🔍 Key Concepts

• ASHRAE refrigerant designations and typical applications for low-pressure centrifugal chillers • Which refrigerants are considered low-pressure vs. high-pressure (compare typical evaporator pressures) • Environmental phase-out of CFCs like R-11 and what type of refrigerant commonly replaced them in similar equipment

💭 Think About

• First, decide which options are typically used in centrifugal chillers versus smaller DX (direct expansion) systems • Then, think about which refrigerant has similar low operating pressures and was adopted as a near-term/short-term replacement when R-11 was phased out • Eliminate any refrigerants that are mainly used in high-pressure systems like residential or automotive A/C

✅ Before You Answer

• Check which choices are classed as low-pressure refrigerants in chiller applications • Confirm which option historically replaced CFC-11 (R-11) in large low-pressure centrifugal chillers during the CFC phase-out • Verify that the candidate refrigerant was commonly marketed as a drop-in or near drop-in replacement for R-11 in similar equipment