R-421A Refrigerant Facts & Info Sheet

R-421A is a highly efficient hydrofluorocarbon that is a drop-in replacement for R22 refrigerant. It consists of 2 components; that is, 58% of R-125 and 42% of R-134A.

The refrigerant blend came into existence at a time when governments had signed a treaty to eliminate ozone-depleting refrigerants. Although R22 had a low impact on the ozone layer, the little amounts that sneaked into the atmosphere caused damage to it.

Most experts recommend R-421A because it’s environmentally friendly. It doesn’t affect the ozone layer since it doesn’t have chlorine and has a global warming potential of 2,631. Secondly, you can quickly charge an R22 system with this blend without changing the oil. Yes, the refrigerant is compatible with mineral oil, which R22 systems use.

So, what else do you need to know about R-421A?

In this article, we will provide you with an in-depth analysis of the refrigerant. We hope that you’ll have all the information you need to know about it by the end of this article, including the facts, pressure temperature chart, and its pros and cons.

Let’s jump right into it.

Facts Table

Name - Scientific:Mixture of R-125/134a (58±1/42±1)
Name (2):421A
Name (3):Choice 421A
Chemistry:58±1% C2HF5 · 42±1% C2H2F4
Status:Active & Growing
Future:Might be phased out by the year 2024
System Type:Medium temperature systems
Application:Vehicle Air Conditioning & Transport Refrigeration
Application (2):Bakery applications
Application (3):Walk-in coolers
Application (4):Industrial Refrigeration
Application (5):Heat pumps
Replacement For:R22
Ozone Depletion Potential:0
Global Warming Potential:2631
Global Warming Risk:Very Low
Toxicity Levels:A (No Toxicity Identified.)
Flammability Levels:Not Flammable
Lubricant Required:POE, PAG, MO
Boiling Point:−40.2 °C or −41.2 °C
Critical Temperature:82.9°C or 181.2 °F
Critical Pressure:568.4 psia
Temperature Glide:None
Molar Mass:111.74 g·mol−1
Density:546.8 kg/m3
Critical Density0.55 kg/m3
Melting Point:−103 °C or -153.4 °F
Manufacturers:Various Including: Choice Refrigerants, A-GAS, and Uiszl
Manufacturing Facilities:All Over Including: USA, Mexico, EU, China, and others.
Color:Colorless gas
Odor:Low concentrations: none.
EPA Certification Required:Yes
Require Certification to Purchase?Yes
Cylinder Color:Blue
Purchasing:Buy R-421A in Bulk

PT Chart

PT charts are essential guides for technicians, especially when diagnosing any HVAC system. The charts provide critical information on the refrigerant’s pressure at different temperatures and states. Further, they provide facts such as subcool, superheat, and the specific saturation point of the refrigerant.

Note that each refrigerant has its PT chart. Without it, you won’t be able to know how much refrigerant you should charge into your system, and at what pressure and temperature. Because remember, charging the refrigerant at a lower or higher pressure or temperature than recommended can lead to the system’s failure. Your refrigeration system or HVAC system will overwork when trying to freeze or cool your space. Some parts, too, might end up not functioning.

Here’s a detailed PT chart for R421A.

Temp (F)Liquid Phase Pressure (psig)Vapor Phase Pressure (psig)


So, what are some of the uses of this refrigerant? Well, you’ll find it in medium and low temperature systems as an R22 drop-in replacement.

Although there are many R22 substitutes, R421A fits the puzzle quite well, even better than R410A. This is why. For you to recover R22 out of a system and replace it with R410A, you’ll need to remove the mineral oil from the system and charge it with synthetic oil – otherwise known as Poly Olester Oil (POE). You also need to change a few other things in the system, such as the dryer. For most technicians, this is expensive and time-consuming.

For R421A, the case is different. Once you remove the R22 from the HVAC system, you don’t have to remove mineral oil when charging R421A since it’s compatible with mineral oil and POE.

So, if you have an old HVAC system that uses R22, R421A would be the best retrofit. Here are some of the systems that use R421A:

  • AC/ split systems
  • Heat pumps
  • Dairy chillers
  • Refrigerated transportation
  • Walk-in coolers
  • Reach in storage
  • Bakery applications


Why should you consider using the refrigerant? One of the most obvious reasons is that it doesn’t harm the environment. R421A is a Hydrofluorocarbon and has an ozone depletion potential of 0. Even if it leaks into the atmosphere, it can’t affect the ozone layer.

Besides this, it is easy to use. Compared to other R22 retrofits, it has similar pressure-temperature dependence to R22. This comes with various benefits. For technicians, when recharging the refrigerant into a system that used R22 initially, you don’t have to worry about replacing the system’s components or even changing the lubricant. Recharging R421A into the system is easy and saves money and time.

The refrigerant is also safe to use. It has an A1 rating by ASHRAE. Further, since it doesn’t have hydrocarbons, it’s not flammable.

Since R421A consists of two components, this reduces the temperature glide. There’s less fragmentation at high temperatures, which is a problem experienced when using blends with more than two components.


Experts agree that although R22 harmed the ozone layer, it was efficient. In fact, none of the replacements in the market have been able to come to its level in terms of efficiency and system performance. Therefore, even though R421A might be a good retrofit, the chances are that your system might end up overworking to cool your space once you charge the system with the refrigerant. Sometimes, the system might fail to work at the same level as when using R22.

The other problem with R421A is that it has a high global warming potential. It’s a common problem with all hydrofluorocarbons, and it’s the reason why there’s a plan to phase these refrigerants out by the year 2024. Hence, soon, refrigerant manufacturers might need to look for environmentally friendly alternatives such as HFOs and hydrocarbons.


We’ve come to the end, folks. I hope this article provides detailed information on R421A. As you can see, the refrigerant works well with R22 systems; hence, if you were looking for an affordable alternative for an older system, this would fit perfectly.

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