R290 (Propane) as alternative refrigerant
R290 (propane) can also be used as a substitute refrigerant. Being an organic compound (hydrocarbon), it has no ozone depletion potential and a negligible direct global warming effect. To take into consideration however, is a certain contribution to summer smog.
Pressure levels and refrigerating capacity are similar to R22, and its temperature behaviour is as favourable as with R134a.
There are no particular problems with materials. In contrast to NH3, copper materials are suitable as well, so that it can be used in semi-hermetic and hermetic compressors. Common mineral oils of HCFC systems can be used here as a lubricant over a wide application range. Polyol esters (POE) and polyalpha olefins (PAO) offer even more favorable properties.
Refrigeration plants with R290 have been in operation world-wide for many years, mainly in industry – it is a "proven" refrigerant.
Meanwhile R290 is also used in smaller compact systems with low refrigerant charges like residential air-conditioning units and heat pumps. Furthermore, a rising trend can be observed in its use with commercial refrigeration systems and chillers.
Propane is offered also as a mixture with isobutane (R600a) or ethane (R170), in order to provide a performance similar to halocarbon refrigerants. Pure isobutane is mostly intended as a substitute for R12 in small systems (preferably domestic refrigerators and freezers).
The disadvantage of hydrocarbons is their high flammability, therefore they are classified as refrigerants of safety group A3. Based on the refrigerant charges commonly used in commercial systems, the system design and risk analysis must be in accordance with explosion protection regulations.
Semi-hermetic compressors in so-called "hermetically sealed" systems are in this case subject to regulations for hazardous zone 2 (only seldom and short term risk). Safety demands include special devices to protect against excess pressures and special arrangements for the electrical system. In addition, measures are required to ensure hazard free ventilation to effectively prevent a flammable gas mixture in case of refrigerant leakage.
Design requirements are defined by standards (e.g. EN378) and may vary in different countries. For systems applied in the EU, an assessment according to EC Directive 94/9/EC (ATEX) may become necessary as well. With open compressors, this will possibly lead to a classification in zone 1 ‒ which demands, however, electrical equipment in special flame-proof design.
