Cooling without compromise: How drives are accelerating the transition to cleaner refrigerants
Switching from synthetic refrigerants in HVACR applications to more sustainable natural alternatives is a necessary step on the journey to Net Zero. However, the use of A2L and A3 refrigerants has implications for the design and use of HVACR devices and systems, as ABB’s Oliver Woolley explains.
Around the world, governments and regions are moving to phase out refrigerants with a high global warming potential (GWP), in favour of refrigerants with a lower environmental impact. While the shift to more sustainable natural refrigerants is a welcome and necessary step on the road to Net Zero, these refrigerants have different characteristics to their synthetic counterparts. In the HVACR industry this therefore creates new challenges for machine builders and system integrators in engineering protections and mitigations to accommodate the higher flammability of these more environmentally friendly refrigerants.
Refrigerant safety groups
Different types of refrigerant fall into different safety groups, which are denoted by a letter indicating toxicity, and a number indicating flammability. There are currently eight different classifications (A1, A2L, A2, A3, B1, B2L, B2 and B3).
A1 refrigerants have the lowest toxicity and flammability, while B3 refrigerants have the highest. ‘L’ sub-classes indicate that a substance burns more slowly when ignited.
Refrigerants in the A1 group are generally synthetic compounds such as chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). These offer excellent stability and low flammability, and have consequently been used extensively in refrigeration applications for decades. However, CFCs, HFCs and HCFCs all have an extremely high GWP, and are therefore terrible for the environment. Indeed, CFCs were banned in 1987 for this reason, while HFCs and HCFCs are both being phased out in favourof more sustainable natural alternatives. This means that designers and builders of heat pumps and chillers have had to find more environmentally friendly refrigerants to use.
Alternatives to A1
With A1 refrigerants increasingly out of the picture, A2L and A3 alternatives are playing an increasingly important role in the transition to better sustainability, and are now widely used in HVAC systems, refrigeration units and other cooling applications. However, while natural A2L and A3 refrigerants have a low toxicity and a much lower GWP compared to A1s, their higher number in the safety classification indicates that they are more flammable. Devices and systems operating near A2L or A3 refrigerants therefore require additional safety provisions to ensure that they are not a potential source of ignition.
The applicable standard here is IEC/UL 60335-2-40, which governs the safe use of electrical appliances with A2L and A3 refrigerants. It mandates rigorous safety protocols to ensure that devices do not emit arcs, sparks or create hot surfaces that could potentially act as ignition sources. This includes variable speed drives, which are widely used in HVACR systems to improve energy efficiency and provide precision control over fan or pump motors. Crucially, the standard covers both whole systems and the products that make up those systems, so each component part – if operating near to the refrigerant – must comply.
Mitigating the risks
On the face of it, integrators therefore have two options. One is to mount the drive remotely, away from the application. However, this is not always practical or desirable for chiller or heat pump OEMs, who prefer to sell their systems as integrated packages to reduce cabling and maximise the use of space. System integrators also like to have all components of the system local to the application for ease of installation, operation and maintenance.
Another solution is to use a drive which is certified to IEC/ UL 60335-2-40. These will have undergone comprehensive testing to verify that they do not emit arcs, sparks or hot surfaces that could act as ignition sources in the presence of refrigerant leaks. Drives have DC bus capacitors which store electrical energy. If that energy is stored for too long then the drive can become an ignition risk. To achieve compliance, a drive must therefore have integrated safe torque off (STO) functionality, which disables torque and shuts off the voltage from the drive to the motor within SIL3 parameters, without the need for external relays. It is also vitally important to only use the drive according to its nominal limits to avoid any overheating, as any ignition around flammable refrigerants can potentially cause a threat to life.
Using drives safely with A2L and A3 refrigerants
ABB is one of only a handful of drive suppliers whose products conform to IEC/UL 60335-2-40 for both A2L and A3 refrigerants. ABB’s ACS (general purpose drives) and ACH (HVAC drives) ranges are now fully compliant. These drives have undergone comprehensive testing to verify that they do not emit arcs, sparks or hot surfaces that could act as ignition sources in the presence of refrigerant leaks. Built-in STO provides an integrated safety mechanism to disable torque without the need for external safety relays, while electromagnetic compatibility (EMC) and additional thermal management have been included to minimise operational risks
in sensitive environments. This ensures their safe integration into systems utilising refrigerants with lower GWP.
This is good news for OEMs, their customers and end users, who can confidently use and rely on ABB drives when working near modern refrigeration equipment. This gives the key benefits of increasing energy efficiency, reducing integration costs, without unnecessary concern about ignition safety, thus enabling the green transition.
The transition to natural, less toxic A2L and A3 refrigerants is not just a trend – it’s a necessity for a sustainable future. Natural refrigerants offer significantly lower GWP numbers, require a smaller amount and pose minimal risk to the environment in the event of a leak, making them a preferred choice for businesses cautious about the environment. With the latest generation of A2L and A3-compliant drives, machine builders can streamline their design and certification processes, while ensuring that their refrigeration systems meet the highest standards.
