Analysis of R134a Cabinets from the First Series Production in 1990

Series production of R134a compressors started in 1990. 200 compressors, from the very first series, were built into cabinets placed in an apartment house in Denmark. Cabinets with R12 compressors were placed in the same apartment house as well. The cabinets have two separate cooling systems; one for a cold cabinet and one for a freezer. 10 running cabinets were called back for analysis; 7 cabinets with R134a compressors and 3 cabinets with R12 compressors. Analysis of the cabinets comprises both the refrigeration systems and the compressor from each system. From the refrigeration system the refrigerant, the filter dryer and the capillary tube are analysed; the refrigerant is verified on composition, the filter dryer on water-uptake and the capillary tube is examined for flow rate changes. Further the amount and composition of deposited material are determined . The performance of the compressor is verified. After disassembling the compressor, the refrigeration oil is analysed and the mechanical parts are evaluated. The overall conclusion is that the reliability of R134a and R12 cabinets is equal. INTRODUCTION In the years 1988-1989 the European compressor manufacturers were facing a major challenge from the market: a redesign of the compressors for R12 to R134a as fast as possible. Many problems, which are today considered trivial, had to be solved by the pioneers in this development, e.g. finding a substitute for mineral oils, establishing new guidelines for compressor cleanness etc. For the involved companies and persons it was a very exciting period of time, during which most of the well-known hermetic chemistry for R12 systems had to be scrapped. After a hectic period of development it was possible to produce the first series of compressors for R134a in 1990. In this paper some of these are analysed after 5 years of life time. DESCRIPTION OF CABINETS Each cabinet comprises two separate refrigeration systems, one for the cold cabinet and one for the freezer. The volumes of the cold cabinet and the freezer are 197 I and 89 I, respectively. The cold cabinet is equipped with automatic defrosting. The displacement of the compressors used in the R134a cabinets for the cold cabinet and the freezer, respectively, was 4 cm (TL4F) for both. For the R12 cabinets a 2.5 cm (Tl2.5A) compressor was used for the cold cabinet and a 3 cm (TL3A) compressor was used for the freezer. ANALYSIS OF THE REFRIGERATION SYSTEM Filter dryer Each refrigeration system is equipped with a pencil dryer filled with approximately 7.5g of XH? molecular sieve beads. After dismounting of the filter dryers they were placed in an oven at 190°C for 50h to determine the total water-uptake, which was found as the difference in weight before and after the reactivation. The refrigerant was removed with dry nitrogen before the first weighing. Using this method a level of water-uptake is achieved. It should be noted that the condition for the pencil dryers from the beginning is not known. The average water-uptake for the R 134a and R 12 systems is shown below: Average water-uptake, system I R134a system, n = 14 0.194g r R12 system, n = 6 0.117g Table 1. Average water-uptake in filter dryers from cabinets.