Why is a purge recovery unit typically...

🔍 Key Concepts

• Low-pressure centrifugal chillers often run with the evaporator (low side) at or below atmospheric pressure • What a purge recovery unit actually does: remove non‑condensable gases (like air) and recover refrigerant from that stream • How air gets into a sealed refrigeration system and what effect non‑condensables have on efficiency and corrosion

💭 Think About

• Ask yourself: under what normal operating condition would air be most likely to be drawn into the chiller, even if the system is supposedly sealed? • Which choice describes a situation that is continuous or ongoing during normal operation, rather than just a one‑time event like initial evacuation or occasional maintenance? • Which option best explains why you would need a device that continuously separates air from refrigerant and returns the refrigerant to the system?

✅ Before You Answer

• Identify which option mentions the low side being below atmospheric pressure, and think about how that affects any small leaks. • Eliminate any choice that describes something that is only occasional (like opening for maintenance) instead of a normal, ongoing operating condition. • Make sure the option you pick clearly ties to the need to handle air (non‑condensables) plus refrigerant together, so that refrigerant can be recovered instead of lost.

Why is a purge recovery unit typically fitted on low-pressure centrifugal chillers?

such a chiller can operate at a pressure below atmospheric pressure on the low side thus drawing in air through any low side leaks

low-pressure chillers use extremely low boiling point refrigerants

evacuation of the air from a low-pressure chiller prior to charging with refrigerant is not possible

low-pressure chillers are routinely opened for maintenance thus introducing air at each opening

🔍 Key Concepts

💭 Think About

✅ Before You Answer