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I have a small commercial building that I am putting in a new cast iron boiler.  It is an old monoflo system with a two inch steel pipe main and 3/4 branches to registers.  (Fin tube cabinet type).  It also has an add on in the back of the building with a one pipe 1 inch line... The supply house designers said the two inch line is over sized and decreased the boiler loop to 1-1/2" and the zone comes off 1-1/4 to the supply to the two inch monoflo side of the system.  Just wondering if this will be adequate.


  • Ironman
    Ironman Member Posts: 7,379

    What is the output of the boiler and what is the EDR of the loop?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
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