Resulting design criteria / Converting existing R502 plants

The compressor and the components which are matched to R502 can remain in the system in most cases. The limitations in the application range must however be considered: Higher discharge gas temperature than R502 with R402B, R403A and R408A or higher pressure levels with R402A and R403B (classifications according to ASHRAE nomenclature).

The good solubility characteristics of R22 and R290 increase the risk that, after conversion of the plant, possible deposits of oil decomposition products containing chlorine are dissolved and find their way into the compressor and control devices. Systems where chemical stability was already insufficient with R502 operation (bad maintenance, low drier capacity, high thermal loading) are particularly at risk.

Thus, generously dimensioned suction gas filters and liquid line driers should be installed for cleaning before conversion, and an oil change should be made after approximately 100 hours operation. Further checks are recommended.

The operating conditions with R502 (including discharge gas temperature and suction gas superheat) should be noted so that a comparison can be made with the values after conversion. Depending upon the results, control devices should possibly be reset and other additional measures should be taken as required.