ASHRAE Journal - March 2021 - 34

ROUNDTABLE

for flammable refrigerants and in compliance with
safety 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 be
given to slight impacts on capacity and more importantly impacts on reduced efficiency. Retrofitting R-134a
equipment with flammable refrigerants will not be
allowed 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 storage
and 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 improved
EER) while reducing direct GWP by ~70% , they have
been adopted by leading food retailers globally over the
last decade to meet internal sustainability goals and
regulatory 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 and
optimized 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 these
gases 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
34

ASHRAE JOURNAL

ashrae.org

MARCH 2021

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 is
on 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't
allow 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 developed
by refrigerant manufacturers and component OEMs
have qualified their full lines for R-448A/R-449A service.
The refrigerant conversions are relatively simple with
key 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 gone
from 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, these
alternatives 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?

http://ashrae.org

ASHRAE Journal - March 2021

Table of Contents for the Digital Edition of ASHRAE Journal - March 2021