With the phaseout of HCFC refrigerants such as R-22 and the impending phasedown of HFCs such as R-404A and R-507, food retailers are looking at lower-GWP solutions for their refrigeration equipment. Retrofitting an entire store with refrigeration equipment that uses ultra-low GWP options such as CO₂ or ammonia can be prohibitively expensive, which is why many food retailers are choosing to transition their existing units to HFO blends, such as R-448A and R-449A.

With GWPs under 1300 and an A1 classification, R-448A and R-449A are not drop-in refrigerants, and modifications have to be made to the refrigeration equipment before they are used. In the latest webinar from the Environmental Protection Agency’s (EPA’s) GreenChill program, industry experts offered advice on how to properly retrofit a system with HFO blends.

Refrigerant Regulatory Shift

Chuck Allgood, Ph.D., refrigerant technology leader at Chemours, started off the webinar by discussing how recent federal regulations, such as the American Innovation in Manufacturing (AIM) Act, will affect the commercial refrigeration industry. This Act, which was passed by Congress last December, gives the Environmental Protection Agency (EPA) the authority to phase down high-GWP HFC refrigerants, and the agency is expected to issue regulations soon that detail how it will administer the phasedown.

“The AIM Act will affect our industry in three ways,” said Allgood. “First, there will be rulemaking on the HFC production and consumption rules, which will determine the amount of HFC or carbon equivalent quota that is out there and how that's divided up. From that baseline, we’ll be stepping down production, but we don’t have all the final numbers yet. Second is HFC management, particularly how it will impact reclaim, recovery, recycle, and all those types of activities. And third, there will be sector-based controls, which is an application-by-application and refrigerant-by-refrigerant approach to rulemaking.”

There are also regulations at the state level, most notably California, which has implemented its own phasedown schedule for HFCs, said Andrew Pansulla, technical service engineer at Chemours. Under their new mandate, starting Jan. 1, 2022, commercial refrigeration systems that contain more than 50 pounds of refrigerant will have a 150-GWP limit for newly constructed and fully remodeled facilities. In existing facilities, there are two different methods that food retailers can employ to decrease their carbon emissions.

“The first is the greenhouse gas potential — or GHGp — and that is the charge of a certain refrigerant times the GWP of that refrigerant. The different GHGps will be added up across a whole store’s footprint to calculate the total GHGp,” said Pansulla. “The second method is the weighted average GWP, which is calculated by taking the total charge of all refrigerants within the portfolio and dividing that by the GHGp to get the weighted average GWP.”

All stores in California must achieve an average GWP of less than 1,400 or reduce their GHGp by 55% or more by 2030.

With the impending phasedown of HFCs, food retailers across the country should be taking steps now to ensure future regulatory compliance, said Pansulla. This includes making sure refrigeration equipment is properly maintained and leak-free and retrofitting to lower-GWP refrigerants, which can extend the life of existing equipment.

“Reducing charge is another powerful way to lower the GHGp. It won't necessarily change the weighted average GWP much, but with a lot of the improvements in different architectures, there are ways to continue to use existing refrigerants but reduce a store’s carbon footprint by reducing the charge,” he said. “Finally, remodeling and redesigning equipment can help reach regulatory compliance goals.”

Successful Retrofits

When it comes to retrofitting an existing refrigeration system with an HFO blend such as R-448A or R-449A, there are three steps contractors should follow to ensure a smooth transition, said Doug Starasinic, senior applications engineer at Honeywell. The first step is to conduct a comprehensive site survey, which should be performed well in advance of the retrofit. The survey should include checking the compressors for compatibility, addressing/fixing system deficiencies, reviewing expansion valves, and employing leak prevention measures.

The second step is store coordination and preplanning, which involves ordering parts and refrigerant; training technicians; performing system changes/upgrades; changing oil from mineral to POE; changing suction and liquid filters and driers; upgrading the controller with the pressure curves for the HFO blend; and checking/repairing leaks.

“If it’s an R-22 or other HCFC retrofit, there will be a lot of gaskets to replace, so make sure those are ready to go,” said Starasinic. “Technicians also need to be trained about refrigerant glide, because a lot of them are still confused. Basically, the more you can do ahead of time, the better. We find that you can change the oil about a week ahead of time and it's not going to cause any problems.”

And finally, the third step is the actual retrofit, which includes:

• Reminding store personnel the day prior to the retrofit;
• Securing food safety, whether it is with dry ice, plastic sheeting, etc.;
• Recovering existing refrigerant;
• Recording the amount of refrigerant removed (including refrigerant previously removed);
• Breaking the vacuum from the recovery machine;
• Replacing seals, gaskets, and valves as needed;
• Replacing expansion valves and adding adjustment kits as determined in the survey;
• Replacing driers and filers;
• Evacuating the system;
• Charging the system;
• Adjusting expansion valves;
• Adjusting pressure controls; and
• Labeling components and systems.

“From our experience, I would say that the toughest part is evacuating the system,” said Starasinic. “The biggest thing is to have really good vacuum pumps and a lot of them. This also just takes a lot of time to pull it down because a valve or gasket may pop, and you're back where you started. You also really need to pay attention to the expansion valves. When you're going from R-404A to one of the HFO blends, there is a danger of floodback, so be very cognizant of that. If you follow all these steps, you're going to have a 30-year-old system that's going to go for another 20 or 30 years and be energy efficient.”

Indeed, when retrofitting from an HFC such as R-404A to an HFO blend such as R-448A or R-449, an efficiency gain of 5% to 10% is expected. Because of its thermodynamic properties, there is no efficiency gain when retrofitting R-22 to an HFO blend; however, the tune-ups made during the retrofit process should result in energy savings, said Starasinic.

Common Questions

While retrofitting refrigeration equipment to HFO blends is a fairly common occurrence these days, refrigerant manufacturers still field a number of questions from contractors and technicians about the process. Punsella said one of the most commonly asked questions is whether fractionation will cause any issues when using R-448A or R-449A.

“The answer is no,” he said. “The system effects of fractionation on refrigerants like R-448A and R-449A are insignificant. If a system develops a leak with either R-448A or R-449A, contractors can top off that existing charge with virgin liquid refrigerant, and there will be no significant performance differences.”

Another frequently asked question is, what are the major changes that need to be made to R-22 or R-404A systems when retrofitting to HFO blends? While some of these have already been covered, Punsella noted that the biggest pain points are oil changes and critical elastomeric seals.

“If it’s an R-22 system using mineral oil, and you’re retrofitting to R-448A or R-449A, which uses POE oil, the elastomeric seals will need to be changed out to prevent leaking post-retrofit,” he said. “For R-404A retrofits, the big issues are TXV and demand cooling needs for low-temperature refrigeration. Make sure you know ahead of time about the TXVs and the adjustments that they need to ensure that the system will not have floodback. For R-402A and R-408A retrofits, unfortunately, they have the pain points for both R-22 and R-404A, including the oil, seals, and TXVs.”

Contractors have also asked whether R-448A and R-449A can be mixed, given their similar performance characteristics. Again, the answer is no, said Punsella.

“No two refrigerants should ever be mixed,” he said. “If refrigerants are mixed, you're going to change the pressure-temperature relationship of the refrigerant, and there will be no way to accurately measure things like superheat and subcooling.”

Finally, Punsella said contractors often ask him whether current leak detectors will work with HFO blends such as R-448A and R-449A. And the answer to this question is yes, they will — any leak detector that can detect an HFC refrigerant can be used with HFO blends.

When it comes to ensuring a retrofit goes smoothly, Allgood stressed that it all comes down to proper planning on the part of the contractor.

“Make sure you have the right people in place, as well as enough people,” he said. “There will be people working on cases and those working in the machine room, and others who come in early to run around and check for leaks. And be sure to coordinate with store personnel, so they know you’re coming — don’t surprise the manager with a bunch of activity that he/she is not expecting, or it’s not going to go well.

Follow the steps outlined above, and the odds of a successful retrofit will definitely be in the contractor’s favor.