In all the years that I have been writing and teaching, I have found that one of the hardest concepts for people in the hydronics business to understand is the concept and explanation surrounding what has been called the “point of no pressure change,” or PONPC. This concept is very simple, but hard to explain, and even harder for people to see it in their mind’s eye. During a recent code hearing, it was pointed out to me that the pressure at the PONPC will in fact change ...

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