After installing a field piped split system, which gas is recommended for initial pressurization and leak checking?

Using nitrogen for initial pressurization and leak checking of a field-piped split system is recommended because nitrogen is an inert gas that does not react with the materials typically used in HVAC systems. When performing these procedures, it is crucial to ensure that the system is leak-free before introducing refrigerants. Nitrogen can be safely used at high pressures, and it is non-toxic and non-flammable, making it a suitable choice for testing the integrity of the system.

Moreover, nitrogen helps to prevent moisture from entering the system, which is vital because moisture can lead to corrosion and other issues when refrigerants are later introduced. This is particularly important for systems using refrigerants like R-22 or others, as moisture can react with these substances, creating acids that can damage the system.

In contrast, using air can introduce moisture, which is problematic for the reasons mentioned above. R-22 is a refrigerant and should not be utilized for pressurization and leak checking before the system is fully assembled and tested. Carbon dioxide is also not a suitable choice for this application, as it can create unnecessary complications and may not provide accurate leak detection. Therefore, nitrogen is the optimal choice for safely ensuring the integrity and readiness of the HVAC system.