Commercial refrigeration systems are notoriously leaky. According to the Environmental Protection Agency’s (EPA’s) GreenChill program, the typical GreenChill program, the typical supermarket has an annual leak rate of about 25%, and the average store contains about 3,500 pounds of refrigerant. This translates into being a large financial and operational burden for food retailers, especially as the cost of refrigerants continues to increase due to the HFC phasedown.
The North American Sustainable Refrigeration Council (NASRC) hopes to solve this problem through its leak reduction initiative, which is being spearheaded by a group of its retailer-members. Under this initiative, retailers identified the top leak issues in refrigeration equipment and developed specific equipment specifications that could help mitigate those leaks. In a recent webinar, NASRC detailed its findings, which included calling on OEMs to make six improvements to their equipment in order to reduce leaks.
Refrigeration Consultant, Raley’s supermarkets
Leaks and Their Causes
One of the main reasons why food retailers want to make sure their refrigeration systems do not leak is that refrigerant is becoming very expensive and prices are likely going to go even higher. That’s because the phasedown outlined in the AIM Act will drive a decrease in the supply and availability of high-GWP HFCs such as R-407A. In fact, a 70% reduction in HFC production comes into effect in 2029, and this will likely affect the availability — and price — of R-448A and R-449A, which are common retrofit refrigerants in the commercial refrigeration space.
“The supply is going to be going down, and the natural consequence is an increase in price,” said Danielle Wright, executive director of the NASRC. “If we look at similar phasedown impacts that happened in Europe with the F-gas regulations, we saw up to a 900% increase in certain HFC prices … a similar forecast is projected here in the United States.”
That is why it is so important to pinpoint where leaks occur. Edward Estberg, a refrigeration consultant at Raley’s supermarkets, was part of the NASRC research group that identified those problem areas in refrigeration systems.
“We broke it down into four categories: the cases and the fixtures, the machine room and the racks, the condenser, and then the connecting piping,” said Estberg. “Then we identified the failures in each of those areas, and it was interesting to note that about 90% of the leaks occurred between the fixtures and the machine room. In some chains, it was greater in the machine room and in others it was greater in the fixtures, but all combined, about 90% of the leaks were in the manufactured products. Condensers contributed to about 3% of the leaks and the connecting piping about 7% of the leaks.”
As to what caused the leaks, Estberg said they found four main issues: thermal expansion and contraction, corrosion, abrasion, and vibration. To reduce the instances of these issues occurring, the committee recommended six measures, with the first — and most controversial — measure being to recommend that OEMs use much thicker copper tubing in the display cases, walk-in coils, in all the piping, and on the racks.
“Thicker tubing will resist corrosion, stress, and abrasion more than the thinner tubing, which I think is pretty obvious,” said Estberg. “We're looking for longevity. If we double the thickness of the copper tubing, we might get 20 years before we have a leak, and that would be a really good thing. Right now, some of these leaks are starting at 7, 8, and 9 years. A lot of the leaks are on the return bends, so one of the things that we think would really help is a heavier, thicker wall tubing in all the evaporators and on the condensers.”
The second measure addresses the abrasion problem and calls for OEMs to isolate any material, tubing, or part that carries refrigerant from any contact with any other metals. Estberg explained that when copper piping carrying refrigerant comes into contact with other metals and wiring, thermal cycling can cause friction that wears away the piping over time, resulting in leaks.
“There's no technology change needed here, we are asking the manufacturers to use a little more care in putting these cases together and clamping that tubing with a softer material so that it can't ever come in contact with a foreign material,” said Estberg.
The third measure addresses flare nuts, which can loosen due to vibration or thermal cycling, and calls for eliminating any flare fitting on copper tubing, except where needed for sensors and other equipment connections.
“There are a couple of easy solutions,” said Estberg. “Don't use flares, use solder fittings. If you have to have a mechanical connection, use a double ferrule compression fitting and wherever you can, solder joints and just eliminate the flare nuts all together. Rotolock valves are also an issue, because if they're on the suction line, there is thermal, and of course in the machine room, there’s vibration. So for measure four, it's a simple matter of eliminating the rotolock and going to a flange valve, or at the very least, have rotolock manufacturers find some way to put a set screw in here, so these cannot work loose.”
The fifth measure concerns the leaks that can occur during shipping and the committee recommends that OEMs add a temporary pressure gauge or indicator to visually confirm that the system is pressurized after arriving on site.
“We know the manufacturers do a very good job of pressurizing in the factory and generally, the equipment comes without leaks,” said Estberg. “But during freight, it bounces around on rail cars or on trucks, lots of times because they haven't clamped it right and the tubing is too thin, and leaks occur. It would be a big help to the retailers if, when the equipment arrives, we know whether it has a leak or not. So putting an inexpensive pressure gauge on every piece of equipment would be a big help.”
The sixth and final measure calls for OEMs to regulate CO2 release valves. Estberg noted that with high-pressure refrigerants such as CO2, one of the problems experienced by retailers is that the pressure relief valves are not resetting.
“That's one of the reasons why CO2 leak rates are somewhere between 50% and 100% a year,” he said. “We don't have a solution for this yet, but we want to point it out. We're hoping that the manufacturers can come up with a relief valve that reseats properly. It's either particles getting in there or possibly dry ice when they release. Generally when there is a release, you end up dumping the entire charge, which isn’t a huge expense, but you have six or eight hours of downtime getting the CO2 into the system, so this is a very serious problem.”
Executive Director NASRC
Wright noted that due to the increased costs these measures will add to equipment and manufacturing, NASRC is exploring potential solutions with major refrigeration OEMs. One of the main concerns for OEMs is whether there’s a market for these measures, as well as whether the market will accept the higher costs of equipment.
“If the costs do increase, competition is a consideration, because if a manufacturer takes the time to standardize these measures but the other competing OEMs do not and therefore, their product is available at a lower price, are there assurances that the market will continue to choose their product?” Wright asked. “OEMs need consensus from the market on these equipment specifications and a commitment to the incremental costs that will be as a result, as well as the ability to scale the solution.”
On the retailer side, more data is needed on the incremental cost of the leak reduction measures, as well as data on the payback to justify the upfront investment, said Wright. But the bottom line is that everyone has a stake in reducing refrigerant leaks, because they drive up costs for businesses.
“The whole purpose of running the refrigeration system is to keep food cold,” said Wright. “Having leaky equipment not only increases service and maintenance costs, but can also result in suboptimal performance and compromised product integrity. And it's not just HFC systems that leak; natural refrigerant systems leak as well. While there is a negligible climate impact and an exemption from compliance, it's still bad for business.”