R290 as a Drop In? - Short #234 · HVAC School - For Techs, By Techs summary

Key takeaways

Using R290 as a drop-in refrigerant for R22 systems is neither safe nor legal.
R290 has superior refrigerant properties, but its flammable nature and legal limitations make it impractical for standard HVAC applications.
The future of HVAC refrigerants may include more environmentally friendly options like R290, given that proper safety practices evolve in the industry.

Summary

Introduction to R290 and R22

In this episode of the HVAC School Podcast, Bryan responds to a listener's query regarding the usage of R290 as a drop-in refrigerant for R22 systems. He clarifies that while R290 (propane) and R22 (chlorodifluoromethane) share similar refrigerant properties and operating characteristics, substituting one for the other in HVAC systems is neither legal nor safe due to the flammability and explosive nature of R290.

Properties and Risks of R290

Bryan dives deep into the similarities between R290 and R22, noting that R290 has a higher latent heat of vaporization, making it effective for cooling. However, he emphasizes the considerable risks involved with using R290—namely, its flammability and the legal constraints limiting its charge to 500 grams per appliance in the U.S. He also warns against using R290 blends marketed as drop-ins, stressing that while they may work in theory, they pose significant safety dangers.

Future of Refrigerants and Safety Practices

Looking ahead, Bryan discusses the potential for R290 in the future, especially in sealed systems. He indicates that with the HVAC industry's push for lower Global Warming Potential (GWP) refrigerants, and advancements in safety practices (like flame-free fittings), R290 could play a more significant role. However, he reiterates the need for careful handling and compliance with safety regulations before transitioning to more flammable refrigerants.

Show notes

In this short podcast episode, Bryan answers a listener-submitted question about using R-290 as a drop-in refrigerant for R-22 systems. It is NOT safe to use R-290 as a drop-in, but there are some similar properties between the two and some interesting thought experiments within this topic.

R-290 is propane, a hydrocarbon that belongs to the family of natural refrigerants. R-22 is an HCFC refrigerant that has undergone a manufacturing/importation phaseout in the USA. They are both single-component refrigerants, not blends. Both of them have similar operating pressures and oil carry. However, the latent heat of vaporization of R-290 is almost double that of R-22, which makes it extremely effective as a refrigerant.

The main issue with using R-290 is that it is highly flammable and explosive (A3), and it has very small charges (500 grams). Around 2010, some people started selling R-290 blends as drop-in alternatives for R-22. In theory, that combination would work very well, but it is not a safe or legal option.

R-290 is currently used in sealed, self-contained equipment. However, it could be the future, especially if our industry goes for refrigerants with lower GWPs and uses flame-free fittings and tubing cutters. It's also worth noting that A2L refrigerants do not contain R-290 or any other hydrocarbons, but it is possible that the industry will gradually embrace the more flammable refrigerants like R-290.

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R290 as a Drop In? - Short #234