Peter, Suva 95, aka Suva X, aka KCD-9515 is a refrigerant blend of R-23 and R-116. It have a dew point curve almost identical to R-503, and it has a temperature glide of about 1F. So for all practical purposes, it is an azeotrope like R-503.

R-13 and R-503 are on their way out, since they're both CFCs. R-23 was the only HFC game in town for awhile. Problem with it is its inherently high operating discharge temperatures. You generally needed some means of suction gas desuperheating to prevent oil breakdown problems.

Suva 95 looks good. You can use R-503 TEV for Suva 95, though you will get about 20 percent less capacity out of it compared to R-503. You may need to look at TEV sizing, and possibly other component sizing.

Andy Schoen

aschoen@mo.net

Peter Kesselman writes:
>We ordered some SUVA-95 directly from DuPont yesterday. It's in limited supply and you can't get it anywhere else for now. Do you have any hands-on experience with it?

I only have heard comments from servicemen who have retrofitted systems from R-13/R-503/R-23 to Suva 95. Everyone was pleased with the results. They were quite happy with the discharge temperatures. I also know the chamber manufacturers are quite interested in it. I would expect to see new chambers using Suva 95 coming out soon.

>Does this mean that all recently shipped R23 units have marginal discharge temps? We sell refurbished environmental chambers so naturally, everything is a retrofit. Are chamber mfrs just taking risks with R23 until something better comes along?

Unfortunately, R-23 was the only game in town, unless you didn't mind using ethane (R-170). BTW, ethane has been used as a low temperature chamber refrigerant for many years. Problem, of course, is its flammability. Manufacturers tend to shun flammable refrigerants for product liability reasons.

>DuPont recommends only POE. Could you get away with Mineral Oil if you added Pentane as with R13/503? Compressor mfrs are no help since they don't design for very-low-temp applications (voids the warranty).

I know a few retrofits using AB oil and Suva 95. I believe R-12 (so much for having a CFC-free machine) was added for oil return. Personal opinion: I doubt POE oil is really necessary if you already are using pentane/R-12/etc. to get oil back. However, I believe there exists a suitable POE oil for low temperature chamber applications.

I would be inclined to try it both ways. BTW, you can always tell the pioneers: they're the ones with the arrows in their backs. :-)

>TEV's available with SUVA-95 charge?

Not necessary, Suva 95 is so close to R-503's saturation charge that there is no reason to reformulate the thermostatic charge. But you need to figure you are only going to get about 80 percent of the valve's R-503 rating when using Suva 95.

Andy Schoen