Einstein’s definition of insanity was doing the same thing over and over and expecting different results. If that’s true, there are definitely some “insane” hydronic system designers in North America. They repeatedly cling to certain piping layouts, even though existing projects using those layouts have experienced problems.
One incorrect piping layout that I’ve seen repeated many times could be described as a morphing of primary/secondary piping and a classic header-type multizone distribution system. I’ve seen it as installed hardware and in neatly prepared CAD drawings created by professional engineers. The latest rendition of this problematic piping layout popped up in an email sent to me for review. My conclusion: It’s time to write about this problem — again — and try to dissuade others from repeating it.