RACA Journal August 2020 | Page 20

Feature COMPRESSORS AND THEIR CONTINUAL DEVELOPMENT By Ntsako Khosa Compressors play a crucial role in ensuring an HVAC unit works effectively. An air conditioner compressor is used to remove the heat-laden vapour refrigerant from the evaporator of the air conditioning system. In laymen's terms, the compressor compresses or squeezes the vapour into a smaller volume at a higher temperature. The external-drive compressor has a crankshaft that is driven by a pulley and belt system. An electric motor can also be used to drive it directly. The hermetic compressor has a motor which is sealed inside a housing with the compressor, hence a crankshaft seal is not required. The motor rotor is located either at the top or bottom of the unit. “Selecting the correct compressor for an application will depend entirely on the design application criteria, however, the type of compressor may vary between residential, commercial and industrial applications,” says Alistair Bell, Technical Sales Engineer at Danfoss. There are five types of air conditioner compressor that are commonly used in the HVAC industry as Bell explains: • Reciprocating: The most commonly used can be used in appliances, residential A/C, light commercial A/C, commercial A/C, refrigeration, and industrial applications • Rotary: Can be used in appliances and residential A/C units. • Scroll: Can be used in residential, light commercial A/C, commercial A/C, and refrigeration applications. • Screw: Can be used in commercial A/C, refrigeration, and industrial applications. • Centrifugal: Can be used in commercial A/C systems. “Compressor technology has undergone significant developments in the last hundred years. Almost all the compressors mentioned in this article have reached a high level of perfection. Today, different compressors are available for different applications, starting from small hermetic reciprocating and rotary compressors for domestic refrigerators to very large screw and centrifugal compressors for huge industrial and commercial refrigeration and air conditioning applications. If all your data is in line with the manufacturer’s specifications, your compressor runs well. IMD 18 RACA Journal I August 2020 www.hvacronline.co.za