COMPRESSORS
The implementation of A2L compressor technology
Hari Nagendraprasad, product manager at Tecumseh discusses the use of low-GWP A2L refrigerants in compressors.
I
t’s less than three months to 2021 when the refrigeration industry will face another step as a significant reduction of HFCs placed into the market (less than 50%) pursuing European F-Gas regulation against CO2
Toxicity A, No charge restriction Flammability 2L 6m3
x LFL = 2,5kg emission. A year later,
in 2022 refrigerants with GWP >150 will be banned in most of the commercial refrigeration applications. With these two significant changes to come, manufacturers, distributors and installers need to anticipate their product line transitions. They will be the key players of environmental transition in the field, focusing a bit more on safety compliance, regulations for stocking, distribution and following the new security guidelines for installation. With this scenario it will be important to consider and analyse the Low GWP refrigerants, already available, becoming clearly a sustainable cooling option.
Natural refrigerant R290 which is classified as A3 ( flammable) refrigerant and the blend refrigerants R455A(145), R454C(146) and R1234yf(4) classified as A2L ( Mildly Flammable) carry the low GWP values that can be used in various commercial refrigeration application as alternatives to R404A and R134a .
Considering R290, the current charge limit has been defined at 150gr. As we write, the recent IEC60335-2-89 amendment to increase thecharge limits of propane refrigerant from 150g to 500g allowing the use of R290 in higher volume cabinets up to 3 door reach-in coolers and freezers may generate conflict and questions at customers. Its implementation and integration into EN standards will certainly be slow and will take time. Moving to A2L refrigerants is a good answer for manufacturers and customers to the CO²
emission reduction.
Furthermore, the increase up to 500gr does not fulfil certain applications where the higher refrigerant charge quantities are inevitable; for instance, a remote condensing unit for a cold room, a milk tank etc. Therefore moving to A2L is the sustainable solution when considering low GWP refrigerant offer. For these applications allowable charge limits for R455A, R454C are well above the 500g limit of R290. If we calculate the authorised charge quantities as per EN378, for a negative temperature cold room of 85m3 Volume, we can see that the values are much higher than the charge limits for propane.
Example: Location of the system is considered as Category b Class II (R455A):
28 November 2020 20% x LFL x VRoom = 7,19kg So,
R455A 7,19 kg (LFL = = 0,423kg/m3 R454C 4,62 kg (LFL = 0,272kg/m3 R1234yf 4,91 kg
) (LFL = 0,289kg/m3 )
Each type of refrigerant has its own pros and cons, which means that opposing natural with blends does not make sense. This choice might be clearly driven by the end user environmental positioning. Application type and size, location are to be considered also. While mentioning safety we usually refer to Refrigerant Properties. The minimum ignition energy (MIE) required to ignite A2Ls is 1200 to 4000 time higher than A3s. Once ignited, the A2Ls also burn much slower than the A3s, with close to 30 times slower burning velocity and the severity of the flames in A2L are low as the Heat of combustion is four times lower than A3. A2L (R454C, R455A & R1234yf) refrigerants score better over A3 R290 with higher authorized charge limits for remote and integral applications and offers better safety with favourable flammability characteristics.
Performance
The Total Environmental Warming Index (TEWI) has two components, one is direct contribution by refrigerant emission into the atmosphere, in case of leakage (GWP) and the other is indirect contribution due to the energy production, transport & consumption by the refrigerating system over its life cycle. Nowadays, condensing unit products have to comply with the European Ecodesign Directive.
It’s a known fact the compressors are key for obtaining the higher efficiency and performance in any refrigeration application. The reciprocating technology remained the most robust, reliable & cost-effective technology for the commercial refrigeration applications over several decades. Recent advances in the field of manufacturing and motor technologies design have significantly improved the efficiency levels.
The below performance comparison done for the compressors shows good efficiency levels for the medium
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