🔍 Key Concepts

• Behavior of low-pressure refrigerant systems relative to atmospheric pressure • How air and moisture can enter a chiller and why they are a problem • Purpose of a purge-recovery unit in a refrigeration system

💭 Think About

• Think about what happens when a system operates at a pressure lower than the outside air. Through which paths could outside air get into the system? • What kinds of non‑condensable gases or contaminants might accumulate in a low‑pressure chiller, and what device is used to remove and capture them? • Consider whether the need for purge‑recovery is caused by the system’s normal operating pressure, leaks at seals and gaskets, or both.

✅ Before You Answer

• Verify whether low-pressure chillers typically run under vacuum (i.e., below atmospheric pressure) on the refrigerant side. • Consider if gaskets and shaft seals are perfect barriers or if some air infiltration is expected over time in low‑pressure systems. • Match the function of a purge-recovery unit (removing and recovering refrigerant while venting non‑condensables) to the statements in the options.