R134 is just a material which we support with RGP files and with the Redlich Kwong equation of state.
Thus it should be fairly simple to set up a simulation using R134.
However there are a few things you should be aware of:
If you are not doing phase change or the operating range of the device is at low enough pressure (or high enough temperature) you may not need to use Redlich Kwong or an RGP file. Specifying an Ideal Gas may be good enough.
If you need to do phase change (condensation) then R-134 calculations are setup exactly the same as for steam, other than picking the different materials of course.
For R-134 though we only have the Redlich Kwong EOS. The RGP files are for R134a.
It is worth noting that if you are modelling boiling/evaporation/non-equilibrium then condensation is a bit trickier.
All the real gas properties are currently only setup for equilibrium condensation modelling.