There are many questions surrounding the safe use of mildly flammable refrigerants, which is why The ACHR NEWS asked Philip Johnston, general manager in charge of transitioning to low-GWP refrigerants at Daikin Applied, and Nathan Walker, senior vice president of corporate marketing at Goodman Manufacturing, to discuss some of the technical details of R-32.

ACHR NEWS: In terms of properties and performance, how does R-32 compare to R-410A (e.g., efficiency, capacity, pressures, discharge temperatures)?

Johnston: With R-32, the refrigerant itself has greater thermodynamic capacity and efficiency over R-410A and R-454B [another A2L refrigerant]. In practical terms, that means the efficiency is typically higher when dropped into the same unit design as R-410A — and if using the same compressor, then R-32 will have higher capacity.

We found in tests of a Daikin inverter compressor rooftop unit with identical hardware, the use of R-32 improved IEER at nominal capacity by 8% as compared to R-410A and 11% as compared to R-454B. With R-32, an inverter driven compressor will run more slowly to achieve the same capacity as R-410A, meaning a large drop in power consumption, improving the EER and IEER. We also tested R-454B the same way and found it needed higher compressor speeds to get to full load capacities, and that follows its expected thermodynamic properties. As a result, its tested efficiency was lower than R-410A. So, the takeaway is lower electrical consumption for R-32, resulting in lower operating costs and a lower carbon footprint.

R-32 does operate at a slightly higher pressure and a slightly higher discharge temperature than R-410A. While some may say this higher discharge temperature is a potential issue, we don’t believe it is. Daikin and other compressor manufacturers have developed compressors for R-32 already. In fact, over 40 companies are selling R-32 products around the world already, to the tune of over 100 million units in operation and growing every day. They made the switch, because it’s pretty easy to design units that can get improved performance with environmental benefits using R-32.

ACHR NEWS: As a mildly flammable refrigerant, will there be significant differences between R-32 and R-410A systems? What changes will be made to the components and accessories used in R-32 systems? Will technicians notice any difference?

Walker: From a residential standpoint, I think technicians be surprised about how simple a typical piece of equipment will be and how similar it will be to today’s equipment. From the outside, except for some additional labels, technicians really won’t be able to tell the difference between R-32 and R-410A units. Some components will be adapted to optimize R-32 application, but not because it is an A2L refrigerant. Major components like compressors and expansion valves will need to be adapted to match capacity and mass flow, but that would be true for any new refrigerant. Inside some systems, however, technicians will see some minor differences like refrigerant leak detectors, printed circuit boards (PCBs) that control the fans a bit differently, and maybe a few more. Having said that, though, in the simplest products like PTACs or small ground-source heat pumps (WSHPs), the refrigerant charge levels are so small that detectors aren’t needed, and they’ll look pretty much the same as comparable R-410A models.

Johnston: For applied products, it’s a bit different than residential, and we expect a few more changes. For example, with a larger air-cooled chiller, R-32 allows us to use smaller compressors to get the same capacity. Smaller diameter piping is an option as well, because we can move less R-32 to achieve the same capacity, giving us much lower charge levels. On some of our larger applied rooftop units, we’ll have more than one refrigerant detector sensor to deal with the unlikely event that a leak occurs in more than one location. However, they’ll be integral to the unit and tied into the unit controls, so there will be no fuss for the installing contractor. We’ll also expect to change compressor and piping locations away from larger power electronics, but these modifications will be taken care of by us. The new units will still look like chillers and rooftop units.

ACHR NEWS: Can refrigerant lines from R-22 and R-410A systems be reused with R-32? Or should they be replaced when a new system is installed?

Walker: Each installation is different and requires on-site examination and for the installer to follow all local codes and installation instructions. Having said that, we expect that most applications could utilize the existing refrigerant lines. As the OEM, we’d want the proper steps to be taken, and that would include checking line set material, evacuation, pressure check, etc.

We do, however, suggest that technicians flush the line sets to remove any residual refrigerant and oil. This is considered best practice in general, but even more important when changing a system from one refrigerant to another. The oil used by compressor manufacturers for R-32 or any new refrigerant may be different than the existing system, so a flush is a good idea.

Ultimately for R-32, provided the refrigerant lines are the appropriate diameter and length as specified in the installation instructions, it should be just fine to use the existing line set if it is properly cleaned and examined.

ACHR NEWS: How does the charge size of an R-32 system compare to R-410A? What do technicians need to know about charging a system with R-32 — how does it differ from R-410A?

Walker: Our analysis tells us that most R-32 units will have a lower charge than similar R-410A units. The actual value really depends on the type of equipment, what options are installed, how well optimized was the design, etc. We expect to see charges averaging 20-25% lower in most products, including WSHPs, rooftops, chillers, and so on, but could be up to 40% lower in certain applications.

The process of charging itself, however, should not be much different. As always, though, technicians working with any refrigerant should be properly trained to handle the refrigerant. For any A2L, they should consider situational safety and take appropriate measures, such as using proper tools, making sure no ignition sources are close by, and ensuring there is adequate ventilation.

With any A2L, the UL standards require the technician to purge the circuit with an inert gas and to do pressure and leak checks. Provided they take the appropriate measures, charging should be the same as R-22 or R-410A.

Johnston: Another significant point is that R-32 has an important advantage over other A2Ls, because R-32 is a single component refrigerant and not a blend. Similar to the simpler days when R-22 was the standard, technicians don’t have to worry about composition change over time, they can top up a unit, and they can charge in liquid and gas phases, making it easier to reuse and reclaim than zeotropic blends. Some alternative replacements have two or three different components in their blends, and if that composition changes, so could performance like capacity, efficiency, flammability, and toxicity.

ACHR NEWS: Will technicians need any new tools, test instruments, recovery machines, etc., in order to work with R-32? If so, please describe. Is the recovery process the same as that of R-410A?

Walker: Most of the tools should be same. For example, if the gauge manifold and hoses support R-410A, technicians will likely be able to use it with R-32 as well, provided superheat and subcooling are recalculated based upon the properties of R-32. To leak check, technicians will have to check that their sniff detector will detect R-32, and they should not use a torch type detector for A2L refrigerants. For recovery, technicians should make sure the recovery unit or vacuum pump is approved for A2L refrigerants.

ACHR NEWS: Is the installation and service of an R-32 system much different than that of an R-410A system? Are there different procedures that installers need to be practice when installing these systems, particularly if soldering and brazing are required?

Walker: The simple answer is there are some differences; however, the differences are roughly the same as would be expected with any change of refrigerant, similar to having gone from R-22 to R-410A. For installing the standard split system, technicians must still make sure to choose an AHRI-rated combination, connect the line set, connect the electrical, properly charge the system, check airflow, etc., and away they go. For single package system, the installation should be no different than today. As always, technicians should pay attention to the instructions and warnings, especially the charging allowances, in the installation instructions.

For procedures, because the new refrigerants are mildly flammable, during installation, service and at end of life, technicians will need to take care to have well-ventilated work areas, check for residual refrigerant before brazing, etc.

Johnston: For commercial applications, there will likely be some changes in how certain products are applied, which is why design engineers for a given application should become very familiar with ASHRAE Standard 15. As an example, some applications may require field-installed leak detectors that are tied into the building automation system. At times, one may need ventilation systems that are triggered by these detectors. Similar systems are required for A1 refrigerants as well, if they may exceed the refrigerant concentration limit (RCL). Essentially, the installation of the system itself will be very similar to today’s equipment, but there may be some applications differences.

ACHR NEWS: Do you expect different procedures or requirements with transporting R-32 in a service truck or storing it in a warehouse when compared to R-410A?

Johnston: AHRI has a task force that is working on transportation and storage, so more will come from that. For storage of cylinders, right now the codes limit storage to maximum 150 pounds per control area if no sprinklers and 300 pounds if have sprinklers. Because A2Ls are mildly flammable and very difficult to ignite, we believe these values might be increased.

For storage of equipment, it’s treated based upon the building code, too. What does that mean? According to the safety standards, storage is limited by the RCL, so for a given room volume, one might be able to store many small residential units with low refrigerant charge levels, but maybe not a larger piece of equipment with the same total charge, so it would have to be stored in a larger space or outside.

For transportation by the contractor to site, we expect both cylinders and equipment to be covered as materials of trade, meaning they can generally be moved from storage to job site like they are now. Currently, materials of trade is applied for paints, lubricants, and welding gases in which contractors carry today.

ACHR NEWS: Some technicians may have concerns about installing or servicing a unit that uses a mildly flammable refrigerant. What advice would you give them that might allay those fears?

Walker: I’d remind technicians of two things. First, many technicians had similar fears about changing from R-22 to R-410A because of the increase in operating pressures. However, despite the worries around that refrigerant transition, the industry managed that transition very well. Second, I’d remind everyone that there are over 100 million R-32 units operating today in over 90 countries, and we are not aware of any serious incidents. Many safety features, warnings, and training will be put into place to reduce likelihood of problems. Follow the road signs and directions and be smart, technicians do that, all will be okay.

Johnston: I’d like to add that we should look at a refrigerant change as an opportunity. There are several benefits of R-32 that other countries already enjoy and that we soon will as well. Improved product efficiency, lower charge levels, not to mention lower GWP – changing refrigerant helps improve the world. We at Daikin are glad to do our part to help with that effort.

Listen to a podcast of this interview.