A New A/C Refrigerant Joins the Global Warming Fight

Why the new tri-blend R456A is a drop-in replacement for R-134a.

Worldwide automotive R-134a systems number in the hundreds of millions, creating a huge market for a non-HFC substitute. (Kia)

A tri-part blend refrigerant, R-456A, has been introduced as a service replacement for the original refrigerant in R-134a automotive air conditioning systems. The reaction likely is: Why would anyone want this? A blend would seem to raise all manner of complications. R-134a itself proved safe and works well, so a changeover to R-456A might seem pointless.

Pressure-temperature graph shows how close are the R-134a and R-456A curves, which obviates any concern with system calibration parts. (Koura Global)

That once was true. R-134a had been relatively cheap and it even has even been used to change over systems from R-12, which was phased out for environmental reasons including ozone layer depletion. But a law enacted last year, the American Innovation and Manufacturing (AIM) Act, upset that picture.

The AIM Act sets a 15-year schedule for a U.S. phaseout of HFCs (hydrofluorocarbon gases) to reduce global warming and the phaseout has already affected worldwide supplies of R-134a, a primary HFC application. Europe has a more aggressive HFC phaseout schedule and has just begun to use the R456A blend because R-134a supplies there are very tight and prices are soaring. The U.S. is not far behind: prices have more than tripled, typically running up to $400 for a 30-lb. (13.6-kg) tank.

And that’s with just the first step in the U.S. phaseout (10% cut in production, based on 2011-2013 usage). A 40% HFC reduction is required within five years, 70% in 10 years, and finally, 85% in 15 years (by 2036). Reducing production is not a matter of just “closing a spigot,” so being sure to run just ahead of a regulation can lead to severe shortages in the phaseout period.

Sub-700 GWP

An SAE-certified R-134a recovery machine can be repurposed to recover refrigerant from R-134a systems and recharge them to R-456A. (Mobile Air Climate Systems Assoc.)

R-456A is being sold by Koura Global, a long-established fluorochemical company previously known as Mexichem and ICI (for Imperial Chemical Industries), producer of the refrigerant brand Klea. Koura is being followed to market by a Honeywell three-part refrigerant blend. Marketed under the Solstice brand, Honeywell’s product consists of 45% R-134a, 49% R-1234ze (a mildly-flammable refrigerant in a class of gasses called hydrofluoroolefins) and 6% R-32 — another mildly flammable refrigerant that is added to improve cooling performance.

The fluorochemical industry’s supply approach is to use the R-456A blend as an R-134a supply extender, by combining it with R-1234ze, which although mildly-flammable, has a near-zero global warming impact. This supply extension originally led to R-513A, a blend of R-134a and R-1234yf, another HFO that replaced R-134a in cars. The R-513A blend was introduced by Honeywell and Chemours in 2021 as an R-134a substitute for chillers and related non-automotive applications and is widely sold in Europe.

Worldwide, automotive R-134a systems number in the hundreds of millions. The refrigerant was used from 1992 until the 2013 introduction of mildly flammable HFO R-1234yf, with A/C system modifications to mitigate the flammability risk. So, a non-HFC automotive substitute for R-134a service should have a large market. The R-456A blend is a near-azeotrope, which means there is minimal separation of the component gasses throughout the refrigeration cycle.

As the accompanying pressure-temperature graph shows, R-456A is very close to R-134a. Combined with the near-azeotropic characteristic of the blend, it’s unnecessary to change the operating calibration parts of the R-134a system to use R-456A.

Replacing much of the R-134a with the R-1234ze HFO, with its near-zero global warming potential, results in the R-456A’s global warming potential (GWP) measuring under 700, vs. 1430 for pure 134a (The GWP of a gas refers to the total contribution to global warming resulting from the emission of one unit of that gas relative to one unit of the reference gas, CO2, which is assigned a value of 1).

R-456A tanks are identified by the label, not by the color of the tank. (Mobile Air Climate Systems Assoc.)

Automotive R-134a systems were never designed for changeover to a refrigerant with flammability concerns, so to be usable, a substitute must be non-flammable. Because the HFO is only mildly flammable, a roughly 50-50 blend with non-flammable R-134a and the near-azeotropic characteristic, maintains overall non-flammability and the R-456A blend is a drop-in replacement.

R-1234ze is lower in cost than R-1234yf, so using it in R-456A adds to the price competitiveness of the R-456A blend compared with R-134a, according to Chris Seeton, applications director at Koura.

Other automotive refrigerants have been packaged in color-coded tanks—white with red band for R-1234yf, solid light blue for R-134a and solid white for R-12. However, there will be no specified color-coding for a blend’s tank, just a large label. The Klea tanks currently happen to be painted gray.

The R465A changeover

The R-134a system oil does not need to be removed for service with R-456A. A high-quality PAG 46 (polyalkylene glycol) oil is recommended for service, with Shrieve Zerol HD 46 specified by Koura. Unlike the previous major A/C refrigerant retrofits, (R-12 to R-134a) R-456A is a true drop-in. Although a dedicated recovery/recharge machine is mentioned in the Klea conversion procedure to R-456A, an out-of-warranty R-134a machine that was certified to SAE J2788 can be repurposed. The only caution is a machine with an internal cylinder should contain at least 50% of the charge to maintain the blend composition.

The existing R-134a vehicle service ports need not be changed, vs. the retrofit fittings specified when R-12 systems were retrofitted to R-134a. Koura’s Seeton said the R-456A tanks would be supplied with labels (identifying the changeover), to be affixed underhood in retrofitted cars.

Checking the system for leaks is the same as with R-134a. Because R-456A contains R-134a, an SAE-certified electronic leak detector (J2791, J2913) will detect a leak and so is recommended. A reputable R-1234yf-compatible trace dye also is acceptable. It mixes with oil in the system and provides a visible leak indication under a black or blue light.

“R-456A is designed to work with any percentage of R-134a, so it is tolerant of normal variations in its own composition,” Seeton explained. As a result, he said there is no need for mandatory reformation of a R-456A blend whose composition is affected by leakage.

Koura ‘s changeover procedure is to evacuate the vehicle system from both A/C service ports, for maximum effectiveness in recovery of the R-134a and deep-vacuuming for a minimum of 20 minutes to complete the process. Add enough of the Koura-recommended service procedure oil (Shrieve Zerol HD46) to equal any amount removed in the recovery procedures, plus 15 ml (0.50 oz.).

Once charging R-456A (to the same amount as the R-134a system held) is complete, start the engine and turn on the A/C to circulate the refrigerant andconfirm cooling is at least equal to the R-134a system. Turn off the A/C, disconnect the lines and refit the service valve caps.

Seeton said an application for listing R-456A under “SNAP´ (the U.S. EPA’s Significant New Alternative Policy) for non-ozone-depleting automotive replacement refrigerants, is being readied and is expected to be submitted before the end of 2022.