There are all sorts of complicated refrigerant acronyms: HFC, HCFC, CFC. Let's also not forget the mythical zeotropic, azeotropic, and near-azeotropic descriptors. Let's simplify those. (Though if you want to go back to the basics first, check out this article on refrigerant basics.)

CFC – Refrigerants that are really bad for the ozone layer. They are almost all gone. R-12 and R-11 are examples.

HCFC – Refrigerants that are bad for the ozone layer but not as bad as CFCs. The most common example is R-22, which is also being phased out and replaced.

HFC – Refrigerants that aren't bad for the ozone layer, but they add to global warming through the greenhouse effect. The most common one is R-410a.

When it comes to the whole zeotropic/azeotropic classification system, the main thing you need to know is that older refrigerants were often just one type of molecule. That meant that they condensed and evaporated consistently, and it didn't matter if you added them to the system as vapor or liquid. These simple refrigerants were known as PURE refrigerants.

Today, we mostly work with HFC and HCFC blends. These blends can be azeotropic, which means they blend together and act as one refrigerant. Otherwise, they can be zeotropic, which means they have “glide” that results in different boiling and condensing temperatures of the refrigerants mixed in. Rubber meets the road in a refrigerant with high glide when you need separate “condensing” and “boiling” temperatures on the PT chart. R-407C is an example of a high-glide zeotropic refrigerant, where R-410a has nearly 0 glide. While R-410a is TECHNICALLY zeotropic, it is so close to being azeotropic that the industry coined the phrase near-azeotropic.

In all blends, you must charge the refrigerant as a liquid to prevent the refrigerants from separating in the vapor state. As always, when charging liquid in the suction line, add it slowly and carefully, allowing all the liquid to boil off before entering the compressor to prevent flooding/slugging.

—Bryan