In this excerpt from his Classic Hydronics seminar, Dan Holohan explains how primarysecondary pumping works in a onepipe hot water heating system. Dan talks about valves, circulators, flow rate, pressure drop, blending temperatures, and more. Want to learn more? Visit https://heatinghelp.com/. Want to be an expert? Get a copy of Dan Holohan’s book Classic Hydronics: https://www.amazon.com/ClassicHydron...