What is done to "break the vacuum" in a refrigeration system?

In a refrigeration system, "breaking the vacuum" refers to the process of reintroducing a gas into the system after it has been evacuated to remove moisture and contaminants. Using oxygen-free dry nitrogen is the appropriate method for this task. Oxygen-free dry nitrogen is preferred because it is inert and will not react with the refrigerants or moisture that may be present in the system, thus maintaining the integrity of the refrigeration circuit.

When a system is under vacuum, introducing nitrogen allows it to have a slight positive pressure, helping to prevent the ingress of moisture or air when components are opened or serviced. This practice is critical to ensure that moisture does not enter the system as water can lead to the formation of acids which can damage the compressor and other components.

Injecting water is counterproductive as it introduces an unwanted element into the system. Applying heat could potentially expand any remaining contaminants or moisture, but it does not effectively break the vacuum in the controlled manner needed. Opening the system to air introduces atmospheric moisture and oxygen, which can severely compromise the system's functionality and lead to corrosion and other issues. Thus, using oxygen-free dry nitrogen is the correct and recommended method for breaking the vacuum in a refrigeration system.