How to Add Freon to a Mini Split: A Comprehensive Guide

Adding refrigerant (commonly referred to as “freon”) to a mini split air conditioning system is a delicate process that requires precision and attention to detail. This comprehensive guide will walk you through the step-by-step process of safely and effectively adding refrigerant to your mini split system, ensuring optimal performance and energy efficiency.

Preparing for the Task

Before you begin, it’s crucial to have the right tools and equipment on hand. You’ll need the following:

  1. Manifold Gauge Set: This tool is essential for monitoring the system’s pressure and controlling the amount of refrigerant being added.
  2. Refrigerant Tank: The tank should contain the appropriate refrigerant type for your mini split system, typically R-410A.
  3. Refrigerant Hoses: These hoses will connect the manifold gauge set to the refrigerant tank and the mini split system.
  4. Vacuum Pump: This pump is used to evacuate the system of any air or moisture before adding refrigerant.
  5. Leak Detection Solution: This solution will help you identify any potential leaks in the system.
  6. Personal Protective Equipment (PPE): Wear gloves, safety glasses, and appropriate clothing to protect yourself during the process.

Identifying the Low-Pressure Port

how to add freon to a mini splitImage source: Flickr

The first step in adding refrigerant to your mini split system is to locate the low-pressure port on the compressor. This port is typically marked with a blue or “L” symbol and is located on the suction line of the compressor.

To ensure a secure connection, carefully inspect the port for any debris or damage. If necessary, use a small brush or compressed air to clean the port before attaching the manifold gauge set.

Connecting the Manifold Gauge Set

  1. Attach the Blue Line: Securely connect the blue line of the manifold gauge set to the low-pressure port on the compressor. Double-check the connection to ensure it is tight and leak-free.
  2. Attach the Yellow Line: Connect the yellow line of the manifold gauge set to the refrigerant tank. Again, make sure the connection is tight and secure.
  3. Verify Connections: Carefully inspect all connections to confirm they are properly sealed and free of any leaks. Use the leak detection solution if necessary.

Evacuating the System

Before adding refrigerant, it’s crucial to evacuate the system of any air or moisture. This step helps ensure the proper functioning of the mini split system and prevents potential damage.

  1. Connect the Vacuum Pump: Attach the center (red) line of the manifold gauge set to the vacuum pump.
  2. Evacuate the System: Turn on the vacuum pump and allow it to run until the low-pressure gauge reads a deep vacuum, typically around 500 microns or lower.
  3. Monitor the Vacuum: Closely monitor the low-pressure gauge to ensure the system maintains the desired vacuum level. If the vacuum level starts to rise, there may be a leak in the system that needs to be addressed.

Adding Refrigerant

  1. Turn on the Mini Split: With the manifold gauge set properly connected, turn on the mini split system and set it to cooling mode. This will allow you to monitor the system’s pressure as you add refrigerant.
  2. Pulse the Refrigerant: Slowly and carefully open the valve on the refrigerant tank, allowing small pulses of refrigerant to enter the system. Observe the low-pressure gauge and adjust the amount of refrigerant accordingly.
  3. Monitor the Pressure: The ideal low-pressure reading for a properly charged mini split system is typically around 117-120 psi. If the pressure is too high or too low, adjust the amount of refrigerant being added.
  4. Repeat as Needed: Continue to add small pulses of refrigerant, monitoring the pressure, until the system is properly charged. Avoid overcharging the system, as this can lead to various issues.

Purging the Hoses

Before disconnecting the manifold gauge set, it’s essential to purge the hoses to remove any remaining refrigerant. This step helps prevent the release of refrigerant into the atmosphere.

  1. Loosen the Connections: Slightly loosen the connection at the mini split unit, leaving the manifold gauge set connected.
  2. Pulse the Refrigerant: Carefully open the valve on the refrigerant tank, allowing a small pulse of refrigerant to flow through the hoses and push out any remaining air.
  3. Disconnect the Hoses: Once the hoses are purged, you can safely disconnect the manifold gauge set from the mini split system and the refrigerant tank.

Remember, adding refrigerant to a mini split system should only be performed by a qualified professional if you are not comfortable with the process. Improper handling of refrigerants can be hazardous and may lead to system damage or personal injury.


  1. Add 410a refrigerant to MiniSplit system?
  2. How to safely Top up R410a in a mini split?
  3. Add Refrigerant to Mini-Split Air Conditioner Step-by-Step