The Biggest Loser

Blissful Ignorance: For most of the past four decades, my hydronic training centered on
choosing a circulator that met, or exceeded, the required GPM rate while overcoming the system’s
head losses in each zone. Our hydronic piping zones were like fat wide highways where traffic was
light with very little need on our part to pay close attention to those kinds of details and there were few
choices for residential circulators. Pretty much one size fit all. Zone valves were prone to failure and
leaking, so I became a devout advocate for utilizing circulators, which were reliable and long-lived –
unless you over-oiled the motor bearing-cups.

New mixing strategies emerged: PEX tubing with radiant heating; hi-head-loss boilers; injection
temperature zones; 4-, 3-, and 2-way mixing valves; and the need to comprehend Cv-values
corresponding to the required GPM flow rates each dictated which circulator was chosen based on
the manufacturers’ hydraulic curve. The need to properly size circulators to their corresponding zone
of responsibility became much more critical and model choices expanded exponentially. Our focus
was centered on providing customers with high-efficiency heat sources while utilizing heat emitters
designed for efficient delivery of comfort-energy. Miserly fuel use coupled with hydronically-delivered
comfort – it couldn’t get any better than that – or could it?

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