Panasonic CU-PW9DKE Service Manual

Panasonic CU-PW9DKE Service Manual Manual pdf 39 page image

10 Installation and Serving Air Conditioner Using R410A10.1. OUTLINE10.1.1 About R410A Refrigerant1. Converting air conditioners to R410ASince it was declared in1974 that chlorofluorocarbons (CFC), hydro chlorofluorocarbons (HCFC) and other substances posea destructive danger to the ozone layer in the earth´s upper stratosphere (20 to 40 km above the earth), measures have beentaken 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 ozonedestroying potential. International regulations (the Montreal Protocol Ozone-Damaging Substances) and the domestic laws ofvarious 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, thepressure of R410A is approximately 1.6 times as high at the same refrigerant temperature, but the energyefficiency is about the same. Consisting of hydrogen (H), fluorine (F) and carbon (C), R410A is an HFCrefrigerant. Another typical HFC refrigerant is R407C. While the energy efficiency of R407C is some what inferiorto that of R410A, it offers the advantage of having pressure characteristics which are about the same as those ofR22, and is used mainly in packaged Acs.2. The characteristics of HFC (R410A) refrigerantsa. Chemical characteristicsThe 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 causean oxygen deficiency if it leaks into a closed room since it collects in the lower area of the room. It also generatestoxic gas when it isdirectly exposed to a flame, so it must be used in a well ventilated environment where it willnot collect.Table 1 Physical comparison of R410A and R22Composition (wt%)Boiling point (°C)Vaporizing pressure (25°C)Saturated vapor densityFlammabilityOzone-destroying point (ODP)Global-warming point (GWP)R410AR32/R125(50/50)-51.41.56 Mpa(15.9 kgf/cm2)64.0 kg/m3Non-flammable01730R22R22(100)-40.80.94 Mpa(9.6 kgf/cm2)44.4 kg/m3Non-flammable0.0051700b. Compositional change (pseudo-azeotropic characteristics)R410A is a pseudo-azeotropic mixture comprising the two components R32 and R125. Multi-componentrefrigerants with these chemical characteristics exhibit little compositional change even from phase changesdue to vaporization 9or condensation), which means that there is little change in the circulating refrigerantcomposition 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 liquidphase inside a cylinder or other container, charging should basically begin with the liquid side.c. Pressure characteristicsAs seen in Table 2, the gas pressure of R410A is approximately 1.6 times as high as that of R22 at the samerefrigerant temperature, which means that special R410A tools and materials with high-pressure specificationsmust be used for all refrigerant piping work and servicing.Table 2 Comparison of R410A and R22 saturated vapor densityR410A0.300.701.352.303.734.15R220.140.400.811.422.332.60Refrigerant Temperature( )-20020406065°C39CS-PW9DKE / CU-PW9DKE / CS-PW12DKE / CU-PW12DKE