ROUNDTABLE©ASHRAE www.ashrae.org. Used with permission from ASHRAE Journal at www.opteon.com. This article may not be copied nor distributed in either paper or digitalform without ASHRAE’s permission. For more information about ASHRAE, visit www.ashrae.org.

Charles Allgood, Ph.D.,
Refrigerant Technology
Leader, Chemours, Newark,
Del.

Philip Johnston, P.Eng.,
Member ASHRAE, Product
General Manager, Daikin
Applied Americas, Maple
Grove, Minn.

Sarah Kim, Ph.D., Member
ASHRAE, Research Scientist,
Arkema, King of Prussia, Pa.,
vice chair of SSPC 34.

Steve Kujak, Member
ASHRAE, Director of Next
Generation Refrigerant
Research, Trane
Technologies, LaCrosse,
Wis., chair of SSPC 34.

Samuel Yana Motta, Ph.D.,
Member ASHRAE, Research
Fellow (Heat Transfer,
Refrigeration and AC),
Honeywell, Charlotte, N.C.

A Conversation on
Refrigerants
ASHRAE Journal conducted a roundtable with refrigerants experts to discuss the future of refrigerants.
What are potential alternatives for R-123, and what attributes
make these good low global warming potential (GWP) alternatives for R-123?
Steve Kujak: Refrigerant technology has matured sufficiently in the last decade to offer a number of good
replacements for R-123 and R-134a in large water-cooled
centrifugal chiller products. All these options are new
olefin (HFO) refrigerants. which are nonflammable(ASHRAE Standard 34-2019 Class 1) and which allows
them to be readily adopted using existing product standards and building codes.
A near design-compatible option for R-123 designs isR-514A (ASHRAE Class B1). R-514A is an azeotropic blendof ultralow GWP (< 10) refrigerants R-1336mzz(Z) and
R-1130(E), with nearly the same capacity and efficiency
as R-123 and is in wide adoption at this time as a replacement for R-123.
Another option available is R-1233zd(E) for use in centrifugal chillers. R-1233zd(E) is a ASHRAE Class A1 refrigerant with about a 40% higher capacity than R-123 withsimilar efficiency, but requires a new chiller design.
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A lesser-known emerging option is R-1224yd(Z) with acapacity about 60% higher than R-123 with similar efficiency. R-1224yd(Z) has similar capacity to R-245fa andwould be considered a design-compatible replacement for
HVAC&R equipment using R-245fa. Many organic Rankine
cycle (ORC) are using R-245fa, and R-1224yd(Z) is underconsideration as a replacement for these applications.
Philip Johnston: The new refrigerants currently available for low pressure water cooled centrifugal chillers
are R-1233zd(E) and R-514A, with a third refrigerant,
R-1224yd(Z) showing potential as an emerging solution.
R-1233zd(E) has key attributes we look for in a new
refrigerant solution. It is classified as an “A1” (lower toxicity, with no flame propagation) by Standard 34-2019.
It is a single working fluid, making it easier to reclaim
and has high efficiency. It will also be used in other sectors beside large chillers (including foams and solvents),
driving global demand and large-scale production. Thissuggests competitive pricing and widespread availability
going forward. Working pressures are slightly higher
than R-11 and R-123, meaning heat exchangers will beROUNDTABLE

designed for working pressures
above 15 psig (100 kPa) and carry
ASME certification.
R-514A is a blend (75%
R-1336mzzZ/25% R-1130E)
designed to be close to R-123 inpressures and capacities. Like
R-123 it is a higher toxicity fluid(ASHRAE “B1”), which may limit
its market acceptance. It is primarily used in existing R-123
Ivan Rydkin., Associate
Member ASHRAE,
designs for new equipment
Refrigerants Technicalapplications.
Lead, North America, Daikin
Sarah Kim: In addiAmerica, Rochester, N.Y., vicetion,
I would like to add thatchair of SSPC 147.
R-1233zd(E) has a very low GWP
of 1,1 which makes it suitable as a long-term solution.
With advancement in technology, it is expected that
R-1233zd(E)-based low pressure solutions will replacesome of the medium pressure smaller capacity chillers
due to its superior efficiency and the nonflammablenature of the fluid per Standard 34-2019.
Are any of these more optimal solutions than others?
Johnston: R-1233zd(E) has been the refrigerant ofchoice for new equipment designs, with multiple manufacturers designing new chillers based on this fluid. The“A1” rating, high efficiency and single working fluid are
key attributes driving this.
Kujak: All alternatives in this category are acceptable for use in large capacity water cooled chillers.
They are all high efficiency and all easy to handle. Even
though a number of these replacements are not designcompatible replacements for R-134a, manufacturers
are announcing their use as primary options to replace
existing R-134a products.
Can any of these alternatives be used to retrofit existing R-123
chillers?
Charles Allgood: Yes, R-514A was developed specifically as a replacement for R-123 in both existing R-123
chillers and new systems similar in design to traditional
R-123 systems.
Kujak: Yes, R-514A is a near design-compatible option
for R-123 designs, and engineered retrofits are available.
Any refrigerant retrofit requires proper considerations
to the impact on the application and the chiller performance. In the last transition, a large number of R-11
units were retrofitted to R-123. R-123 with a GWP of 77 isalready considered a low GWP, so the cost of future R-123
will be unaffected by a GWP based refrigerant allocation
restriction. Thirty years of experience with R-11 showsthat R-123 will be available long into the future beyond
the expected life of the equipment.
Johnston: With proper preparation, it would be possible to use R-514A in an existing R-123 chiller. For example, an oil flush and change is required, and impeller
and/or gear changes may also be needed. It would be
best to consult the chiller manufacturer about the possibilities and performance impacts.
What about using natural refrigerants in large water cooled
chillers?
Kujak: Natural refrigerants like ammonia (R-717) are
seeing incrementally more adoption in this area for
comfort cooling, but its toxicity is limiting its use in large
refrigerant charge systems. Hydrocarbons are not being
adopted in this area because of significant safety concerns, and carbon dioxide (R-744) efficiency is too low andits pressure is too high to warrant any consideration.
Johnston: Due to their highly toxic and highly flammable properties, refrigerants such as R-717 or hydrocarbons are not preferred in these types of high charge
size systems, especially when installed outside of industrial settings. Many of these large building chillers arein use in densely populated urban environments where
the risks of using ammonia are too high, or simply notallowed by local regulations.
What are potential alternatives for R-134a and what attributes
make these good low GWP alternatives for R-134a?
Allgood: R-513A is the leading nonflammable, low
GWP replacement for R-134a in a wide variety of applications including low temperature ice rink chillers,
low-temperature/medium temperature commercial
refrigeration systems (stand-alone, cascade, distributed
architectures) and comfort cooling chillers. Numerous
OEMs have commercialized equipment based on
R-513A. Its similarity to R-134a in terms of capacity, efficiency and pressures with ~50% reduction in GWP havealso made it the preferred choice when retrofitting an
existing R-134a system in the field.
Kujak: The HFC GWP regulations are a phasedown
process rather than a phaseout process that was required
during the ozone depletion regulation. As such, the regulation realizes that as refrigerant technology matures,interim moderate GWP refrigerants may be required astransitional fluids to enable the phasedown process and
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lessen the impact of the refrigerant transition.
R-513A is one of those candidates to replace R-134a.
R-513A is an Standard 34-2019 A1 refrigerant with a GWP
of 630, which is >50% lower in GWP than R-134a. R-513A
has similar capacity, pressures and efficiency to R-134a,
which makes it an ideal candidate for adoption to replace
R-134a. R-513A is an azeotropic blend of ultralow GWP
R-1234yf and R-134a. Products are available using thisrefrigerant, and since R-513A is near design compatible toR-134a, retrofitting is possible.
Johnston: R-513A, an HFO/HFC blend (56%R-1234yf/44%R-134a), was developed as an “A1” solution, adding enough R-134a to the R-1234yf to move into
the nonflammable classification. This is viewed as aninterim solution, as the GWP is higher than the GWP of
R-1234yf and R-1234ze(E) (~1), and the efficiency is worse
than R-134a. This means it may actually be a negative forthe climate when compared to R-134a.
Since R-513A is considered an interim alternative, what will be
the long-term solutions?
Allgood: Longer term products like pure HFO-1234yf
with a GWP <1, or R-516A with a GWP <150 would provide
similar performance to R-513A, with an A2L classification. Other products, like R-1234ze(E) and R-515B provide the industry additional options in this general performance category, but with higher boiling points andlower capacity, they may be more limited in use. The A2L
solutions such as R-1234yf, R-1234ze and R-516A cannot
be used as retrofit refrigerants and will only be appliedin new systems designed for flammable refrigerants andin compliance with safety standards and codes.
Kujak: Obtaining lower GWP than R-513A requires the
adoption of flammable refrigerants. Ultralow (<10 GWP)
GWP R-1234yf and R-516A (<150 GWP), both Standard
34-2019 Class A2L, are both possible solutions. R-516A
is an azeotropic blend of R-1234yf, R-134a and R-152a.
Each has similar capacity to R-134a, but each is flammable, which will require different product design andapplication changes to allow their use. R-516A has beenshown to be similar in capacity and efficiency to R-513A,
so logistically it would be a preferred refrigerant toR-1234yf, which is lower in efficiency.
Other leading candidates are ultralow GWP R-1234ze(E)(ASHRAE Class A2L) and R-515B (<300 GWP ASHRAEClass A1), which is an azeotropic blend of R-1234ze(E) with
R-227ea. R-1234ze(E) and R-515B are both 25% lower incapacity in comparison to R-134a, so they don’t make ideal
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candidates as direct replacements for R-134a, but with aredesign can perform similarly to R-134a.
Johnston: R-515B (91% R 1234zeE/9% R 227ea), witha GWP less than 300, is a longer-term A1 blend option.
This can operate in the new long-term R-1234ze(E)compressor designs, with better efficiency than R-513A.
HFO-1234yf and HFO-1234ze(E) are viewed as long-term
low GWP alternatives to R-134a. Both are single working fluids with properties similar to R-134a. R-1234yf
offers similar capacity to R-134a, with about a 5% efficiency penalty. This makes it attractive for automotive
air-conditioning applications, as the compressor size
remains about the same. R-1234ze(E) offers similar
efficiency to R-134a but with about a 25% loss in capacity when compared to R-134a. Because of the similar
efficiency, R-1234ze(E) is the refrigerant of choice for
HVAC applications, and compressor designs will have to
be changed to recover the 25% capacity gap from R-134a
drop-in designs. Both carry an ASHRAE “A2L” (lower toxicity, lower flammability) designation that will requirechanges to current building codes in many areas.
Kim: R-516A is an azeotropic blend with a very low GWPof 131.1 Refrigerants with <150 GWP are generally recognized as long-term solutions by various government entities in Europe (F-Gas), and California (CARB). As R-516A
has zero glide, it is easier to handle, unlike zeotropic
blends that can fractionate, and a whole system recovery
would likely be needed in case of a system leak. Although
R-516A should be used in new systems as an A2L fluid,
R-516A is the lowest GWP fluid with matching capacityand efficiency to R-134a. Thus, R-516A would minimize
the amount of design changes an OEM would encounterversus some of the other choices in this space.
Samuel Yana Motta: If regulations allow GWP <300,
R-515B is a good long-term option. It helps minimize thecost of mitigation for flammable 2L refrigerants. If regulations require GWP <150, R-1234ze is the best long-term
option.
Can any of these alternatives be used to retrofit existing R-134achillers?
Allgood: R-513A is very similar to R-134a in terms of
capacity, efficiency and pressures and, with ~50% reduction in GWP, have also made it the preferred choice
when retrofitting an existing R-134a installation. As
previously noted, the A2L solutions such as R-1234yf,
R-1234ze and R-516A cannot be used as retrofit refrigerants and will only be applied in new systems designed

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for flammable refrigerants and in compliance withsafety standards and codes.
Kujak: Retrofitting is possible with R-513A. However
it requires an engineer retrofit with possible changes
needed in lubricant, and consideration needs to begiven to slight impacts on capacity and more importantly impacts on reduced efficiency. Retrofitting R-134a
equipment with flammable refrigerants will not beallowed because of their flammability.
What about using natural refrigerants as a replacement for
R-134a equipment?
Kujak: Natural refrigerants like ammonia (R-717)
are seeing incrementally more adoption in this area
for comfort cooling, but its toxicity is limiting its use.
Hydrocarbons are not being adopted in this area
because of significant safety concerns with flammability,
and carbon dioxide (R-744) efficiency is too low and too
high pressure to warrant any consideration.
What are potential alternatives for R-404A and what attributes
make these good low GWP alternatives for R-404A?
Allgood: R-448A/R-449A are the leading nonflammable replacements for R-404A/R-507 in commercial
refrigeration, particularly in the traditional supermarket parallel rack system designs, but also in cold storageand other industrial refrigeration applications—even
those still relying on R-22. Due to their nonflammability(a requirement when retrofitting R-404A) and excellent
performance match (equivalent capacity and improvedEER) while reducing direct GWP by ~70% , they havebeen adopted by leading food retailers globally over thelast decade to meet internal sustainability goals andregulatory requirements.
Ivan Rydkin: R-448A, R-449A and R-407H are emerging
HFO/HFC or HFC blend solutions with GWP below 1,500.
These are all class A1 refrigerants and are handled andoptimized in the same way technicians are already used
to. With R-407H, it’s the same exact chemistry as R-407A
and R-407C, which has been proven over the last 20 years.
We expect that new installations and all R-404A retrofits
can be completed with these gases and likely be in compliance with the overall phasedown through the 20+ year
lifetimes of the systems. So, engineers specifying thesegases today should be able to design for the long term.
Kujak: Unfortunately, fluorinated refrigerant technology options continue to be less ideal as R-404A
replacements. In the last transition, R-404A was an
ideal candidate to replace R-502 and R-22 since it had
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similar capacity and more importantly lower compressor discharge temperature and low temperature glide.
Refrigerant temperature glide is an important attribute for a number of reasons, but the largest impact ison heat exchanger design and selection. Compressor
discharge temperature is important to allow the adoption of the refrigerant without changes to compressor
designs to provide discharge superheat cooling.
In the R-404A space, a number of interim GWP
ASHRAE Class A1 candidates (GWPs from 1,200 to 1,500)
have emerged as acceptable replacements for R-404A(GWP >3900). These candidates are blends of existing HFCs, like R-32, R-125, R-134a with R-1234yf and
R-1234ze(E). R-448A, R-449A and R-452A (for transport
refrigeration applications) are candidates that are being
adopted globally. Unfortunately, these refrigerants are
blends with elevated temperature glide, which doesn’tallow them to be adopted in all R-404A applications,such as flooded evaporators. In addition, other lower
HFC blends with similar attributes have been developed
as well in the R-407 series of refrigerants, which are
blends of R-32, R-125 and R-134a.
Can any of these alternatives be used to retrofit existing R-404A
equipment?
Allgood: Conversion guidelines have been developedby refrigerant manufacturers and component OEMs
have qualified their full lines for R-448A/R-449A service.
The refrigerant conversions are relatively simple withkey factors needing attention being expansion valve
adjustments and discharge temperature mitigation.
Rydkin: Yes, they can with proper preparatory work.
The changes may include simple system adjustments,
TXVs, EXVs and updating the controller with new firmware, which is something the refrigeration industry
companies and technicians are expert at, having gonefrom R-12 to R-502/R-22 to R-404A/R-507A and now
to the next generation. For retrofits, R-448A, 449A
and 407H can be drop-in for the last few R-22 systems(requiring an oil change), and they are “near” drop in
for R-404A/R-507A systems (requiring TXV adjustment
or replacement for low temp). For new systems, thesealternatives provide an energy efficiency benefit up to
12% over R-404A and are used in the well-known equipment/compressors, so there are years of technical experience with these systems out in the industry.
Since many lower GWP alternatives are considered an interim
alternative. What will be the long-term solutions?

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Rydkin: We will see A2L refrigerants below GWP 150
such as the R-454 series, R-468A, R-455A as potential
alternatives for some applications, with likely more on
the horizon. We see all refrigerants as playing a role in themix. This is a change from previous generations where
the majority of cooling was centralized R-404A. In the
future, a combination of solutions will likely be applied,with end users utilizing some portion of centralized CO2
systems, stand-alone A3 hydrocarbon systems and standalone and distributed A2L refrigeration systems.
Kujak: Going lower in GWP to a limit of <300 GWP, forexample, requires the adoption of flammable refrigerants, either A2L (HFO/HFC blends) or A3 (hydrocarbons). In this area, HFO/HFC blends typically are similar
to performance of the interim GWP candidates, but they
are just as flammable.
Product safety standards are allowing higher chargesof hydrocarbons, and both R-600a (isobutane) and
R-290 (propane) are being used and sold today in the
U.S. in small portable refrigeration and air-conditioning
products. Hydrocarbons are higher efficiency than theirfluorinated alternatives, but their high combustibility
restricts their use to small, multi-circuit products.
What about using natural refrigerants as a replacement for
R-404A applications?
Kujak: Ammonia is seeing some more innovation inthis area by the appearance of smaller capacity package
products such as air- or water-cooled chillers. In addition, carbon dioxide (R-744) is seeing wide adoption
in cooler ambient climates where its lower efficiency
impacts can be mitigated through advanced thermodynamic cycles. In addition, cascade systems (two refrigeration systems in series) are seeing more use in hotter
climates, which takes into account the optimal attributesof a fluorinated refrigerant in the higher temperature
operational conditions and R-744 used in the lower temperature operational conditions.
Product safety standards are allowing higher chargesof hydrocarbons, and both R-600a (isobutane) and
R-290 (propane) are being used and sold today in the
U.S. in small portable refrigeration and air-conditioning
products. Hydrocarbons are higher efficiency than theirfluorinated alternatives, but their high combustibility restricts their use to small, multi-circuit products.
Hydrocarbons are becoming mainstream in smaller
charge (<0.33 lb [<150 g]) refrigeration systems like bottle coolers and small package cases.

As you notice from the discussion, increased productfragmentation is occurring and will continue in this
HVAC&R market area with multiple refrigerants used toserve cooling needs from small capacity to large capacity.
Rydkin: We see these industrial gases being usedvery effectively today, and that shouldn’t change in the
future; for certain applications each of the three gases(ammonia, CO2, and hydrocarbons), or a combination,
may provide the best choice. A balance of efficiency,
safety, and environmental impact combined with total
cost of ownership will likely be the deciding factor. At theend of the day, a refrigerant and system solution for agas station, a food delivery service, a mid-size supermarket or a full-size supermarket could be very different.
What are potential alternatives for R-410A? R-32 (HFC) and
R-454B (HFO/HFC blend) are emerging solutions, and what
attributes make these good lower GWP alternatives for R-410A?
Are there others?
Kujak: Long-term low GWP replacements for R-410A(R-410A is 50/50 blend of R-32/R-125) is by far the mostchallenging technology area. There are two leadinginterim GWP candidates, pure R-32 (GWP 675) and R-32
blended with ultralow GWP R-1234yf to lower its GWP(GWP 460), which is called R-454B. Both are ASHRAEClass A2L and each has their beneficial attributes. R-454B
is a lower GWP more design-compatible refrigerant for
R-410A, while R-32 is a single refrigerant with higher
capacity. R-32 adoption by OEMs requires a complete
redesign of product platforms to optimize its use for both
capacity, efficiency and more importantly high compressor discharge temperatures. R-454B is a close R-410A
design-compatible refrigerant and only requires minor
system design changes. R-454B also has the advantage
of being lower GWP, which will likely allow its use longer
into the regulatory future. Current regulatory actions aretargeting a GWP of <750 for R-410A from 2024 to 2026.
An emerging nonflammable (ASHRAE class A1) <750
GWP candidate, R-466A, is under heavy consideration by
a number of manufacturers. Being nonflammable it thencould be easily adopted as a replacement for R-410A andreduce the complexity of using flammable refrigerants.
R-466A is a blend of R-32, R-125 with an ultralow GWP
nonflammable refrigerant R-13I1 or trifluoroiodomethane. R-13I1 is not a new refrigerant, but it was discounted
in the last transition because of chemical stability andmaterials compatibility concerns. Compatibility additives
and materials changes are likely required to allow its use.
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R-466A would be an ideal interim solution until further
until further innovation could lead to even lower GWP
nonflammable alternatives. Myself and my colleagues
have written a number of papers on the performance andpotential compatibility needs for R-466A.
Johnston: Both R-32 and R-454B have lower GWP than
R-410A. They are also both classified A2L (lower toxicity
and lower flammability) by Standard 34-2019. There areseveral attributes of alternates for consideration, often
viewed in “spider charts” to help visualize pros and cons.
Some of these attributes include capacity, efficiency, safety,
economy, chemical stability, chemical reactivity, availability, etc. Each application and each alternative should be
reviewed holistically to consider all attributes.
R-32 has a GWP of 675, 68% lower than R-410A’s GWP.
However, the GWP does not tell the whole story as it is nota measure of efficiency. While R-32 systems could reduce
refrigerant charge in certain equipment up to 40%, whichsaves in direct emissions, 60% to 95% of climate impact
over the product life cycle is from indirect emissions frompower generation. Test data found that full- and part-load
efficiency rating metrics can be improved by up to 12%with R-32 over R-410A, so equipment can be designed toconsume less electricity over the equipment’s lifetime.
Some of the proposed blends like R-454B and R-452B
have similar capacities to R-410A, but I think R-32 is preferable to other alternatives. That’s because R-1234yf, thecommon HFO component added to make these blends,
has 40% of capacity and 95% of efficiency of R-410A. To use
R-1234yf directly would require significant compressorchanges in residential and light commercial equipment,
and very large piping and heat exchangers—not goodvalue. Because R-32 is a readily available commodity, it
has the potential to make a service tech’s life easier. As asingle component, R-32 can be charged in either liquid or
gas phases and can be more easily reclaimed.
R-466A, an A1 nonflammable proprietary blend containing trifluoroiodomethane (CF3I) or R-13I1, has beenannounced as an R-410A alternative. It is a three-component blend (49%R-32/11.5% R-125/39.5% R-13I1) with aglide of 1.5 Δ°C. It takes the excellent performing lower
GWP refrigerant R-32 and blends it with two other chemicals that have flame-retarding characteristics, impacting
performance. Regarding R-13I1, the “I” is iodine and theC-I bond is weak, making it, in our opinion, questionable for stability and for compatibility with materials
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reliability, durability and performance problems overtime. Increased glide limits its use in DX heat exchangers and can result in changes to blend concentrations as
a result of leaks and recharging, impacting performanceand safety classifications. A three component non-azeotropic blend with questionable stability certainly will be
more difficult to manage through supply chain and reclamation that enables the reduction goals for GWP of HFCs.
Published information suggests R-466A has slightly lower
performance than R-410A, and less than the performanceof pure R-32. R-466A’s GWP of 733 GWP is within targeted
thresholds <750. However, it requires more charge than
R-410A by estimates of 10% to 25%, compared to R-32’s
GWP of 675 with charge levels 25% to 40% less than R-410A.
Any extra charge means more charge that could leak, so
R-466A’s “effective” GWP is higher than R-32’s.
R-466A is an A1 class, but it as has a refrigerant concentration limit (RCL) of only 6.2 lb/Mcf (99 g/m3) driven
by its toxicity rather than flammability, and that compares to R-410A with a RCL of 26 lb/Mcf (420 g/m3). Withrequiring 10% to 25% more charge compared to R-410A
systems, charge limitations in real-world applications
would still be an issue.
No major North American equipment or compressor
manufacturers have announced or shared that they aredeveloping equipment and component parts around thisrefrigerant. This suggests it is not presently viewed as a
viable candidate. Further, R-466A is only produced insmall quantities today, which potentially makes the blend
expensive, which is concerning for the low-income sector
and developing nations and inhibits broad-scale adoption.
Allgood: The two leading alternatives to R-410A in air
conditioning are R-454B and R-32, which several OEMs
have announced plans to use in new generations of systems. Both are classified by Standard 34-2019 as lower
flammability (2L) refrigerants and based on the equipment standards that have been developed, they will only
be used in new systems and cannot be used as retrofit
gases. The finalization of safety standards and updatingof building codes, along with training of the technician
workforce, are key milestones in these new refrigerants
becoming mainstream in North America.
R-454B and R-32 differ in several key technical aspects
such as GWP: R-454B (466) vs R-32 (675). This difference can have implications in later years for long-term
compliance with global HFC phasedown regulations. Differences in oil compatibility and discharge

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temperatures, along with overall system design compatibility when compared to R-410A system designs are alsoa consideration.
The technology barriers to designing a nonflammable
R-410A solution are many, and they have to do with theperformance characteristics desired versus the fluid
properties available. When looking at fluid choice, flammability is one element of consideration, but it not the
only consideration. As mentioned previously, refrigerantstability, materials of compatibility, overall environmental
impact and total system cost are other factors included in
fluid selection. OEMs evaluate all of these factors closely
and make determinations based on the total picture andwhat will serve their customers and market best for the
lifetime the equipment is expected to deliver.
Can any of these alternatives (R-32 and R-454B) be used to retrofit existing R-410A equipment?
Kujak: No! Under no circumstances should these flammable refrigerants (ASHRAE Class 2L, 2 or 3) be used toretrofit existing R-410A equipment. Serious safety situation could result. Much marketing of primarily R-32 andto a lesser extent R-454B and their potential benefits has
led to inquiries to retrofit installed R-410A equipment.
On the other hand, R-466A potentially could be usedas engineered retrofit for some R-410A products sinceR-466A is nonflammable (ASHRAE Class 1). This will
be an interesting opportunity to watch and see how it
develops for existing R-410A equipment.
Are these current alternatives (R-32 & R-454B) considered along-term low GWP solution?
Johnston: Yes. Because of R-32’s availability, low cost andexcellent performance, it is already used in large quantities in R-410A and most alternative low GWP blends. Given
R-410A’s wide use today, we know R-410A, and therefore
R-32, will be in the service chain for several years to comeas high GWP HFCs are phased down gradually.
Kujak: No. Both R-32 (GWP 675) and R-454B (GWP
466) will be adopted to replace R-410A as interim GWP
steps until phasedown regulations push them out of use.
Much debate is occurring how long the adoption window will last, but it is estimated to be the 2030 to 2036
time frame before other lower GWP refrigerants will beneeded to meet the regulations. Refrigerant researchand innovation are underway on lower GWP alternatives
to allow the transition from <750 GWP alternatives tomore long-term sustainable GWP limits, with <300 GWP
as a possible target.

What about using natural refrigerants as a replacement for
R-410A applications?
Johnston: Natural refrigerants, for example R-290 (propane) with its A3 classification, are being used in small systems in very small charge quantities in residential refrigeration applications. As mentioned above, each refrigerant
must be evaluated for each application in a variety ofcharacteristics. The difficulty then for application of A3
refrigerants into larger capacity systems, which are thenorm in residential and commercial buildings, is that due
to the larger charge sizes necessary, the much lower (about
10 times) flammable concentration limits and much lower
minimum ignition energy (MIE), it is much more difficult to apply such A3 refrigerants. For consideration ofother natural refrigerants, characteristics such as toxicity(R-717) or pressure (R-744) either mean they can’tt be usedin human comfort applications due to current building
codes (R-717) or major system designs and efficiency canbe problematic (R-744). Ammonia, hydrocarbons and CO2
have not been widely pursued in this segment due to toxicity, safety and energy efficiency issues.
Kujak: Product standards are allowing higher chargesof hydrocarbons, and both R-600a (isobutane) and
R-290 (propane) are being used in small portable refrigeration and air-conditioning products. Hydrocarbons
are higher efficiency than their fluorinated alternatives,
but their high combustibility restricts their use to small,hermetically sealed multi-circuit products.
Carbon dioxide (R-744) is thermodynamically too
low in efficiency to be given much consideration inthis space other than in applications without efficiency
restrictions. Ammonia (R-717) is not considered a possible alternative in applications requiring direct refrigerant expansion.
It is expected that product fragmentation will occur in
the R-410A space with hydrocarbon being used in small
hermetically sealed portable room air conditioner (RAC)
products. Some large charge products will migrate toother available technological architecture, like chillers
or other indirect refrigerant products.

References
1. Myhre, G, D. Shindell, F-M Bréon, Collins,
W, et al. 2013. “Anthropogenic and naturalradiative forcing.” In: Climate Change 2013: The
Physical Science Basis. Contribution of Working Group I
to the Fifth Assessment Report of the Intergovernmental
Panel on Climate Change. Cambridge and New York: https://bit.ly/3o6Pw0R
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Cambridge University Press.
MARCH 2021

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