Hi all,

I found these and thought I would post the links for all to see.

The first link deals with control valves and their purpose.
http://www.danfoss.com/NR/rdonlyres/...0/RG00A502.pdf

The second link deals with On-Off controls (pressure & temperature switches)
http://www.danfoss.com/NR/rdonlyres/...0/RF5XA102.pdf

These should provide a very good description of the basic requirements.

Enjoy.