What is the best retrofit blend for HCFC-22? Technicians and equipment owners are asking this question more often as we approach the next step down in the production of R-22. It sounds like a simple question, yet the answer will depend on several key factors.
There is a fundamental difference between air conditioning and refrigeration. That difference has to do with evaporator temperature. R-22 air conditioners, with evaporator temperatures between 35°F and 50°, will behave much differently than refrigeration systems running at 20° (medium temperature) or –20° (low temperature). Some blends will match R-22 properties in a/c and others will be better suited for lower temperature operations.
Another difference might be design capacity and run time for the intended application. Air conditioners are sized for the hottest few days of the year and will cycle considerably most of the time. A/C can tolerate lower capacity blends by simply running a little longer. Storage refrigeration applications are also sized for 18 to 20 hours run time during the day. Lower capacity blends can also be tolerated in these systems because there is allowance for longer run times. Where systems are sized to match the capacity of the load, or seem to be running all the time, blends with higher capacity will be needed to maintain equipment performance.
Smaller, self-contained refrigeration equipment or air conditioners will generally involve much less work to service or retrofit. If major components need replacement, it may often be easier to replace the entire unit, although replacement cost will also be a consideration. Blends that require component replacements or major oil changes may not be the best choice. Service of larger installations will more likely involve component replacement and planned retrofits can be more comprehensive in terms of leak repair, seal or gasket replacement, oil changes, or adjustments of controls, which opens up the choice of retrofit blend.
When doing your homework on R-22 alternative blends, don’t settle for a quick “one size fits all” solution. Depending on your application temperature, run time, and equipment size, you may find there are different answers to the question, “What should I use?”
[Editor’s note: The material was prepared by National Refrigerants, www.refrigerants.com.]
Publication date: 12/07/2009
December 7, 2009