What is the minimum pressure that charging lines can be in NH3 systems?

The minimum pressure that charging lines can be in NH3 (ammonia) systems is 350 psi. This is primarily due to the properties of ammonia as a refrigerant and the safety requirements associated with its handling.

In ammonia systems, the pressure needs to be maintained at levels that ensure proper operation and safety. A minimum of 350 psi allows for effective charging and functioning of the system while minimizing the risk of vapor lock and ensuring that the ammonia remains in a liquid state under normal operating conditions. This is crucial since ammonia refrigeration systems rely on maintaining specific pressures for efficiency, safety, and performance.

Ammonia is typically handled at elevated pressures, and the established industry standards reflect this. Ensuring that charging lines maintain a pressure of at least 350 psi helps to prevent issues that may arise from lower pressures, including inefficient system operation and potential safety hazards.

The other options suggest lower values than what is required for proper ammonia system operations according to the relevant codes and best practices for safety. Thus, recognizing 350 psi as the minimum pressure aligns with these safety standards and operational guidelines in NH3 systems.