REFRIGERANTSGeneralThere is a wide variety of refrigerants used in air conditioning equipment depending on the application. In general the most common refrigerants used in the industry belong to the following three categories - CFC - These are the Chloro Fluoro Carbon refrigerants, such as R, R!, R", R#, etc. These refrigerants were identified as the most harmful to $%one layer by the &ontreal 'rotocol, and werephased out in !(((. )owever they are still being used in the older machines, with precautions to minimi%e release in accordance with *'+ regulations. The most common application of these refrigerant is in the large centrifugal chillers. R! was also used commonly in the older cars for air condition. )CFC - These are the )ydro Chloro Fluoro Carbon refrigerants, such as R!!, R!", etc. These refrigerants were identified as slightly harmful to the $%one layer by &ontreal 'rotocol, and will be completely phased out by !("(. ,ee the *'+ lin- below for the different stages of the phaseout. The R!! refrigerant is commonly used in reciprocating type of compressors, while R!" is used in centrifugal chillers as a temporary replacement for R. )FC - These are the )ydro Fluoro Carbon refrigerants, such as R"#a. These are the new refrigerants that do not harm the $%one layer, and are being used in the newer machines to replace the CFC and )CFC. R"#a is now commonly used as a replacement of R! and R.((, and in all new cars air conditioning systems. R#(/c is used as a replacement for R!!. $ne of the other common )FC used in new equipment now is R#(a.There is e0tensive research going on to identify new refrigerants that can be used to replace the CFC and )CFC refrigerants. Currently R"#a is the most commonly used new refrigerant. The various refrigerants have different characteristics, which ma-e them suitable for a particular application.Following lin- provides more useful information on *'+ regulations for refrigerants -Refrigerant Analysis+ periodic refrigerant analysis is important to detect and control contaminants in the refrigerant, which can result in degradation 1 failure of the various components, and cause inefficient operation of the unit. + log of the periodic refrigerant analysis should be maintained for trending. Refrigerants should be tested for the following contaminants 2 &oisture +cid 'articulate1solids $rganic matter 2 sludge, wa0, tars 3on-condensable gasesMoisture -&oisture is one of the primary causes of contamination-related problems in a refrigeration system. It also results in formation of some of the other contaminants mentioned above, which in turn cause further damage to the chiller or 45 unit. 'resence of moisture results in following undesirable effects6 Ice formation in evaporator, e0pansion valve or orifice. 4egradation of lubricating oil due to hydrolysis. +cid formation due to hydrolysis of refrigerant in the presence of moisture andhigh temperature. Corrosion of metals. Copper platingThe copper plating phenomenon essentially involves carryover of copper ions from e0changer tubes to the steel surfaces. +lthough the e0act mechanism is not completely understood, it involves the followingthree steps, 7 o0idation of the copper due to contaminants such as air, moisture 8 acid, !7 solubili%ation and transport of copper ions by the lubricant, "7 deposition of the copper on hot clean steel surfaces such as bearings. *0cessive copper plating can result in a compressor failure. Typically copper plating is a concern in systems with high level of contaminants and high bearing temperatures.The most common causes for high moisture in the system are6 9ater lea-age in a chiller evaporator, or water cooled condenser. :ow pressure side lea- resulting in entrance of air carrying moisture ;typical problem innegative pressure machines7 Improper service procedures, i.e. system left open to atmosphere.In case of moisture introduction due to improper service procedures, the dryer will eventually reduce the moisture content resulting in a decreasing trend. If the trend is not decreasing then the li-ely reasons are the first two causes, which require shutting down the chiller for repair. If the chiller cannot be shutdown, it may be possible to temporarily provide on-line cleaning of the refrigerant to maintain the moisture within acceptable limits, depending on the si%e of the lea-. $nline cleaning is similar to a -idney function using a portable cleanup unit.&oisture is normally absorbed in the refrigerant or lubricant, but free-water can also be present. The solubility of water varies with different refrigerants. ;similar to R!7 R.((( ( - !.> ;similar to R!7 > R", R#, R"#a, R.(( data are not available in +,)R+*. +bove data is based on similarity with the other refrigerants ;R.(( is an a%eotrope of R! 8 R.!a7.Testing method for moisture is specified in +RI /((. ?ased on above discussion and operating e0perience, the acceptance criteria for moisture should be as follows6 Refrigerant3ormal+lertFault ppm by wt ppm by wtppm by wt R( - !( !( - "( @"( R!( - !( !( - !. @!. R!!( - "( "( - #( @#( R"( - !(!( - "(@"( R#( - !(!( - !.@!. R"#a( - !(!( - !.@!. R.((( - !(!( - !.@!.+lert :evel +ctions Increase frequency of sampling refrigerant to !0 ,ample lubricating oil with ne0t sample of refrigerant to chec- for any signs of degradation Chec- all potential causes of high moisture, and fi0 as required. Chec- moisture indicators rigorously. Chec- for any signs of lubricating oil degradation Change filter dryers1desiccants as requiredFault :evel +ctions Re-sample refrigerant to verify results Recycle and clean refrigerant on line Change all filter dryers1desiccants. If trend continues, schedule a shutdown of the chiller and fi0 lea-s.Acids+ refrigeration system can contain two types of acids, organic and inorganic, depending on the type of refrigerant and oil being used. $rganic acids ;such as oleic acid7 are formed as a result of decomposition of oil at high temperature in the presence of air as the o0idi%ing agent. These acids are slow to react, soluble in oil, do not vapori%e, and typically found in relatively small quantities in the oil sump. Inorganic acids ;such as hydrochloric acid and hydrofluoric acid7 are formed as a result of decomposition of refrigerants at high temperature in the presence of moisture. These acids are highly reactive, soluble in water, vapori%e, and typically found to be the dominant acids that may be present. Therefore, inorganic acids are the real problem in a refrigerant system, which results in degradation of the equipment internals. The maAor contributors to acid formation in a system are the presence of moisture and abnormally high temperatures around the compressor i.e. bearings, motor windings, terminations, compressor discharge etc. The presence of acids is specially ha%ardous in case of semi-hermetic and hermetic compressors, since the acid vapor in refrigerant goes over motor windings and can eventually lead to motor burnout. Therefore the amount of acids in a system should be -ept to an absolute minimum, and +RI /((specifications should be followed strictly, i.e., ma0imum allowable limit for acid in all refrigerants should beppm by weight.The acids in a refrigeration system can be -ept to a minimum by -eeping the refrigerant dry and preventing abnormally high temperatures in the system. 4esiccant used in a filter dryer may be capable of removing the acids, but the capacity and efficiency depends on several factors and is difficult to determine.Testing method for acids is as specified in +RI /((. ?ased on above discussion and operating e0perience, the acceptance criteria for acid should be as follows6 Refrigerant3ormal+lert Fault ppm by wt ppm by wt ppm by wt+ll( - (.B(.B - .(@(+lert :evel +ctions Increase frequency of sampling refrigerant to !0 Chec- all potential causes of high acid, and fi0 as required. Change filter dryers1desiccants as required.Fault :evel +ctions Re-sample refrigerant to verify results Recycle and clean refrigerant on line until acid concentration drops to acceptable level. Change all filter dryers and desiccants.Particulate/solids -The solid contaminants can include metallic particles, chemical compounds or Aust dirt. The solids found in a system normally result from wear, corrosion and chemical brea-down of the internals, or material left in the system during servicing. The solid contaminants can create problems such as scoring compressor cylinder walls and bearings, damaging motor insulation, plugging lubrication holes, plugging filter1dryers, plugging e0pansion valves etc. The solid contaminants are removed to a great e0tent by the filter dryer, but it needs to be si%ed to handle it without adding too much pressure drop in the system.Testing method for particulate1solids, and the acceptance criteria should be as specified in +RI/(( for all refrigerants. +ny visual presence of dirt, rust or other particulate contamination should be reported as alertcondition.If particulate1solids are found, the refrigerant filter should be replaced. If the problem persists in-spite of changing the filter several times, on-line cleaning of the refrigerant may be required.3ote6 ,ome labs will only give a pass or fail result of this test. If particulate1solids are found, it may be necessary to have the lab give additional details such as si%e, quantity, color and particle type to provide a better clue on the source.rganic matter ! sludge" #a$" tars$rganic contaminants are typically due to decomposition1degradation of organic materials in the system such as oil, insulation, varnish, gas-ets etc. These can circulate in the system and plug small orifices. $rganic contaminants dissolved in the liquid refrigerant may precipitate at lower temperature in the e0pansion device, resulting in plugged capillary tubes or stic-y e0pansion valves. $rganic contaminants can also coat heat transfer surfaces resulting in cooling inefficiency. ,ince heat degrades most organic materials, operating conditions with e0cessively high temperatures should be avoided. If an organic contaminant is dissolved in the liquid refrigerant, it may not be removed by the filter-dryer.Testing method for organic matter is specified in +RI /(( for )igh ?oiling Residue test.+RI specifies (.(C by volume of high boiling residue for most new or recycled refrigerants. )owever, this is not practical for operating machines due to miscibility of lubricating oils in refrigerants, i.e. oil carryover. ?ased on operating e0perience, the acceptance criteria for organic matter should be as follows6 Refrigerant 3ormal +lert Fault C by Dol. C by Dol.C by Dol. +ll( - (. (. - (.! @(.! +lert :evel +ctions Increase frequency of sampling refrigerant to !0 Change refrigerant filters as required.Fault :evel +ctions Re-sample refrigerant to verify results Recycle and clean refrigerant on line till levels drop to acceptable levels. Change all refrigerant filters.Non-condensa%le Gases -3on-condensable gases are chemically inert gases, which do not liquefy in the condenser. This contaminant typically results from incomplete evacuation, low side air in-lea-age, chemical reactions 8 decomposition of materials at high temperature.Typically the first two causes are the primary reasons for high non-condensable gases. These gases reduce cooling efficiency, cause high starting and running currents, and result in higher than normal compressor discharge pressure 8 temperature, which speeds up undesirable chemical reactions.Testing method for non-condensable gases is specified in +RI /((.The quantity of non-condensable gases that is harmful depends on the design and si%e of the refrigeration unit and the nature of the refrigerant. +RI /(( specifies a limit of ..C of non-condensable gases by volume for most new or recycled refrigerants, which is unrealistic to maintain continuously in an operating system, especially the negative pressure machines. ?ased on operating e0perience, the acceptance criteria for non-condensa%le gases should be as follows6 Refrigerant3ormal +lertFault C by Dol.C by Dol. C by Dol. +ll ( - .. - (@(+lert :evel +ctions Review operating parameters to confirm high non-condensable gases. Increase frequency of sampling refrigerant to !0 Chec- purge unit1dehydrator for proper operation Increase purge rate. Caution should be observed to avoid e0cessive loss of refrigerant due to purge unit inefficiency.Fault :evel +ctions Re-sample refrigerant to verify results If acceptable levels are not achieved, shutdown the machine and repair the lea-s or faulty purge operation, as applicable. If the machine cannot be shutdown, recycle and clean refrigerant on line until it reaches acceptable level.il AnalysisThe oil analysis provides a Eloo- insideF a compressor without disassembly. 9hen unacceptablewear conditions develop inside the compressor, a corresponding detectable change in the characteristics of theoil will become evident. The results from oil analysis should be used in conAunction with vibration analysis and bearing temperatures to detect e0cessive bearing wear. + log of the periodic oil analysis should be maintained to provide the trend.The oil sample should be tested for the following properties6 &etal wear &oisture +cidity Discosity ,olid residue&'A( )ESIGN;,ee additional information under the G4esign CalculationG and G4esign :in-sG buttons on the left7This ,ection provides a description of the design process, available design software, equipmentselection 8 si%ing guidelines, and typical systems used for )D+C.)esign Process -The basic design process involves various steps as follows - 4etermine the design parameters of the conditioned space - temperature, humidity, air quality, etc. Calculate the cooling loads" *eating loads" and air flo# re+uirements based on the above design parameters.H