ASHRAE Journal - March 2021 - 32

ROUNDTABLE

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 this
refrigerant, and since R-513A is near design compatible to
R-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 an
interim 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 for
the 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 and
lower 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 applied
in new systems designed for flammable refrigerants and
in 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 and
application changes to allow their use. R-516A has been
shown to be similar in capacity and efficiency to R-513A,
so logistically it would be a preferred refrigerant to
R-1234yf, which is lower in efficiency.
Other leading candidates are ultralow GWP R-1234ze(E)
(ASHRAE Class A2L) and R-515B (<300 GWP ASHRAE
Class A1), which is an azeotropic blend of R-1234ze(E) with
R-227ea. R-1234ze(E) and R-515B are both 25% lower in
capacity in comparison to R-134a, so they don't make ideal
32

ASHRAE JOURNAL

ashrae.org

MARCH 2021

candidates as direct replacements for R-134a, but with a
redesign can perform similarly to R-134a.
Johnston: R-515B (91% R 1234zeE/9% R 227ea), with
a 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 require
changes to current building codes in many areas.
Kim: R-516A is an azeotropic blend with a very low GWP
of 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 capacity
and efficiency to R-134a. Thus, R-516A would minimize
the amount of design changes an OEM would encounter
versus 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 the
cost 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-134a
chillers?
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

http://ashrae.org

ASHRAE Journal - March 2021

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