ASHRAE Journal - March 2021 - 36

ROUNDTABLE

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 and
potential 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 are
several 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 not
a measure of efficiency. While R-32 systems could reduce
refrigerant charge in certain equipment up to 40%, which
saves in direct emissions, 60% to 95% of climate impact
over the product life cycle is from indirect emissions from
power 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 to
consume 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, the
common 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 compressor
changes in residential and light commercial equipment,
and very large piping and heat exchangers-not good
value. Because R-32 is a readily available commodity, it
has the potential to make a service tech's life easier. As a
single 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 been
announced as an R-410A alternative. It is a three-component blend (49%R-32/11.5% R-125/39.5% R-13I1) with a
glide 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 the
C-I bond is weak, making it, in our opinion, questionable for stability and for compatibility with materials
as a result of potential acid formation. This can lead to
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MARCH 2021

reliability, durability and performance problems over
time. 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 performance
and 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 performance
of 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). With
requiring 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 are
developing equipment and component parts around this
refrigerant. This suggests it is not presently viewed as a
viable candidate. Further, R-466A is only produced in
small 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 updating
of 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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