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764 CHAPTER 47 1965 Guide And Data Book stability more easily. This test requires either pre-heating of the air to a relatively high temperature, or in the case ofan' air-cooled unit, that the air leaving the condenser be used for the evaporator. The second arrangement is ample and in expensive, but may cause wide variation in performance if the system is not controlled carefully. The primary function of the factory performance test is to' assure that a unit is constructed and assembled properly.- Therefore, all equipment must be compared to a standard unit. Normal causes of malfunction in a complete refrigera tion system are overcharging, undercharging, presence of noncondensable gases in the system, blocked capillaries or tubes, and excessive power. To determine the validity and' sensitivity of any test procedure, the best approach is to use' a unit with known characteristics, and then to establish limits for deviations from the test standard. If the established - limits for charging are 1 ounce of refrigerant, for example, the test unit is charged first with the correct amount of re frigerant, and then with one ounce more and one ounce less.' If tins procedure does not establish clearly defined limits, it cannot be considered satisfactory. This procedure should' be followed with regard to all variables which influence per formance and result in deviations from established limits.' Once more it must be emphasised that all equipment must be: carefully maintained and calibrated if tests are to have any., significance. Gages must be checked at regular intervals'ana protected from vibration. Capillary test lines must be kept clean and free of contamination. Power leads must be kept- in good repair to eliminate high-resistance connection, and; electrical meters must be calibrated and protected if consistent data are to be secured. ' In plants where testing of components and manufacturing control have been perfected to such a degree that the average, unit may be expected to perform satisfactorily, units are: tested only long enough to find major flaws. Complete testing, of some units from tima to time assures product reliability. This approach is sound and economical, because complete' testing of all units greatly taxes power and plant capacity.. - When the evaporator load is static, as in the case of re- ' frigerators or freezers, time, temperature, and power meas urements can be utilized to measure performance. The time- elapsed between start and first compressor shut-off, or the, average on-andoff period during a predetermined number`of cycles in either a controlled or known ambient temperature, can be used to determine performance. Also, suction and dis charge temperatures in connection with power readings are' used to establish conformity to standard. On units where the' necessary connections are available, pressure readings may be taken. Such readings, however, are usually possible only on units where loss of refrigerant is not critical, because gages can hardly be connected and Htfinonnertad without some loss of refrigerant. In factory performance testing, plus or minus ten percent deviation from rated capacity, and from ten' to fifteen percent' from rated power are accepted. This takes into consideration both deviations due to the test method used and the normal system variance. Results under calorimeter measurement should vary less than five percent for a well designed unit. Testing of Components Testing of components used in refrigeration systems must be based upon a thorough understanding of use and purpose of the component. Pressure switches are calibrated and adjusted with air in a bench test, and need'not be checked again, if there is no Hangr of blocked passages or pull-down trip-out during the operation of the switch. However, if the switch-is brazed into the final assembly, precautions are needed to pre-. vent blocking of the switch capillary. Capillaries used in refrigeration systems are checked by air testing. When the capillary limits are known it is relatively easy to establish a flow rate and pressure drop test for elimi-. nating crimped or improperly sized tubing. When several capillaries are used in a distributor, a series of water manome ters are used to check for unbalanced flow and to find dam aged or incorrectly sized tubes. In plants having good manufacturing control, only sample- testing of evaporators and condensers is necessary.' Close control of coils during manufacture will lead to the detection of improper expansion, poor bonding, split fins, or uneven spacing. Proper inspection, therefore, will often eliminate the need for costly test equipment. In testing the sample, either a complete evaporator or condenser, or a section of the heat transfer surface is tested. Since liquid-to-liquid furnishes the most easily *nd accurately measurable heat transfer medium, a tube or coil can be tested by passing water through it while it is immersed in a bath of water. The temperature of the bath is kept constant, and capacity found by measuring the coil flow rate and the temperature differential between water entering and leaving the coiL REFERENCES 1 M. B. Goddard: Moisture in Freon refrigerating systems (Refrigerating Engineering, September 1945, p. 215). * L. W. Lareen and J. Elliot: Factory methods for dehydrating refrigeration compressors (Refrigerating Engineering, De cember 1953, p. 1325). * H. A. Blair and J. Calhoun: Evacuation and dehydration of field installations (Refrigerating Engineering, August 1946, p. 125). 4 Private communication to ASRE from R. R. Pickett. * E. W. McGovern (Refrigeration Service Engineering, VoL 7, No. 3, 1939, p. 23). * W. B. Anderson: Domestic refrigerating units---their manu facture and testing (Refrigerating Engineering, May 1941,' p. 323). T W. P. Griest: Notes on moisture determination in refrigerant (Refrigerating Engineering, May 1941, p. 316). * A. M. Fenwick: Paper presented at 1940 meeting of Refrigera tion Service Engineers Society. I H. L. Flenner and W. R. Calverly: The determination of moisture in liquid sulfur dioxide (Refrigerating Engineering, May 1931, p.344). i* R. H. Dinsmoor (Refrigeration Service Engineering, VoL 7, No. 8,1939, p. 34). u W. A. Pennington (Analytical Chemistry, No. 21, 1941, p. 766). u Standard Methods of Rating and Testing High-Side Liquid Line Driers (ASHRAE Standard 35B-1656). u F. T. Reed: Moisture determination in refrigerant oil solu tions by the Karl Fischer method (Refrigerating Engineering, July 1954, p. 65). 14 Methods of Testing Electrical Insulating Oils (ASTM Specifi cation D 117-58). u J. D. Morton and L. K. Fuchs: Determination of moisture in fluorocarbons (ASHRAE Transactions, VoL 66, 1960, p. 434). " A. F. Banning, A. A. Ebert, and C. F. Irwin: Water determi nation in Freon-12 by infra-red spectrometry (Refrigerating Engineering, February 1948, p. 166). II R. A. Gray: Improved method to test desiccants, driers use drier refrigerant in recirculating unit (Air Conditioning and Re frigeration News, November 11, 1957). 14 E. S. Taylor: New instrument for moisture analysis of "Freon'' fluormated hydrocarbons (Refrigerating Engineer ing, July 1956, p. 41). 11W. R. Brisken: Moisture migration in hermetic refrigeration systems (Refrigerating Engineering, July 1955, p. 42). ** EL R. Weaver and R. Riley (National Bureau of Standards Research Paper RP1865, 1948, p. 40). CHAPTER 48 CONTAMINANT CONTROL IN REFRIGERANT SYSTEMS Contaminants: Moisture; Copper Plating; Residual Solvent; Metallic Contaminants, Flux, and Dirt; Nonconcfensobfe Gases; Anti freeze Agents; Design and Operating Conditions; High and Low Temperatures; Field Assembly; Materials in Systems: Experimental Methods for Evaluation; Refrigerants; lubricant*; Hermetic Motor Insulation; Driers THE contaminants in a refrigerant system include not Copper Plating only dirt and moisture which may- remain after manu facture and installation but also acid, sludge, and other prod The formation of a film of metallic copper on mpfrAHic sur ucts of the chemical reactions which take place while the sys faces in refrigeration compressors is known as copper plating tem is operating. In some cases, the copper deposit may become heavy enough This chapter will diarawai the various contaminants, the to interfere with the operation of the compressor and, in ex effect of design and operating conditions, and the charac treme cases, lead to failure. The causes and mechanism of teristics and limitations of various materials used in re copper plating have been studied***'4-* and explained in frigerant systems. general terms, although the reactions are complex and com Hie major factors in the formation of contaminants in a plete details are lacking. refrigerant system during operation are: (1) the damgn and op It is apparent that copper plating takes place in two steps. erating conditions, and (2) the system components and ma First, copper must be dissolved in the oiL Then, in a separate terials. An improper combination of these two factors gen reaction, it must be precipitated or plated from the solution. erally is the cause of contaminant problems. Some factors which affect these two steps are listed in Table 1. Because many of the problems involved have complicated The most important factor in dissolving copper is the inter-relationships which cannot be studied in the-laboratory, quality of the oil, but there is at present no universal agree some problems found in actual systems cannot be explained ment on how to measure the quality of the oil. Steinle4** has completely on the basis of laboratory tests. However, there shown a direct correlation between the composition of the oil has been increasing interest in and investigation of the prob and its ability to dissolve copper. He concluded that an oil lems caused by various contaminants in refrigerant systems.1 wiQ not cause copper plating if it meets the following tests: oleoresin content below 0.3 percent, sulfur content below 0.2 CONTAMINANTS percent, aniline point above 212 F, and a Philipp-Tiffaay test of at least 96 hr. Oleoresin is a term used by Steinle for a Contaminants are those substances present in the refriger ating system which do not serve any useful function in the proper operation of the equipment. They originate as re siduals from manufacturing processes, assembly, and installa tion, or from the malfunction of the,equipment itself. Some contaminants, such as moisture, are always present. Others are formed when adverse operating conditions are imposed on the equipment or from reactions caused by an improper dunce of components. Generally, they are present in small, quantities which do not adversely; affect operating charac teristics. Equipment manufacturers generally extreme care to remove, or avoid the formation of, undesirable sub stances (see Chapter 47). When equipment is properly engi- nerd, processed, and maintained, contaminants are kept' st a low level. It must be recognized, however, that in mass production processes a small quantity of substandard equip ment may be produced in spite of rigid quality controL If manufacturing processes go out of control or if recognized practices for assembly and maintenance are not followed, contaminants can remain or form, in quantities that may *6sd to eventual equipment failure. portion of a lubricating oil that > be removed from the oil by chromatographic separation because of its more polar' nature compared with the bulk of the ofl. It is interesting to note that Kvalnes and Pannelee did not find direct relation ship between any one of these ehemleal characteristics refrigerant breakdown in sealed-tube tests* Divers7 found good correlation between: (1) the Modified Continental Oxidation Test, (2) a simple copper plating pro clivity test using carbon tetrachloride with the sample oil, and (3) many years of service experience. Steinle* and McGovern* have shown that when copper is dissolved by lubricating oil, it is present as an organic copper compound and is not soluble in water. Steinle isolated such a compound and determined its composition. The copper is as sociated with carbon, oxygen, and sulfur, indii-aiing that it is dissolved by the polar or oleoresin constituents in the oiL The low incidence of copper plating in modern equipment due primarily to the improved quality of available lubricating oils. The presence of oxygen contributes to the solubility of copper by reacting with the oil to form additional polar com pounds which have an effect similar to the oleoresins which Moisture may already be present. This is one reason why air should be Water or moisture is always present in refrigerating equip ment. Hie control of moisture in refrigerant systems is discussed in Chapters 47 and 49. removed from refrigeration equipment. The rate of solution of copper, by lubricating oDs is con siderably increased at higW temperatures! McGovern* _ found that more than 40 times as much copper was dissolved at 200 F as at 75 F in a one-month test. However, the tempera^ ture is more difficult to control than the other factors affecting 765