Converting existing R12 plants to R134a

At the beginning this subject was discussed very controversially, several conversion methods were recommended and applied. Today there is a general agreement on technically and economically matching solutions.

The characteristics of ester oils are very favourable here: Under certain conditions they can be used with CFC refrigerants, they can be mixed with mineral oils and tolerate a proportion of chlorine up to a few hundred ppm in an R134a system.

The remaining moisture content has, however, an enormous influence. Very thorough evacuation (removal of remaining chlorine and dehydration) is therefore essential, as well as the installation of generously dimensioned driers. There is doubtful experience with systems where the chemical stability was already insufficient with R12 operation e.g. with bad maintenance, small drier capacity, high thermal loading. Increased deposition of oil decomposition products containing chlorine is found often. These products are released by the influence of the highly polarized mixture of ester oil and R134a and find their way into the compressor and control devices. Conversion should therefore be limited to systems which are in a good condition.