🔍 Key Concepts

• Low-pressure centrifugal chillers and how non-condensable gases accumulate • Purpose and function of a purge-recovery unit • Where in a chiller non-condensables tend to collect (relative to evaporator vs condenser)

💭 Think About

• Think about whether non-condensable gases will gather in the coldest, lowest-pressure part of the system or in the warmest, highest-pressure part. • Consider which component of a low-pressure chiller is operated below atmospheric pressure and tends to "pull in" air and other non-condensables. • Ask yourself: Does the purge-recovery unit remove gases from the refrigerant liquid area, or from the vapor space where unwanted gases accumulate?

✅ Before You Answer

• Identify which component (evaporator or condenser) operates at lower pressure in a low-pressure chiller. • Determine where non-condensable gases are most likely to collect: at the top or bottom of that component. • Verify whether the purge-recovery unit is designed to draw from a vapor space rather than from a liquid or directly from the compressor suction.