Fancy Refrigerant Words

graph

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

Related Tech Tips

Thoughtful Termination (Of Wires)
When you are checking a unit of any kind, you should be keeping your eyes open for signs of arcing and melting at all of your wire connections and contact points. We find issues with melting terminals on contactors and in disconnects regularly. Still, We rarely think about the relationship between circuit ampacity, wire size, […]
Read more
Pool Heat Pumps, The Basics
Note: My brother Nathan wrote this a few years back, and I only did some minor editing. A pool heat pump is essentially a water-cooled air conditioner in reverse. It usually has a large air evaporator on the outside that looks like a condenser coil and a heat exchanger (usually tube-in-tube) on the inside. A […]
Read more
Drains and Double traps
Double traps are no good. That's the end of this tech tip. Okay, here's some detail: Anytime your drain goes up and down more than once, you have a double trap UNLESS you place an air vent between the two traps that vents ABOVE the drain inlet. The double trap causes drainage issues because air […]
Read more

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from