Construction World May 2017

PHASING OUT Hydro chlorofluorocarbon The Montreal Protocol of 1987 and its amend- ments on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion.

Hydro carbons (R600) and (R290) are being looked at for small refrigeration units. These refrigerants are highly flammable and need special handling skills. Methylene Fluoride (R32) is being considered for use in room and packaged air conditioners. It is classified mildly flammable. HFO 1234yf and it family of refrigerants are used in car air conditioning and Chillers but it is mildly flammable but has energy efficiency advantages. With packaged air conditioning units the refrigerant charge with HC and HFO may be too large. CO 2 systems will become more common for supermarket and cold room refrigeration, but R410a and R417 will be in use for some time until the Department of Environmental Affairs starts a phase out for HFC refrigerants as is being done in first world countries. Refrigerants are classified on the basis of ASHRAE standard 34. Refrigerants are the gasses that are the compounds that make the refrigeration work. They are classified by reference numbers, safety classes and limits on concentration in parts per million for permissible exposure levels or occupation exposure levels. The refrigeration process provides the motion of the gas from a low temperature and pressure to a high temperature and pressure and condensation to a liquid in the condenser. 

The two ozone treaties have been ratified by 197 parties, which includes 196 states and the European Union, making them the first universally ratified treaties in United Nations history. The Protocol is structured around several groups of Ozone Depleting (ODS) and Global Warming Potential (GWP) substances that are classified according to chemical families. For each group there is a timetable for the phasing out of the production and consumption of the substances with the aim to eliminate them completely The phasing out process for HCFC’s was gazetted in South Africa in 2014 when all the country had to phase out R22 (HCFCs). By 2030 use must be down to 2,5% of the 2013 baseline The change in the refrigerants are placing a great burden of responsibility on the refrigeration practitioners as the mechanics have to change to the new refrigerants not being as easy to use as the older R12 and R22. The skills of the installing mechanics will have to be improved in order to handle the new gasses as not everyone knows how the gasses will react in the long run How phase-out of HFC refrigerants, e.g. R134a and R410a impact on the equipment currently being installed will be next on the plan being proposed by the Department of Environmental Affairs. Natural refrigerants are coming into favour like Carbon Dioxide known as R744 is being used in supermarkets. Some systems use CO 2 as a secondary refrigerant in a 2 stage cascade system. Ammonia R717 is sometimes used as the primary refrigerant. Some people consider that these systems are easier to use, but new skills are needed for installation and maintenance.

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CONSTRUCTION WORLD MAY 2017