Drop on in
In the August 2012 issue of Supply House Times, I wrote an article about how some companies are now offering explosive hydrocarbon refrigerants as “drop-in replacements” for the soon-to-be-gone R22, which is used in millions of residential air conditioners.
Since then I have received several letters from readers telling me the larger refrigerant manufacturers do, in fact, have their own “drop-in replacements” for R22 in these applications.
Is that true? What we are finding is a Jekyll and Hyde situation among some manufacturing companies, because their engineering departments don’t recommend such applications, but their marketing departments do (I know because I’ve spoken separately to them all).
Ask your refrigerant manufacturer rep who says you can use their product as a replacement for R22 in residential applications this question: “Is your company willing to state in writing that it guarantees its R22 replacement will work safely in residential A/C and heat-pump units?” They won’t, because they can’t, because they don’t!
Most R22 residential A/C and heat-pump units use orifice or capillary-tube metering where the proper charge has to be within 1/2-oz. to achieve maximum efficiency and maximum compressor life. The only way to achieve this is either by weighing in the charge (you have to compensate for line sizes and lengths and for filter driers), or by using complicated charging charts that require a precise balance of outdoor-air temperatures, suction-line (or indoor wet bulb) temperatures and liquid-line temperatures. This varies by manufacturer and design efficiency. But who will invest in developing such charts and determining the proper weights for using the new refrigerants in these old units, on all efficiencies and brands?
Miscibility and oil return problemThe new refrigerants are designed for replacement of R22 in commercial applications where the existing mineral oil can be replaced with synthetics, since they are not miscible enough with the oil to allow it to return to the compressor. However, you cannot replace the oil in the welded hermetic compressors that are used in residential A/C units.
In an application bulletin that I recently received from Trane Co. on “Use of the alternative ‘drop in’ HCFC-22 replacement refrigerant R-438A in single compressor/single speed residential split and package systems,” I found these statements:
“The refrigerant manufacturer’s (Dupont) data indicates system performance may be negatively impacted by as much as 10% when using R-438A as opposed to using R-22. In addition, R-22 systems have compressors originally charged with mineral oil, which is not miscible with the liquid phase of R438A. The refrigerant manufacturer’s retrofit guide recommends adding 10 to 20% POE oil to the system if the oil level drops continuously in the compressor sump. Since the compressors used in residential systems do not contain a sight glass and to alleviate the concern of falling oil levels, a small amount of POE oil must be added to the system per the instructions listed in this bulletin when retrofitting a system with R-438A … Using an alternate refrigerant as a ‘drop-in’ replacement should be considered as a last resort.”
Then I asked an engineer from a compressor manufacturer (Copeland) what he thought of the idea and was told, “It’s risky, but it might work where there are no suction accumulators or oversized or long suction risers. However, we couldn’t warranty it.” So, A/C service companies that try this trick are all alone when it comes to liability.
Recognize that most high-efficiency A/C units, those with scroll compressors and all heat pumps employ suction accumulators. Also, all roof-mounted split systems have suction risers. Yes, that’s the majority of R22 units that were sold over the past few years.
Is there any solution to this problem? Yes! Get everyone involved in the recovery and recycling of R22 before it’s all gone!