Hi Dan,

What's an expansion valve to do?
All it can do is try to work.

It has been my experience that by using the concepts of useful and non-useful in the context of subcooling and superheat discussions you can get the point across.

If either one does not provide some benefit to system performance or efficiency it is a wasted effort.

Most of the people who posted to this were moderators. Some were regular RE members, but all came with very good thoughts and ideas.

I feel it is these types of discussions that help the younger people a lot. This is the sort of thing you don't learn in school, but can provide some good background information for service tech's and system designers.

Peter had a very good question too about the ice on the suction valve. It all comes down to using the refrigerant tables and the basics.

After all of the discussion on subcooling pros & cons. I have another question related to this subject. I will warn you that this is a term I developed and use, but it points out another area that can be addressed here.

What is positive subcooling and negative subcooling?

I"ll provide a hint: It has to do with two stage systems and booster compressors.