What might be necessary during evacuation if there is a large amount of moisture in the system?

In scenarios where there is a significant amount of moisture in the system during the evacuation process, using nitrogen to increase pressure can be an effective solution. When moisture is present, it can lead to the formation of ice or frost in the recovery device and on the evaporator, which can impede the vacuum and the system's ability to remove refrigerant effectively.

By introducing nitrogen, you increase the pressure within the system, which can help push out the moisture and allow for better removal of the refrigerant during the evacuation process. Additionally, it helps to ensure that the recovery unit can operate effectively without freezing up, thus maintaining the efficiency of the evacuation.

This method is particularly useful in systems that have been exposed to high humidity or have had leaks that allowed moisture ingress. By enhancing the pressure, you create a more conducive environment for proper evacuation and recovery, minimizing the risk of damage or ineffective moisture removal.

Other methods, such as using oil, may not effectively address the issue of moisture, and stopping the evacuation entirely could lead to further complications by allowing moisture to remain in the system. Using a different recovery method may not always resolve the fundamental issue of moisture and could further complicate the evacuation process.