When recharging a refrigeration system with R-11, what vapor pressure "Hg vacuum is necessary in the shells before charging with liquid refrigerant?

To determine the appropriate vapor pressure in inches of mercury ("Hg) vacuum before charging a refrigeration system with R-11, it's essential to understand the properties of the refrigerant and the conditions required for safe and effective charging.

R-11 is a chlorofluorocarbon (CFC) refrigerant, which, like other refrigerants, must be handled in a way that prevents the introduction of moisture into the system. When charging the system, achieving a high-quality vacuum is pivotal. This ensures that the system is free from air and moisture, both of which can compromise performance and lead to corrosion.

The recommended vacuum level before charging R-11 is typically around 16.9 "Hg. This level is achievable with proper vacuum pumping procedures and indicates that the pressure within the system is sufficiently low to minimize the risk of any contaminants. A vacuum of 16.9 "Hg ensures that any residual moisture is evaporated, and the system is ready for the introduction of liquid refrigerant without risking damage or efficiency losses.

Other pressures listed, while they might seem adequate at first glance, could either leave some moisture or air in the system or not be optimal for the specific requirements of R-11 in terms of its charging conditions. Therefore, maintaining