil filling point on the oil separator to link it with the oil tank; this hose must be of the right size and capacity for the unit, and it must be clean, dry, and free of non-condensable gases to prevent moisture from entering the system. 3. Open the oil filling valve on the oil separator. 4. Oil must be filled into the oil separator until the oil level reaches the middle of the top sight glass. 5. If there is pressure in the system, a makeshift cold fusion method can be used to find a solution. IV. Charging with refrigerant: Before charging the refrigerant, it is also necessary to ensure that there is a vacuum inside the unit, and to know the type of refrigerant used for that particular model of unit as well as the amount required for charging. Additionally, all electrical inspections must include circuit testing and motor testing; otherwise, it is not recommended to charge the refrigerant directly. Since the test content has not yet been organized, it can be obtained privately through Leng Hui if needed. It should be noted that freezing of water in the heat exchanger must be avoided; next is the charging of the refrigerant. 1. Open all manual valves for drain and vent valves, and close all valves through which liquid refrigerant could enter the water-containing heat exchanger. 2. Use the filling point and other suitable points to connect yourself to the refrigerant container with a filling hose. The filling hose should be clean, dry, and free of condensable gases to prevent moisture from entering the unit. 3. To allow the refrigerant to enter the unit, the valves on the unit and the refrigerant container should be opened. Note: The refrigerant charging must be paused when 14.7 Psia is reached.