During a residential service call, a technician finds the unit completely out of refrigerant. What should the technician use to pressurize the system?

Using an inert gas to pressurize a refrigeration system that is completely out of refrigerant is the correct approach due to several reasons related to safety and system integrity. Inert gases, such as nitrogen, do not react chemically with the materials in the refrigerant system. They are used to safely pressurize the system for leak testing and to ensure that the system remains free of moisture and contaminants.

When nitrogen is introduced into the system, it helps establish a baseline pressure, allowing the technician to check for leaks without risking any reactions that could occur with other gases. This method is essential because if an oxygen-rich environment were introduced, it could lead to potential combustion or reactions that can damage the system.

Refrigerant alone is not suitable for pressurization in this scenario, as it would not help detect leaks effectively without the risk of releasing harmful amounts of gas into the atmosphere. Using air is also inappropriate; it contains moisture that can lead to internal corrosion and potentially contaminate the refrigerant.

Overall, using an inert gas ensures that the technician can safely assess and work on the system while maintaining its operational integrity.