“Life is difficult” is the first sentence from the book The Road Less Travelled by M. Scott Peck. In the same manner, this article starts out, “Flow control is difficult.” If it was not difficult, there would not have been so much debate about it over the years. There would not have been so many engineering opinions about it over the years. There would not have been so many product developments over the years that promise to be the answer to proper flow control in an HVAC hydronic system.
However, all that being said, flow control need not be as difficult as it is sometimes perceived to be. Keep it simple is a good way to begin thinking through the design of any HVAC hydronic flow control system and piping design. One simple thing to keep in mind: What is not directly measured is not directly controlled.