Refrigerant Transition

In a session about the current refrigerant transition, John Maiorana, product support manager at Arkema, gave attendees a brief overview of the AIM Act, the federal legislation passed in December 2020 to phase down high-GWP refrigerants like R-410A in HVACR equipment. He explained that starting January 1, 2025, the legislation requires manufacturers to only use refrigerants with less than 700 GWP in most air conditioners and heat pumps.

REFRIGERANT TRANSITION: Arkema’s John Maiorana gave a presentation about the current refrigerant transition. (Staff photo)

“While these refrigerants represent a very small amount of the aggregate gases in the upper atmosphere, they have a lot of heat-trapping capability,” he said. “That is why we are getting rid of some of the higher-GWP refrigerants. For example, R-410A has a GWP of 2,088, compared to CO₂, which has a GWP of 1. That is why any refrigerant over 700 GWP is basically gone.”

Taking the place of high-GWP refrigerants like R-410A in air conditioners and heat pumps are lower-GWP alternatives, such as R-32 and R-454B. ASHRAE has classified both as A2L refrigerants, which means they are mildly flammable.

“The A2L category was initiated by ASHRAE, which uses three different measurements: how fast something burns (burning velocity), how much is needed to burn (lower flammability limit, or LFL), and then when it burns, how much heat energy is created (heat of combustion). These things are pretty important,” said Maiorana.

Burning velocity varies significantly among refrigerants, he explained, noting that R-290 (propane) burns at 39 centimeters per second, while R-32 burns at 6.7 centimeters per second and R-1234yf burns at just 1.5 centimeters per second. Slower burn rates enhance safety by reducing the likelihood of rapid combustion and explosion in the event of a leak.

The LFL is the minimum concentration of a flammable substance — in this case, a refrigerant — that is capable of ignition when there is a sufficient mixture of air and the substance. It’s expressed as refrigerant percentage by volume, so the lower the number, the greater the probability for ignition. Propane (R-290), for example, ignites at just 2.1% concentration, while R-32 requires 14.4%, and R-1234yf requires 6.1%, said Maiorana.

The heat of combustion is a measurement of the amount of heat released when a substance, such as refrigerant, burns. R-290 produces 46.2 joules per kilogram, while R-32 and R-1234yf produce much lower values, at 9 and 10.7 joules per kilogram, respectively, he said.

New Refrigerants

As noted earlier, R-32 and R-454B will be replacing R-410A in many types of comfort cooling equipment, and each has unique characteristics that make them suitable for different applications. R-454B is a blend containing nearly 70% R-32, with the remainder composed of R-1234yf, while R32 is a single-component refrigerant.

Many manufacturers, particularly those producing ductless systems, are transitioning to R-32, said Maiorana. This is due to R-32’s ability to provide more heat exchange in a smaller compartment, combined with the advantage of having no glide (the temperature range over which a refrigerant blend evaporates or condenses at a given pressure).

In contrast, Maiorana said that R-454B offers closer compatibility with R-410A equipment, making it an easier transition for manufacturers. Its lower GWP of 466, compared to R32's GWP of 675, also aligns more closely with future environmental regulations, which could potentially extend its usability, he said.

If future regulations call for even lower GWP in air conditioners in heat pumps, than the architecture of the equipment will have to change, said Maiorana.

“Basically, it will mean a little chiller outside the house that is cooling or heating a fluid, whether it be a glycol solution or water, and having that come in and do the heat exchange.”

Safety Features

There will be a few differences between R-410A equipment and systems using an A2L refrigerant, such as R-32 and R-454B, said Maiorana. The primary difference will be the addition of a refrigerant detection system (RDS), which is required by safety standard, UL 60335-2-40, and continuously monitors for refrigerant leaks.

“The RDS is constantly sniffing, and once it sniffs a significant leak, it's going to tell the compressor to shut off and keep the blower running,” he said. “Then the blower's going to keep running, and once the RDS sniffs below the threshold set by UL, everything comes back on. Now, if all the refrigerant leaks out, then you will have a low refrigerant issue, which requires a technician to come in and fix it.”

The RDS is required on systems containing over 4.5 pounds of refrigerant, although Maiorana noted that many manufacturers are opting to install it on all models for consistency and simplicity in production.

Another difference is that A2L systems will use spark-proof wiring to further reduce ignition risks. Maiorana noted that this wiring does not need to be “explosion-proof” due to the lower flammability of A2L refrigerants.

Overall, the differences between R-410A and A2L equipment are quite minor, said Maiorana, making the shift to A2L refrigerants relatively smooth — especially compared to the last transition from R-22 to R-410A. That change required significant equipment redesigns due to relatively larger coils needed in R-410A systems. With this transition, he said, “Homeowners are unlikely to even notice a difference.”