R32, R452B, R454B: Which lower-GWP refrigerants can you use to replace R410A?

R410A phase down has already started in Europe and North America, as well as in other countries such as Australia and New Zealand.

This quota mechanism is already affecting prices and availability. This, together with national policies taxing CO₂ equivalence, has led to a growing demand for lower-GWP alternatives.

There are many lower-GWP refrigerants available. R32 is a popular choice, due to its availability, performance and efficiency, but R454B and R452B also offer convenience and, potentially, low system qualification costs. Further alternatives are also entering the market.

To know more about the refrigerant regulations and options

Lower-GWP refrigerants are generally flammable, which means safety standards and building codes need to be revised to reflect their potential impact.

This flammability will sometimes lead to restrictions where systems can be installed or the maximum charge—and hence capacity—that can be used. It also means components need to be compatible with flammable refrigerants, to ensure they can't be considered an ignition source.

Technology and components suitable for lower-GWP refrigerants are well developed and have been available on the market since 2018—allowing OEMs to start creating compatible systems.

However, there is currently no perfect drop-in replacement for R410A. With any lower-GWP alternative, OEMs need to deal with at least one drawback—whether flammability, availability, or compatibility with materials. In each case, the challenge is finding the best compromise for their users, targets and designs.

Although refrigerant transition means component and system optimizations are necessary, the cost and performance improvements can be significant in the medium term.

R32, R452B, and R454B replacements for R410A are all classed as 2L: mildly flammable.

These A2L refrigerants offer only moderate limitations in charge for direct expansion systems and no limitations for indirect expansion systems such as chillers, when located outdoor or in technical rooms. But regardless of their location, local safety standards and building codes must always be adhered to.

Our technical paper on the possibilities and limitations of flammable refrigerants gives some guidance on how to make the most of the opportunity, safely.

R32, R452B, and R454B all have a low toxicity class, "A"—the same as R410A and R22.

R32, R452B, and R454B are all good options for air conditioning systems. However, the best option varies by application. Refrigerants with ultra-low GWP will be important in the longer term.

Scroll chillers, rooftop units, and air handling units

Medium term: R32, R452B, R454B

Longer term: R1234ze, R515B, R516A

Large centrifugal and screw chillers (up to 1.5 MW)

Medium term: R513A, R1234ze, R515B

Longer term: R1234ze, R515B,

Very large centrifugal and screw chillers (over 1.5 MW)

Medium term: R1233zd, R1336mzz(Z), R514A

Longer term: R1233zd, R1336mzz(Z), R514A

Dedicated heat pumps (air to water)

Medium term: R454C, R290

Longer term: R454C, R290

Dedicated heat pumps (brine to water, or water to water)

Medium term: R454C, R454B

Longer term: R454C

A/A systems (Rooftops, Air Handling Units, VRF, Split systems, CRAC)

Medium term: R410A, R32 or R454B (with new system architecture), R466 if viable

Longer term: R32 or R454B (with new system architecture), R466 if viable, and maybe a move to lower density if needed

As a straight R410A system replacement, R32 has around 10% more capacity. As a result, a new system built for R32 will deliver higher cooling capacity, or require smaller displacement compressors to achieve the same capacity. Efficiency gains over R410A are expected, provided the system and component designs have been optimized for R32.

However, R32 has a high discharge temperature which can limit its operating envelope unless the issue is handled by design or some type of injection.

R452B is the closest drop-in equivalent to R410A in terms of capacity and efficiency. R454B delivers slightly less capacity, but has the benefit of an even lower GWP. Both refrigerants allow the fastest conversion from R410A and—if the system uses the Danfoss component portfolio—give multi-refrigerant flexibility, allowing late-line customization.

If a system redesign is necessary, R32 is a good choice with a good $/TR or €/kW ratio. However, for applications that are already very energy efficient, a simple drop-in using R452B or R454B will minimize system redesign costs—enabling late-line customization in some cases. For the end users and the building owners, all are very viable options.

R32 in an air conditioning chiller: impact on system design

• Requires redesign and sizing to achieve optimum performance
• Needs several components and settings to be adjusted, including the expansion valve, liquid line pipe, suction line, solenoid valve, and discharge line
• The compressor could be oversized and may need changing
• GWP is AR5-677 / 675-AR5 (measured at AR4)

R452B or R454B in an air conditioning chiller: impact on system design

• Designed to be close to a drop-in alternative
• Potential multi-refrigerant flexibility
• GWP is 698 for R452B and 466 for R454B—meaning it could potentially be a longer-term solution