The Retrofit Option
But now with virgin R-22 being phased out, folks are revisiting a new range of HFCs specifically targeted for low- and medium-temperature system retrofits.
One example is HFC-427A, which has already accumulated case histories and a track record at a range of sites. The refrigerant has nearly identical operating pressures and similar performance characteristics to R-22 for use in a wide range of air conditioning applications, according to Arkema, which markets the refrigerant under the brand name Forane® 427A. Arkema recently issued a report on four such projects.
SUPERMARKETThe Sherm’s Thunderbird Markets in Roseburg, Ore., retrofitted three racks, each with three to four semi-hermetic compressors. Store maintenance manager Frank Bartyzal said he was interested in R-427A because it could match R-22 capacity and efficiency while reducing compressor discharge temperatures.
The retrofit involved compressors from 22 to 30 hp. The mechanicals included a low-temperature rack for ice cream cases (-25°F evaporator, -10° case temperature), a low- temperature rack for frozen food (-15°, 0°), and a medium-temperature rack for deli cases and store heat reclaim (20°, 38°). The overall initial charge was 2,400 pounds.
According to a statement from Arkema, “The retrofit was a success with case temperatures maintained at the desired set levels while reducing compressor discharge temperatures. In addition, the retrofit actually reduced the total operating energy costs of the racks by an average of 7 percent.”
WAREHOUSE-TYPE SUPERMARKETFiesta Food Warehouse in Fontana, Calif., also retrofitted three racks each with three to four semi-hermetic compressors. The structure is a warehouse type of store. Engineering supervisor Tim Grant was looking for a greener substitute for R-22.
In each store there were systems at 25°, 15° and 35° with a total of 12 compressors divided among three section groups with two receivers. The compressors used alkyl benzene oil which was kept following the conversion. No components were changed during the retrofit except the filter driers. There were minor setting adjustments to the TXV and controls to optimize the system.
According to Arkema, “The refrigeration racks at the store reached their set temperatures quickly after the retrofit. Operating pressures were at similar levels with R-427A as with R-22. Compressor discharge temperatures were significantly reduced after the retrofit, which indicates the compressors are now running cooler than before.”
BABY FOOD FACTORYLes Aliments La Mere Poule is a baby food factory in Saint-Leonard, Quebec, Canada. The retrofit project involved a food preparation area where a R-22 refrigeration system uses a semi-hermetic reciprocating compressor with a rooftop-mounted condenser and a ceiling-mounted evaporator assembly. The total refrigerant charge was 55 pounds of R-22 and room temperature was the 55°F needed in the prep room during food processing operations.
According to Arkema, “Initial readings were taken to establish the system’s performance with R-22. Recovery of the R-22 was followed by a change of the compressor oil to POE, replacement of system filters, and deep evacuation. Optimizing of the system charge produced the same charge weight for R-427A as was used with R-22.” There were no other changes.
“Operating pressures with R-427A were close to those measured with R-22, while compressor discharge temperatures and amperage draw were both lower.”
COMPUTER ROOM AIR CONDITIONINGR-427A was used to retrofit an air conditioning system for a computer server room at the Canada Revenue Agency in Sudbury, Ontario, Canada. The room is cooled by two identical air conditioning systems. So in this case, it was decided to do a side-by-side comparison by putting R-427A in one system and the other continuing to use R-22. Each system has two individual circuits powered by reciprocating compressors. There were also reclaim systems for capturing high-side heat rejection for domestic water heating.
“After recovering the R-22 charge, the compressor oil was drained and replaced with POE, the filter drier was replaced and the system evacuated,” said Arkema.
“The service room is operating normally, with no noticeable differences in cooling performance. Operating pressures of the system were nearly identical for both refrigerants. A 40° decrease in compressor discharge temperature and noticeably lower compressor circuit draws were observed after switching to 427A.”
For more information, visit www.forane-us.com.
Publication date: 03/08/2010