REFRIGERANTS
The ‘f’ word: tackling A2L flammability
Over the last few years there has been an increasing amount of very low GWP refrigerants available in the market and new products continue to be developed each year. Allan Harper, Climalife UK managing director discusses.
T
he main driver behind the development and introduction of these new refrigerants is their low global warming potential. Refrigerants all have a value relative to CO2 as the baseline, for their global warming potential and there is increasing pressure for the GWP value to be reduced in order to meet both the F-Gas regulation and the UK carbon emissions net zero 2050 target. By 2030 the current F-Gas Legislation requires the CO2 equivalent tonnes of refrigerant being placed on the market to be reduced by 79% from the baseline figure set in 2015. To meet the phase down steps, the move to even lower GWP products needs to gather pace and will require the greater use of A2L refrigerants. The very low GWP A2L refrigerants need to be used in
new equipment and this has already started to enter the market to meet the requirement for transitioning to A2L refrigerants.
So, if the products are available and the new equipment has come to market then why aren’t we all transitioning to A2L’s straight away? Well, a big part of this is where the ‘F’ word comes into it – Flammability. The A2L Classification – What it means These low GWP refrigerants are usually flammable, which gives them their ASHRAE classification of A2L.
Most of the commonly used HFC and HFC/HFO blend refrigerants are classified as A1 meaning that they have very low toxicity and zero flammability. The term A2L refers to a safety classification based on ISO
817 and ASHRAE Standard 34 for toxicity and flammability. Toxicity is divided into two categories, A for lower toxicity, B for higher toxicity, whilst flammability is divided into four groups; 1, 2L, 2 and 3; assigned depending on several
24 December 2020
flammability parameters including Lower flammability Limit (LFL), Heat of Combustion and Burning Velocity. 1 is non- flammable, 2 is lower flammability, 3 is higher flammability, whilst the 2L category is often referred to as mildly flammable. and has a requirement that the burning velocity must be 10cm/sec or below. For example, R-32 has burning velocity 6.1 cm/sec and R-1234yf 1.5 cm/sec. The overall difference between A1 refrigerants such as R-410A and A2L refrigerants such as R-32, is that the A2L refrigerant has the ability to propagate a flame in the right circumstances. The refrigerants will burn, but the burning velocity will be 10cm/sec or lower.
A crucial step for achieving a level of risk that is as minimal as possible, is having adequate risk management in place. One of the first steps to minimising the risk is to avoid the release of refrigerant from the cylinder or the system. This involves safety procedures being in place from the moment the cylinder is filled and transported to when it is being installed and the system serviced. Providing the concentration level remains below the lower flammability limit (LFL) and above the upper flammability limit (UFL), then a flammable refrigerant will not ignite. Safety standards such as ISO 5149 and EN378 specify that they should remain well below the LFL to reduce any risks in case of system leaks, therefore it is important that standards are closely followed when using A2L refrigerants to charge systems.
All applications should have a valid risk assessment whatever classification the refrigerant falls into, however a critical stage of conducting a risk assessment for an A2L refrigerant should be to identify any possible scenarios where an ignition source could be present along with a
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