For years, they ran on such CFCs as R-12 and -502. With the phaseout of those refrigerants, however, manufacturers moved to a variety of interim HCFC blends. At first, those blends were identified by manufacturer nomenclature (i.e., MP39, HP80, and HP81), but then they became identified by ASHRAE designations (R-401A, -402A, and -402B). R-401A is a mix of R-22, -152a, and -124; the latter two each have R-125, -290, and -22 in slightly different percentages.
The arrival of HFCs found the ice machine market quickly embracing R-404A (a mixture of R-125, -143a, and -134a) on most medium- to large-tonnage equipment; R-134a was used in smaller models.
Still EvolvingThe story does not end there. There are always those trying yet another refrigerant or two to see if the ultimate issue - better efficiency - can be achieved.
Consider the technical people at ICOR International in Indianapolis. One refrigerant they feel strongly about is an HFC marketed as One Shotâ„¢, which, at the time of this writing was awaiting ASHRAE designation and safety classification. The refrigerant can be used for "system performance gains with minimal, if any, system changes," said Jim Terry, manager of Engineering Services.
In low- and medium-temperature applications, Terry said the refrigerant can be considered as a replacement for R-402A, -402B, -404A, -408A, -502, and -507A; it also can be looked at as a replacement in low-temperature systems that have been running on R-22.
To examine the refrigerant's possible use in an ice machine, a new, water-cooled ice machine was brought to the Indianapolis R&D center. The machine is listed by ARI as being capable of producing about 800 pounds of ice in 24 hours, and was charged with R-404A by the manufacturer.
Ice production and power consumption data were measured at three condensing temperatures for both refrigerants. R-404A data was used as a baseline.
According to Terry, "At 100 degrees F condensing, the power consumption with One Shot was 3 percent less and 720 pounds more ice were produced over a 30-day period. At 110 degrees condensing, power consumption was 5 percent less and 900 pounds of additional ice were produced over a 30-day period. And at 120 degrees condensing, the power consumption was 6 percent less and the ice produced was 1,080 pounds more over a 30-day period."
"The unit ran with an open bin and operated continuously," noted Jamey Hale, ICOR technical support supervisor. "In real life, the unit would cycle off/on at the bin switch. Quicker bin recovery means more time off, increasing the power savings even more."
Freezer FindingsThe engineers then decided to perform similar research on a reach-in freezer that had R-404A installed at the factory. They conducted tests on power consumption during pulldown, comparing One Shot with R-404A and -507A (the latter is a blend of R-125 and -143a).
The reach-in freezer was operated to determine the lower temperature achieved and the power consumed during a continuous operation test over a fixed period of time, Terry indicated. The condenser ambient temperature was 70 degrees. At the beginning of each test, after a 24-hour soak, the interior starting temperature was 68 degrees.
The freezer was charged at spec plate weight with R-404A and -507A, and at 109 percent of the spec weight with One Shot. The original POE oil charge was utilized. The system maintained a three-eighths level in the sight glass throughout all tests, according to the engineers.
"After 150 minutes of testing, One Shot has 4 percent less power consumption than R-404A and 3 percent less power consumption than R-507A," said Terry. "In the same amount of time, [it] achieved 11 percent colder temperature than R-404A and 4 percent colder temperature than R-507A."
Terry said the oil was then changed to a mineral oil (3GS). After three flushes, the system achieved 97-percent oil concentration. "The system was then operated with varying loads, achieving different levels of coil frost, from light to blocked coil."
He said the unit had one defrost per day. "The thermostat was jumped for continuous operation and has been operating in excess of 60 days. The oil has not varied from the three-eighths level."
For more information, visit www.icorinternational.com.
Publication date: 07/05/2004