If you’re an HVAC technician, it’s important to know how to properly vacuum and charge refrigerant on a mini split unit. This process ensures that the system is free from leaks, moisture, and air, making it ready for refrigerant. In this article, we will outline the step-by-step procedure to vacuum and charge refrigerant on a mini split unit.

Step 1: Pressure Testing

Before starting the vacuuming process, it is crucial to pressure test the refrigerant tubing. This step helps identify any leaks, especially at the flare joints. By finding and fixing leaks beforehand, you can avoid pulling in moisture and air during the vacuuming process.

Step 2: Valve Core Removal

To begin the vacuuming process, you will need to remove the valve core at the designated port. This port is usually a 5/16 inch size. By using a valve core removal tool, you can easily remove the valve core and prepare the system for vacuuming.

Step 3: Connecting the Vacuum Pump

Once the valve core is removed, it’s time to connect the vacuum pump. Attach the vacuum hose to the port where the valve core was removed. Ensure a secure connection to prevent any leaks during the vacuuming process.

Step 4: Purging the Air

Before starting the vacuum pump, it is essential to purge the air from the system. Open the valve slightly to allow the air to escape. This step ensures that only refrigerant and not air enters the system during the vacuuming process.

Step 5: Zeroing the Scale

If you need to add refrigerant to the system, it’s important to zero the scale. This step ensures accurate measurement of the refrigerant being added. Make sure the scale is properly zeroed before proceeding.

Step 6: Adding Refrigerant

If additional refrigerant is required, connect the refrigerant bottle to the valve core removal tool. Ensure that the bottle is in the upside-down position to allow only liquid refrigerant to come out. Open the valve to allow the refrigerant to flow into the system. Measure the required amount of refrigerant using the scale.

Step 7: Leak Checking

After adding the refrigerant, it’s crucial to perform a leak check. Close the valve and check if the valve core is properly sealed. Use a bubble leak detector or a tester to check for any leaks. If no bubbles are observed, the system is leak-free.

Step 8: Reassembling and Testing

Once the leak check is complete, reassemble the system by putting the valve core back in and tightening the valves. Make sure to put the caps back on the valves. Finally, turn on the system and ensure it is functioning properly.

By following these steps, you can effectively vacuum and charge refrigerant on a mini split unit. Remember to always prioritize safety and accuracy during the process. If you’re unsure or inexperienced, it’s best to consult a professional HVAC technician for assistance.