THE CHEMISTRY OF AIR CONDITIONING
Refrigerants Terminology;
MCE
The MCE, short for Maximum Cycle Efficiency, is the maximum efficiency that can be achieved when using the particular refrigerant for heat transfer. It determines how well the heat exchanger will work in the building.
ODP
The ODP, short for Ozone Depletion Potential, is the measurement of how destructive the coolant is to the Ozone layer. It uses refrigerant R11 as a calibration with an ODP of 1.0.
The lower the ODP the better the refrigerant is for the Environment & the Ozone Layer.
GWP
The GWP, short for Global Warming Potential, is the measurement of how bad the refrigerant is for the environment, with regard to Carbon Dioxide and Global warming. This is calculated over a hundred year period. The lower the value the better.
Refrigerant Chemistry
R404A
Is a blend of hydro fluorocarbon (HFC) compounds
(44% = R125, 52% = R143a, 4% = R134a) It has no chlorine content, no ODP, but a high GWP. Maximum cycle efficiency = 75.7%, ODP = 0.0, GWP = 3750
R11
Is a Chlorofluorocarbon (CFC) compound with a high chlorine content and ODP and highGWP Maximum cycle efficiency = 90.5%, ODP = 1.0, GWP = 4000
R22
Is a Hydro chlorofluorocarbon (HCFC) compound with a low chlorine content and ozone depletion potential and a medium direct GWPl. Maximum cycle efficiency = 83.3%, ODP= 0.05, GWP = 1700
R134a
Is a Hydro fluorocarbon (HFC) compound with no chlorine content, no ODP, and a medium GWP. MCE = 83.5%, ODP = 0.0, GWP = 1300
R407C
Is a blend of hydro fluorocarbon (HFC) compounds (23% = R32, 25% = R125, 52% =R134a). It has no chlorine content, no ODP, and only a modest DGW potential. MCE = 80.41%, ODP = 0.0, GWP = 1610
R410A
Is a blend of hydro fluorocarbon (HFC) compounds (50% = R32, 50% = R125) It has no chlorine content, no ODP, and only a modest GWP. MCE 76.3%, ODP = 0.0, GWP1890.
Refrigerant Legislation
Current EU guidelines for the use of different refrigerant chemicals are as follows;
R11
The EU has banned the sale of all new and recycled CFC refrigerants within the EU from 31 December 1999. For maintenance and servicing there is a proposed ban on CFC refrigerants within the EU from 31 December 2000. This will apply to virgin, recovered, recycled and reclaimed refrigerant.
R22
Proposed ban on use in new cooling systems (>100kW) from 2001. Ban on use in all new cooling systems from 2003. Ban on use in new heat pumps from 2004. From 2010 only recycled and reclaimed refrigerant will be permitted for service.
R134a There are no current restrictions on use of this refrigerant
R404A There are no current restrictions on use of this refrigerant
R407C There are no current restrictions on use of this refrigerant
R410A There are no current restrictions on use of this refrigerant
Refrigerant Suitability
R11 The low pressures and high volume characteristics of this refrigerant make it suitable for centrifugal coolers. It is still found in many coolers installed from 1970 on.
R22 Still the most widely used refrigerant.
Its high pressures and low volumes make it particularly suited to positive displacement compressors. It has a wide range of possible applications because of its high critical temperature. Excellent performance in heat pumps and suits all heat exchanger types.
R134a Its low pressures / high volume characteristics make R134a most suited to centrifugal and high speed compressors, its high critical temperature allows a wide application range and gives good performance in heat pumps and so suits all types of heat exchangers.
R404A The high pressures / low volume flows of this refrigerant suits positive displacement compressors.Best used in heat exchangers because of its low critical temperature.
R407C The high critical temperature and high pressures / low volume flows of this refrigerant suit positive displacement compressors and allows a wide application range. It requires counterflow heat exchangers to minimise effect of glide and thereby yield optimum performance.
R410A Very high pressures / low volume flows, low critical temperatures.
Suits positive displacement compressors, limited application range. Suits all heat exchanger types. Very high operating pressures restricts applications to small units and systems of less than 100KW.
