Changing refrigerants

[Ranken]

Purchased an older walk in cooler that was charged with r12 want to change to 134a what kind of oil do I need to use has aklyate synthetic in it now or would there be a better choice of refrigerants

[chemi-cool]

You need to emty the compressor, charge with POE, the oil viscosity depends on evaporating temp,

Run some refrigerant oil cleaner through the pipe work, pushing it with OFN, replace the TXV to 134 one, new drier, good vacuum, charge and run the unit.

[Ranken]

Thanks will try that

[Ranken]

Would there be a better choice of refrigerant other than 134a

[deulengame]

Check out Lindes "Retrofit Guide", they suggest a few alternatives like R423A, R426A, R437A depending on application, and suggests oil changes.
Remember to renew gaskets and check the superheat settings