Panasonic CS/CU-YW9DKE Service Manual page 39

10 Installation and Serving Air Conditioner Using R410A
10.1. OUTLINE
10.1.1 About R410A Refrigerant
1. Converting air conditioners to R410A
Since it was declared in1974 that chlorofluorocarbons (CFC), hydro chlorofluorocarbons (HCFC) and other substances pose
a destructive danger to the ozone layer in the earth´s upper stratosphere (20 to 40 km above the earth), measures have been
taken around the world to prevent this destruction.
The R22 refrigerant which has conventionally been used in ACs is an HCFC refrigerant and, therefore, possesses this ozone
destroying potential. International regulations (the Montreal Protocol Ozone-Damaging Substances) and the domestic laws of
various countries call for the early substitution of R22 by a refrigerant which will not harm the ozone layer.
In ACs, the HFC refrigerant which has become the mainstream alternative called R410A.Compared with R22, the
pressure of R410A is approximately 1.6 times as high at the same refrigerant temperature, but the energy
efficiency is about the same. Consisting of hydrogen (H), fluorine (F) and carbon (C), R410A is an HFC
refrigerant. Another typical HFC refrigerant is R407C. While the energy efficiency of R407C is some what inferior
to that of R410A, it offers the advantage of having pressure characteristics which are about the same as those of
R22, and is used mainly in packaged Acs.
2. The characteristics of HFC (R410A) refrigerants
a. Chemical characteristics
The chemical characteristics of R410A are similar to those of R22 in that both are chemically stable, non-
flammable refrigerants with low toxicity.
However, just like R22, the specific gravity of R410A gas is heavier than that of air. Because of this, it can cause
an oxygen deficiency if it leaks into a closed room since it collects in the lower area of the room. It also generates
toxic gas when it isdirectly exposed to a flame, so it must be used in a well ventilated environment where it will
not collect.
Composition (wt%)
Boiling point (°C)
Vaporizing pressure (25°C)
Saturated vapor density
Flammability
Ozone-destroying point (ODP)
Global-warming point (GWP)
b. Compositional change (pseudo-azeotropic characteristics)
R410A is a pseudo-azeotropic mixture comprising the two components R32 and R125. Multi-component
refrigerants with these chemical characteristics exhibit little compositional change even from phase changes
due to vaporization 9or condensation), which means that there is little change in the circulating refrigerant
composition even when the refrigerant leaks from the gaseous section of the piping.
Accordingly, R410A can be handled in almost the same manner as the single-component refrigerant R22.
However, when charging, because there is a slight change in composition between the gas phase and the liquid
phase inside a cylinder or other container, charging should basically begin with the liquid side.
c. Pressure characteristics
As seen in Table 2, the gas pressure of R410A is approximately 1.6 times as high as that of R22 at the same
refrigerant temperature, which means that special R410A tools and materials with high-pressure specifications
must be used for all refrigerant piping work and servicing.
Refrigerant Temperature( )
-20
0
20
40
60
65
Table 1 Physical comparison of R410A and R22
R32/R125(50/50)
1.56 Mpa(15.9 kgf/cm2)
Non-flammable
Table 2 Comparison of R410A and R22 saturated vapor density
°C
R410A
-51.4
64.0 kg/m3
0
1730
R410A
0.30
0.70
1.35
2.30
3.73
4.15
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CS-YW9DKE / CU-YW9DKE / CS-YW12DKE / CU-YW12DKE
R22
R22(100)
-40.8
0.94 Mpa(9.6 kgf/cm2)
44.4 kg/m3
Non-flammable
0.005
1700
R22
0.14
0.40
0.81
1.42
2.33
2.60