We recently worked with a large supermarket retailer on looking at how to reduce their usage of R-22 in locations. Retrofitting a system to use different gas is done for a number of reasons: 

• The lack of availability of the original gas, most commonly due to environmental legislation (e.g. HCFC phase down) 
• Corporate responsibility: a policy decision to use refrigerants that provide greater benefit to the environment. 
• The availability of new refrigerants providing performance benefits, such as lower power consumption. 

The implications of retrofitting a system depend on the equipment and gas involved. In some cases, it is a very easy process with minimal system changes, for example minor changes to expansion valves. However in other cases, retrofitting a system can be a more complex process, potentially involving oil changes, system flushes or even changes to portions of the refrigeration system.  

An increasing number of new refrigerants, including many natural refrigerants, are flammable. Therefore these gases are not suitable for retrofitting existing fluorocarbon refrigerant systems without substantial re-designs to the existing equipment. Linde strongly recommends that flammable refrigerants are only used in systems designed specifically for those gases.