ALTERNATIVE REFRIGERANTS
of R32 with some HFOs such as R1234ze and R1234yf have higher critical temperatures than R410A, so may be more suitable for high ambient climates, albeit with the disadvantage of reduced capacity and higher cost in some cases. Further, all of these R32-based alternatives to R410A are fl ammable to a degree. R32 has already been introduced commercially in smaller units in Japan and Europe and in some Asian countries. Although many systems have historically used
non-fl ammable refrigerants, the move towards lower GWP alternatives has led to the introduction of more fl ammable fl uids. Many of the new low GWP refrigerants, such as the HFOs, fall into the 2L category, which means they have low toxicity but are mildly fl ammable; R32 is one of these mildly fl ammable lower GWP 2L fl uids. Whilst fl ammable refrigerants can be used safely in many circumstances with appropriate equipment and training, their use in air conditioning is banned in many countries including in France and Italy. Even where their use is permitted, most safety codes and standards have yet to be updated to include the 2L fl ammability category requiring them to be treated as if they were extremely fl ammable such as propane.
AHRI (the Air Conditioning, Heating and Refrigeration Institute) has done extensive research evaluating alternative refrigerants using samples from chemical manufacturers including Mexichem, but there is more work to be done to ensure the safe use of these 2L fl uids. With health and safety in mind, it is also vital to ensure technicians are educated on the handling of these fl ammable refrigerants before they are used for installation and servicing. Diff erent refrigerants have varying levels of suitability for hot climates; there is always a trade-off between effi ciency, capacity and fl ammability. For example, R134A is non- fl ammable, has a higher critical temperature and is more effi cient at high ambient temperatures, but has only around two thirds of the capacity of R22 requiring larger compressor displacement to achieve the same cooling duty.
Mechanical options
There are also mechanical options that can improve the performance of an air conditioning system in high ambient temperatures, such as investing in larger and more effi cient heat exchanger designs and using the highest effi ciency variable speed fan motors and control
systems. Additions to the air conditioning equipment, such as a larger condenser may increase effi ciency but can also increase the size and cost of the air conditioning system . Whilst the improved performance will result in reduced operating costs, those benefi ts need to be weighed against the higher initial purchase cost - something you should consider and balance at the outset.
In many countries, moving towards zero ozone depletion is the environmental priority but looking to the future, the air conditioning industry must also work towards lowering the carbon footprint of air conditioning use, looking at both effi ciency improvement as well as refrigerant GWP. While in some countries, it might be an option to move straight from R22 to R32 this may not be possible or practicable for safety or regulatory reasons in others. Inevitably, an increase in the use of refrigeration and air conditioning in high ambient temperature environments will result in an increased carbon footprint - the key is to fi nd the right technologies to reduce this impact as much as possible. It turns out that the challenges in a hot climate are very similar to the ones we face across the globe.
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