I'm looking through various alternatives to R-22, for use in already designed systems. We would strongly prefer a refrigerant that does not require hydroscopic oils, since we have had trouble with customers in the past mishandling their systems ("don't mess with the settings" just doesn't seem to work sometimes).

One item that is mentioned as a potential replacement for air conditioning only (not for use in colder evaporator systems or certain other situations) is R-417A / NU-22 / Isceon 59.

It looks like R-417A is being used by some OEMs in the USA already:
http://www.flagshipmarine.com/flagshipgoesgreen.html

I'ver read some of the propaganda from Rhodia ( http://www.isceon-refrigerants.co.uk ) and ICORs literature (http://www.icorinternational.com/literature.html). I've also read all the anti-R-417A stuff that DuPont refrigerants has put out, yet I also see that DuPont has recently purchased R-417A production capacity from Rhodia, so perhaps that propaganda will change soon.

There is a lot of conversion information available from these two manufacturers, and how to tune a system for this particular blend. However, I am particularly interested if anyone out there has dealt with redesign of an R-22 system to use this refrigerant.

Oh, and before you suggest R-410a instead, we have looked at that, and the critical point is awfully low. From time to time our systems wind up in places where condenser air can be 120-130 deg. F, and 410a has a critical point such that a severe redesign of the entire system would be necessary. Also, as our customers typically already have some of our R-22 systems in place, we would like to design a system so that they don't have to carry two sets of refrigerant gauges, etc. to deal with two different pressure ranges - R-22 and R-410a.

Since an R-417a system could probably be designed around the same condensers, compressors, and evaporators, and possibly use the same oil (we would likely use AB oil as apparently there can still be oil circulation issues on some systems with mineral oil and this refrigerant), it looks like it has a lot of possibilities.

However, I would like to know what the real experience is.