Technical
GWP < 2500 from 2020 onwards. However, the quantity
limitation through the ‘phase-down’ will also lead to
significantly restricted availability. Due to the extremely high
demand for R410A, a timely switch to alternatives is needed
in the EU.
R417A/417B/422D/438A
AS SUBSTITUTES FOR R22
Similar to the development of R422A, one aim of developing
these blends was to provide chlorine-free refrigerants (ODP
= 0) for the simple conversion of existing R22 plants.
R417A was introduced to the market years ago and is also
offered under the trade name ISCEON MO59 (Chemours). This
substitute for R22 contains the blend components R125/R134a/
R600 and therefore differs considerably from, for example,
R407C with a correspondingly high proportion of R32.
Meanwhile, a further refrigerant based on identical
components, but with a higher R125 content, has been
offered under the ASHRAE designation R417B. Due to its
lower R134a content, its volumetric refrigerating capacity
and pressure levels are higher than for R417A. This results
in different performance parameters and a different
focus within the application range. The same applies to a
further blend with the same main components, but R600a
as hydrocarbon additive. It is offered under trade name
ISCEON MO29 (Chemours) and listed as R422D in the
ASHRAE nomenclature. Another refrigerant belonging
to the category of HFC/HC blends was introduced in 2009
under the trade name ISCEON MO99 (Chemours) – ASHRAE
classification R438A. This formulation was designed
especially for a higher critical temperature for applications
in hot climate areas. The base components are R32, R125,
R134a, R600 and R601a. Like R407C, all four substitute
refrigerants are zeotropic blends with a more or less
significant temperature glide. In this respect, the criteria
described for R407C also apply here.
Apart from a similar refrigeration capacity, there are
fundamental differences in thermodynamic properties
and in oil transport behaviour. The high proportion of
R125 causes a higher mass flow with R417A/B and R422D
than with R407C, a lower discharge gas temperature and
a relatively high superheating enthalpy. These properties
indicate that there are differences in the optimisation of
system components, and a heat exchanger between liquid
and suction lines is of advantage. Despite the predominant
proportion of HFC refrigerants, conventional lubricants can
50
RACA Journal I August 2020
www.hvacronline.co.za