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7.2.5 Ducted commercial packaged (self-contained) air conditioners Ducted commercial packaged air conditioners and heat pumps (“rooftop” units) are single self- contained units, which comprise an integral fan and heat exchanger assembly which is connected by means of ducting to the air distribution system of the commercial structure; see Figure 7-11. The other part of the package is the condensing unit, normally with an air cooled condenser and compressors, which are often hermetic scrolls, although hermetic and semi-hermetic reciprocating and screw machines are sometimes employed. The majority of ducted commercial packaged air conditioners and heat pumps are mounted on the roof or outside on the ground of offices, shops, restaurants or institutional facilities. In some GCC countries, units are installed on the roof of large single home residences providing easy access for service without going into the living space. Multiple units containing one or more compressors are often used to condition the enclosed space of low-rise shopping centres, shops, schools or other moderate size commercial structures. They are offered in a wide range of capacities from around 7 kW to over 700 kW and have specific refrigerant charges of around 0.3 to 0.5 kg per kW of cooling capacity. Most ducted systems historically used HCFC-22, whilst in non-A 5 countries R-410A is mainly used and to a lesser extent R-407C, which is used more frequently in regions with higher ambient conditions and R-744 is offered in some Northern European countries. Annual market is currently about 1 million units (Gloёl et al, 2014; JRAIA, 2015), with about one-third in Article 5 and two-thirds in non-Article 5 countries. The estimated installed population is around 20 million. Figure 7-11: Example of ducted commercial packaged unit 7.3 Options for new equipment As discussed in Chapter 2, there are several factors that should be considered when selecting an alternative refrigerant. Accordingly, this section provides a summary of the most viable HCFC-22 replacement candidates for new air-conditioners, based on the current information available to the RTOC. Several single component HFC refrigerants have been investigated as replacements for HCFC-22, although previously, HFC-134a was the only single component HFC that has been commercially used in air conditioning systems to a limited extent. Air conditioners have become available with HC-290 and HFC-32 as single component refrigerants. A number of HFC blends have also emerged as replacements for HCFC-22 in air conditioning systems. Various compositions of HFC-32, HFC-125, HFC-134a, HFC-1234yf and HFC-1234ze are being offered as non-ODS replacements for HCFC-22. The two most widely used HFC blends to replace HCFC-22 are R- 407C and R-410A. However, both R-407C and R-410A have GWPs close to that of HCFC-22 (Table 2-7 and 2-8) and are therefore considered to be too high for long-term use under the Kigali Amendment. 138 2018 TOC Refrigeration, A/C and Heat Pumps Assessment ReportPDF Image | Heat Pumps Technical Options
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