ASHRAE Journal - March 2021 - 35

ROUNDTABLE

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 the
mix. 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, for
example, 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 charges
of 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 their
ﬂuorinated 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 in
this 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 attributes
of 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 charges
of 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 their
ﬂuorinated 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 product
fragmentation is occurring and will continue in this
HVAC&R market area with multiple refrigerants used to
serve cooling needs from small capacity to large capacity.
Rydkin: We see these industrial gases being used
very 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 the
end of the day, a refrigerant and system solution for a
gas 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 most
challenging technology area. There are two leading
interim 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 ASHRAE
Class 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 are
targeting 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 then
could be easily adopted as a replacement for R-410A and
reduce 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 and
materials compatibility concerns. Compatibility additives
and materials changes are likely required to allow its use.
MARCH 2021

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