When pressurizing a refrigeration system with nitrogen, what method should always be used?

When pressurizing a refrigeration system with nitrogen, it is essential to charge through a pressure regulator. This method ensures that the nitrogen is introduced into the system at a controlled and safe pressure. Using a pressure regulator helps prevent the introduction of excessive pressure that could potentially damage the system components. Charging directly without regulation can lead to very high pressure spikes, risking damage to the system or creating a safety hazard.

Utilizing a gas recovery bag does not apply when charging nitrogen, as that method is typically used for recovering refrigerants rather than for charging systems. Similarly, charging at high pressure can likewise introduce unsafe conditions, making it critical to manage the pressure carefully through a regulated approach. Therefore, using a pressure regulator maintains safety and equipment integrity during the process.