Posted by RC on September 14, 2001 at 06:33:04: via: or 63.106.106.2
It appears that HC-12a was originally formulated to be a drop in replacement for R12 but for some reason (legal?) it has been reformulated to be a drop in replacement for R134a. Originally it had a higher ratio of propane to isobutane and that the current lower ratio of propane to isobutane has reduced the cooling in older (R12) systems. A solution used by some is to "boost" the system by addition of propane to the mix. Legallities and safety aside, does anyone know how much propane to add to the current crop of HC-12a (Duracool and ES, etc.) to have it work best in a system originally designed for R12?
Just to make things more interesting, what would be the effect on temperature if R22 was added to boost HC-12a instead of propane? Because the R22 would not be changing the fraction of propane already in the system, would a greater fraction of R22 be needed? Would the HC-12a fraction be sufficient for use with mineral oil? Or would the R22 just remain a gas in the system and reduce the cooling ability of the mixture even further?
-RC