On substances that deplete the ozone layer
Options for existing equipment
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- 7.4.1 Replacement refrigerants only
- 7.4.2 Retrofit refrigerants
- 7.4.3 Conversion to flammable refrigerants
7.4 Options for existing equipmentAs the HCFC phase-out proceeds in non-Article 5 or Article 5 countries, there remains a need to service the installed population of products until the end of their useful lives. When servicing these products the treatment of refrigerant can fall into the following categories:
Most of these categories are likely to be important for Article 5 countries because systems are often repaired several times in order to extend their useful lives. There are a large number of Low Volume Consuming (LVC) countries, which import rather than manufacture air-conditioners where most of the HCFC consumption is used to service the installed base of air-conditioners. In these countries, HCFC consumption can be reduced by the use of service refrigerants or by retrofitting existing equipment to non-ODP refrigerants. An additional less desirable option because of cost would be to replace the existing equipment before the end of its useful life. In non-Article 5 countries, unit replacement is more common because the costs associated with performing a major repair or retrofit can often be greater than the cost to replace the product. The need for retrofit and replacement refrigerants will largely be determined by the size of the installed population of HCFC-22 products, HCFC phase-out schedule, allowed “service tail”3, the availability of HCFC-22 and the recovery and reclaim practices in place leading up to the phase-out. The installed population of air conditioners and heat pumps has an average service life in non-Article 5 countries of 15 to 20 years and may be longer in Article 5 countries. Therefore, implementing recovery and reclaim programmes coupled with the availability of replacement and retrofit refrigerants could help reduce the demand for HCFC-22. 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 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”. 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. 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. 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.
Although not conventionally used for air conditioners, Bolaji (2011) compared R-404A and R-507A against HCFC-22 in a window air conditioner. The average refrigeration capacities of R-507A and R-404A were 4.7% higher and 8.4% lower than that of HCFC-22, respectively, while the average COP were increased by 10.6% and reduced by 16.0%. 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 selection of the many commercially available HCFC-22 replacement blends is listed in Table 7-2. Compressor and system manufacturers often carry out evaluations of such refrigerant options and provide recommendations as to which they believe are suitable for use in their equipment. Information on the application of these blends can be obtained from manufacturers. It may also be recognised that since some HCFC-22 compressors are now supplied with POE oils, R-407C or similar HFCs could in principle be used as a direct replacement. There are a number of criteria that should be achieved in order for a replacement only refrigerant to be selected and these are discussed in Chapter 2.
Whilst many of the proposed blends are seldom used, R-407C has been demonstrated to be an acceptable retrofit refrigerant and has seen widespread use in some regions. This is especially the case in regions with high ambient temperatures as the capacity drop at elevated temperatures is relatively lower than that of R-410A, although there is some loss in capacity and efficiency compared to HCFC 22. Devotta et al. (2005a) found a 2-8% drop in capacity and 8-14% increase in COP when a window type HCFC-22 air conditioner was retrofitted with R-407C. Conversely, a drop of about 7% in COP was observed by Raghavan and Pss (2010). Gopalnarayanan and Rolotti (2000) tested a reversible split system in both cooling and heating mode and found that in cooling mode R-407C capacity matched that of HCFC-22 and there was a marginal increase in COP when the oil was changed from a mineral to a POE oil. However, in heating mode, there was a capacity and COP drop of less than 5%. Fathouh et al. (2010) found that the cooling capacity and COP was around 8% and 6% lower, respectively for R-407C. Judge et al (1995) tested two different units and showed that in one, the cooling capacity was marginally lower than HCFC-22 with 10% loss in COP, whereas in another unit there was a marginal increase in capacity and a 5% drop in COP. As indicated, provided that the compressor already uses a mineral oil, a change from HCFC-22 to R-407C requires that the existing naphthenic mineral oil or alkyl benzene synthetic oil lubricant be replaced and filter driers that are able to absorb breakdown products from synthetic lubricants should also be installed. The disadvantage of using high glide blends is the need to remove and replace the entire charge during servicing to avoid substantial composition shift. However, because R-407C has a moderate glide, laboratory and field experience indicates R-407C can be serviced without replacing the entire refrigerant charge with minimal impact on performance. The other HFC blends will tend to have similar practical implications as R-407C. The criteria for selecting a suitable retrofit refrigerant are discussed in section Chapter 2. 7.4.3 Conversion to flammable refrigerantsHC refrigerants such as HC-290, HC-1270 and blends including these as well as HC-170 and R-E170 (e.g., R-433A, R-433B, R-433C, R-441A and R-443A) are being used as conversion replacements for HCFC-22 in some regions, typically in small systems (such as window and single splits). Some countries are including this approach in their HCFC phase-out strategies, whilst the practice is not legal in other countries (such as in USA). While these refrigerants may provide capacity and efficiency close to HCFC-22 (see examples in section 7.3), this practice can create a significant safety hazard because of the flammability of these refrigerants. In general, HCs are not recommended for use in systems that have not been specifically designed appropriately. If HCs are being considered then the applicable safety standards and codes of practice should be strictly followed. The GIZ Handbook for Hydrocarbon Safety (GIZ, 2010) is one source of information on the utilisation of these refrigerants. In addition to the above, there are also some other mixtures with class 3 flammability being marketed, which in addition to HCs also comprise R-E170 (dimethyl ether) and HFC-152a. For example, Park et al. (2009a) measured performance of R-431A and HCFC-22 under air-conditioning and heat pumping conditions. Results showed that the COP of R-431A is 4% higher than that of HCFC-22 while the capacity of R-431A is similar under both conditions. Comparing the performance of R-432A and HCFC-22, Park et al. (2009b) showed that the COP and capacity of R-432A are 9% and 2 – 6% higher for both conditions. Directory: meeting meeting -> Program description meeting -> Iea shcp/pvps working Group on pv/t solar Systems meeting -> Office of the collector: jagatsinghpur (st & sc development Section) meeting -> World meteorological organization meeting -> WG/hwsor action item summary (Current as of 28 Feb 2013) meeting -> Review of the past hurricane season meeting -> Review of the past hurricane season reports of hurricanes, tropical storms, tropical disturbances and related flooding during meeting -> Town of seabrook island meeting -> World meteorological organization Download 1.63 Mb. Share with your friends:
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