One solution is to commit to a total replacement with the upfront costs often offset over a fairly short period of time by the higher efficiencies of the latest models.
Still, if an older unit can be retrofitted with some non-CFC refrigerant, that might be the way to go. And it was the route the NutraSweet® Company went when it came to its manufacturing plant in Augusta, Ga. That facility had a 30-year-old, 1,100-ton R-12 chiller.
"Initially, we thought our only choice was to pay upwards of $1 million for a new chiller," said Dennis Rascon, site maintenance services coordinator for NutraSweet.
"That would have meant re-moving the old chiller from the skid, which is an unwieldy and time-consuming process."
But keeping the unit running on R-12 also posed problems, he said.
"We knew that R-12 is a highly regulated refrigerant, so price and availability would always be a problem."
Adding to the challenges of the situation was the effort to get the chiller to reach full capacity. A new management team nixed the new unit option by saying the plant would have to make do for the time being with the chiller it had.
The chiller in question cools a storage tank holding water used in refining a component of the sweetening agent aspartame. If the water temperature rises above 50 degrees F during refining, the entire batch of product has to be scrapped.
"Running the chiller in the condition it was in was kind of like trying to run an eight-cylinder car on two cylinders," Rascon said. "You can get by with the skips and stalls for awhile as long as the demand allows you to run the system with less than a full refrigerant load. But we knew that eventually we weren't going to be able to meet our production quotas unless we did something to solve this problem."
Service Help
Samuel Smith, a service technician for AirCond of Smyrna, Ga., had worked for a number of years to keep the unit running. In 2001, he and his team tore it down, rebuilt the bearings and drive system, and installed new gaskets in the entire system.Rascon had considered adding more R-12 at that time. But an economic downturn associated with the 2001 recession necessitated cost-cutting measures, he said. And the company officials balked at paying the price for any available R-12.
"We kept going with what we had," said Smith. "We just had enough R-12 to run the chiller at a very small demand load. But we knew we needed a better solution."
The solution that came to mind was to use a so-called interim refrigerant. But even that consideration needed study.
"We had heard that less-expensive R-12 interims were not good for larger industrial uses," said Rascon. "But our local Trane dealer put us in touch with refrigerant manufacturer CFC Refimax, and Charlie Allomong and Randy Perry [of CFC Refimax] gave us a presentation on R-416A. That sold us."
According to Allomong and Perry, several aspects of the refrigerant made it a good choice for the application.
"First," said Perry, "R-416A delivers R-12 performance at a fraction of the cost. Second, it is a near-azeotrope and has the lowest glide of any of the R-12 alternative refrigerants. Third, refrigerant separation or fractionization is not an issue, which allows for multiple ‘top-offs.' Fourth, it is compatible with mineral oil and alkabenzene oil. Finally, it is readily available, since it is available from more than 1,000 supply houses coast to coast."
The refrigerant is a blend of 59 percent HFC-134a, 39.5 percent HCFC-124, and 1.5 percent isobutane. R-416A has an A-1 ASHRAE safety classification and an A-1 classification for toxicity.
Conversion
Rascon said chiller conversions could be a challenge for a contractor. Attention has to be paid to safety measures in an industrial chemical plant, proper permits are needed, and proper procedures must be followed. In the case of the NutraSweet plant, technicians from CFC Refimax carried Association of Reciprocal Safety Council (ARSC) certification.They also had taken site-specific training to make sure they are aware of safety guidelines and personal protection equipment (PPE) requirements. Each tech had a rig with a safety harness, steel-toed shoes, gloves, long-sleeved work shirt, safety glasses, goggles, and other equipment that may be needed on site.
Perry, who is National Service Supervisor of CFC Refimax, worked with a company technician to first flush the system free of mineral oil and other contaminants. They used the company's RPS portable recovery/recycling unit. The RPS can reclaim or process refrigerant to ARI 700-95 standards on-site and in one pass, according to the company. It can remove oil, moisture, air, rust, particulates, and other contaminants at speeds up to 2,700 pounds per hour.
The technology proved valuable to NutraSweet because the chiller contained considerable mineral oil. "If you get refrigeration oil in the evaporator, you lose heat transfer because oil is an excellent insulator," Perry said. "That makes oil very detrimental to a chiller's overall operation. For every three percent of oil in the system, you often have as high as a seven to eight percent loss in efficiency. And when you lose efficiency, it adversely affects your cost of operation.
"Experience has taught us that with a very clean system, machines go back to performing the way they were meant to perform. That's significant, because so many chillers in industrial settings operate at substandard levels due to the adverse effects of contaminants."
In the NutraSweet project, CFC Refimax technicians used the RPS to recover the R-12 and reclaim it to the ARI-700-95 Standard. They then recharged the R-12 into the chiller and ran the chiller for several minutes to sweep residual oil and contamination from the system. The process was repeated to remove more contamination. The oil was drained from the chiller's oil sump and lubrication circuits, and the system was flushed with recycled R-12.
Then Smith and AirCond technicians moved in to change oil filters. Before the final flush, an AirCond technician charged the chiller with fresh POE oil, started the system up with the R-12, and ran it for a few minutes. Then the CFC Refimax technician used the RPS to recover the R-12 one more time.
The final step in the conversion was to pull the system down to 29.8 inches of vacuum to remove all residual R-12, and then charge it with just enough R-416A for the chiller to function at top capacity. According to those involved in the project, the chiller started up right away, ran smoothly at top capacity, and consistently cooled the water to the proper temperature.
Rascon noted a number of things the CFC Refimax technician did that might be good ideas for any contractor to do who might be working on a project like this.
"He took copious notes, conducted re-sedimentation samples to determine how clean the R-12 was, and kept me posted on how everything was going."
An added benefit for the equipment owner was the willingness of CFC Refimax to purchase the recovered R-12 at a price that offset much of the cost of the project.
Two months after the job was completed, Rascon reported the chiller was still performing well.
For more information, contact CFC Refimax at 800-406-2292.
Publication date: 09/06/2004
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