Old beverage air refrigerator. the new compressor is rated for 134 unit is r12 with cap tube. What needs to be done to change refrigerant to 134. Usually, we work on walk-ins where we can change txv
Majority of time 85% of R12 by weight will suffice but if proper charge is unknown I've charged until suction line frosts while charging in 1 oz increments. After frost is observed slowly bleed excess charge off at suction port until frost leaves. Typically charge will be <8oz and <18oz & suction pressure >5PSIG & , 40PSIG dependent on load. Have used this method for years with 100% success. As always, hard vacuum, new dryer & brazed access ports.
Depends on the year of manufacture of the original compressor. If it had mineral oil it would take several changes with a intern refrigerant like R409 and Aylkabenzene oil. Otherwise your setting yourself up for a reaction with the R134 and the residual mineral oil. Usually blocking the cap tube. R409 can be used as a replacement for R12.
You should also be aware of the following;
Retrofitting Considerations: Equipment built for R-12 will be sized a bit too small compared to equipment built for R-134a. In order to do the same job, an R-134a system will need a larger compressor and larger heat exchangers. As a result, a system that is retrofitted from R-12 to R-134a will have lower capacity (run longer) and will probably develop higher head pressures (not enough condenser area). The lubricant will also need to be flushed and replaced with POE.
This is a coversion chart for 134;
Thanks. Have to charnge compressor so new one is 134a ready
Brian Perry 410-808-1995
It's the residual mineral oil in the condenser and evaporator that are the problem. It has to be less than 5% of the lubricant. If you can get some R123 and pump it through as a flush you'll be ok. Section 608 puts R134 out next month, So you may want to explore something else. As of this moment, I don't know what is available. Or coming down the road.
The only difference between a R12, R134, or R12 replacement is the oil in it. It is the same motor and displacement. If it was for a R22 it would have a smaller displacement. R502, R404 even smaller. But the same motors. Back when Copemetic was the king of reliable refrigeration compressors you would start with a R502, then bore it out for R22 service, and again bore it out for R12. Thats why the big core charge.
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