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EPA 608 Core Exam·Substitute Refrigerants & Oils

How should zeotropic refrigerant blends be charged?

  1. AAs a vapor only
  2. As a liquid only
  3. CEither liquid or vapor is acceptable
  4. DWith a mixing valve

Correct answer

As a liquid only

Why

Zeotropic blends must be charged as liquid to prevent fractionation (separation of components).

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

Exam-style practice question. Not an official EPA exam question.