In direct expansion (DX) air conditioning, comfort cooling and heat pumps, HCFCs (R22) refrigerants are being replaced by HFCs (R407C and others). The reasons are predominantly for that of direct emissions to the atmosphere and not efficiency, which is the greater contributor to global warming.
Equipment manufacturers have made changes to improve refrigerant containment and system efficiency, but the emphasis from the policy makers remains with the global warming potential (GWP) of refrigerant and in their opinion "HFCs are not a sustainable technology in the long term" due to their GWP. Whether we agree or disagree, they have a point and if available we should take a greener alternative.
Whilst HFCs are a step in the right direction with zero ozone depletion, there is another option available, when the application is suitable, hydrocarbon (HC) refrigerant, a group of natural substances who's benefits combine efficiency with zero ozone depletion and negligible GWP. The issue with HCs is their flammability, although the industry is no stranger to flammable gas for direct and indirect heating, as with any new concept we must engineer systems with additional safety to overcome any concerns of potential users.
Systems requiring full fresh air ventilation with cooling or heat pump where the unit is complete with an integral refrigeration system, is one example where there is a possibility of operating with HC refrigerant. For safe operation there is a maximum concentration level per unit volume of room space, should the refrigerant leak into the occupied zone. Correct design ensures that this concentration will not be exceeded for systems providing fresh air at room temperature (tempered air) or when serving large areas such as function rooms, call centres where full fresh air ventilation is selected over recirculation, due to the number of occupants. The air handling equipment will require certain modifications resulting in an additional cost over standard R407C units of approximately 5% initially, but anticipate a negligible increase with larger scale production.
With the possibility of some future refrigerant supply shortages, it may be time to consider if some applications provide the opportunity of selecting equipment engineered suitable for operation with a flammable refrigerant, which comes complete with environmental advantages.
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