Thank you DrAmine for your reply.

I double checked all my material properties and they are all correct. I have put a link for my case-setup in the first message, so if u can take a look on it, and tell me what's incorrect, cause I haven't found the error.

Can you please explain more about how to correct the Tref. In the material properties I set the Tref as temperature of saturation (534.55 K) for both water and steam.