- AA blend that acts like a single refrigerant
- A blend with components that have different boiling points and can fractionate
- CA blend that doesn't require oil
- DA blend safe for the ozone layer
Correct answer
A blend with components that have different boiling points and can fractionate
Why
Zeotropic blends have components with different boiling points, can fractionate, and experience temperature glide during phase change (e.g., R-407C with ~8°F glide). Note: R-410A is technically near-azeotropic with negligible glide (~0.3°F) and behaves almost like a single refrigerant in practice.
The concept behind this question
Substitute refrigerants have to be evaluated as a system with their lubricant, not swapped in isolation. Mineral oil works with CFCs and HCFCs but does not circulate properly with most HFCs, which is why HFC systems generally use polyolester (POE) oil — and POE is strongly hygroscopic, so it absorbs atmospheric moisture fast when left open. Substitutes must also be approved for the specific end use under EPA's SNAP program, and newer A2L refrigerants are mildly flammable, which changes the handling and equipment rules that apply.
More questions on this topic
- Polyolester (POE) oil is used with which type of refrigerants?
- What is the Global Warming Potential (GWP) used to measure?
- What type of refrigerant is R-410A?
- At what pressure does R-410A typically operate on the high side compared to R-22?
- What is a 'blend' refrigerant?
- What is 'fractionation' of a refrigerant blend?
Exam-style practice question. Not an official EPA exam question.