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Using the existing refrigerant following a repair, one can follow normal practices using virgin, recycled or reclaimed refrigerant (i.e., typically HCFC-22). For refrigerant replacement only, HCFC-22 is replaced with a blend, but without changing the lubricant used in the original equipment or any other system component. Refrigerants used for this activity are sometimes referred to as “service blends” or “drop-ins” (see sections 7.4.1 and 7.4.2 below). Such a change in refrigerant in most cases results in a lower capacity and/or efficiency, different operating pressures, temperatures and compressor power compared to HCFC-22. Retrofit refers to not only changing the refrigerant, but also system components such as lubricant (although not always necessary), filter dryer (if required) and more extensive modifications which could include the replacement of the compressor, refrigerant, lubricant, dryer, expansion device, and purging and flushing the system to remove all residual lubricant from the system. Retrofitting can be substantially more costly than using existing refrigerant, replacing the refrigerant without additional changes or even unit replacement; it is probably not cost effective if either the compressor or heat exchangers have to be replaced. Conversion is where the existing refrigerant is replaced with another without necessarily having to address the refrigeration circuit components and lubricant in the same way as retrofit, but because the replacement refrigerant is flammable, the external aspects of the equipment, such as potential sources of ignition, have to be addressed. However, since this is a complex process and can lead to unforeseen safety risks, it is not normally recommended. Again, such a change in refrigerant can affect capacity and/or efficiency, operating pressures, temperatures, lubricity, etc., to HCFC equipment. In the case of refrigerant replacement and retrofit in HCFC systems, the GWP of the new should also be given consideration as many blends have a GWP higher than HCFC. In all cases, before changing the refrigerant it is recommended that the system manufacturer be consulted. 7.4.1 Replacement refrigerants only There are several refrigerants currently introduced to replace HCFC-22 for servicing. They generally combine two or more HFC refrigerants with a small amount of HC (or certain HFC refrigerants, such a HFC-227ea), which are added to the blend to enable the refrigerant to work with the naphthenic mineral-oil-based and alkyl benzene lubricants which were historically used in nearly all HCFC-22 air conditioning systems. Thus these refrigerants attempt to mimic the performance of HCFC-22. However, they seldom perform as well as HCFC-22; having either lower capacity, efficiency or both. Examples of findings from earlier studies are reported in (UNEP, 2015), whilst noting that in the majority of cases the studied alternatives were found to exhibit worse performance (cooling capacity and COP) than HCFC-22. In addition to the performance and efficiency impacts the blends may not perform the same for oil return. HCs are added to allow for the oil return, but it may not be as effective and problems could result at lower loads and extreme operating point seen during high ambient temperatures and heat pump operation. A non-exhaustive selection of the many commercially available HCFC- 22 replacement blends include R-417A, R-417B, R-422A, R-422B, R-422C, R-422D, R-424A, R-425A, R-428A, R-434A, R-438A and R-442A. Some compressor and manufacturers of larger systems carry out evaluations of selected refrigerant options and provide recommendations as to which they believe are suitable for use in the equipment, whilst in other cases manufacturers explicitly warn against such replacements. Information on the application of these blends can be obtained from manufacturers. 2018 TOC Refrigeration, A/C and Heat Pumps Assessment Report 147PDF Image | Heat Pumps Technical Options
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